stream: Split cli/srv specific code out of stream.c

The dev/user in general is only interested about one side of the stream
when looking at the code. Since the stream.c file is tarting to be quite
large/bloated, this patch splits its content into stream_cli.c and
stream_srv.c to make it easier to improve/extend and review.
Keep common code between cli and srv in stream.c, and add a private header
to contain references to it.

Change-Id: I22af01bba2040eb320ba48fd1b46c090c98be159

6 files changed, 1938 insertions, 1786 deletions

diff --git a/include/osmocom/netif/Makefile.am b/include/osmocom/netif/Makefile.am
index 92712a9..3d8a56b 100644
--- a/include/osmocom/netif/Makefile.am
+++ b/include/osmocom/netif/Makefile.am
@@ -1,3 +1,7 @@
+noinst_HEADERS = \
+	stream_private.h \
+	$(NULL)
+
 osmonetif_HEADERS = amr.h		\
 		    datagram.h		\
 		    jibuf.h		\
diff --git a/include/osmocom/netif/stream_private.h b/include/osmocom/netif/stream_private.h
new file mode 100644
index 0000000..8f83a25
--- /dev/null
+++ b/include/osmocom/netif/stream_private.h
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <osmocom/core/socket.h>
+
+#include "config.h"
+
+#ifdef HAVE_LIBSCTP
+#include <netinet/sctp.h>
+	#define OSMO_STREAM_MAX_ADDRS OSMO_SOCK_MAX_ADDRS
+	/*
+	* Platforms that don't have MSG_NOSIGNAL (which disables SIGPIPE)
+	* usually have SO_NOSIGPIPE (set via setsockopt).
+	*/
+	#ifndef MSG_NOSIGNAL
+	#define MSG_NOSIGNAL 0
+	#endif
+#else
+	#define OSMO_STREAM_MAX_ADDRS 1
+#endif
+
+/*! \addtogroup stream
+ *  @{
+ */
+
+enum osmo_stream_mode {
+	OSMO_STREAM_MODE_UNKNOWN,
+	OSMO_STREAM_MODE_OSMO_FD,
+	OSMO_STREAM_MODE_OSMO_IO,
+};
+
+int stream_sctp_sock_activate_events(int fd);
+int stream_setsockopt_nodelay(int fd, int proto, int on);
+
+/*! @} */
diff --git a/src/Makefile.am b/src/Makefile.am
index f12085d..66888c6 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -22,6 +22,8 @@ libosmonetif_la_SOURCES = amr.c			\
 			  prim.c		\
 			  rs232.c		\
 			  rtp.c			\
+			  stream_cli.c		\
+			  stream_srv.c		\
 			  stream.c
 
 if ENABLE_LIBSCTP
diff --git a/src/stream.c b/src/stream.c
index 9ff1df9..5674c4b 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -1,5 +1,6 @@
 /* (C) 2011 by Pablo Neira Ayuso <pablo@gnumonks.org>
  * (C) 2015-2016 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
  * All Rights Reserved.
  *
  * SPDX-License-Identifier: GPL-2.0+
@@ -44,13 +45,10 @@
 #include <osmocom/core/socket.h>
 
 #include <osmocom/netif/stream.h>
+#include <osmocom/netif/stream_private.h>
 
 #include "config.h"
 
-#ifdef HAVE_LIBSCTP
-#include <netinet/sctp.h>
-#endif
-
 #include <osmocom/netif/sctp.h>
 
 
@@ -68,32 +66,6 @@
  */
 
 #ifdef HAVE_LIBSCTP
-/*
- * Platforms that don't have MSG_NOSIGNAL (which disables SIGPIPE)
- * usually have SO_NOSIGPIPE (set via setsockopt).
- */
-#ifndef MSG_NOSIGNAL
-#define MSG_NOSIGNAL 0
-#endif
-
-#define LOGSCLI(cli, level, fmt, args...) \
-	LOGP(DLINP, level, "CLICONN(%s,%s){%s} " fmt, \
-	     cli->name ? : "", \
-	     cli->sockname, \
-	     get_value_string(stream_cli_state_names, (cli)->state), \
-	     ## args)
-
-#define LOGSLNK(link, level, fmt, args...) \
-	LOGP(DLINP, level, "SRV(%s,%s) " fmt, \
-	     link->name ? : "", \
-	     link->sockname, \
-	      ## args)
-
-#define LOGSSRV(srv, level, fmt, args...) \
-	LOGP(DLINP, level, "SRVCONN(%s,%s) " fmt, \
-	     srv->name ? : "", \
-	     srv->sockname, \
-	      ## args)
 
 /* is any of the bytes from offset .. u8_size in 'u8' non-zero? return offset or -1 if all zero */
 static int byte_nonzero(const uint8_t *u8, unsigned int offset, unsigned int u8_size)
@@ -188,7 +160,7 @@ static int sctp_setsockopt_events_linux_workaround(int fd, const struct sctp_eve
 }
 #endif // HAVE_LIBSCTP
 
-static int sctp_sock_activate_events(int fd)
+int stream_sctp_sock_activate_events(int fd)
 {
 #ifdef HAVE_LIBSCTP
 	struct sctp_event_subscribe event;
@@ -214,7 +186,7 @@ static int sctp_sock_activate_events(int fd)
 #endif
 }
 
-static int setsockopt_nodelay(int fd, int proto, int on)
+int stream_setsockopt_nodelay(int fd, int proto, int on)
 {
 	int rc;
 
@@ -237,1758 +209,4 @@ static int setsockopt_nodelay(int fd, int proto, int on)
 }
 
 
-/*
- * Client side.
- */
-
-enum osmo_stream_cli_state {
-	STREAM_CLI_STATE_CLOSED,	 /* No fd associated, no timer active */
-	STREAM_CLI_STATE_WAIT_RECONNECT, /* No fd associated, has timer active to try to connect again */
-	STREAM_CLI_STATE_CONNECTING,	 /* Fd associated, but connection not yet confirmed by peer or lower layers */
-	STREAM_CLI_STATE_CONNECTED,	 /* Fd associated and connection is established */
-	STREAM_CLI_STATE_MAX
-};
-
-static const struct value_string stream_cli_state_names[] = {
-	{ STREAM_CLI_STATE_CLOSED,	 "CLOSED" },
-	{ STREAM_CLI_STATE_WAIT_RECONNECT, "WAIT_RECONNECT" },
-	{ STREAM_CLI_STATE_CONNECTING,     "CONNECTING" },
-	{ STREAM_CLI_STATE_CONNECTED,      "CONNECTED" },
-	{ 0, NULL }
-};
-
-#define OSMO_STREAM_CLI_F_RECONF	(1 << 0)
-#define OSMO_STREAM_CLI_F_NODELAY	(1 << 1)
-
-#ifdef HAVE_LIBSCTP
-#define OSMO_STREAM_MAX_ADDRS OSMO_SOCK_MAX_ADDRS
-#else
-#define OSMO_STREAM_MAX_ADDRS 1
-#endif
-
-enum osmo_stream_mode {
-	OSMO_STREAM_MODE_UNKNOWN,
-	OSMO_STREAM_MODE_OSMO_FD,
-	OSMO_STREAM_MODE_OSMO_IO,
-};
-
-struct osmo_stream_cli {
-	char *name;
-	char sockname[OSMO_SOCK_NAME_MAXLEN];
-	enum osmo_stream_mode mode;
-	union {
-		struct osmo_fd			ofd;
-		struct osmo_io_fd		*iofd;
-	};
-	struct llist_head		tx_queue;
-	struct osmo_timer_list		timer;
-	enum osmo_stream_cli_state	state;
-	char				*addr[OSMO_STREAM_MAX_ADDRS];
-	uint8_t			 	addrcnt;
-	uint16_t			port;
-	char				*local_addr[OSMO_STREAM_MAX_ADDRS];
-	uint8_t			 	local_addrcnt;
-	uint16_t			local_port;
-	int				sk_domain;
-	int				sk_type;
-	uint16_t			proto;
-	int (*connect_cb)(struct osmo_stream_cli *cli);
-	int (*disconnect_cb)(struct osmo_stream_cli *cli);
-	int (*read_cb)(struct osmo_stream_cli *cli);
-	int (*iofd_read_cb)(struct osmo_stream_cli *cli, struct msgb *msg);
-	int (*write_cb)(struct osmo_stream_cli *cli);
-	void				*data;
-	int				flags;
-	int				reconnect_timeout;
-};
-
-void osmo_stream_cli_close(struct osmo_stream_cli *cli);
-
-/*! \brief Re-connect an Osmocom Stream Client
- *  If re-connection is enabled for this client
- *  (which is the case unless negative timeout was explicitly set via osmo_stream_cli_set_reconnect_timeout() call),
- *  we close any existing connection (if any) and schedule a re-connect timer */
-void osmo_stream_cli_reconnect(struct osmo_stream_cli *cli)
-{
-	osmo_stream_cli_close(cli);
-
-	if (cli->reconnect_timeout < 0) {
-		LOGSCLI(cli, LOGL_INFO, "not reconnecting, disabled\n");
-		return;
-	}
-
-	cli->state = STREAM_CLI_STATE_WAIT_RECONNECT;
-	LOGSCLI(cli, LOGL_INFO, "retrying reconnect in %d seconds...\n",
-		cli->reconnect_timeout);
-	osmo_timer_schedule(&cli->timer, cli->reconnect_timeout, 0);
-}
-
-/*! \brief Check if Osmocom Stream Client is in connected state
- *  \param[in] cli Osmocom Stream Client
- *  \return true if connected, false otherwise
- */
-bool osmo_stream_cli_is_connected(struct osmo_stream_cli *cli)
-{
-	return cli->state == STREAM_CLI_STATE_CONNECTED;
-}
-
-static void osmo_stream_cli_close_iofd(struct osmo_stream_cli *cli)
-{
-	if (!cli->iofd)
-		return;
-
-	osmo_iofd_close(cli->iofd);
-}
-
-static void osmo_stream_cli_close_ofd(struct osmo_stream_cli *cli)
-{
-	if (cli->ofd.fd == -1)
-		return;
-	osmo_fd_unregister(&cli->ofd);
-	close(cli->ofd.fd);
-	cli->ofd.fd = -1;
-}
-
-/*! \brief Close an Osmocom Stream Client
- *  \param[in] cli Osmocom Stream Client to be closed
- *  We unregister the socket fd from the osmocom select() loop
- *  abstraction and close the socket */
-void osmo_stream_cli_close(struct osmo_stream_cli *cli)
-{
-	int old_state = cli->state;
-
-	if (cli->state == STREAM_CLI_STATE_CLOSED)
-		return;
-	if (cli->state == STREAM_CLI_STATE_WAIT_RECONNECT) {
-		osmo_timer_del(&cli->timer);
-		cli->state = STREAM_CLI_STATE_CLOSED;
-		return;
-	}
-
-
-	switch (cli->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		osmo_stream_cli_close_ofd(cli);
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		osmo_stream_cli_close_iofd(cli);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-
-	cli->state = STREAM_CLI_STATE_CLOSED;
-
-	if (old_state == STREAM_CLI_STATE_CONNECTED) {
-		LOGSCLI(cli, LOGL_DEBUG, "connection closed\n");
-		if (cli->disconnect_cb)
-			cli->disconnect_cb(cli);
-	}
-}
-
-static inline int osmo_stream_cli_fd(const struct osmo_stream_cli *cli)
-{
-	switch (cli->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		return cli->ofd.fd;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		if (cli->iofd)
-			return osmo_iofd_get_fd(cli->iofd);
-	default:
-		break;
-	}
-	return -EINVAL;
-}
-
-static void osmo_stream_cli_read(struct osmo_stream_cli *cli)
-{
-	LOGSCLI(cli, LOGL_DEBUG, "message received\n");
-
-	if (cli->read_cb)
-		cli->read_cb(cli);
-}
-
-static int osmo_stream_cli_write(struct osmo_stream_cli *cli)
-{
-#ifdef HAVE_LIBSCTP
-	struct sctp_sndrcvinfo sinfo;
-#endif
-	struct msgb *msg;
-	int ret;
-
-	if (llist_empty(&cli->tx_queue)) {
-		osmo_fd_write_disable(&cli->ofd);
-		return 0;
-	}
-	msg = llist_first_entry(&cli->tx_queue, struct msgb, list);
-	llist_del(&msg->list);
-
-	if (!osmo_stream_cli_is_connected(cli)) {
-		LOGSCLI(cli, LOGL_ERROR, "send: not connected, dropping data!\n");
-		return 0;
-	}
-
-	LOGSCLI(cli, LOGL_DEBUG, "sending %u bytes of data\n", msgb_length(msg));
-
-	switch (cli->sk_domain) {
-	case AF_UNIX:
-		ret = send(cli->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
-		break;
-	case AF_UNSPEC:
-	case AF_INET:
-	case AF_INET6:
-		switch (cli->proto) {
-#ifdef HAVE_LIBSCTP
-		case IPPROTO_SCTP:
-			memset(&sinfo, 0, sizeof(sinfo));
-			sinfo.sinfo_ppid = htonl(msgb_sctp_ppid(msg));
-			sinfo.sinfo_stream = msgb_sctp_stream(msg);
-			ret = sctp_send(cli->ofd.fd, msgb_data(msg), msgb_length(msg),
-					&sinfo, MSG_NOSIGNAL);
-			break;
-#endif
-		case IPPROTO_TCP:
-		default:
-			ret = send(cli->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
-			break;
-		}
-		break;
-	default:
-		ret = -ENOTSUP;
-	}
-
-	if (ret >= 0 && ret < msgb_length(msg)) {
-		LOGSCLI(cli, LOGL_ERROR, "short send: %d < exp %u\n", ret, msgb_length(msg));
-		/* Update msgb and re-add it at the start of the queue: */
-		msgb_pull(msg, ret);
-		llist_add(&msg->list, &cli->tx_queue);
-		return 0;
-	}
-
-	if (ret < 0) {
-		if (errno == EPIPE || errno == ENOTCONN) {
-			osmo_stream_cli_reconnect(cli);
-		}
-		LOGSCLI(cli, LOGL_ERROR, "received error %d in response to send\n", errno);
-	}
-
-	msgb_free(msg);
-
-	if (llist_empty(&cli->tx_queue))
-		osmo_fd_write_disable(&cli->ofd);
-
-	return 0;
-}
-
-static int _setsockopt_nosigpipe(struct osmo_stream_cli *cli)
-{
-#ifdef SO_NOSIGPIPE
-	int ret;
-	int val = 1;
-	ret = setsockopt(osmo_stream_cli_fd(cli), SOL_SOCKET, SO_NOSIGPIPE, (void *)&val, sizeof(val));
-	if (ret < 0)
-		LOGSCLI(cli, LOGL_DEBUG, "Failed setting SO_NOSIGPIPE: %s\n", strerror(errno));
-	return ret;
-#else
-	return 0;
-#endif
-}
-
-static void stream_cli_handle_connecting(struct osmo_stream_cli *cli, int res)
-{
-	int error, ret = res;
-	socklen_t len = sizeof(error);
-
-	int fd = osmo_stream_cli_fd(cli);
-	OSMO_ASSERT(fd >= 0);
-
-	if (ret < 0) {
-		osmo_stream_cli_reconnect(cli);
-		return;
-	}
-	ret = getsockopt(fd, SOL_SOCKET, SO_ERROR, &error, &len);
-	if (ret >= 0 && error > 0) {
-		osmo_stream_cli_reconnect(cli);
-		return;
-	}
-
-	/* If messages got enqueued while 'connecting', keep WRITE flag
-	   up to dispatch them upon next main loop step */
-	if (cli->mode == OSMO_STREAM_MODE_OSMO_FD && llist_empty(&cli->tx_queue))
-		osmo_fd_write_disable(&cli->ofd);
-
-	/* Update sockname based on socket info: */
-	osmo_sock_get_name_buf(cli->sockname, sizeof(cli->sockname), osmo_stream_cli_fd(cli));
-
-	LOGSCLI(cli, LOGL_DEBUG, "connection established\n");
-	cli->state = STREAM_CLI_STATE_CONNECTED;
-	switch (cli->sk_domain) {
-	case AF_UNIX:
-		_setsockopt_nosigpipe(cli);
-		break;
-	case AF_UNSPEC:
-	case AF_INET:
-	case AF_INET6:
-		if (cli->proto == IPPROTO_SCTP) {
-			_setsockopt_nosigpipe(cli);
-			sctp_sock_activate_events(fd);
-		}
-		break;
-	default:
-		break;
-	}
-	if (cli->connect_cb)
-		cli->connect_cb(cli);
-}
-
-static int osmo_stream_cli_fd_cb(struct osmo_fd *ofd, unsigned int what)
-{
-	struct osmo_stream_cli *cli = ofd->data;
-
-	switch (cli->state) {
-	case STREAM_CLI_STATE_CONNECTING:
-		stream_cli_handle_connecting(cli, 0);
-		break;
-	case STREAM_CLI_STATE_CONNECTED:
-		if (what & OSMO_FD_READ) {
-			LOGSCLI(cli, LOGL_DEBUG, "connected read\n");
-			osmo_stream_cli_read(cli);
-		}
-		if (what & OSMO_FD_WRITE) {
-			LOGSCLI(cli, LOGL_DEBUG, "connected write\n");
-			osmo_stream_cli_write(cli);
-		}
-		break;
-	default:
-		/* Only CONNECTING and CONNECTED states are expected, since they are the only states
-		 * where FD exists: */
-		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
-	}
-	return 0;
-}
-
-static void cli_timer_cb(void *data);
-
-/*! \brief Create an Osmocom stream client
- *  \param[in] ctx talloc context from which to allocate memory
- *  This function allocates a new \ref osmo_stream_cli and initializes
- *  it with default values (5s reconnect timer, TCP protocol)
- *  \return allocated stream client, or NULL in case of error
- */
-struct osmo_stream_cli *osmo_stream_cli_create(void *ctx)
-{
-	struct osmo_stream_cli *cli;
-
-	cli = talloc_zero(ctx, struct osmo_stream_cli);
-	if (!cli)
-		return NULL;
-
-	cli->mode = OSMO_STREAM_MODE_UNKNOWN;
-	cli->sk_domain = AF_UNSPEC;
-	cli->sk_type = SOCK_STREAM;
-	cli->proto = IPPROTO_TCP;
-
-	cli->state = STREAM_CLI_STATE_CLOSED;
-	osmo_timer_setup(&cli->timer, cli_timer_cb, cli);
-	cli->reconnect_timeout = 5;	/* default is 5 seconds. */
-	INIT_LLIST_HEAD(&cli->tx_queue);
-
-	return cli;
-}
-
-static void stream_cli_iofd_read_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
-{
-	struct osmo_stream_cli *cli  = osmo_iofd_get_data(iofd);
-
-	switch (cli->state) {
-	case STREAM_CLI_STATE_CONNECTING:
-		stream_cli_handle_connecting(cli, res);
-		break;
-	case STREAM_CLI_STATE_CONNECTED:
-		if (res == 0)
-			osmo_stream_cli_reconnect(cli);
-		else if (cli->iofd_read_cb)
-			cli->iofd_read_cb(cli, msg);
-		break;
-	default:
-		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
-	}
-}
-
-static void stream_cli_iofd_write_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
-{
-	struct osmo_stream_cli *cli = osmo_iofd_get_data(iofd);
-
-	switch (cli->state) {
-	case STREAM_CLI_STATE_CONNECTING:
-		stream_cli_handle_connecting(cli, res);
-		break;
-	case STREAM_CLI_STATE_CONNECTED:
-		if (msg && res <= 0) {
-			osmo_stream_cli_reconnect(cli);
-			LOGSCLI(cli, LOGL_ERROR, "received error %d in response to send\n", res);
-		}
-		break;
-	default:
-		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
-	}
-}
-
-static struct osmo_io_ops osmo_stream_cli_ioops = {
-	.read_cb = stream_cli_iofd_read_cb,
-	.write_cb = stream_cli_iofd_write_cb,
-
-	.segmentation_cb = NULL,
-};
-
-/*! \brief Set a name on the cli object (used during logging)
- *  \param[in] cli stream_cli whose name is to be set
- *  \param[in] name the name to be set on cli
- */
-void osmo_stream_cli_set_name(struct osmo_stream_cli *cli, const char *name)
-{
-	osmo_talloc_replace_string(cli, &cli->name, name);
-	if (cli->mode == OSMO_STREAM_MODE_OSMO_IO && cli->iofd)
-		osmo_iofd_set_name(cli->iofd, name);
-}
-
-/*! \brief Set the remote address to which we connect
- *  \param[in] cli Stream Client to modify
- *  \param[in] addr Remote IP address
- */
-void
-osmo_stream_cli_set_addr(struct osmo_stream_cli *cli, const char *addr)
-{
-	osmo_stream_cli_set_addrs(cli, &addr, 1);
-}
-
-/*! \brief Set the remote address set to which we connect.
- *  Useful for protocols allowing connecting to more than one address (such as SCTP)
- *  \param[in] cli Stream Client to modify
- *  \param[in] addr Remote IP address set
- *  \return negative on error, 0 on success
- */
-int osmo_stream_cli_set_addrs(struct osmo_stream_cli *cli, const char **addr, size_t addrcnt)
-{
-	int i = 0;
-
-	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
-		return -EINVAL;
-
-	for (; i < addrcnt; i++)
-		osmo_talloc_replace_string(cli, &cli->addr[i], addr[i]);
-	for (; i < cli->addrcnt; i++) {
-			talloc_free(cli->addr[i]);
-			cli->addr[i] = NULL;
-	}
-
-	cli->addrcnt = addrcnt;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the remote port number to which we connect
- *  \param[in] cli Stream Client to modify
- *  \param[in] port Remote port number
- */
-void
-osmo_stream_cli_set_port(struct osmo_stream_cli *cli, uint16_t port)
-{
-	cli->port = port;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-}
-
-/*! \brief Set the local port number for the socket (to be bound to)
- *  \param[in] cli Stream Client to modify
- *  \param[in] port Local port number
- */
-void
-osmo_stream_cli_set_local_port(struct osmo_stream_cli *cli, uint16_t port)
-{
-	cli->local_port = port;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-}
-
-/*! \brief Set the local address for the socket (to be bound to)
- *  \param[in] cli Stream Client to modify
- *  \param[in] port Local host name
- */
-void
-osmo_stream_cli_set_local_addr(struct osmo_stream_cli *cli, const char *addr)
-{
-	osmo_stream_cli_set_local_addrs(cli, &addr, 1);
-}
-
-/*! \brief Set the local address set to which we connect.
- *  Useful for protocols allowing bind to more than one address (such as SCTP)
- *  \param[in] cli Stream Client to modify
- *  \param[in] addr Local IP address set
- *  \return negative on error, 0 on success
- */
-int osmo_stream_cli_set_local_addrs(struct osmo_stream_cli *cli, const char **addr, size_t addrcnt)
-{
-	int i = 0;
-
-	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
-		return -EINVAL;
-
-	for (; i < addrcnt; i++)
-		osmo_talloc_replace_string(cli, &cli->local_addr[i], addr[i]);
-	for (; i < cli->local_addrcnt; i++) {
-			talloc_free(cli->local_addr[i]);
-			cli->local_addr[i] = NULL;
-	}
-
-	cli->local_addrcnt = addrcnt;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the protocol for the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \param[in] proto Protocol (like IPPROTO_TCP (default), IPPROTO_SCTP, ...)
- */
-void
-osmo_stream_cli_set_proto(struct osmo_stream_cli *cli, uint16_t proto)
-{
-	cli->proto = proto;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-}
-
-/*! \brief Set the socket type for the stream server link
- *  \param[in] cli Stream Client to modify
- *  \param[in] type Socket Type (like SOCK_STREAM (default), SOCK_SEQPACKET, ...)
- *  \returns zero on success, negative on error.
- */
-int osmo_stream_cli_set_type(struct osmo_stream_cli *cli, int type)
-{
-	switch (type) {
-	case SOCK_STREAM:
-	case SOCK_SEQPACKET:
-		break;
-	default:
-		return -ENOTSUP;
-	}
-	cli->sk_type = type;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the socket type for the stream server link
- *  \param[in] cli Stream Client to modify
- *  \param[in] type Socket Domain (like AF_UNSPEC (default for IP), AF_UNIX, AF_INET, ...)
- *  \returns zero on success, negative on error.
- */
-int osmo_stream_cli_set_domain(struct osmo_stream_cli *cli, int domain)
-{
-	switch (domain) {
-	case AF_UNSPEC:
-	case AF_INET:
-	case AF_INET6:
-	case AF_UNIX:
-		break;
-	default:
-		return -ENOTSUP;
-	}
-	cli->sk_domain = domain;
-	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the reconnect time of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \param[in] timeout Re-connect timeout in seconds or negative value to disable auto-reconnection */
-void
-osmo_stream_cli_set_reconnect_timeout(struct osmo_stream_cli *cli, int timeout)
-{
-	cli->reconnect_timeout = timeout;
-}
-
-/*! \brief Set application private data of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \param[in] data User-specific data (available in call-back functions) */
-void
-osmo_stream_cli_set_data(struct osmo_stream_cli *cli, void *data)
-{
-	cli->data = data;
-}
-
-/*! \brief Get application private data of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \returns Application private data, as set by \ref osmo_stream_cli_set_data() */
-void *osmo_stream_cli_get_data(struct osmo_stream_cli *cli)
-{
-	return cli->data;
-}
-
-/*! \brief Get the stream client socket description.
- *  \param[in] cli Stream Client to examine
- *  \returns Socket description or NULL in case of error */
-char *osmo_stream_cli_get_sockname(const struct osmo_stream_cli *cli)
-{
-	static char buf[OSMO_SOCK_NAME_MAXLEN];
-
-	osmo_sock_get_name_buf(buf, OSMO_SOCK_NAME_MAXLEN, osmo_stream_cli_fd(cli));
-
-	return buf;
-}
-
-/*! \brief Get Osmocom File Descriptor of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \returns Pointer to \ref osmo_fd */
-struct osmo_fd *
-osmo_stream_cli_get_ofd(struct osmo_stream_cli *cli)
-{
-	OSMO_ASSERT(cli->mode == OSMO_STREAM_MODE_OSMO_FD);
-	return &cli->ofd;
-}
-
-/*! \brief Set the call-back function called on connect of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \param[in] connect_cb Call-back function to be called upon connect */
-void
-osmo_stream_cli_set_connect_cb(struct osmo_stream_cli *cli,
-	int (*connect_cb)(struct osmo_stream_cli *cli))
-{
-	cli->connect_cb = connect_cb;
-}
-
-/*! \brief Set the call-back function called on disconnect of the stream client socket
- *  \param[in] cli Stream Client to modify
- *  \param[in] disconnect_cb Call-back function to be called upon disconnect */
-void osmo_stream_cli_set_disconnect_cb(struct osmo_stream_cli *cli,
-				       int (*disconnect_cb)(struct osmo_stream_cli *cli))
-{
-	cli->disconnect_cb = disconnect_cb;
-}
-
-/*! \brief Set the call-back function called to read from the stream client socket
- *  This function will configure osmo_stream_cli to use osmo_ofd internally.
- *  \param[in] cli Stream Client to modify
- *  \param[in] read_cb Call-back function to be called when we want to read */
-void
-osmo_stream_cli_set_read_cb(struct osmo_stream_cli *cli,
-			    int (*read_cb)(struct osmo_stream_cli *cli))
-{
-	OSMO_ASSERT(cli->mode != OSMO_STREAM_MODE_OSMO_IO);
-	cli->mode = OSMO_STREAM_MODE_OSMO_FD;
-	cli->read_cb = read_cb;
-}
-
-/*! \brief Set the call-back function called to read from the stream client socket
- *  This function will configure osmo_stream_cli to use osmo_iofd internally.
- *  \param[in] cli Stream Client to modify
- *  \param[in] read_cb Call-back function to be called when data was read from the socket */
-void
-osmo_stream_cli_set_read_cb2(struct osmo_stream_cli *cli,
-			    int (*read_cb)(struct osmo_stream_cli *cli, struct msgb *msg))
-{
-	OSMO_ASSERT(cli->mode != OSMO_STREAM_MODE_OSMO_FD);
-	cli->mode = OSMO_STREAM_MODE_OSMO_IO;
-	cli->iofd_read_cb = read_cb;
-}
-
-/*! \brief Destroy a Osmocom stream client (includes close)
- *  \param[in] cli Stream Client to destroy */
-void osmo_stream_cli_destroy(struct osmo_stream_cli *cli)
-{
-	osmo_stream_cli_close(cli);
-	osmo_timer_del(&cli->timer);
-	msgb_queue_free(&cli->tx_queue);
-	talloc_free(cli);
-}
-
-/*! \brief DEPRECATED: use osmo_stream_cli_set_reconnect_timeout() or osmo_stream_cli_reconnect() instead!
- * Open connection of an Osmocom stream client
- *  \param[in] cli Stream Client to connect
- *  \param[in] reconect 1 if we should not automatically reconnect
- *  \return negative on error, 0 on success
- */
-int osmo_stream_cli_open2(struct osmo_stream_cli *cli, int reconnect)
-{
-	int ret;
-
-	/* we are reconfiguring this socket, close existing first. */
-	if ((cli->flags & OSMO_STREAM_CLI_F_RECONF) && cli->ofd.fd >= 0)
-		osmo_stream_cli_close(cli);
-
-	cli->flags &= ~OSMO_STREAM_CLI_F_RECONF;
-
-	switch (cli->proto) {
-#ifdef HAVE_LIBSCTP
-	case IPPROTO_SCTP:
-		ret = osmo_sock_init2_multiaddr(AF_UNSPEC, SOCK_STREAM, cli->proto,
-						(const char **)cli->local_addr, cli->local_addrcnt, cli->local_port,
-						(const char **)cli->addr, cli->addrcnt, cli->port,
-						OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
-		break;
-#endif
-	default:
-		ret = osmo_sock_init2(AF_UNSPEC, SOCK_STREAM, cli->proto,
-				      cli->local_addr[0], cli->local_port,
-				      cli->addr[0], cli->port,
-				      OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
-	}
-
-	if (ret < 0) {
-		if (reconnect)
-			osmo_stream_cli_reconnect(cli);
-		return ret;
-	}
-	osmo_fd_setup(&cli->ofd, ret, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_cli_fd_cb, cli, 0);
-
-	if (cli->flags & OSMO_STREAM_CLI_F_NODELAY) {
-		ret = setsockopt_nodelay(cli->ofd.fd, cli->proto, 1);
-		if (ret < 0)
-			goto error_close_socket;
-	}
-
-	if (osmo_fd_register(&cli->ofd) < 0)
-		goto error_close_socket;
-
-	cli->state = STREAM_CLI_STATE_CONNECTING;
-	return 0;
-
-error_close_socket:
-	close(cli->ofd.fd);
-	cli->ofd.fd = -1;
-	return -EIO;
-}
-
-/*! \brief Set the NODELAY socket option to avoid Nagle-like behavior
- *  Setting this to nodelay=true will automatically set the NODELAY
- *  socket option on any socket established via \ref osmo_stream_cli_open
- *  or any re-connect.  You have to set this _before_ opening the
- *  socket.
- *  \param[in] cli Stream client whose sockets are to be configured
- *  \param[in] nodelay whether to set (true) NODELAY before connect()
- */
-void osmo_stream_cli_set_nodelay(struct osmo_stream_cli *cli, bool nodelay)
-{
-	if (nodelay)
-		cli->flags |= OSMO_STREAM_CLI_F_NODELAY;
-	else
-		cli->flags &= ~OSMO_STREAM_CLI_F_NODELAY;
-}
-
-/*! \brief Open connection of an Osmocom stream client
- *  By default the client will automatically reconnect after default timeout.
- *  To disable this, use osmo_stream_cli_set_reconnect_timeout() before calling this function.
- *  \param[in] cli Stream Client to connect
- *  \return negative on error, 0 on success */
-int osmo_stream_cli_open(struct osmo_stream_cli *cli)
-{
-	int ret, fd = -1;
-
-	/* we are reconfiguring this socket, close existing first. */
-	if ((cli->flags & OSMO_STREAM_CLI_F_RECONF) && osmo_stream_cli_fd(cli) >= 0)
-		osmo_stream_cli_close(cli);
-
-	cli->flags &= ~OSMO_STREAM_CLI_F_RECONF;
-
-	switch (cli->sk_domain) {
-	case AF_UNIX:
-		ret = osmo_sock_unix_init(cli->sk_type, 0, cli->addr[0], OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
-		break;
-	case AF_INET:
-	case AF_INET6:
-	case AF_UNSPEC:
-		switch (cli->proto) {
-#ifdef HAVE_LIBSCTP
-		case IPPROTO_SCTP:
-			ret = osmo_sock_init2_multiaddr(cli->sk_domain, cli->sk_type, cli->proto,
-							(const char **)cli->local_addr, cli->local_addrcnt, cli->local_port,
-							(const char **)cli->addr, cli->addrcnt, cli->port,
-							OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
-			break;
-#endif
-		default:
-			ret = osmo_sock_init2(cli->sk_domain, cli->sk_type, cli->proto,
-					      cli->local_addr[0], cli->local_port,
-					      cli->addr[0], cli->port,
-					      OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
-		}
-		break;
-	default:
-		return -ENOTSUP;
-	}
-
-	if (ret < 0) {
-		osmo_stream_cli_reconnect(cli);
-		return ret;
-	}
-
-	fd = ret;
-
-	if (cli->flags & OSMO_STREAM_CLI_F_NODELAY) {
-		ret = setsockopt_nodelay(fd, cli->proto, 1);
-		if (ret < 0)
-			goto error_close_socket;
-	}
-
-	switch (cli->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		osmo_fd_setup(&cli->ofd, fd, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_cli_fd_cb, cli, 0);
-		if (osmo_fd_register(&cli->ofd) < 0)
-			goto error_close_socket;
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		if (!cli->iofd)
-			cli->iofd = osmo_iofd_setup(cli, fd, cli->name, OSMO_IO_FD_MODE_READ_WRITE, &osmo_stream_cli_ioops, cli);
-		if (!cli->iofd)
-			goto error_close_socket;
-
-		if (osmo_iofd_register(cli->iofd, fd) < 0)
-			goto error_close_socket;
-		osmo_iofd_notify_connected(cli->iofd);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-
-	cli->state = STREAM_CLI_STATE_CONNECTING;
-	return 0;
-
-error_close_socket:
-	cli->state = STREAM_CLI_STATE_CLOSED;
-	close(fd);
-	if (cli->mode == OSMO_STREAM_MODE_OSMO_FD)
-		cli->ofd.fd = -1;
-	return -EIO;
-}
-
-static void cli_timer_cb(void *data)
-{
-	struct osmo_stream_cli *cli = data;
-
-	LOGSCLI(cli, LOGL_DEBUG, "reconnecting\n");
-	osmo_stream_cli_open(cli);
-}
-
-/*! \brief Enqueue data to be sent via an Osmocom stream client
- *  \param[in] cli Stream Client through which we want to send
- *  \param[in] msg Message buffer to enqueue in transmit queue */
-void osmo_stream_cli_send(struct osmo_stream_cli *cli, struct msgb *msg)
-{
-	OSMO_ASSERT(cli);
-	OSMO_ASSERT(msg);
-
-	switch (cli->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		msgb_enqueue(&cli->tx_queue, msg);
-		osmo_fd_write_enable(&cli->ofd);
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		osmo_iofd_write_msgb(cli->iofd, msg);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-}
-
-/*! \brief Receive data via an Osmocom stream client
- *  \param[in] cli Stream Client through which we want to send
- *  \param msg pre-allocate message buffer to which received data is appended
- *  \returns number of bytes read; <=0 in case of error */
-int osmo_stream_cli_recv(struct osmo_stream_cli *cli, struct msgb *msg)
-{
-	int ret;
-	OSMO_ASSERT(cli);
-	OSMO_ASSERT(msg);
-
-	ret = recv(cli->ofd.fd, msg->data, msg->data_len, 0);
-	if (ret < 0) {
-		if (errno == EPIPE || errno == ECONNRESET) {
-			LOGSCLI(cli, LOGL_ERROR, "lost connection with srv\n");
-		}
-		osmo_stream_cli_reconnect(cli);
-		return ret;
-	} else if (ret == 0) {
-		LOGSCLI(cli, LOGL_ERROR, "connection closed with srv\n");
-		osmo_stream_cli_reconnect(cli);
-		return ret;
-	}
-	msgb_put(msg, ret);
-	LOGSCLI(cli, LOGL_DEBUG, "received %d bytes from srv\n", ret);
-	return ret;
-}
-
-void osmo_stream_cli_clear_tx_queue(struct osmo_stream_cli *cli)
-{
-	switch (cli->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		msgb_queue_free(&cli->tx_queue);
-		/* If in state 'connecting', keep WRITE flag up to receive
-		* socket connection signal and then transition to STATE_CONNECTED: */
-		if (cli->state == STREAM_CLI_STATE_CONNECTED)
-			osmo_fd_write_disable(&cli->ofd);
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		osmo_iofd_txqueue_clear(cli->iofd);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-}
-
-/*
- * Server side.
- */
-
-#define OSMO_STREAM_SRV_F_RECONF	(1 << 0)
-#define OSMO_STREAM_SRV_F_NODELAY	(1 << 1)
-
-struct osmo_stream_srv_link {
-	struct osmo_fd		ofd;
-	char			*name;
-	char			sockname[OSMO_SOCK_NAME_MAXLEN];
-	char			*addr[OSMO_STREAM_MAX_ADDRS];
-	uint8_t			addrcnt;
-	uint16_t		port;
-	int			sk_domain;
-	int			sk_type;
-	uint16_t		proto;
-	int (*accept_cb)(struct osmo_stream_srv_link *srv, int fd);
-	void			*data;
-	int			flags;
-};
-
-static int osmo_stream_srv_link_ofd_cb(struct osmo_fd *ofd, unsigned int what)
-{
-	int ret;
-	int sock_fd;
-	struct osmo_sockaddr osa;
-	socklen_t sa_len = sizeof(osa.u.sas);
-	struct osmo_stream_srv_link *link = ofd->data;
-
-	ret = accept(ofd->fd, &osa.u.sa, &sa_len);
-	if (ret < 0) {
-		LOGP(DLINP, LOGL_ERROR, "failed to accept from origin peer, reason=`%s'\n",
-		     strerror(errno));
-		return ret;
-	}
-	sock_fd = ret;
-
-	switch (osa.u.sa.sa_family) {
-	case AF_UNIX:
-		LOGSLNK(link, LOGL_DEBUG, "accept()ed new link on fd %d\n",
-			sock_fd);
-		break;
-	case AF_INET6:
-	case AF_INET:
-		LOGSLNK(link, LOGL_DEBUG, "accept()ed new link from %s\n",
-			osmo_sockaddr_to_str(&osa));
-
-		if (link->proto == IPPROTO_SCTP) {
-			ret = sctp_sock_activate_events(sock_fd);
-			if (ret < 0)
-				goto error_close_socket;
-		}
-		break;
-	default:
-		LOGSLNK(link, LOGL_DEBUG, "accept()ed unexpected address family %d\n",
-			osa.u.sa.sa_family);
-		goto error_close_socket;
-	}
-
-	if (link->flags & OSMO_STREAM_SRV_F_NODELAY) {
-		ret = setsockopt_nodelay(sock_fd, link->proto, 1);
-		if (ret < 0)
-			goto error_close_socket;
-	}
-
-	if (!link->accept_cb) {
-		ret = -ENOTSUP;
-		goto error_close_socket;
-	}
-
-	ret = link->accept_cb(link, sock_fd);
-	if (ret)
-		goto error_close_socket;
-	return 0;
-
-error_close_socket:
-	close(sock_fd);
-	return ret;
-}
-
-/*! \brief Create an Osmocom Stream Server Link
- *  A Stream Server Link is the listen()+accept() "parent" to individual
- *  Stream Servers
- *  \param[in] ctx talloc allocation context
- *  \returns Stream Server Link with default values (TCP)
- */
-struct osmo_stream_srv_link *osmo_stream_srv_link_create(void *ctx)
-{
-	struct osmo_stream_srv_link *link;
-
-	link = talloc_zero(ctx, struct osmo_stream_srv_link);
-	if (!link)
-		return NULL;
-
-	link->sk_domain = AF_UNSPEC;
-	link->sk_type = SOCK_STREAM;
-	link->proto = IPPROTO_TCP;
-	osmo_fd_setup(&link->ofd, -1, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_srv_link_ofd_cb, link, 0);
-
-	return link;
-}
-
-/*! \brief Set a name on the srv_link object (used during logging)
- *  \param[in] link server link whose name is to be set
- *  \param[in] name the name to be set on link
- */
-void osmo_stream_srv_link_set_name(struct osmo_stream_srv_link *link, const char *name)
-{
-	osmo_talloc_replace_string(link, &link->name, name);
-}
-
-/*! \brief Set the NODELAY socket option to avoid Nagle-like behavior
- *  Setting this to nodelay=true will automatically set the NODELAY
- *  socket option on any socket established via this server link, before
- *  calling the accept_cb()
- *  \param[in] link server link whose sockets are to be configured
- *  \param[in] nodelay whether to set (true) NODELAY after accept
- */
-void osmo_stream_srv_link_set_nodelay(struct osmo_stream_srv_link *link, bool nodelay)
-{
-	if (nodelay)
-		link->flags |= OSMO_STREAM_SRV_F_NODELAY;
-	else
-		link->flags &= ~OSMO_STREAM_SRV_F_NODELAY;
-}
-
-/*! \brief Set the local address to which we bind
- *  \param[in] link Stream Server Link to modify
- *  \param[in] addr Local IP address
- */
-void osmo_stream_srv_link_set_addr(struct osmo_stream_srv_link *link,
-				      const char *addr)
-{
-	osmo_stream_srv_link_set_addrs(link, &addr, 1);
-}
-
-/*! \brief Set the local address set to which we bind.
- *  Useful for protocols allowing bind on more than one address (such as SCTP)
- *  \param[in] link Stream Server Link to modify
- *  \param[in] addr Local IP address
- *  \return negative on error, 0 on success
- */
-int osmo_stream_srv_link_set_addrs(struct osmo_stream_srv_link *link, const char **addr, size_t addrcnt)
-{
-	int i = 0;
-
-	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
-		return -EINVAL;
-
-	for (; i < addrcnt; i++)
-		osmo_talloc_replace_string(link, &link->addr[i], addr[i]);
-	for (; i < link->addrcnt; i++) {
-			talloc_free(link->addr[i]);
-			link->addr[i] = NULL;
-	}
-
-	link->addrcnt = addrcnt;
-	link->flags |= OSMO_STREAM_SRV_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the local port number to which we bind
- *  \param[in] link Stream Server Link to modify
- *  \param[in] port Local port number
- */
-void osmo_stream_srv_link_set_port(struct osmo_stream_srv_link *link,
-				      uint16_t port)
-{
-	link->port = port;
-	link->flags |= OSMO_STREAM_SRV_F_RECONF;
-}
-
-/*! \brief Set the protocol for the stream server link
- *  \param[in] link Stream Server Link to modify
- *  \param[in] proto Protocol (like IPPROTO_TCP (default), IPPROTO_SCTP, ...)
- */
-void
-osmo_stream_srv_link_set_proto(struct osmo_stream_srv_link *link,
-			  uint16_t proto)
-{
-	link->proto = proto;
-	link->flags |= OSMO_STREAM_SRV_F_RECONF;
-}
-
-
-/*! \brief Set the socket type for the stream server link
- *  \param[in] link Stream Server Link to modify
- *  \param[in] type Socket Type (like SOCK_STREAM (default), SOCK_SEQPACKET, ...)
- *  \returns zero on success, negative on error.
- */
-int osmo_stream_srv_link_set_type(struct osmo_stream_srv_link *link, int type)
-{
-	switch (type) {
-	case SOCK_STREAM:
-	case SOCK_SEQPACKET:
-		break;
-	default:
-		return -ENOTSUP;
-	}
-	link->sk_type = type;
-	link->flags |= OSMO_STREAM_SRV_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set the socket type for the stream server link
- *  \param[in] link Stream Server Link to modify
- *  \param[in] type Socket Domain (like AF_UNSPEC (default for IP), AF_UNIX, AF_INET, ...)
- *  \returns zero on success, negative on error.
- */
-int osmo_stream_srv_link_set_domain(struct osmo_stream_srv_link *link, int domain)
-{
-	switch (domain) {
-	case AF_UNSPEC:
-	case AF_INET:
-	case AF_INET6:
-	case AF_UNIX:
-		break;
-	default:
-		return -ENOTSUP;
-	}
-	link->sk_domain = domain;
-	link->flags |= OSMO_STREAM_SRV_F_RECONF;
-	return 0;
-}
-
-/*! \brief Set application private data of the stream server link
- *  \param[in] link Stream Server Link to modify
- *  \param[in] data User-specific data (available in call-back functions) */
-void
-osmo_stream_srv_link_set_data(struct osmo_stream_srv_link *link,
-				 void *data)
-{
-	link->data = data;
-}
-
-/*! \brief Get application private data of the stream server link
- *  \param[in] link Stream Server Link to modify
- *  \returns Application private data, as set by \ref osmo_stream_cli_set_data() */
-void *osmo_stream_srv_link_get_data(struct osmo_stream_srv_link *link)
-{
-	return link->data;
-}
-
-/*! \brief Get description of the stream server link e. g. 127.0.0.1:1234
- *  \param[in] link Stream Server Link to examine
- *  \returns Link description or NULL in case of error */
-char *osmo_stream_srv_link_get_sockname(const struct osmo_stream_srv_link *link)
-{
-	static char buf[INET6_ADDRSTRLEN + 6];
-	int rc = osmo_sock_get_local_ip(link->ofd.fd, buf, INET6_ADDRSTRLEN);
-	if (rc < 0)
-		return NULL;
-
-	buf[strnlen(buf, INET6_ADDRSTRLEN + 6)] = ':';
-
-	rc = osmo_sock_get_local_ip_port(link->ofd.fd, buf + strnlen(buf, INET6_ADDRSTRLEN + 6), 6);
-	if (rc < 0)
-		return NULL;
-
-	return buf;
-}
-
-/*! \brief Get Osmocom File Descriptor of the stream server link
- *  \param[in] link Stream Server Link
- *  \returns Pointer to \ref osmo_fd */
-struct osmo_fd *
-osmo_stream_srv_link_get_ofd(struct osmo_stream_srv_link *link)
-{
-	return &link->ofd;
-}
-
-/*! \brief Set the accept() call-back of the stream server link
- *  \param[in] link Stream Server Link
- *  \param[in] accept_cb Call-back function executed upon accept() */
-void osmo_stream_srv_link_set_accept_cb(struct osmo_stream_srv_link *link,
-	int (*accept_cb)(struct osmo_stream_srv_link *link, int fd))
-
-{
-	link->accept_cb = accept_cb;
-}
-
-/*! \brief Destroy the stream server link. Closes + Releases Memory.
- *  \param[in] link Stream Server Link */
-void osmo_stream_srv_link_destroy(struct osmo_stream_srv_link *link)
-{
-	osmo_stream_srv_link_close(link);
-	talloc_free(link);
-}
-
-/*! \brief Open the stream server link.  This actually initializes the
- *  underlying socket and binds it to the configured ip/port
- *  \param[in] link Stream Server Link to open
- *  \return negative on error, 0 on success */
-int osmo_stream_srv_link_open(struct osmo_stream_srv_link *link)
-{
-	int ret;
-
-	if (link->ofd.fd >= 0) {
-		/* No reconfigure needed for existing socket, we are fine */
-		if (!(link->flags & OSMO_STREAM_SRV_F_RECONF))
-			return 0;
-		/* we are reconfiguring this socket, close existing first. */
-		osmo_stream_srv_link_close(link);
-	}
-
-	link->flags &= ~OSMO_STREAM_SRV_F_RECONF;
-
-	switch (link->sk_domain) {
-	case AF_UNIX:
-		ret = osmo_sock_unix_init(link->sk_type, 0, link->addr[0], OSMO_SOCK_F_BIND);
-		break;
-	case AF_UNSPEC:
-	case AF_INET:
-	case AF_INET6:
-		switch (link->proto) {
-#ifdef HAVE_LIBSCTP
-		case IPPROTO_SCTP:
-			ret = osmo_sock_init2_multiaddr(link->sk_domain, link->sk_type, link->proto,
-							(const char **)link->addr, link->addrcnt, link->port,
-							NULL, 0, 0, OSMO_SOCK_F_BIND);
-			break;
-#endif
-		default:
-			ret = osmo_sock_init(link->sk_domain, link->sk_type, link->proto,
-					     link->addr[0], link->port, OSMO_SOCK_F_BIND);
-		}
-		break;
-	default:
-		ret = -ENOTSUP;
-	}
-	if (ret < 0)
-		return ret;
-
-	link->ofd.fd = ret;
-	if (osmo_fd_register(&link->ofd) < 0) {
-		close(ret);
-		link->ofd.fd = -1;
-		return -EIO;
-	}
-
-	OSMO_STRLCPY_ARRAY(link->sockname, osmo_stream_srv_link_get_sockname(link));
-	return 0;
-}
-
-/*! \brief Check whether the stream server link is opened
- *  \param[in] link Stream Server Link to check */
-bool osmo_stream_srv_link_is_opened(const struct osmo_stream_srv_link *link)
-{
-	if (!link)
-		return false;
-
-	if (link->ofd.fd == -1)
-		return false;
-
-	return true;
-}
-
-/*! \brief Close the stream server link and unregister from select loop
- *  Does not destroy the server link, merely closes it!
- *  \param[in] link Stream Server Link to close */
-void osmo_stream_srv_link_close(struct osmo_stream_srv_link *link)
-{
-	if (!osmo_stream_srv_link_is_opened(link))
-		return;
-
-	osmo_fd_unregister(&link->ofd);
-	close(link->ofd.fd);
-	link->ofd.fd = -1;
-}
-
-#define OSMO_STREAM_SRV_F_FLUSH_DESTROY	(1 << 0)
-
-struct osmo_stream_srv {
-	struct osmo_stream_srv_link	*srv;
-	char				*name;
-	char				sockname[OSMO_SOCK_NAME_MAXLEN];
-	enum osmo_stream_mode mode;
-	union {
-		struct osmo_fd			ofd;
-		struct osmo_io_fd		*iofd;
-	};
-	struct llist_head		tx_queue;
-	int (*closed_cb)(struct osmo_stream_srv *peer);
-	int (*read_cb)(struct osmo_stream_srv *peer);
-	int (*iofd_read_cb)(struct osmo_stream_srv *peer, struct msgb *msg);
-	void				*data;
-	int				flags;
-};
-
-static void stream_srv_iofd_read_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
-{
-	struct osmo_stream_srv *conn = osmo_iofd_get_data(iofd);
-	LOGSSRV(conn, LOGL_DEBUG, "message received (res=%d)\n", res);
-
-	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
-		LOGSSRV(conn, LOGL_INFO, "Connection is being flushed and closed; ignoring received message\n");
-		msgb_free(msg);
-		return;
-	}
-
-	if (res <= 0) {
-		osmo_stream_srv_set_flush_and_destroy(conn);
-		if (osmo_iofd_txqueue_len(iofd) == 0)
-			osmo_stream_srv_destroy(conn);
-	} else if (conn->iofd_read_cb) {
-		conn->iofd_read_cb(conn, msg);
-	}
-}
-
-static void stream_srv_iofd_write_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
-{
-	struct osmo_stream_srv *conn = osmo_iofd_get_data(iofd);
-	LOGSSRV(conn, LOGL_DEBUG, "connected write\n");
-
-	if (res == -1)
-		LOGSSRV(conn, LOGL_ERROR, "error to send: %s\n", strerror(errno));
-
-	if (osmo_iofd_txqueue_len(iofd) == 0)
-		if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
-			osmo_stream_srv_destroy(conn);
-}
-
-static struct osmo_io_ops srv_ioops = {
-	.read_cb = stream_srv_iofd_read_cb,
-	.write_cb = stream_srv_iofd_write_cb,
-};
-static int osmo_stream_srv_read(struct osmo_stream_srv *conn)
-{
-	int rc = 0;
-
-	LOGSSRV(conn, LOGL_DEBUG, "message received\n");
-
-	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
-		LOGSSRV(conn, LOGL_INFO, "Connection is being flushed and closed; ignoring received message\n");
-		return 0;
-	}
-
-	if (conn->read_cb)
-		rc = conn->read_cb(conn);
-
-	return rc;
-}
-
-static void osmo_stream_srv_write(struct osmo_stream_srv *conn)
-{
-#ifdef HAVE_LIBSCTP
-	struct sctp_sndrcvinfo sinfo;
-#endif
-	struct msgb *msg;
-	int ret;
-
-	if (llist_empty(&conn->tx_queue)) {
-		osmo_fd_write_disable(&conn->ofd);
-		return;
-	}
-	msg = llist_first_entry(&conn->tx_queue, struct msgb, list);
-	llist_del(&msg->list);
-
-	LOGSSRV(conn, LOGL_DEBUG, "sending %u bytes of data\n", msg->len);
-
-	switch (conn->srv->sk_domain) {
-	case AF_UNIX:
-		ret = send(conn->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
-		break;
-	case AF_INET:
-	case AF_INET6:
-	case AF_UNSPEC:
-		switch (conn->srv->proto) {
-#ifdef HAVE_LIBSCTP
-		case IPPROTO_SCTP:
-			memset(&sinfo, 0, sizeof(sinfo));
-			sinfo.sinfo_ppid = htonl(msgb_sctp_ppid(msg));
-			sinfo.sinfo_stream = msgb_sctp_stream(msg);
-			ret = sctp_send(conn->ofd.fd, msgb_data(msg), msgb_length(msg),
-					&sinfo, MSG_NOSIGNAL);
-			break;
-#endif
-		case IPPROTO_TCP:
-		default:
-			ret = send(conn->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
-			break;
-		}
-		break;
-	default:
-		ret = -1;
-		errno = ENOTSUP;
-	}
-
-	if (ret >= 0 && ret < msgb_length(msg)) {
-		LOGSSRV(conn, LOGL_ERROR, "short send: %d < exp %u\n", ret, msgb_length(msg));
-		/* Update msgb and re-add it at the start of the queue: */
-		msgb_pull(msg, ret);
-		llist_add(&msg->list, &conn->tx_queue);
-		return;
-	}
-
-	if (ret == -1) /* send(): On error -1 is returned, and errno is set appropriately */
-		LOGSSRV(conn, LOGL_ERROR, "error to send: %s\n", strerror(errno));
-
-	msgb_free(msg);
-
-	if (llist_empty(&conn->tx_queue)) {
-		osmo_fd_write_disable(&conn->ofd);
-		if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
-			osmo_stream_srv_destroy(conn);
-	}
-}
-
-static int osmo_stream_srv_cb(struct osmo_fd *ofd, unsigned int what)
-{
-	struct osmo_stream_srv *conn = ofd->data;
-	int rc = 0;
-
-	LOGSSRV(conn, LOGL_DEBUG, "connected read/write (what=0x%x)\n", what);
-	if (what & OSMO_FD_READ)
-		rc = osmo_stream_srv_read(conn);
-	if (rc != -EBADF && (what & OSMO_FD_WRITE))
-		osmo_stream_srv_write(conn);
-
-	return rc;
-}
-
-/*! \brief Create a Stream Server inside the specified link
- *  \param[in] ctx talloc allocation context from which to allocate
- *  \param[in] link Stream Server Link to which we belong
- *  \param[in] fd system file descriptor of the new connection
- *  \param[in] read_cb Call-back to call when the socket is readable
- *  \param[in] closed_cb Call-back to call when the connection is closed
- *  \param[in] data User data to save in the new Stream Server struct
- *  \returns Stream Server in case of success; NULL on error */
-struct osmo_stream_srv *
-osmo_stream_srv_create(void *ctx, struct osmo_stream_srv_link *link,
-	int fd,
-	int (*read_cb)(struct osmo_stream_srv *conn),
-	int (*closed_cb)(struct osmo_stream_srv *conn), void *data)
-{
-	struct osmo_stream_srv *conn;
-
-	OSMO_ASSERT(link);
-
-	conn = talloc_zero(ctx, struct osmo_stream_srv);
-	if (conn == NULL)
-		return NULL;
-
-	conn->mode = OSMO_STREAM_MODE_OSMO_FD;
-	conn->srv = link;
-	osmo_fd_setup(&conn->ofd, fd, OSMO_FD_READ, osmo_stream_srv_cb, conn, 0);
-	conn->read_cb = read_cb;
-	conn->closed_cb = closed_cb;
-	conn->data = data;
-	INIT_LLIST_HEAD(&conn->tx_queue);
-
-	osmo_sock_get_name_buf(conn->sockname, sizeof(conn->sockname), fd);
-
-	if (osmo_fd_register(&conn->ofd) < 0) {
-		LOGSSRV(conn, LOGL_ERROR, "could not register FD\n");
-		talloc_free(conn);
-		return NULL;
-	}
-	return conn;
-}
-
-/*! \brief Create a Stream Server inside the specified link
- *  \param[in] ctx talloc allocation context from which to allocate
- *  \param[in] link Stream Server Link to which we belong
- *  \param[in] fd system file descriptor of the new connection
- *  \param[in] data User data to save in the new Stream Server struct
- *  \returns Stream Server in case of success; NULL on error */
-struct osmo_stream_srv *
-osmo_stream_srv_create2(void *ctx, struct osmo_stream_srv_link *link, int fd, void *data)
-{
-	struct osmo_stream_srv *conn;
-
-	OSMO_ASSERT(link);
-
-	conn = talloc_zero(ctx, struct osmo_stream_srv);
-	if (conn == NULL)
-		return NULL;
-
-	conn->mode = OSMO_STREAM_MODE_OSMO_IO;
-	conn->srv = link;
-
-	osmo_sock_get_name_buf(conn->sockname, sizeof(conn->sockname), fd);
-
-	conn->iofd = osmo_iofd_setup(conn, fd, conn->sockname,
-				     OSMO_IO_FD_MODE_READ_WRITE, &srv_ioops, conn);
-	if (!conn->iofd) {
-		talloc_free(conn);
-		return NULL;
-	}
-	conn->data = data;
-
-	if (osmo_iofd_register(conn->iofd, fd) < 0) {
-		LOGSSRV(conn, LOGL_ERROR, "could not register FD %d\n", fd);
-		talloc_free(conn);
-		return NULL;
-	}
-
-	return conn;
-}
-
-/*! \brief Set a name on the srv object (used during logging)
- *  \param[in] conn server whose name is to be set
- *  \param[in] name the name to be set on conn
- */
-void osmo_stream_srv_set_name(struct osmo_stream_srv *conn, const char *name)
-{
-	osmo_talloc_replace_string(conn, &conn->name, name);
-	if (conn->mode == OSMO_STREAM_MODE_OSMO_IO && conn->iofd)
-		osmo_iofd_set_name(conn->iofd, name);
-}
-
-/*! \brief Set the call-back function when data was read from the stream server socket
- *  Only for osmo_stream_srv created with osmo_stream_srv_create2()
- *  \param[in] conn Stream Server to modify
- *  \param[in] read_cb Call-back function to be called when data was read */
-void osmo_stream_srv_set_read_cb(struct osmo_stream_srv *conn, int (*read_cb)(struct osmo_stream_srv *conn, struct msgb *msg))
-{
-	OSMO_ASSERT(conn && conn->mode == OSMO_STREAM_MODE_OSMO_IO);
-	conn->iofd_read_cb = read_cb;
-}
-
-/*! \brief Set the call-back function called when the stream server socket was closed
- *  \param[in] conn Stream Server to modify
- *  \param[in] closed_cb Call-back function to be called when the connection was closed */
-void osmo_stream_srv_set_closed_cb(struct osmo_stream_srv *conn, int (*closed_cb)(struct osmo_stream_srv *conn))
-{
-	OSMO_ASSERT(conn);
-	conn->closed_cb = closed_cb;
-}
-
-/*! \brief Prepare to send out all pending messages on the connection's Tx queue
- *  and then automatically destroy the stream with osmo_stream_srv_destroy().
- *  This function disables queuing of new messages on the connection and also
- *  disables reception of new messages on the connection.
- *  \param[in] conn Stream Server to modify */
-void osmo_stream_srv_set_flush_and_destroy(struct osmo_stream_srv *conn)
-{
-	conn->flags |= OSMO_STREAM_SRV_F_FLUSH_DESTROY;
-}
-
-/*! \brief Set application private data of the stream server
- *  \param[in] conn Stream Server to modify
- *  \param[in] data User-specific data (available in call-back functions) */
-void
-osmo_stream_srv_set_data(struct osmo_stream_srv *conn,
-				 void *data)
-{
-	conn->data = data;
-}
-
-/*! \brief Get application private data of the stream server
- *  \param[in] conn Stream Server
- *  \returns Application private data, as set by \ref osmo_stream_srv_set_data() */
-void *osmo_stream_srv_get_data(struct osmo_stream_srv *conn)
-{
-	return conn->data;
-}
-
-/*! \brief Get Osmocom File Descriptor of the stream server
- *  \param[in] conn Stream Server
- *  \returns Pointer to \ref osmo_fd */
-struct osmo_fd *
-osmo_stream_srv_get_ofd(struct osmo_stream_srv *conn)
-{
-	return &conn->ofd;
-}
-
-/*! \brief Get the master (Link) from a Stream Server
- *  \param[in] conn Stream Server of which we want to know the Link
- *  \returns Link through which the given Stream Server is established */
-struct osmo_stream_srv_link *osmo_stream_srv_get_master(struct osmo_stream_srv *conn)
-{
-	return conn->srv;
-}
-
-/*! \brief Destroy given Stream Server
- *  This function closes the Stream Server socket, unregisters from
- *  select loop, invokes the connection's closed_cb() callback to allow API
- *  users to clean up any associated state they have for this connection,
- *  and then de-allocates associated memory.
- *  \param[in] conn Stream Server to be destroyed */
-void osmo_stream_srv_destroy(struct osmo_stream_srv *conn)
-{
-	switch (conn->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		osmo_fd_unregister(&conn->ofd);
-		close(conn->ofd.fd);
-		msgb_queue_free(&conn->tx_queue);
-		conn->ofd.fd = -1;
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		osmo_iofd_free(conn->iofd);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-	if (conn->closed_cb)
-		conn->closed_cb(conn);
-	talloc_free(conn);
-}
-
-/*! \brief Enqueue data to be sent via an Osmocom stream server
- *  \param[in] conn Stream Server through which we want to send
- *  \param[in] msg Message buffer to enqueue in transmit queue */
-void osmo_stream_srv_send(struct osmo_stream_srv *conn, struct msgb *msg)
-{
-	OSMO_ASSERT(conn);
-	OSMO_ASSERT(msg);
-	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
-		LOGSSRV(conn, LOGL_DEBUG, "Connection is being flushed and closed; ignoring new outgoing message\n");
-		msgb_free(msg);
-		return;
-	}
-
-	switch (conn->mode) {
-	case OSMO_STREAM_MODE_OSMO_FD:
-		msgb_enqueue(&conn->tx_queue, msg);
-		osmo_fd_write_enable(&conn->ofd);
-		break;
-	case OSMO_STREAM_MODE_OSMO_IO:
-		osmo_iofd_write_msgb(conn->iofd, msg);
-		break;
-	default:
-		OSMO_ASSERT(false);
-	}
-}
-
-#ifdef HAVE_LIBSCTP
-static int _sctp_recvmsg_wrapper(int fd, struct msgb *msg)
-{
-	struct sctp_sndrcvinfo sinfo;
-	int flags = 0;
-	int ret;
-
-	ret = sctp_recvmsg(fd, msgb_data(msg), msgb_tailroom(msg),
-			NULL, NULL, &sinfo, &flags);
-	msgb_sctp_msg_flags(msg) = 0;
-	msgb_sctp_ppid(msg) = ntohl(sinfo.sinfo_ppid);
-	msgb_sctp_stream(msg) = sinfo.sinfo_stream;
-	if (flags & MSG_NOTIFICATION) {
-		union sctp_notification *notif = (union sctp_notification *)msgb_data(msg);
-		LOGP(DLINP, LOGL_DEBUG, "NOTIFICATION %u flags=0x%x\n", notif->sn_header.sn_type, notif->sn_header.sn_flags);
-		msgb_put(msg, sizeof(union sctp_notification));
-		msgb_sctp_msg_flags(msg) = OSMO_STREAM_SCTP_MSG_FLAGS_NOTIFICATION;
-		switch (notif->sn_header.sn_type) {
-		case SCTP_ASSOC_CHANGE:
-			LOGP(DLINP, LOGL_DEBUG, "===> ASSOC CHANGE:");
-			switch (notif->sn_assoc_change.sac_state) {
-			case SCTP_COMM_UP:
-				LOGPC(DLINP, LOGL_DEBUG, " UP\n");
-				break;
-			case SCTP_COMM_LOST:
-				LOGPC(DLINP, LOGL_DEBUG, " LOST\n");
-				/* Handle this like a regular disconnect */
-				return 0;
-			case SCTP_RESTART:
-				LOGPC(DLINP, LOGL_DEBUG, " RESTART\n");
-				break;
-			case SCTP_SHUTDOWN_COMP:
-				LOGPC(DLINP, LOGL_DEBUG, " SHUTDOWN COMP\n");
-				break;
-			case SCTP_CANT_STR_ASSOC:
-				LOGPC(DLINP, LOGL_DEBUG, " CANT STR ASSOC\n");
-				break;
-			}
-			break;
-		case SCTP_SEND_FAILED:
-			LOGP(DLINP, LOGL_DEBUG, "===> SEND FAILED\n");
-			break;
-		case SCTP_PEER_ADDR_CHANGE:
-			{
-			char addr_str[INET6_ADDRSTRLEN + 10];
-			struct sockaddr_storage sa = notif->sn_paddr_change.spc_aaddr;
-			osmo_sockaddr_to_str_buf(addr_str, sizeof(addr_str),
-						 (const struct osmo_sockaddr *)&sa);
-			LOGP(DLINP, LOGL_DEBUG, "===> PEER ADDR CHANGE: %s %s err=%s\n",
-			     addr_str, osmo_sctp_paddr_chg_str(notif->sn_paddr_change.spc_state),
-			     (notif->sn_paddr_change.spc_state == SCTP_ADDR_UNREACHABLE) ?
-				osmo_sctp_sn_error_str(notif->sn_paddr_change.spc_error) : "None");
-			}
-			break;
-		case SCTP_SHUTDOWN_EVENT:
-			LOGP(DLINP, LOGL_DEBUG, "===> SHUTDOWN EVT\n");
-			/* Handle this like a regular disconnect */
-			return 0;
-		}
-		return -EAGAIN;
-	}
-	return ret;
-}
-#endif
-
-/*! \brief Receive data via Osmocom stream server
- *  \param[in] conn Stream Server from which to receive
- *  \param msg pre-allocate message buffer to which received data is appended
- *  \returns number of bytes read, negative on error.
- *
- *  If conn is an SCTP connection, additional specific considerations shall be taken:
- *  - msg->cb is always filled with SCTP ppid, and SCTP stream values, see msgb_sctp_*() APIs.
- *  - If an SCTP notification was received when reading from the SCTP socket,
- *    msgb_sctp_msg_flags(msg) will contain bit flag
- *    OSMO_STREAM_SCTP_MSG_FLAGS_NOTIFICATION set, and the msgb will
- *    contain a "union sctp_notification" instead of user data. In this case the
- *    return code will be either 0 (if conn is considered dead after the
- *    notification) or -EAGAIN (if conn is considered still alive after the
- *    notification) resembling the standard recv() API.
- */
-int osmo_stream_srv_recv(struct osmo_stream_srv *conn, struct msgb *msg)
-{
-	int ret;
-	OSMO_ASSERT(conn);
-	OSMO_ASSERT(msg);
-
-	switch (conn->srv->sk_domain) {
-	case AF_UNIX:
-		ret = recv(conn->ofd.fd, msgb_data(msg), msgb_tailroom(msg), 0);
-		break;
-	case AF_INET:
-	case AF_INET6:
-	case AF_UNSPEC:
-		switch (conn->srv->proto) {
-#ifdef HAVE_LIBSCTP
-		case IPPROTO_SCTP:
-			ret = _sctp_recvmsg_wrapper(conn->ofd.fd, msg);
-			break;
-#endif
-		case IPPROTO_TCP:
-		default:
-			ret = recv(conn->ofd.fd, msgb_data(msg), msgb_tailroom(msg), 0);
-			break;
-		}
-		break;
-	default:
-		ret = -ENOTSUP;
-	}
-
-	if (ret < 0) {
-		if (errno == EPIPE || errno == ECONNRESET) {
-			LOGSSRV(conn, LOGL_ERROR, "lost connection with client\n");
-		}
-		return ret;
-	} else if (ret == 0) {
-		LOGSSRV(conn, LOGL_ERROR, "connection closed with client\n");
-		return ret;
-	}
-	msgb_put(msg, ret);
-	LOGSSRV(conn, LOGL_DEBUG, "received %d bytes from client\n", ret);
-	return ret;
-}
-
-void osmo_stream_srv_clear_tx_queue(struct osmo_stream_srv *conn)
-{
-	msgb_queue_free(&conn->tx_queue);
-	osmo_fd_write_disable(&conn->ofd);
-	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
-		osmo_stream_srv_destroy(conn);
-}
-
 /*! @} */
diff --git a/src/stream_cli.c b/src/stream_cli.c
new file mode 100644
index 0000000..5cd6931
--- /dev/null
+++ b/src/stream_cli.c
@@ -0,0 +1,954 @@
+/* (C) 2011 by Pablo Neira Ayuso <pablo@gnumonks.org>
+ * (C) 2015-2016 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <time.h>
+#include <sys/fcntl.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+
+#include <osmocom/core/timer.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/osmo_io.h>
+#include <osmocom/core/panic.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/socket.h>
+
+#include <osmocom/netif/stream.h>
+#include <osmocom/netif/stream_private.h>
+
+#include "config.h"
+
+#include <osmocom/netif/sctp.h>
+
+
+/*! \addtogroup stream Osmocom Stream Socket (client side)
+ *  @{
+ *
+ *  This code is intended to abstract any use of stream-type sockets,
+ *  such as TCP and SCTP.  It offers client side implementation,
+ * fully integrated with the libosmocore select loop abstraction.
+ */
+
+/*! \file stream_cli.c
+ *  \brief Osmocom stream socket helpers (client side)
+ */
+
+#define LOGSCLI(cli, level, fmt, args...) \
+	LOGP(DLINP, level, "CLICONN(%s,%s){%s} " fmt, \
+	     cli->name ? : "", \
+	     cli->sockname, \
+	     get_value_string(stream_cli_state_names, (cli)->state), \
+	     ## args)
+
+/*
+ * Client side.
+ */
+
+enum osmo_stream_cli_state {
+	STREAM_CLI_STATE_CLOSED,	 /* No fd associated, no timer active */
+	STREAM_CLI_STATE_WAIT_RECONNECT, /* No fd associated, has timer active to try to connect again */
+	STREAM_CLI_STATE_CONNECTING,	 /* Fd associated, but connection not yet confirmed by peer or lower layers */
+	STREAM_CLI_STATE_CONNECTED,	 /* Fd associated and connection is established */
+	STREAM_CLI_STATE_MAX
+};
+
+static const struct value_string stream_cli_state_names[] = {
+	{ STREAM_CLI_STATE_CLOSED,	 "CLOSED" },
+	{ STREAM_CLI_STATE_WAIT_RECONNECT, "WAIT_RECONNECT" },
+	{ STREAM_CLI_STATE_CONNECTING,     "CONNECTING" },
+	{ STREAM_CLI_STATE_CONNECTED,      "CONNECTED" },
+	{ 0, NULL }
+};
+
+#define OSMO_STREAM_CLI_F_RECONF	(1 << 0)
+#define OSMO_STREAM_CLI_F_NODELAY	(1 << 1)
+
+struct osmo_stream_cli {
+	char *name;
+	char sockname[OSMO_SOCK_NAME_MAXLEN];
+	enum osmo_stream_mode mode;
+	union {
+		struct osmo_fd			ofd;
+		struct osmo_io_fd		*iofd;
+	};
+	struct llist_head		tx_queue;
+	struct osmo_timer_list		timer;
+	enum osmo_stream_cli_state	state;
+	char				*addr[OSMO_STREAM_MAX_ADDRS];
+	uint8_t				addrcnt;
+	uint16_t			port;
+	char				*local_addr[OSMO_STREAM_MAX_ADDRS];
+	uint8_t				local_addrcnt;
+	uint16_t			local_port;
+	int				sk_domain;
+	int				sk_type;
+	uint16_t			proto;
+	int (*connect_cb)(struct osmo_stream_cli *cli);
+	int (*disconnect_cb)(struct osmo_stream_cli *cli);
+	int (*read_cb)(struct osmo_stream_cli *cli);
+	int (*iofd_read_cb)(struct osmo_stream_cli *cli, struct msgb *msg);
+	int (*write_cb)(struct osmo_stream_cli *cli);
+	void				*data;
+	int				flags;
+	int				reconnect_timeout;
+};
+
+void osmo_stream_cli_close(struct osmo_stream_cli *cli);
+
+/*! \brief Re-connect an Osmocom Stream Client
+ *  If re-connection is enabled for this client
+ *  (which is the case unless negative timeout was explicitly set via osmo_stream_cli_set_reconnect_timeout() call),
+ *  we close any existing connection (if any) and schedule a re-connect timer */
+void osmo_stream_cli_reconnect(struct osmo_stream_cli *cli)
+{
+	osmo_stream_cli_close(cli);
+
+	if (cli->reconnect_timeout < 0) {
+		LOGSCLI(cli, LOGL_INFO, "not reconnecting, disabled\n");
+		return;
+	}
+
+	cli->state = STREAM_CLI_STATE_WAIT_RECONNECT;
+	LOGSCLI(cli, LOGL_INFO, "retrying reconnect in %d seconds...\n",
+		cli->reconnect_timeout);
+	osmo_timer_schedule(&cli->timer, cli->reconnect_timeout, 0);
+}
+
+/*! \brief Check if Osmocom Stream Client is in connected state
+ *  \param[in] cli Osmocom Stream Client
+ *  \return true if connected, false otherwise
+ */
+bool osmo_stream_cli_is_connected(struct osmo_stream_cli *cli)
+{
+	return cli->state == STREAM_CLI_STATE_CONNECTED;
+}
+
+static void osmo_stream_cli_close_iofd(struct osmo_stream_cli *cli)
+{
+	if (!cli->iofd)
+		return;
+
+	osmo_iofd_close(cli->iofd);
+}
+
+static void osmo_stream_cli_close_ofd(struct osmo_stream_cli *cli)
+{
+	if (cli->ofd.fd == -1)
+		return;
+	osmo_fd_unregister(&cli->ofd);
+	close(cli->ofd.fd);
+	cli->ofd.fd = -1;
+}
+
+/*! \brief Close an Osmocom Stream Client
+ *  \param[in] cli Osmocom Stream Client to be closed
+ *  We unregister the socket fd from the osmocom select() loop
+ *  abstraction and close the socket */
+void osmo_stream_cli_close(struct osmo_stream_cli *cli)
+{
+	int old_state = cli->state;
+
+	if (cli->state == STREAM_CLI_STATE_CLOSED)
+		return;
+	if (cli->state == STREAM_CLI_STATE_WAIT_RECONNECT) {
+		osmo_timer_del(&cli->timer);
+		cli->state = STREAM_CLI_STATE_CLOSED;
+		return;
+	}
+
+
+	switch (cli->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		osmo_stream_cli_close_ofd(cli);
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		osmo_stream_cli_close_iofd(cli);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+
+	cli->state = STREAM_CLI_STATE_CLOSED;
+
+	if (old_state == STREAM_CLI_STATE_CONNECTED) {
+		LOGSCLI(cli, LOGL_DEBUG, "connection closed\n");
+		if (cli->disconnect_cb)
+			cli->disconnect_cb(cli);
+	}
+}
+
+static inline int osmo_stream_cli_fd(const struct osmo_stream_cli *cli)
+{
+	switch (cli->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		return cli->ofd.fd;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		if (cli->iofd)
+			return osmo_iofd_get_fd(cli->iofd);
+	default:
+		break;
+	}
+	return -EINVAL;
+}
+
+static void osmo_stream_cli_read(struct osmo_stream_cli *cli)
+{
+	LOGSCLI(cli, LOGL_DEBUG, "message received\n");
+
+	if (cli->read_cb)
+		cli->read_cb(cli);
+}
+
+static int osmo_stream_cli_write(struct osmo_stream_cli *cli)
+{
+#ifdef HAVE_LIBSCTP
+	struct sctp_sndrcvinfo sinfo;
+#endif
+	struct msgb *msg;
+	int ret;
+
+	if (llist_empty(&cli->tx_queue)) {
+		osmo_fd_write_disable(&cli->ofd);
+		return 0;
+	}
+	msg = llist_first_entry(&cli->tx_queue, struct msgb, list);
+	llist_del(&msg->list);
+
+	if (!osmo_stream_cli_is_connected(cli)) {
+		LOGSCLI(cli, LOGL_ERROR, "send: not connected, dropping data!\n");
+		return 0;
+	}
+
+	LOGSCLI(cli, LOGL_DEBUG, "sending %u bytes of data\n", msgb_length(msg));
+
+	switch (cli->sk_domain) {
+	case AF_UNIX:
+		ret = send(cli->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
+		break;
+	case AF_UNSPEC:
+	case AF_INET:
+	case AF_INET6:
+		switch (cli->proto) {
+#ifdef HAVE_LIBSCTP
+		case IPPROTO_SCTP:
+			memset(&sinfo, 0, sizeof(sinfo));
+			sinfo.sinfo_ppid = htonl(msgb_sctp_ppid(msg));
+			sinfo.sinfo_stream = msgb_sctp_stream(msg);
+			ret = sctp_send(cli->ofd.fd, msgb_data(msg), msgb_length(msg),
+					&sinfo, MSG_NOSIGNAL);
+			break;
+#endif
+		case IPPROTO_TCP:
+		default:
+			ret = send(cli->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
+			break;
+		}
+		break;
+	default:
+		ret = -ENOTSUP;
+	}
+
+	if (ret >= 0 && ret < msgb_length(msg)) {
+		LOGSCLI(cli, LOGL_ERROR, "short send: %d < exp %u\n", ret, msgb_length(msg));
+		/* Update msgb and re-add it at the start of the queue: */
+		msgb_pull(msg, ret);
+		llist_add(&msg->list, &cli->tx_queue);
+		return 0;
+	}
+
+	if (ret < 0) {
+		if (errno == EPIPE || errno == ENOTCONN)
+			osmo_stream_cli_reconnect(cli);
+		LOGSCLI(cli, LOGL_ERROR, "received error %d in response to send\n", errno);
+	}
+
+	msgb_free(msg);
+
+	if (llist_empty(&cli->tx_queue))
+		osmo_fd_write_disable(&cli->ofd);
+
+	return 0;
+}
+
+static int _setsockopt_nosigpipe(struct osmo_stream_cli *cli)
+{
+#ifdef SO_NOSIGPIPE
+	int ret;
+	int val = 1;
+	ret = setsockopt(osmo_stream_cli_fd(cli), SOL_SOCKET, SO_NOSIGPIPE, (void *)&val, sizeof(val));
+	if (ret < 0)
+		LOGSCLI(cli, LOGL_DEBUG, "Failed setting SO_NOSIGPIPE: %s\n", strerror(errno));
+	return ret;
+#else
+	return 0;
+#endif
+}
+
+static void stream_cli_handle_connecting(struct osmo_stream_cli *cli, int res)
+{
+	int error, ret = res;
+	socklen_t len = sizeof(error);
+
+	int fd = osmo_stream_cli_fd(cli);
+	OSMO_ASSERT(fd >= 0);
+
+	if (ret < 0) {
+		osmo_stream_cli_reconnect(cli);
+		return;
+	}
+	ret = getsockopt(fd, SOL_SOCKET, SO_ERROR, &error, &len);
+	if (ret >= 0 && error > 0) {
+		osmo_stream_cli_reconnect(cli);
+		return;
+	}
+
+	/* If messages got enqueued while 'connecting', keep WRITE flag
+	   up to dispatch them upon next main loop step */
+	if (cli->mode == OSMO_STREAM_MODE_OSMO_FD && llist_empty(&cli->tx_queue))
+		osmo_fd_write_disable(&cli->ofd);
+
+	/* Update sockname based on socket info: */
+	osmo_sock_get_name_buf(cli->sockname, sizeof(cli->sockname), osmo_stream_cli_fd(cli));
+
+	LOGSCLI(cli, LOGL_DEBUG, "connection established\n");
+	cli->state = STREAM_CLI_STATE_CONNECTED;
+	switch (cli->sk_domain) {
+	case AF_UNIX:
+		_setsockopt_nosigpipe(cli);
+		break;
+	case AF_UNSPEC:
+	case AF_INET:
+	case AF_INET6:
+		if (cli->proto == IPPROTO_SCTP) {
+			_setsockopt_nosigpipe(cli);
+			stream_sctp_sock_activate_events(fd);
+		}
+		break;
+	default:
+		break;
+	}
+	if (cli->connect_cb)
+		cli->connect_cb(cli);
+}
+
+static int osmo_stream_cli_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	struct osmo_stream_cli *cli = ofd->data;
+
+	switch (cli->state) {
+	case STREAM_CLI_STATE_CONNECTING:
+		stream_cli_handle_connecting(cli, 0);
+		break;
+	case STREAM_CLI_STATE_CONNECTED:
+		if (what & OSMO_FD_READ) {
+			LOGSCLI(cli, LOGL_DEBUG, "connected read\n");
+			osmo_stream_cli_read(cli);
+		}
+		if (what & OSMO_FD_WRITE) {
+			LOGSCLI(cli, LOGL_DEBUG, "connected write\n");
+			osmo_stream_cli_write(cli);
+		}
+		break;
+	default:
+		/* Only CONNECTING and CONNECTED states are expected, since they are the only states
+		 * where FD exists: */
+		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
+	}
+	return 0;
+}
+
+static void cli_timer_cb(void *data);
+
+/*! \brief Create an Osmocom stream client
+ *  \param[in] ctx talloc context from which to allocate memory
+ *  This function allocates a new \ref osmo_stream_cli and initializes
+ *  it with default values (5s reconnect timer, TCP protocol)
+ *  \return allocated stream client, or NULL in case of error
+ */
+struct osmo_stream_cli *osmo_stream_cli_create(void *ctx)
+{
+	struct osmo_stream_cli *cli;
+
+	cli = talloc_zero(ctx, struct osmo_stream_cli);
+	if (!cli)
+		return NULL;
+
+	cli->mode = OSMO_STREAM_MODE_UNKNOWN;
+	cli->sk_domain = AF_UNSPEC;
+	cli->sk_type = SOCK_STREAM;
+	cli->proto = IPPROTO_TCP;
+
+	cli->state = STREAM_CLI_STATE_CLOSED;
+	osmo_timer_setup(&cli->timer, cli_timer_cb, cli);
+	cli->reconnect_timeout = 5;	/* default is 5 seconds. */
+	INIT_LLIST_HEAD(&cli->tx_queue);
+
+	return cli;
+}
+
+static void stream_cli_iofd_read_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
+{
+	struct osmo_stream_cli *cli  = osmo_iofd_get_data(iofd);
+
+	switch (cli->state) {
+	case STREAM_CLI_STATE_CONNECTING:
+		stream_cli_handle_connecting(cli, res);
+		break;
+	case STREAM_CLI_STATE_CONNECTED:
+		if (res == 0)
+			osmo_stream_cli_reconnect(cli);
+		else if (cli->iofd_read_cb)
+			cli->iofd_read_cb(cli, msg);
+		break;
+	default:
+		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
+	}
+}
+
+static void stream_cli_iofd_write_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
+{
+	struct osmo_stream_cli *cli = osmo_iofd_get_data(iofd);
+
+	switch (cli->state) {
+	case STREAM_CLI_STATE_CONNECTING:
+		stream_cli_handle_connecting(cli, res);
+		break;
+	case STREAM_CLI_STATE_CONNECTED:
+		if (msg && res <= 0) {
+			osmo_stream_cli_reconnect(cli);
+			LOGSCLI(cli, LOGL_ERROR, "received error %d in response to send\n", res);
+		}
+		break;
+	default:
+		osmo_panic("%s() called with unexpected state %d\n", __func__, cli->state);
+	}
+}
+
+static struct osmo_io_ops osmo_stream_cli_ioops = {
+	.read_cb = stream_cli_iofd_read_cb,
+	.write_cb = stream_cli_iofd_write_cb,
+
+	.segmentation_cb = NULL,
+};
+
+/*! \brief Set a name on the cli object (used during logging)
+ *  \param[in] cli stream_cli whose name is to be set
+ *  \param[in] name the name to be set on cli
+ */
+void osmo_stream_cli_set_name(struct osmo_stream_cli *cli, const char *name)
+{
+	osmo_talloc_replace_string(cli, &cli->name, name);
+	if (cli->mode == OSMO_STREAM_MODE_OSMO_IO && cli->iofd)
+		osmo_iofd_set_name(cli->iofd, name);
+}
+
+/*! \brief Set the remote address to which we connect
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] addr Remote IP address
+ */
+void
+osmo_stream_cli_set_addr(struct osmo_stream_cli *cli, const char *addr)
+{
+	osmo_stream_cli_set_addrs(cli, &addr, 1);
+}
+
+/*! \brief Set the remote address set to which we connect.
+ *  Useful for protocols allowing connecting to more than one address (such as SCTP)
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] addr Remote IP address set
+ *  \return negative on error, 0 on success
+ */
+int osmo_stream_cli_set_addrs(struct osmo_stream_cli *cli, const char **addr, size_t addrcnt)
+{
+	int i = 0;
+
+	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
+		return -EINVAL;
+
+	for (; i < addrcnt; i++)
+		osmo_talloc_replace_string(cli, &cli->addr[i], addr[i]);
+	for (; i < cli->addrcnt; i++) {
+		talloc_free(cli->addr[i]);
+		cli->addr[i] = NULL;
+	}
+
+	cli->addrcnt = addrcnt;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the remote port number to which we connect
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] port Remote port number
+ */
+void
+osmo_stream_cli_set_port(struct osmo_stream_cli *cli, uint16_t port)
+{
+	cli->port = port;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+}
+
+/*! \brief Set the local port number for the socket (to be bound to)
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] port Local port number
+ */
+void
+osmo_stream_cli_set_local_port(struct osmo_stream_cli *cli, uint16_t port)
+{
+	cli->local_port = port;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+}
+
+/*! \brief Set the local address for the socket (to be bound to)
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] port Local host name
+ */
+void
+osmo_stream_cli_set_local_addr(struct osmo_stream_cli *cli, const char *addr)
+{
+	osmo_stream_cli_set_local_addrs(cli, &addr, 1);
+}
+
+/*! \brief Set the local address set to which we connect.
+ *  Useful for protocols allowing bind to more than one address (such as SCTP)
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] addr Local IP address set
+ *  \return negative on error, 0 on success
+ */
+int osmo_stream_cli_set_local_addrs(struct osmo_stream_cli *cli, const char **addr, size_t addrcnt)
+{
+	int i = 0;
+
+	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
+		return -EINVAL;
+
+	for (; i < addrcnt; i++)
+		osmo_talloc_replace_string(cli, &cli->local_addr[i], addr[i]);
+	for (; i < cli->local_addrcnt; i++) {
+		talloc_free(cli->local_addr[i]);
+		cli->local_addr[i] = NULL;
+	}
+
+	cli->local_addrcnt = addrcnt;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the protocol for the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] proto Protocol (like IPPROTO_TCP (default), IPPROTO_SCTP, ...)
+ */
+void
+osmo_stream_cli_set_proto(struct osmo_stream_cli *cli, uint16_t proto)
+{
+	cli->proto = proto;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+}
+
+/*! \brief Set the socket type for the stream server link
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] type Socket Type (like SOCK_STREAM (default), SOCK_SEQPACKET, ...)
+ *  \returns zero on success, negative on error.
+ */
+int osmo_stream_cli_set_type(struct osmo_stream_cli *cli, int type)
+{
+	switch (type) {
+	case SOCK_STREAM:
+	case SOCK_SEQPACKET:
+		break;
+	default:
+		return -ENOTSUP;
+	}
+	cli->sk_type = type;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the socket type for the stream server link
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] type Socket Domain (like AF_UNSPEC (default for IP), AF_UNIX, AF_INET, ...)
+ *  \returns zero on success, negative on error.
+ */
+int osmo_stream_cli_set_domain(struct osmo_stream_cli *cli, int domain)
+{
+	switch (domain) {
+	case AF_UNSPEC:
+	case AF_INET:
+	case AF_INET6:
+	case AF_UNIX:
+		break;
+	default:
+		return -ENOTSUP;
+	}
+	cli->sk_domain = domain;
+	cli->flags |= OSMO_STREAM_CLI_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the reconnect time of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] timeout Re-connect timeout in seconds or negative value to disable auto-reconnection */
+void
+osmo_stream_cli_set_reconnect_timeout(struct osmo_stream_cli *cli, int timeout)
+{
+	cli->reconnect_timeout = timeout;
+}
+
+/*! \brief Set application private data of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] data User-specific data (available in call-back functions) */
+void
+osmo_stream_cli_set_data(struct osmo_stream_cli *cli, void *data)
+{
+	cli->data = data;
+}
+
+/*! \brief Get application private data of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \returns Application private data, as set by \ref osmo_stream_cli_set_data() */
+void *osmo_stream_cli_get_data(struct osmo_stream_cli *cli)
+{
+	return cli->data;
+}
+
+/*! \brief Get the stream client socket description.
+ *  \param[in] cli Stream Client to examine
+ *  \returns Socket description or NULL in case of error */
+char *osmo_stream_cli_get_sockname(const struct osmo_stream_cli *cli)
+{
+	static char buf[OSMO_SOCK_NAME_MAXLEN];
+
+	osmo_sock_get_name_buf(buf, OSMO_SOCK_NAME_MAXLEN, osmo_stream_cli_fd(cli));
+
+	return buf;
+}
+
+/*! \brief Get Osmocom File Descriptor of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \returns Pointer to \ref osmo_fd */
+struct osmo_fd *
+osmo_stream_cli_get_ofd(struct osmo_stream_cli *cli)
+{
+	OSMO_ASSERT(cli->mode == OSMO_STREAM_MODE_OSMO_FD);
+	return &cli->ofd;
+}
+
+/*! \brief Set the call-back function called on connect of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] connect_cb Call-back function to be called upon connect */
+void
+osmo_stream_cli_set_connect_cb(struct osmo_stream_cli *cli,
+	int (*connect_cb)(struct osmo_stream_cli *cli))
+{
+	cli->connect_cb = connect_cb;
+}
+
+/*! \brief Set the call-back function called on disconnect of the stream client socket
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] disconnect_cb Call-back function to be called upon disconnect */
+void osmo_stream_cli_set_disconnect_cb(struct osmo_stream_cli *cli,
+				       int (*disconnect_cb)(struct osmo_stream_cli *cli))
+{
+	cli->disconnect_cb = disconnect_cb;
+}
+
+/*! \brief Set the call-back function called to read from the stream client socket
+ *  This function will configure osmo_stream_cli to use osmo_ofd internally.
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] read_cb Call-back function to be called when we want to read */
+void
+osmo_stream_cli_set_read_cb(struct osmo_stream_cli *cli,
+			    int (*read_cb)(struct osmo_stream_cli *cli))
+{
+	OSMO_ASSERT(cli->mode != OSMO_STREAM_MODE_OSMO_IO);
+	cli->mode = OSMO_STREAM_MODE_OSMO_FD;
+	cli->read_cb = read_cb;
+}
+
+/*! \brief Set the call-back function called to read from the stream client socket
+ *  This function will configure osmo_stream_cli to use osmo_iofd internally.
+ *  \param[in] cli Stream Client to modify
+ *  \param[in] read_cb Call-back function to be called when data was read from the socket */
+void
+osmo_stream_cli_set_read_cb2(struct osmo_stream_cli *cli,
+			    int (*read_cb)(struct osmo_stream_cli *cli, struct msgb *msg))
+{
+	OSMO_ASSERT(cli->mode != OSMO_STREAM_MODE_OSMO_FD);
+	cli->mode = OSMO_STREAM_MODE_OSMO_IO;
+	cli->iofd_read_cb = read_cb;
+}
+
+/*! \brief Destroy a Osmocom stream client (includes close)
+ *  \param[in] cli Stream Client to destroy */
+void osmo_stream_cli_destroy(struct osmo_stream_cli *cli)
+{
+	osmo_stream_cli_close(cli);
+	osmo_timer_del(&cli->timer);
+	msgb_queue_free(&cli->tx_queue);
+	talloc_free(cli);
+}
+
+/*! \brief DEPRECATED: use osmo_stream_cli_set_reconnect_timeout() or osmo_stream_cli_reconnect() instead!
+ * Open connection of an Osmocom stream client
+ *  \param[in] cli Stream Client to connect
+ *  \param[in] reconect 1 if we should not automatically reconnect
+ *  \return negative on error, 0 on success
+ */
+int osmo_stream_cli_open2(struct osmo_stream_cli *cli, int reconnect)
+{
+	int ret;
+
+	/* we are reconfiguring this socket, close existing first. */
+	if ((cli->flags & OSMO_STREAM_CLI_F_RECONF) && cli->ofd.fd >= 0)
+		osmo_stream_cli_close(cli);
+
+	cli->flags &= ~OSMO_STREAM_CLI_F_RECONF;
+
+	switch (cli->proto) {
+#ifdef HAVE_LIBSCTP
+	case IPPROTO_SCTP:
+		ret = osmo_sock_init2_multiaddr(AF_UNSPEC, SOCK_STREAM, cli->proto,
+						(const char **)cli->local_addr, cli->local_addrcnt, cli->local_port,
+						(const char **)cli->addr, cli->addrcnt, cli->port,
+						OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
+		break;
+#endif
+	default:
+		ret = osmo_sock_init2(AF_UNSPEC, SOCK_STREAM, cli->proto,
+				      cli->local_addr[0], cli->local_port,
+				      cli->addr[0], cli->port,
+				      OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
+	}
+
+	if (ret < 0) {
+		if (reconnect)
+			osmo_stream_cli_reconnect(cli);
+		return ret;
+	}
+	osmo_fd_setup(&cli->ofd, ret, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_cli_fd_cb, cli, 0);
+
+	if (cli->flags & OSMO_STREAM_CLI_F_NODELAY) {
+		ret = stream_setsockopt_nodelay(cli->ofd.fd, cli->proto, 1);
+		if (ret < 0)
+			goto error_close_socket;
+	}
+
+	if (osmo_fd_register(&cli->ofd) < 0)
+		goto error_close_socket;
+
+	cli->state = STREAM_CLI_STATE_CONNECTING;
+	return 0;
+
+error_close_socket:
+	close(cli->ofd.fd);
+	cli->ofd.fd = -1;
+	return -EIO;
+}
+
+/*! \brief Set the NODELAY socket option to avoid Nagle-like behavior
+ *  Setting this to nodelay=true will automatically set the NODELAY
+ *  socket option on any socket established via \ref osmo_stream_cli_open
+ *  or any re-connect.  You have to set this _before_ opening the
+ *  socket.
+ *  \param[in] cli Stream client whose sockets are to be configured
+ *  \param[in] nodelay whether to set (true) NODELAY before connect()
+ */
+void osmo_stream_cli_set_nodelay(struct osmo_stream_cli *cli, bool nodelay)
+{
+	if (nodelay)
+		cli->flags |= OSMO_STREAM_CLI_F_NODELAY;
+	else
+		cli->flags &= ~OSMO_STREAM_CLI_F_NODELAY;
+}
+
+/*! \brief Open connection of an Osmocom stream client
+ *  By default the client will automatically reconnect after default timeout.
+ *  To disable this, use osmo_stream_cli_set_reconnect_timeout() before calling this function.
+ *  \param[in] cli Stream Client to connect
+ *  \return negative on error, 0 on success */
+int osmo_stream_cli_open(struct osmo_stream_cli *cli)
+{
+	int ret, fd = -1;
+
+	/* we are reconfiguring this socket, close existing first. */
+	if ((cli->flags & OSMO_STREAM_CLI_F_RECONF) && osmo_stream_cli_fd(cli) >= 0)
+		osmo_stream_cli_close(cli);
+
+	cli->flags &= ~OSMO_STREAM_CLI_F_RECONF;
+
+	switch (cli->sk_domain) {
+	case AF_UNIX:
+		ret = osmo_sock_unix_init(cli->sk_type, 0, cli->addr[0], OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
+		break;
+	case AF_INET:
+	case AF_INET6:
+	case AF_UNSPEC:
+		switch (cli->proto) {
+#ifdef HAVE_LIBSCTP
+		case IPPROTO_SCTP:
+			ret = osmo_sock_init2_multiaddr(cli->sk_domain, cli->sk_type, cli->proto,
+							(const char **)cli->local_addr, cli->local_addrcnt, cli->local_port,
+							(const char **)cli->addr, cli->addrcnt, cli->port,
+							OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
+			break;
+#endif
+		default:
+			ret = osmo_sock_init2(cli->sk_domain, cli->sk_type, cli->proto,
+					      cli->local_addr[0], cli->local_port,
+					      cli->addr[0], cli->port,
+					      OSMO_SOCK_F_CONNECT|OSMO_SOCK_F_BIND|OSMO_SOCK_F_NONBLOCK);
+		}
+		break;
+	default:
+		return -ENOTSUP;
+	}
+
+	if (ret < 0) {
+		osmo_stream_cli_reconnect(cli);
+		return ret;
+	}
+
+	fd = ret;
+
+	if (cli->flags & OSMO_STREAM_CLI_F_NODELAY) {
+		ret = stream_setsockopt_nodelay(fd, cli->proto, 1);
+		if (ret < 0)
+			goto error_close_socket;
+	}
+
+	switch (cli->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		osmo_fd_setup(&cli->ofd, fd, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_cli_fd_cb, cli, 0);
+		if (osmo_fd_register(&cli->ofd) < 0)
+			goto error_close_socket;
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		if (!cli->iofd)
+			cli->iofd = osmo_iofd_setup(cli, fd, cli->name, OSMO_IO_FD_MODE_READ_WRITE, &osmo_stream_cli_ioops, cli);
+		if (!cli->iofd)
+			goto error_close_socket;
+
+		if (osmo_iofd_register(cli->iofd, fd) < 0)
+			goto error_close_socket;
+		osmo_iofd_notify_connected(cli->iofd);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+
+	cli->state = STREAM_CLI_STATE_CONNECTING;
+	return 0;
+
+error_close_socket:
+	cli->state = STREAM_CLI_STATE_CLOSED;
+	close(fd);
+	if (cli->mode == OSMO_STREAM_MODE_OSMO_FD)
+		cli->ofd.fd = -1;
+	return -EIO;
+}
+
+static void cli_timer_cb(void *data)
+{
+	struct osmo_stream_cli *cli = data;
+
+	LOGSCLI(cli, LOGL_DEBUG, "reconnecting\n");
+	osmo_stream_cli_open(cli);
+}
+
+/*! \brief Enqueue data to be sent via an Osmocom stream client
+ *  \param[in] cli Stream Client through which we want to send
+ *  \param[in] msg Message buffer to enqueue in transmit queue */
+void osmo_stream_cli_send(struct osmo_stream_cli *cli, struct msgb *msg)
+{
+	OSMO_ASSERT(cli);
+	OSMO_ASSERT(msg);
+
+	switch (cli->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		msgb_enqueue(&cli->tx_queue, msg);
+		osmo_fd_write_enable(&cli->ofd);
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		osmo_iofd_write_msgb(cli->iofd, msg);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+}
+
+/*! \brief Receive data via an Osmocom stream client
+ *  \param[in] cli Stream Client through which we want to send
+ *  \param msg pre-allocate message buffer to which received data is appended
+ *  \returns number of bytes read; <=0 in case of error */
+int osmo_stream_cli_recv(struct osmo_stream_cli *cli, struct msgb *msg)
+{
+	int ret;
+	OSMO_ASSERT(cli);
+	OSMO_ASSERT(msg);
+
+	ret = recv(cli->ofd.fd, msg->data, msg->data_len, 0);
+	if (ret < 0) {
+		if (errno == EPIPE || errno == ECONNRESET)
+			LOGSCLI(cli, LOGL_ERROR, "lost connection with srv\n");
+		osmo_stream_cli_reconnect(cli);
+		return ret;
+	} else if (ret == 0) {
+		LOGSCLI(cli, LOGL_ERROR, "connection closed with srv\n");
+		osmo_stream_cli_reconnect(cli);
+		return ret;
+	}
+	msgb_put(msg, ret);
+	LOGSCLI(cli, LOGL_DEBUG, "received %d bytes from srv\n", ret);
+	return ret;
+}
+
+void osmo_stream_cli_clear_tx_queue(struct osmo_stream_cli *cli)
+{
+	switch (cli->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		msgb_queue_free(&cli->tx_queue);
+		/* If in state 'connecting', keep WRITE flag up to receive
+		* socket connection signal and then transition to STATE_CONNECTED: */
+		if (cli->state == STREAM_CLI_STATE_CONNECTED)
+			osmo_fd_write_disable(&cli->ofd);
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		osmo_iofd_txqueue_clear(cli->iofd);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+}
+
+/*! @} */
diff --git a/src/stream_srv.c b/src/stream_srv.c
new file mode 100644
index 0000000..9146028
--- /dev/null
+++ b/src/stream_srv.c
@@ -0,0 +1,937 @@
+/* (C) 2011 by Pablo Neira Ayuso <pablo@gnumonks.org>
+ * (C) 2015-2016 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <time.h>
+#include <sys/fcntl.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+
+#include <osmocom/core/timer.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/osmo_io.h>
+#include <osmocom/core/panic.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/socket.h>
+
+#include <osmocom/netif/stream.h>
+#include <osmocom/netif/stream_private.h>
+
+#include "config.h"
+
+#include <osmocom/netif/sctp.h>
+
+
+/*! \addtogroup stream Osmocom Stream Socket (server side)
+ *  @{
+ *
+ *  This code is intended to abstract any use of stream-type sockets,
+ *  such as TCP and SCTP.  It offers server side implementation,
+ *  fully integrated with the libosmocore select loop abstraction.
+ */
+
+/*! \file stream_srv.c
+ *  \brief Osmocom stream socket helpers (server side)
+ */
+
+#define LOGSLNK(link, level, fmt, args...) \
+	LOGP(DLINP, level, "SRV(%s,%s) " fmt, \
+	     link->name ? : "", \
+	     link->sockname, \
+	      ## args)
+
+#define LOGSSRV(srv, level, fmt, args...) \
+	LOGP(DLINP, level, "SRVCONN(%s,%s) " fmt, \
+	     srv->name ? : "", \
+	     srv->sockname, \
+	      ## args)
+/*
+ * Server side.
+ */
+
+#define OSMO_STREAM_SRV_F_RECONF	(1 << 0)
+#define OSMO_STREAM_SRV_F_NODELAY	(1 << 1)
+
+struct osmo_stream_srv_link {
+	struct osmo_fd		ofd;
+	char			*name;
+	char			sockname[OSMO_SOCK_NAME_MAXLEN];
+	char			*addr[OSMO_STREAM_MAX_ADDRS];
+	uint8_t			addrcnt;
+	uint16_t		port;
+	int			sk_domain;
+	int			sk_type;
+	uint16_t		proto;
+	int (*accept_cb)(struct osmo_stream_srv_link *srv, int fd);
+	void			*data;
+	int			flags;
+};
+
+static int osmo_stream_srv_link_ofd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	int ret;
+	int sock_fd;
+	struct osmo_sockaddr osa;
+	socklen_t sa_len = sizeof(osa.u.sas);
+	struct osmo_stream_srv_link *link = ofd->data;
+
+	ret = accept(ofd->fd, &osa.u.sa, &sa_len);
+	if (ret < 0) {
+		LOGP(DLINP, LOGL_ERROR, "failed to accept from origin peer, reason=`%s'\n",
+		     strerror(errno));
+		return ret;
+	}
+	sock_fd = ret;
+
+	switch (osa.u.sa.sa_family) {
+	case AF_UNIX:
+		LOGSLNK(link, LOGL_DEBUG, "accept()ed new link on fd %d\n",
+			sock_fd);
+		break;
+	case AF_INET6:
+	case AF_INET:
+		LOGSLNK(link, LOGL_DEBUG, "accept()ed new link from %s\n",
+			osmo_sockaddr_to_str(&osa));
+
+		if (link->proto == IPPROTO_SCTP) {
+			ret = stream_sctp_sock_activate_events(sock_fd);
+			if (ret < 0)
+				goto error_close_socket;
+		}
+		break;
+	default:
+		LOGSLNK(link, LOGL_DEBUG, "accept()ed unexpected address family %d\n",
+			osa.u.sa.sa_family);
+		goto error_close_socket;
+	}
+
+	if (link->flags & OSMO_STREAM_SRV_F_NODELAY) {
+		ret = stream_setsockopt_nodelay(sock_fd, link->proto, 1);
+		if (ret < 0)
+			goto error_close_socket;
+	}
+
+	if (!link->accept_cb) {
+		ret = -ENOTSUP;
+		goto error_close_socket;
+	}
+
+	ret = link->accept_cb(link, sock_fd);
+	if (ret)
+		goto error_close_socket;
+	return 0;
+
+error_close_socket:
+	close(sock_fd);
+	return ret;
+}
+
+/*! \brief Create an Osmocom Stream Server Link
+ *  A Stream Server Link is the listen()+accept() "parent" to individual
+ *  Stream Servers
+ *  \param[in] ctx talloc allocation context
+ *  \returns Stream Server Link with default values (TCP)
+ */
+struct osmo_stream_srv_link *osmo_stream_srv_link_create(void *ctx)
+{
+	struct osmo_stream_srv_link *link;
+
+	link = talloc_zero(ctx, struct osmo_stream_srv_link);
+	if (!link)
+		return NULL;
+
+	link->sk_domain = AF_UNSPEC;
+	link->sk_type = SOCK_STREAM;
+	link->proto = IPPROTO_TCP;
+	osmo_fd_setup(&link->ofd, -1, OSMO_FD_READ | OSMO_FD_WRITE, osmo_stream_srv_link_ofd_cb, link, 0);
+
+	return link;
+}
+
+/*! \brief Set a name on the srv_link object (used during logging)
+ *  \param[in] link server link whose name is to be set
+ *  \param[in] name the name to be set on link
+ */
+void osmo_stream_srv_link_set_name(struct osmo_stream_srv_link *link, const char *name)
+{
+	osmo_talloc_replace_string(link, &link->name, name);
+}
+
+/*! \brief Set the NODELAY socket option to avoid Nagle-like behavior
+ *  Setting this to nodelay=true will automatically set the NODELAY
+ *  socket option on any socket established via this server link, before
+ *  calling the accept_cb()
+ *  \param[in] link server link whose sockets are to be configured
+ *  \param[in] nodelay whether to set (true) NODELAY after accept
+ */
+void osmo_stream_srv_link_set_nodelay(struct osmo_stream_srv_link *link, bool nodelay)
+{
+	if (nodelay)
+		link->flags |= OSMO_STREAM_SRV_F_NODELAY;
+	else
+		link->flags &= ~OSMO_STREAM_SRV_F_NODELAY;
+}
+
+/*! \brief Set the local address to which we bind
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] addr Local IP address
+ */
+void osmo_stream_srv_link_set_addr(struct osmo_stream_srv_link *link,
+				      const char *addr)
+{
+	osmo_stream_srv_link_set_addrs(link, &addr, 1);
+}
+
+/*! \brief Set the local address set to which we bind.
+ *  Useful for protocols allowing bind on more than one address (such as SCTP)
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] addr Local IP address
+ *  \return negative on error, 0 on success
+ */
+int osmo_stream_srv_link_set_addrs(struct osmo_stream_srv_link *link, const char **addr, size_t addrcnt)
+{
+	int i = 0;
+
+	if (addrcnt > OSMO_STREAM_MAX_ADDRS)
+		return -EINVAL;
+
+	for (; i < addrcnt; i++)
+		osmo_talloc_replace_string(link, &link->addr[i], addr[i]);
+	for (; i < link->addrcnt; i++) {
+		talloc_free(link->addr[i]);
+		link->addr[i] = NULL;
+	}
+
+	link->addrcnt = addrcnt;
+	link->flags |= OSMO_STREAM_SRV_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the local port number to which we bind
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] port Local port number
+ */
+void osmo_stream_srv_link_set_port(struct osmo_stream_srv_link *link,
+				      uint16_t port)
+{
+	link->port = port;
+	link->flags |= OSMO_STREAM_SRV_F_RECONF;
+}
+
+/*! \brief Set the protocol for the stream server link
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] proto Protocol (like IPPROTO_TCP (default), IPPROTO_SCTP, ...)
+ */
+void
+osmo_stream_srv_link_set_proto(struct osmo_stream_srv_link *link,
+			  uint16_t proto)
+{
+	link->proto = proto;
+	link->flags |= OSMO_STREAM_SRV_F_RECONF;
+}
+
+
+/*! \brief Set the socket type for the stream server link
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] type Socket Type (like SOCK_STREAM (default), SOCK_SEQPACKET, ...)
+ *  \returns zero on success, negative on error.
+ */
+int osmo_stream_srv_link_set_type(struct osmo_stream_srv_link *link, int type)
+{
+	switch (type) {
+	case SOCK_STREAM:
+	case SOCK_SEQPACKET:
+		break;
+	default:
+		return -ENOTSUP;
+	}
+	link->sk_type = type;
+	link->flags |= OSMO_STREAM_SRV_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set the socket type for the stream server link
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] type Socket Domain (like AF_UNSPEC (default for IP), AF_UNIX, AF_INET, ...)
+ *  \returns zero on success, negative on error.
+ */
+int osmo_stream_srv_link_set_domain(struct osmo_stream_srv_link *link, int domain)
+{
+	switch (domain) {
+	case AF_UNSPEC:
+	case AF_INET:
+	case AF_INET6:
+	case AF_UNIX:
+		break;
+	default:
+		return -ENOTSUP;
+	}
+	link->sk_domain = domain;
+	link->flags |= OSMO_STREAM_SRV_F_RECONF;
+	return 0;
+}
+
+/*! \brief Set application private data of the stream server link
+ *  \param[in] link Stream Server Link to modify
+ *  \param[in] data User-specific data (available in call-back functions) */
+void
+osmo_stream_srv_link_set_data(struct osmo_stream_srv_link *link,
+				 void *data)
+{
+	link->data = data;
+}
+
+/*! \brief Get application private data of the stream server link
+ *  \param[in] link Stream Server Link to modify
+ *  \returns Application private data, as set by \ref osmo_stream_cli_set_data() */
+void *osmo_stream_srv_link_get_data(struct osmo_stream_srv_link *link)
+{
+	return link->data;
+}
+
+/*! \brief Get description of the stream server link e. g. 127.0.0.1:1234
+ *  \param[in] link Stream Server Link to examine
+ *  \returns Link description or NULL in case of error */
+char *osmo_stream_srv_link_get_sockname(const struct osmo_stream_srv_link *link)
+{
+	static char buf[INET6_ADDRSTRLEN + 6];
+	int rc = osmo_sock_get_local_ip(link->ofd.fd, buf, INET6_ADDRSTRLEN);
+	if (rc < 0)
+		return NULL;
+
+	buf[strnlen(buf, INET6_ADDRSTRLEN + 6)] = ':';
+
+	rc = osmo_sock_get_local_ip_port(link->ofd.fd, buf + strnlen(buf, INET6_ADDRSTRLEN + 6), 6);
+	if (rc < 0)
+		return NULL;
+
+	return buf;
+}
+
+/*! \brief Get Osmocom File Descriptor of the stream server link
+ *  \param[in] link Stream Server Link
+ *  \returns Pointer to \ref osmo_fd */
+struct osmo_fd *
+osmo_stream_srv_link_get_ofd(struct osmo_stream_srv_link *link)
+{
+	return &link->ofd;
+}
+
+/*! \brief Set the accept() call-back of the stream server link
+ *  \param[in] link Stream Server Link
+ *  \param[in] accept_cb Call-back function executed upon accept() */
+void osmo_stream_srv_link_set_accept_cb(struct osmo_stream_srv_link *link,
+	int (*accept_cb)(struct osmo_stream_srv_link *link, int fd))
+
+{
+	link->accept_cb = accept_cb;
+}
+
+/*! \brief Destroy the stream server link. Closes + Releases Memory.
+ *  \param[in] link Stream Server Link */
+void osmo_stream_srv_link_destroy(struct osmo_stream_srv_link *link)
+{
+	osmo_stream_srv_link_close(link);
+	talloc_free(link);
+}
+
+/*! \brief Open the stream server link.  This actually initializes the
+ *  underlying socket and binds it to the configured ip/port
+ *  \param[in] link Stream Server Link to open
+ *  \return negative on error, 0 on success */
+int osmo_stream_srv_link_open(struct osmo_stream_srv_link *link)
+{
+	int ret;
+
+	if (link->ofd.fd >= 0) {
+		/* No reconfigure needed for existing socket, we are fine */
+		if (!(link->flags & OSMO_STREAM_SRV_F_RECONF))
+			return 0;
+		/* we are reconfiguring this socket, close existing first. */
+		osmo_stream_srv_link_close(link);
+	}
+
+	link->flags &= ~OSMO_STREAM_SRV_F_RECONF;
+
+	switch (link->sk_domain) {
+	case AF_UNIX:
+		ret = osmo_sock_unix_init(link->sk_type, 0, link->addr[0], OSMO_SOCK_F_BIND);
+		break;
+	case AF_UNSPEC:
+	case AF_INET:
+	case AF_INET6:
+		switch (link->proto) {
+#ifdef HAVE_LIBSCTP
+		case IPPROTO_SCTP:
+			ret = osmo_sock_init2_multiaddr(link->sk_domain, link->sk_type, link->proto,
+							(const char **)link->addr, link->addrcnt, link->port,
+							NULL, 0, 0, OSMO_SOCK_F_BIND);
+			break;
+#endif
+		default:
+			ret = osmo_sock_init(link->sk_domain, link->sk_type, link->proto,
+					     link->addr[0], link->port, OSMO_SOCK_F_BIND);
+		}
+		break;
+	default:
+		ret = -ENOTSUP;
+	}
+	if (ret < 0)
+		return ret;
+
+	link->ofd.fd = ret;
+	if (osmo_fd_register(&link->ofd) < 0) {
+		close(ret);
+		link->ofd.fd = -1;
+		return -EIO;
+	}
+
+	OSMO_STRLCPY_ARRAY(link->sockname, osmo_stream_srv_link_get_sockname(link));
+	return 0;
+}
+
+/*! \brief Check whether the stream server link is opened
+ *  \param[in] link Stream Server Link to check */
+bool osmo_stream_srv_link_is_opened(const struct osmo_stream_srv_link *link)
+{
+	if (!link)
+		return false;
+
+	if (link->ofd.fd == -1)
+		return false;
+
+	return true;
+}
+
+/*! \brief Close the stream server link and unregister from select loop
+ *  Does not destroy the server link, merely closes it!
+ *  \param[in] link Stream Server Link to close */
+void osmo_stream_srv_link_close(struct osmo_stream_srv_link *link)
+{
+	if (!osmo_stream_srv_link_is_opened(link))
+		return;
+
+	osmo_fd_unregister(&link->ofd);
+	close(link->ofd.fd);
+	link->ofd.fd = -1;
+}
+
+#define OSMO_STREAM_SRV_F_FLUSH_DESTROY	(1 << 0)
+
+struct osmo_stream_srv {
+	struct osmo_stream_srv_link	*srv;
+	char				*name;
+	char				sockname[OSMO_SOCK_NAME_MAXLEN];
+	enum osmo_stream_mode mode;
+	union {
+		struct osmo_fd			ofd;
+		struct osmo_io_fd		*iofd;
+	};
+	struct llist_head		tx_queue;
+	int (*closed_cb)(struct osmo_stream_srv *peer);
+	int (*read_cb)(struct osmo_stream_srv *peer);
+	int (*iofd_read_cb)(struct osmo_stream_srv *peer, struct msgb *msg);
+	void				*data;
+	int				flags;
+};
+
+static void stream_srv_iofd_read_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
+{
+	struct osmo_stream_srv *conn = osmo_iofd_get_data(iofd);
+	LOGSSRV(conn, LOGL_DEBUG, "message received (res=%d)\n", res);
+
+	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
+		LOGSSRV(conn, LOGL_INFO, "Connection is being flushed and closed; ignoring received message\n");
+		msgb_free(msg);
+		return;
+	}
+
+	if (res <= 0) {
+		osmo_stream_srv_set_flush_and_destroy(conn);
+		if (osmo_iofd_txqueue_len(iofd) == 0)
+			osmo_stream_srv_destroy(conn);
+	} else if (conn->iofd_read_cb) {
+		conn->iofd_read_cb(conn, msg);
+	}
+}
+
+static void stream_srv_iofd_write_cb(struct osmo_io_fd *iofd, int res, struct msgb *msg)
+{
+	struct osmo_stream_srv *conn = osmo_iofd_get_data(iofd);
+	LOGSSRV(conn, LOGL_DEBUG, "connected write\n");
+
+	if (res == -1)
+		LOGSSRV(conn, LOGL_ERROR, "error to send: %s\n", strerror(errno));
+
+	if (osmo_iofd_txqueue_len(iofd) == 0)
+		if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
+			osmo_stream_srv_destroy(conn);
+}
+
+static struct osmo_io_ops srv_ioops = {
+	.read_cb = stream_srv_iofd_read_cb,
+	.write_cb = stream_srv_iofd_write_cb,
+};
+static int osmo_stream_srv_read(struct osmo_stream_srv *conn)
+{
+	int rc = 0;
+
+	LOGSSRV(conn, LOGL_DEBUG, "message received\n");
+
+	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
+		LOGSSRV(conn, LOGL_INFO, "Connection is being flushed and closed; ignoring received message\n");
+		return 0;
+	}
+
+	if (conn->read_cb)
+		rc = conn->read_cb(conn);
+
+	return rc;
+}
+
+static void osmo_stream_srv_write(struct osmo_stream_srv *conn)
+{
+#ifdef HAVE_LIBSCTP
+	struct sctp_sndrcvinfo sinfo;
+#endif
+	struct msgb *msg;
+	int ret;
+
+	if (llist_empty(&conn->tx_queue)) {
+		osmo_fd_write_disable(&conn->ofd);
+		return;
+	}
+	msg = llist_first_entry(&conn->tx_queue, struct msgb, list);
+	llist_del(&msg->list);
+
+	LOGSSRV(conn, LOGL_DEBUG, "sending %u bytes of data\n", msg->len);
+
+	switch (conn->srv->sk_domain) {
+	case AF_UNIX:
+		ret = send(conn->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
+		break;
+	case AF_INET:
+	case AF_INET6:
+	case AF_UNSPEC:
+		switch (conn->srv->proto) {
+#ifdef HAVE_LIBSCTP
+		case IPPROTO_SCTP:
+			memset(&sinfo, 0, sizeof(sinfo));
+			sinfo.sinfo_ppid = htonl(msgb_sctp_ppid(msg));
+			sinfo.sinfo_stream = msgb_sctp_stream(msg);
+			ret = sctp_send(conn->ofd.fd, msgb_data(msg), msgb_length(msg),
+					&sinfo, MSG_NOSIGNAL);
+			break;
+#endif
+		case IPPROTO_TCP:
+		default:
+			ret = send(conn->ofd.fd, msgb_data(msg), msgb_length(msg), 0);
+			break;
+		}
+		break;
+	default:
+		ret = -1;
+		errno = ENOTSUP;
+	}
+
+	if (ret >= 0 && ret < msgb_length(msg)) {
+		LOGSSRV(conn, LOGL_ERROR, "short send: %d < exp %u\n", ret, msgb_length(msg));
+		/* Update msgb and re-add it at the start of the queue: */
+		msgb_pull(msg, ret);
+		llist_add(&msg->list, &conn->tx_queue);
+		return;
+	}
+
+	if (ret == -1) /* send(): On error -1 is returned, and errno is set appropriately */
+		LOGSSRV(conn, LOGL_ERROR, "error to send: %s\n", strerror(errno));
+
+	msgb_free(msg);
+
+	if (llist_empty(&conn->tx_queue)) {
+		osmo_fd_write_disable(&conn->ofd);
+		if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
+			osmo_stream_srv_destroy(conn);
+	}
+}
+
+static int osmo_stream_srv_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	struct osmo_stream_srv *conn = ofd->data;
+	int rc = 0;
+
+	LOGSSRV(conn, LOGL_DEBUG, "connected read/write (what=0x%x)\n", what);
+	if (what & OSMO_FD_READ)
+		rc = osmo_stream_srv_read(conn);
+	if (rc != -EBADF && (what & OSMO_FD_WRITE))
+		osmo_stream_srv_write(conn);
+
+	return rc;
+}
+
+/*! \brief Create a Stream Server inside the specified link
+ *  \param[in] ctx talloc allocation context from which to allocate
+ *  \param[in] link Stream Server Link to which we belong
+ *  \param[in] fd system file descriptor of the new connection
+ *  \param[in] read_cb Call-back to call when the socket is readable
+ *  \param[in] closed_cb Call-back to call when the connection is closed
+ *  \param[in] data User data to save in the new Stream Server struct
+ *  \returns Stream Server in case of success; NULL on error */
+struct osmo_stream_srv *
+osmo_stream_srv_create(void *ctx, struct osmo_stream_srv_link *link,
+	int fd,
+	int (*read_cb)(struct osmo_stream_srv *conn),
+	int (*closed_cb)(struct osmo_stream_srv *conn), void *data)
+{
+	struct osmo_stream_srv *conn;
+
+	OSMO_ASSERT(link);
+
+	conn = talloc_zero(ctx, struct osmo_stream_srv);
+	if (conn == NULL)
+		return NULL;
+
+	conn->mode = OSMO_STREAM_MODE_OSMO_FD;
+	conn->srv = link;
+	osmo_fd_setup(&conn->ofd, fd, OSMO_FD_READ, osmo_stream_srv_cb, conn, 0);
+	conn->read_cb = read_cb;
+	conn->closed_cb = closed_cb;
+	conn->data = data;
+	INIT_LLIST_HEAD(&conn->tx_queue);
+
+	osmo_sock_get_name_buf(conn->sockname, sizeof(conn->sockname), fd);
+
+	if (osmo_fd_register(&conn->ofd) < 0) {
+		LOGSSRV(conn, LOGL_ERROR, "could not register FD\n");
+		talloc_free(conn);
+		return NULL;
+	}
+	return conn;
+}
+
+/*! \brief Create a Stream Server inside the specified link
+ *  \param[in] ctx talloc allocation context from which to allocate
+ *  \param[in] link Stream Server Link to which we belong
+ *  \param[in] fd system file descriptor of the new connection
+ *  \param[in] data User data to save in the new Stream Server struct
+ *  \returns Stream Server in case of success; NULL on error */
+struct osmo_stream_srv *
+osmo_stream_srv_create2(void *ctx, struct osmo_stream_srv_link *link, int fd, void *data)
+{
+	struct osmo_stream_srv *conn;
+
+	OSMO_ASSERT(link);
+
+	conn = talloc_zero(ctx, struct osmo_stream_srv);
+	if (conn == NULL)
+		return NULL;
+
+	conn->mode = OSMO_STREAM_MODE_OSMO_IO;
+	conn->srv = link;
+
+	osmo_sock_get_name_buf(conn->sockname, sizeof(conn->sockname), fd);
+
+	conn->iofd = osmo_iofd_setup(conn, fd, conn->sockname,
+				     OSMO_IO_FD_MODE_READ_WRITE, &srv_ioops, conn);
+	if (!conn->iofd) {
+		talloc_free(conn);
+		return NULL;
+	}
+	conn->data = data;
+
+	if (osmo_iofd_register(conn->iofd, fd) < 0) {
+		LOGSSRV(conn, LOGL_ERROR, "could not register FD %d\n", fd);
+		talloc_free(conn);
+		return NULL;
+	}
+
+	return conn;
+}
+
+/*! \brief Set a name on the srv object (used during logging)
+ *  \param[in] conn server whose name is to be set
+ *  \param[in] name the name to be set on conn
+ */
+void osmo_stream_srv_set_name(struct osmo_stream_srv *conn, const char *name)
+{
+	osmo_talloc_replace_string(conn, &conn->name, name);
+	if (conn->mode == OSMO_STREAM_MODE_OSMO_IO && conn->iofd)
+		osmo_iofd_set_name(conn->iofd, name);
+}
+
+/*! \brief Set the call-back function when data was read from the stream server socket
+ *  Only for osmo_stream_srv created with osmo_stream_srv_create2()
+ *  \param[in] conn Stream Server to modify
+ *  \param[in] read_cb Call-back function to be called when data was read */
+void osmo_stream_srv_set_read_cb(struct osmo_stream_srv *conn, int (*read_cb)(struct osmo_stream_srv *conn, struct msgb *msg))
+{
+	OSMO_ASSERT(conn && conn->mode == OSMO_STREAM_MODE_OSMO_IO);
+	conn->iofd_read_cb = read_cb;
+}
+
+/*! \brief Set the call-back function called when the stream server socket was closed
+ *  \param[in] conn Stream Server to modify
+ *  \param[in] closed_cb Call-back function to be called when the connection was closed */
+void osmo_stream_srv_set_closed_cb(struct osmo_stream_srv *conn, int (*closed_cb)(struct osmo_stream_srv *conn))
+{
+	OSMO_ASSERT(conn);
+	conn->closed_cb = closed_cb;
+}
+
+/*! \brief Prepare to send out all pending messages on the connection's Tx queue
+ *  and then automatically destroy the stream with osmo_stream_srv_destroy().
+ *  This function disables queuing of new messages on the connection and also
+ *  disables reception of new messages on the connection.
+ *  \param[in] conn Stream Server to modify */
+void osmo_stream_srv_set_flush_and_destroy(struct osmo_stream_srv *conn)
+{
+	conn->flags |= OSMO_STREAM_SRV_F_FLUSH_DESTROY;
+}
+
+/*! \brief Set application private data of the stream server
+ *  \param[in] conn Stream Server to modify
+ *  \param[in] data User-specific data (available in call-back functions) */
+void
+osmo_stream_srv_set_data(struct osmo_stream_srv *conn,
+				 void *data)
+{
+	conn->data = data;
+}
+
+/*! \brief Get application private data of the stream server
+ *  \param[in] conn Stream Server
+ *  \returns Application private data, as set by \ref osmo_stream_srv_set_data() */
+void *osmo_stream_srv_get_data(struct osmo_stream_srv *conn)
+{
+	return conn->data;
+}
+
+/*! \brief Get Osmocom File Descriptor of the stream server
+ *  \param[in] conn Stream Server
+ *  \returns Pointer to \ref osmo_fd */
+struct osmo_fd *
+osmo_stream_srv_get_ofd(struct osmo_stream_srv *conn)
+{
+	return &conn->ofd;
+}
+
+/*! \brief Get the master (Link) from a Stream Server
+ *  \param[in] conn Stream Server of which we want to know the Link
+ *  \returns Link through which the given Stream Server is established */
+struct osmo_stream_srv_link *osmo_stream_srv_get_master(struct osmo_stream_srv *conn)
+{
+	return conn->srv;
+}
+
+/*! \brief Destroy given Stream Server
+ *  This function closes the Stream Server socket, unregisters from
+ *  select loop, invokes the connection's closed_cb() callback to allow API
+ *  users to clean up any associated state they have for this connection,
+ *  and then de-allocates associated memory.
+ *  \param[in] conn Stream Server to be destroyed */
+void osmo_stream_srv_destroy(struct osmo_stream_srv *conn)
+{
+	switch (conn->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		osmo_fd_unregister(&conn->ofd);
+		close(conn->ofd.fd);
+		msgb_queue_free(&conn->tx_queue);
+		conn->ofd.fd = -1;
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		osmo_iofd_free(conn->iofd);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+	if (conn->closed_cb)
+		conn->closed_cb(conn);
+	talloc_free(conn);
+}
+
+/*! \brief Enqueue data to be sent via an Osmocom stream server
+ *  \param[in] conn Stream Server through which we want to send
+ *  \param[in] msg Message buffer to enqueue in transmit queue */
+void osmo_stream_srv_send(struct osmo_stream_srv *conn, struct msgb *msg)
+{
+	OSMO_ASSERT(conn);
+	OSMO_ASSERT(msg);
+	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY) {
+		LOGSSRV(conn, LOGL_DEBUG, "Connection is being flushed and closed; ignoring new outgoing message\n");
+		msgb_free(msg);
+		return;
+	}
+
+	switch (conn->mode) {
+	case OSMO_STREAM_MODE_OSMO_FD:
+		msgb_enqueue(&conn->tx_queue, msg);
+		osmo_fd_write_enable(&conn->ofd);
+		break;
+	case OSMO_STREAM_MODE_OSMO_IO:
+		osmo_iofd_write_msgb(conn->iofd, msg);
+		break;
+	default:
+		OSMO_ASSERT(false);
+	}
+}
+
+#ifdef HAVE_LIBSCTP
+static int _sctp_recvmsg_wrapper(int fd, struct msgb *msg)
+{
+	struct sctp_sndrcvinfo sinfo;
+	int flags = 0;
+	int ret;
+
+	ret = sctp_recvmsg(fd, msgb_data(msg), msgb_tailroom(msg),
+			NULL, NULL, &sinfo, &flags);
+	msgb_sctp_msg_flags(msg) = 0;
+	msgb_sctp_ppid(msg) = ntohl(sinfo.sinfo_ppid);
+	msgb_sctp_stream(msg) = sinfo.sinfo_stream;
+	if (flags & MSG_NOTIFICATION) {
+		union sctp_notification *notif = (union sctp_notification *)msgb_data(msg);
+		LOGP(DLINP, LOGL_DEBUG, "NOTIFICATION %u flags=0x%x\n", notif->sn_header.sn_type, notif->sn_header.sn_flags);
+		msgb_put(msg, sizeof(union sctp_notification));
+		msgb_sctp_msg_flags(msg) = OSMO_STREAM_SCTP_MSG_FLAGS_NOTIFICATION;
+		switch (notif->sn_header.sn_type) {
+		case SCTP_ASSOC_CHANGE:
+			LOGP(DLINP, LOGL_DEBUG, "===> ASSOC CHANGE:");
+			switch (notif->sn_assoc_change.sac_state) {
+			case SCTP_COMM_UP:
+				LOGPC(DLINP, LOGL_DEBUG, " UP\n");
+				break;
+			case SCTP_COMM_LOST:
+				LOGPC(DLINP, LOGL_DEBUG, " LOST\n");
+				/* Handle this like a regular disconnect */
+				return 0;
+			case SCTP_RESTART:
+				LOGPC(DLINP, LOGL_DEBUG, " RESTART\n");
+				break;
+			case SCTP_SHUTDOWN_COMP:
+				LOGPC(DLINP, LOGL_DEBUG, " SHUTDOWN COMP\n");
+				break;
+			case SCTP_CANT_STR_ASSOC:
+				LOGPC(DLINP, LOGL_DEBUG, " CANT STR ASSOC\n");
+				break;
+			}
+			break;
+		case SCTP_SEND_FAILED:
+			LOGP(DLINP, LOGL_DEBUG, "===> SEND FAILED\n");
+			break;
+		case SCTP_PEER_ADDR_CHANGE:
+			{
+			char addr_str[INET6_ADDRSTRLEN + 10];
+			struct sockaddr_storage sa = notif->sn_paddr_change.spc_aaddr;
+			osmo_sockaddr_to_str_buf(addr_str, sizeof(addr_str),
+						 (const struct osmo_sockaddr *)&sa);
+			LOGP(DLINP, LOGL_DEBUG, "===> PEER ADDR CHANGE: %s %s err=%s\n",
+			     addr_str, osmo_sctp_paddr_chg_str(notif->sn_paddr_change.spc_state),
+			     (notif->sn_paddr_change.spc_state == SCTP_ADDR_UNREACHABLE) ?
+				osmo_sctp_sn_error_str(notif->sn_paddr_change.spc_error) : "None");
+			}
+			break;
+		case SCTP_SHUTDOWN_EVENT:
+			LOGP(DLINP, LOGL_DEBUG, "===> SHUTDOWN EVT\n");
+			/* Handle this like a regular disconnect */
+			return 0;
+		}
+		return -EAGAIN;
+	}
+	return ret;
+}
+#endif
+
+/*! \brief Receive data via Osmocom stream server
+ *  \param[in] conn Stream Server from which to receive
+ *  \param msg pre-allocate message buffer to which received data is appended
+ *  \returns number of bytes read, negative on error.
+ *
+ *  If conn is an SCTP connection, additional specific considerations shall be taken:
+ *  - msg->cb is always filled with SCTP ppid, and SCTP stream values, see msgb_sctp_*() APIs.
+ *  - If an SCTP notification was received when reading from the SCTP socket,
+ *    msgb_sctp_msg_flags(msg) will contain bit flag
+ *    OSMO_STREAM_SCTP_MSG_FLAGS_NOTIFICATION set, and the msgb will
+ *    contain a "union sctp_notification" instead of user data. In this case the
+ *    return code will be either 0 (if conn is considered dead after the
+ *    notification) or -EAGAIN (if conn is considered still alive after the
+ *    notification) resembling the standard recv() API.
+ */
+int osmo_stream_srv_recv(struct osmo_stream_srv *conn, struct msgb *msg)
+{
+	int ret;
+	OSMO_ASSERT(conn);
+	OSMO_ASSERT(msg);
+
+	switch (conn->srv->sk_domain) {
+	case AF_UNIX:
+		ret = recv(conn->ofd.fd, msgb_data(msg), msgb_tailroom(msg), 0);
+		break;
+	case AF_INET:
+	case AF_INET6:
+	case AF_UNSPEC:
+		switch (conn->srv->proto) {
+#ifdef HAVE_LIBSCTP
+		case IPPROTO_SCTP:
+			ret = _sctp_recvmsg_wrapper(conn->ofd.fd, msg);
+			break;
+#endif
+		case IPPROTO_TCP:
+		default:
+			ret = recv(conn->ofd.fd, msgb_data(msg), msgb_tailroom(msg), 0);
+			break;
+		}
+		break;
+	default:
+		ret = -ENOTSUP;
+	}
+
+	if (ret < 0) {
+		if (errno == EPIPE || errno == ECONNRESET)
+			LOGSSRV(conn, LOGL_ERROR, "lost connection with client\n");
+		return ret;
+	} else if (ret == 0) {
+		LOGSSRV(conn, LOGL_ERROR, "connection closed with client\n");
+		return ret;
+	}
+	msgb_put(msg, ret);
+	LOGSSRV(conn, LOGL_DEBUG, "received %d bytes from client\n", ret);
+	return ret;
+}
+
+void osmo_stream_srv_clear_tx_queue(struct osmo_stream_srv *conn)
+{
+	msgb_queue_free(&conn->tx_queue);
+	osmo_fd_write_disable(&conn->ofd);
+	if (conn->flags & OSMO_STREAM_SRV_F_FLUSH_DESTROY)
+		osmo_stream_srv_destroy(conn);
+}
+
+/*! @} */