src: add generic channel infrastructure and A-bis IPA server support

This patch adds the generic channel infrastructure that allows to
create channel of different types. Each channel has their own
configuration functions.

  struct osmo_chan *chan;
  chan = osmo_chan_create(tall_example, CHAN_ABIS_IPA_SERVER);
  ...

  /* specific configuration functions per supported channel. */
  osmo_chan_abis_ipa_server_set_cb_signalmsg(chan, signal_msg_cb);
  osmo_chan_abis_ipa_unit_add(chan, 1801, 0);

  /* open channel. */
  osmo_chan_open(chan);

The input path requires a callback to be registered. The output path
is handled through:

  int osmo_chan_enqueue(struct osmo_chan *c, struct msgb *msg);

The msg->dst must be set (it can be taken from the original message
to route one reply).

This patch also adds A-bis IPA server support. It has been tested with
e1inp_ipa_bsc_test available in libosmo-abis.

6 files changed, 793 insertions, 1 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index c501a57..06def6c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -6,8 +6,13 @@ INCLUDES = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)
 AM_CFLAGS= -fPIC -Wall $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(COVERAGE_CFLAGS)
 AM_LDFLAGS = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) $(COVERAGE_LDFLAGS)
 
+SUBDIRS = channel
+
 lib_LTLIBRARIES = libosmonetif.la
 
-libosmonetif_la_SOURCES = datagram.c		\
+libosmonetif_la_LIBADD = channel/libosmonetif-channel.la
+
+libosmonetif_la_SOURCES = channel.c		\
+			  datagram.c		\
 			  ipa.c			\
 			  stream.c
diff --git a/src/channel.c b/src/channel.c
new file mode 100644
index 0000000..5aedd83
--- /dev/null
+++ b/src/channel.c
@@ -0,0 +1,52 @@
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/msgb.h>
+
+#include <osmocom/netif/channel.h>
+
+extern struct osmo_chan_type chan_abis_ipa_server;
+
+static struct osmo_chan_type *chan_type[CHAN_MAX] = {
+	[CHAN_ABIS_IPA_SERVER]	= &chan_abis_ipa_server,
+};
+
+struct osmo_chan *osmo_chan_create(void *ctx, int type_id)
+{
+	struct osmo_chan *c;
+
+	if (type_id >= CHAN_MAX)
+		return NULL;
+
+	c = talloc_zero_size(ctx, sizeof(struct osmo_chan) +
+			     chan_type[type_id]->datasiz);
+	if (c == NULL)
+		return NULL;
+
+	c->ops = chan_type[type_id];
+
+	if (c->ops->create(c) < 0) {
+		talloc_free(c);
+		return NULL;
+	}
+	return c;
+}
+
+void osmo_chan_destroy(struct osmo_chan *c)
+{
+	c->ops->destroy(c);
+	talloc_free(c);
+}
+
+int osmo_chan_open(struct osmo_chan *c)
+{
+	return c->ops->open(c);
+}
+
+void osmo_chan_close(struct osmo_chan *c)
+{
+	c->ops->close(c);
+}
+
+int osmo_chan_enqueue(struct osmo_chan *c, struct msgb *msg)
+{
+	return c->ops->enqueue(c, msg);
+}
diff --git a/src/channel/Makefile.am b/src/channel/Makefile.am
new file mode 100644
index 0000000..674cacf
--- /dev/null
+++ b/src/channel/Makefile.am
@@ -0,0 +1,7 @@
+INCLUDES = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)
+AM_CFLAGS= -fPIC -Wall $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(COVERAGE_CFLAGS)
+AM_LDFLAGS = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) $(COVERAGE_LDFLAGS)
+
+noinst_LTLIBRARIES = libosmonetif-channel.la
+
+libosmonetif_channel_la_SOURCES = abis_ipa_server.c
diff --git a/src/channel/abis_ipa_server.c b/src/channel/abis_ipa_server.c
new file mode 100644
index 0000000..bc6bacc
--- /dev/null
+++ b/src/channel/abis_ipa_server.c
@@ -0,0 +1,517 @@
+#include <stdlib.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <sys/socket.h>
+#include <errno.h>
+
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+
+#include <osmocom/gsm/tlv.h>
+
+#include <osmocom/netif/channel.h>
+#include <osmocom/netif/stream.h>
+#include <osmocom/netif/ipa.h>
+
+/* default IPA server ports. */
+#define IPA_TCP_PORT_OML	3002
+#define IPA_TCP_PORT_RSL	3003
+
+static void *abis_ipa_server_tall;
+
+static int oml_accept_cb(struct osmo_stream_server_link *server, int fd);
+static int rsl_accept_cb(struct osmo_stream_server_link *server, int fd);
+
+struct chan_abis_ipa_server {
+	struct osmo_stream_server_link *oml;
+	struct osmo_stream_server_link *rsl;
+
+	struct llist_head bts_list;
+	struct llist_head conn_list;
+
+	void (*signal_msg)(struct msgb *msg, int type);
+};
+
+struct ipa_unit {
+	struct llist_head	head;
+	uint16_t		site_id;
+	uint16_t		bts_id;
+};
+
+struct ipa_conn {
+	struct llist_head		head;
+	struct ipa_unit 		*unit;
+	struct osmo_chan		*chan;
+	struct osmo_stream_server_conn	*oml;
+	struct osmo_stream_server_conn	*rsl;
+};
+
+static int chan_abis_ipa_server_create(struct osmo_chan *chan)
+{
+	struct chan_abis_ipa_server *c =
+		(struct chan_abis_ipa_server *)chan->data;
+	struct ipa_conn *ipa_conn;
+
+	/* dummy connection. */
+	ipa_conn = talloc_zero(chan->ctx, struct ipa_conn);
+	if (ipa_conn == NULL)
+		goto err;
+
+	ipa_conn->chan = chan;
+
+	c->oml = osmo_stream_server_link_create(abis_ipa_server_tall);
+	if (c->oml == NULL)
+		goto err_oml;
+
+	/* default address and port for OML. */
+	osmo_stream_server_link_set_addr(c->oml, "0.0.0.0");
+	osmo_stream_server_link_set_port(c->oml, IPA_TCP_PORT_OML);
+	osmo_stream_server_link_set_accept_cb(c->oml, oml_accept_cb);
+	osmo_stream_server_link_set_data(c->oml, ipa_conn);
+
+	c->rsl = osmo_stream_server_link_create(abis_ipa_server_tall);
+	if (c->rsl == NULL)
+		goto err_rsl;
+
+	/* default address and port for RSL. */
+	osmo_stream_server_link_set_addr(c->rsl, "0.0.0.0");
+	osmo_stream_server_link_set_port(c->rsl, IPA_TCP_PORT_RSL);
+	osmo_stream_server_link_set_accept_cb(c->rsl, rsl_accept_cb);
+	osmo_stream_server_link_set_data(c->rsl, ipa_conn);
+
+	INIT_LLIST_HEAD(&c->bts_list);
+	INIT_LLIST_HEAD(&c->conn_list);
+
+	return 0;
+err_rsl:
+	osmo_stream_server_link_destroy(c->oml);
+err_oml:
+	talloc_free(ipa_conn);
+err:
+	return -1;
+}
+
+static void chan_abis_ipa_server_destroy(struct osmo_chan *chan)
+{
+	struct chan_abis_ipa_server *c =
+		(struct chan_abis_ipa_server *)chan->data;
+	struct ipa_conn *ipa_conn =
+		osmo_stream_server_link_get_data(c->oml);
+
+	talloc_free(ipa_conn);
+	talloc_free(c->rsl);
+	talloc_free(c->oml);
+}
+
+static int chan_abis_ipa_server_open(struct osmo_chan *chan)
+{
+	struct chan_abis_ipa_server *c =
+		(struct chan_abis_ipa_server *)chan->data;
+	struct osmo_fd *ofd;
+	int ret, on = 1;
+
+	if (osmo_stream_server_link_open(c->oml) < 0)
+		goto err;
+
+	ofd = osmo_stream_server_link_get_ofd(c->oml);
+	ret = setsockopt(ofd->fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
+	if (ret < 0)
+		goto err_oml;
+
+	if (osmo_stream_server_link_open(c->rsl) < 0)
+		goto err_oml;
+
+	ofd = osmo_stream_server_link_get_ofd(c->rsl);
+	ret = setsockopt(ofd->fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
+	if (ret < 0)
+		goto err_rsl;
+
+	return 0;
+
+err_rsl:
+	osmo_stream_server_link_close(c->rsl);
+err_oml:
+	osmo_stream_server_link_close(c->oml);
+err:
+	return -1;
+}
+
+static void chan_abis_ipa_server_close(struct osmo_chan *chan)
+{
+	struct chan_abis_ipa_server *c =
+		(struct chan_abis_ipa_server *)chan->data;
+
+	osmo_stream_server_link_close(c->oml);
+	osmo_stream_server_link_close(c->rsl);
+}
+
+static int chan_abis_ipa_server_enqueue(struct osmo_chan *c, struct msgb *msg)
+{
+	osmo_stream_server_conn_send(msg->dst, msg);
+	return 0;
+}
+
+void
+osmo_chan_abis_ipa_server_set_oml_addr(struct osmo_chan *c, const char *addr)
+{
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)&c->data;
+
+	osmo_stream_server_link_set_addr(s->oml, addr);
+}
+
+void
+osmo_chan_abis_ipa_server_set_oml_port(struct osmo_chan *c, uint16_t port)
+{
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)&c->data;
+
+	osmo_stream_server_link_set_port(s->oml, port);
+}
+
+void
+osmo_chan_abis_ipa_server_set_rsl_addr(struct osmo_chan *c, const char *addr)
+{
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)&c->data;
+
+	osmo_stream_server_link_set_addr(s->rsl, addr);
+}
+
+void
+osmo_chan_abis_ipa_server_set_rsl_port(struct osmo_chan *c, uint16_t port)
+{
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)&c->data;
+
+	osmo_stream_server_link_set_port(s->rsl, port);
+}
+
+void
+osmo_chan_abis_ipa_server_set_cb_signalmsg(struct osmo_chan *c,
+	void (*signal_msg)(struct msgb *msg, int type))
+{
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)&c->data;
+
+	s->signal_msg = signal_msg;
+}
+
+static int oml_read_cb(struct osmo_stream_server_conn *conn);
+
+static int oml_accept_cb(struct osmo_stream_server_link *server, int fd)
+{
+	struct osmo_stream_server_conn *conn;
+	struct ipa_conn *ipa_conn = osmo_stream_server_link_get_data(server);
+	struct osmo_fd *ofd;
+
+	conn = osmo_stream_server_conn_create(abis_ipa_server_tall,
+					      server, fd,
+					      oml_read_cb, NULL, ipa_conn);
+	if (conn == NULL) {
+		LOGP(DLINP, LOGL_ERROR, "error while creating connection\n");
+		return -1;
+	}
+
+	ofd = osmo_stream_server_conn_get_ofd(conn);
+
+	/* XXX: better use chan_abis_ipa_server_enqueue. */
+	ipaccess_send_id_req(ofd->fd);
+
+	return 0;
+}
+
+static int rsl_read_cb(struct osmo_stream_server_conn *conn);
+
+static int rsl_accept_cb(struct osmo_stream_server_link *server, int fd)
+{
+	struct osmo_stream_server_conn *conn;
+	struct ipa_conn *ipa_conn = osmo_stream_server_link_get_data(server);
+	struct osmo_fd *ofd;
+
+	conn = osmo_stream_server_conn_create(abis_ipa_server_tall,
+					      server, fd,
+					      rsl_read_cb, NULL, ipa_conn);
+	if (conn == NULL) {
+		LOGP(DLINP, LOGL_ERROR, "error while creating connection\n");
+		return -1;
+	}
+
+	ofd = osmo_stream_server_conn_get_ofd(conn);
+
+	/* XXX: better use chan_abis_ipa_server_enqueue. */
+	ipaccess_send_id_req(ofd->fd);
+
+	return 0;
+}
+
+static struct ipa_unit *
+osmo_ipa_unit_find(struct osmo_chan *c, uint16_t site_id, uint16_t bts_id)
+{
+	struct ipa_unit *unit;
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)c->data;
+
+	llist_for_each_entry(unit, &s->bts_list, head) {
+		if (unit->site_id == site_id &&
+		    unit->bts_id == bts_id)
+			return unit;
+	}
+	return NULL;
+}
+
+int
+osmo_chan_abis_ipa_unit_add(struct osmo_chan *c,
+			    uint16_t site_id, uint16_t bts_id)
+{
+	struct ipa_unit *unit;
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)c->data;
+
+	unit = talloc_zero(c->ctx, struct ipa_unit);
+	if (unit == NULL)
+		return -1;
+
+	unit->site_id = site_id;
+	unit->bts_id = bts_id;
+	llist_add(&unit->head, &s->bts_list);
+
+	return 0;
+}
+
+static struct ipa_conn *
+osmo_ipa_conn_alloc(struct ipa_unit *unit, struct osmo_chan *chan)
+{
+	struct ipa_conn *ipa_conn;
+
+	ipa_conn = talloc_zero(chan->ctx, struct ipa_conn);
+	if (ipa_conn == NULL)
+		return NULL;
+
+	ipa_conn->unit = unit;
+	ipa_conn->chan = chan;
+
+	return ipa_conn;
+}
+
+static struct ipa_conn *
+osmo_ipa_conn_add(struct ipa_unit *unit, struct osmo_chan *chan)
+{
+	struct ipa_conn *ipa_conn;
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)chan->data;
+
+	ipa_conn = osmo_ipa_conn_alloc(unit, chan);
+	if (ipa_conn == NULL)
+		return NULL;
+
+	llist_add(&ipa_conn->head, &s->conn_list);
+
+	return ipa_conn;
+}
+
+static struct ipa_conn *
+osmo_ipa_conn_find(struct ipa_unit *unit, struct osmo_chan *chan)
+{
+	struct ipa_conn *ipa_conn;
+	struct chan_abis_ipa_server *s =
+		(struct chan_abis_ipa_server *)chan->data;
+
+	llist_for_each_entry(ipa_conn, &s->conn_list, head) {
+		if (ipa_conn->unit->site_id == unit->site_id &&
+		    ipa_conn->unit->bts_id == unit->bts_id) {
+			return ipa_conn;
+		}
+	}
+	return NULL;
+}
+
+static void
+osmo_ipa_conn_put(struct ipa_conn *ipa_conn)
+{
+	llist_del(&ipa_conn->head);
+	osmo_stream_server_conn_destroy(ipa_conn->oml);
+	osmo_stream_server_conn_destroy(ipa_conn->rsl);
+	talloc_free(ipa_conn);
+}
+
+static int
+abis_ipa_server_rcvmsg(struct osmo_chan *c,
+		       struct osmo_stream_server_conn *conn,
+		       struct msgb *msg, int type)
+{
+	struct tlv_parsed tlvp;
+	uint8_t msg_type = *(msg->l2h);
+	struct osmo_fd *ofd = osmo_stream_server_conn_get_ofd(conn);
+	char *unitid;
+	int len, ret;
+
+	/* Handle IPA PING, PONG and ID_ACK messages. */
+	if (osmo_ipa_rcvmsg_base(msg, ofd))
+		return 0;
+
+	if (msg_type == IPAC_MSGT_ID_RESP) {
+		struct ipa_unit *unit;
+		struct ipa_conn *ipa_conn;
+		struct ipaccess_unit unit_data;
+
+		DEBUGP(DLMI, "ID_RESP\n");
+		/* parse tags, search for Unit ID */
+		ret = osmo_ipa_idtag_parse(&tlvp, (uint8_t *)msg->l2h + 2,
+						msgb_l2len(msg)-2);
+		DEBUGP(DLMI, "\n");
+		if (ret < 0) {
+			LOGP(DLINP, LOGL_ERROR, "IPA response message "
+				"with malformed TLVs\n");
+			ret = -EINVAL;
+			goto err;
+		}
+		if (!TLVP_PRESENT(&tlvp, IPAC_IDTAG_UNIT)) {
+			LOGP(DLINP, LOGL_ERROR, "IPA response message "
+				"without unit ID\n");
+			ret = -EINVAL;
+			goto err;
+
+		}
+		len = TLVP_LEN(&tlvp, IPAC_IDTAG_UNIT);
+		if (len < 1) {
+			LOGP(DLINP, LOGL_ERROR, "IPA response message "
+				"with too small unit ID\n");
+			ret = -EINVAL;
+			goto err;
+		}
+		unitid = (char *) TLVP_VAL(&tlvp, IPAC_IDTAG_UNIT);
+		unitid[len - 1] = '\0';
+		osmo_ipa_parse_unitid(unitid, &unit_data);
+
+		unit = osmo_ipa_unit_find(c, unit_data.site_id,
+					  unit_data.bts_id);
+		if (unit == NULL) {
+			LOGP(DLINP, LOGL_ERROR, "Unable to find BTS "
+				"configuration for %u/%u/%u, disconnecting\n",
+				unit_data.site_id, unit_data.bts_id,
+				unit_data.trx_id);
+			return 0;
+		}
+		DEBUGP(DLINP, "Identified BTS %u/%u/%u\n",
+			unit_data.site_id, unit_data.bts_id,
+			unit_data.trx_id);
+
+		ipa_conn = osmo_ipa_conn_find(unit, c);
+		if (ipa_conn == NULL) {
+			ipa_conn = osmo_ipa_conn_add(unit, c);
+			if (ipa_conn == NULL) {
+				LOGP(DLINP, LOGL_ERROR, "OOM\n");
+				return 0;
+			}
+			osmo_stream_server_conn_set_data(conn, ipa_conn);
+		}
+
+		if (type == CHAN_SIGN_OML) {
+			if (ipa_conn->oml) {
+				/* link already exists, kill it. */
+				osmo_stream_server_conn_destroy(ipa_conn->oml);
+				return 0;
+			}
+			ipa_conn->oml = conn;
+		} else if (type == CHAN_SIGN_RSL) {
+			if (!ipa_conn->oml) {
+				/* no OML link? Restart from scratch. */
+				osmo_ipa_conn_put(ipa_conn);
+				return 0;
+			}
+			if (ipa_conn->rsl) {
+				/* RSL link already exists, kill it. */
+				osmo_stream_server_conn_destroy(ipa_conn->rsl);
+				return 0;
+			}
+			ipa_conn->rsl = conn;
+		}
+		ret = 0;
+	} else {
+		LOGP(DLINP, LOGL_ERROR, "Unknown IPA message type\n");
+		ret = -EINVAL;
+	}
+err:
+	return ret;
+}
+
+static int read_cb(struct osmo_stream_server_conn *conn, int type)
+{
+	int ret;
+	struct msgb *msg;
+	struct osmo_fd *ofd = osmo_stream_server_conn_get_ofd(conn);
+	struct ipa_conn *ipa_conn = osmo_stream_server_conn_get_data(conn);
+	struct chan_abis_ipa_server *s;
+	struct ipa_head *hh;
+
+	LOGP(DLINP, LOGL_DEBUG, "received message from stream\n");
+
+	msg = osmo_ipa_msg_alloc(0);
+	if (msg == NULL) {
+		LOGP(DLINP, LOGL_ERROR, "cannot allocate message\n");
+		return 0;
+	}
+	ret = osmo_ipa_msg_recv(ofd->fd, msg);
+	if (ret < 0) {
+		LOGP(DLINP, LOGL_ERROR, "cannot receive message\n");
+		msgb_free(msg);
+		/* not the dummy connection, release it. */
+		if (ipa_conn->unit != NULL)
+			osmo_ipa_conn_put(ipa_conn);
+		return 0;
+	} else if (ret == 0) {
+		/* link has vanished, dead socket. */
+		LOGP(DLINP, LOGL_ERROR, "closed connection\n");
+		msgb_free(msg);
+		if (ipa_conn->unit != NULL)
+			osmo_ipa_conn_put(ipa_conn);
+		return 0;
+	}
+
+	hh = (struct ipa_head *) msg->data;
+	if (hh->proto == IPAC_PROTO_IPACCESS) {
+		abis_ipa_server_rcvmsg(ipa_conn->chan, conn, msg, type);
+		msgb_free(msg);
+		return -EIO;
+	}
+
+	ipa_conn = osmo_stream_server_conn_get_data(conn);
+	if (ipa_conn == NULL) {
+		LOGP(DLINP, LOGL_ERROR, "no matching signalling link\n");
+		msgb_free(msg);
+		return -EIO;
+	}
+	if (hh->proto != IPAC_PROTO_OML && hh->proto != IPAC_PROTO_RSL) {
+		LOGP(DLINP, LOGL_ERROR, "wrong protocol\n");
+		return -EIO;
+	}
+	msg->dst = ipa_conn;
+
+	s = (struct chan_abis_ipa_server *)ipa_conn->chan->data;
+	s->signal_msg(msg, type);
+
+	return 0;
+}
+
+static int oml_read_cb(struct osmo_stream_server_conn *conn)
+{
+	return read_cb(conn, CHAN_SIGN_OML);
+}
+
+static int rsl_read_cb(struct osmo_stream_server_conn *conn)
+{
+	return read_cb(conn, CHAN_SIGN_RSL);
+}
+
+struct osmo_chan_type chan_abis_ipa_server = {
+	.type		= CHAN_ABIS_IPA_SERVER,
+	.datasiz	= sizeof(struct chan_abis_ipa_server),
+	.create		= chan_abis_ipa_server_create,
+	.destroy	= chan_abis_ipa_server_destroy,
+	.open		= chan_abis_ipa_server_open,
+	.close		= chan_abis_ipa_server_close,
+	.enqueue	= chan_abis_ipa_server_enqueue,
+};
diff --git a/src/ipa.c b/src/ipa.c
index 27df56f..a4c3a5f 100644
--- a/src/ipa.c
+++ b/src/ipa.c
@@ -1,13 +1,69 @@
 #include <stdlib.h>
 #include <arpa/inet.h>
+#include <string.h>
+#include <unistd.h>
 #include <errno.h>
 
+#include <osmocom/core/linuxlist.h>
 #include <osmocom/core/logging.h>
 #include <osmocom/core/msgb.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/talloc.h>
+
+#include <osmocom/gsm/tlv.h>
+
+#include <osmocom/netif/channel.h>
 #include <osmocom/netif/ipa.h>
 
 #define IPA_ALLOC_SIZE 1200
 
+/*
+ * Common propietary IPA messages:
+ *	- PONG: in reply to PING.
+ *	- ID_REQUEST: first messages once OML has been established.
+ *	- ID_ACK: in reply to ID_ACK.
+ */
+const uint8_t ipa_pong_msg[] = {
+	0, 1, IPAC_PROTO_IPACCESS, IPAC_MSGT_PONG
+};
+
+const uint8_t ipa_id_ack_msg[] = {
+	0, 1, IPAC_PROTO_IPACCESS, IPAC_MSGT_ID_ACK
+};
+
+const uint8_t ipa_id_req_msg[] = {
+	0, 17, IPAC_PROTO_IPACCESS, IPAC_MSGT_ID_GET,
+	0x01, IPAC_IDTAG_UNIT,
+	0x01, IPAC_IDTAG_MACADDR,
+	0x01, IPAC_IDTAG_LOCATION1,
+	0x01, IPAC_IDTAG_LOCATION2,
+	0x01, IPAC_IDTAG_EQUIPVERS,
+	0x01, IPAC_IDTAG_SWVERSION,
+	0x01, IPAC_IDTAG_UNITNAME,
+	0x01, IPAC_IDTAG_SERNR,
+};
+
+static const char *idtag_names[] = {
+	[IPAC_IDTAG_SERNR]	= "Serial_Number",
+	[IPAC_IDTAG_UNITNAME]	= "Unit_Name",
+	[IPAC_IDTAG_LOCATION1]	= "Location_1",
+	[IPAC_IDTAG_LOCATION2]	= "Location_2",
+	[IPAC_IDTAG_EQUIPVERS]	= "Equipment_Version",
+	[IPAC_IDTAG_SWVERSION]	= "Software_Version",
+	[IPAC_IDTAG_IPADDR]	= "IP_Address",
+	[IPAC_IDTAG_MACADDR]	= "MAC_Address",
+	[IPAC_IDTAG_UNIT]	= "Unit_ID",
+};
+
+const char *ipaccess_idtag_name(uint8_t tag)
+{
+	if (tag >= ARRAY_SIZE(idtag_names))
+		return "unknown";
+
+	return idtag_names[tag];
+}
+
+
 struct msgb *osmo_ipa_msg_alloc(int headroom)
 {
 	struct msgb *msg;
@@ -68,3 +124,151 @@ int osmo_ipa_msg_recv(int fd, struct msgb *msg)
 	msgb_put(msg, ret);
 	return ret;
 }
+
+int osmo_ipa_idtag_parse(struct tlv_parsed *dec, unsigned char *buf, int len)
+{
+	uint8_t t_len;
+	uint8_t t_tag;
+	uint8_t *cur = buf;
+
+	memset(dec, 0, sizeof(*dec));
+
+	while (len >= 2) {
+		len -= 2;
+		t_len = *cur++;
+		t_tag = *cur++;
+
+		if (t_len > len + 1) {
+			LOGP(DLMI, LOGL_ERROR, "The tag does not fit: %d\n", t_len);
+			return -EINVAL;
+		}
+
+		DEBUGPC(DLMI, "%s='%s' ", ipaccess_idtag_name(t_tag), cur);
+
+		dec->lv[t_tag].len = t_len;
+		dec->lv[t_tag].val = cur;
+
+		cur += t_len;
+		len -= t_len;
+	}
+	return 0;
+}
+
+int osmo_ipa_parse_unitid(const char *str, struct ipaccess_unit *unit_data)
+{
+	unsigned long ul;
+	char *endptr;
+	const char *nptr;
+
+	nptr = str;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->site_id = ul & 0xffff;
+
+	if (*endptr++ != '/')
+		return -EINVAL;
+
+	nptr = endptr;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->bts_id = ul & 0xffff;
+	if (*endptr++ != '/')
+		return -EINVAL;
+
+	nptr = endptr;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->trx_id = ul & 0xffff;
+
+	return 0;
+}
+
+static int ipaccess_send(int fd, const void *msg, size_t msglen)
+{
+	int ret;
+
+	ret = write(fd, msg, msglen);
+	if (ret < 0)
+		return ret;
+	if (ret < msglen) {
+		LOGP(DLINP, LOGL_ERROR, "ipaccess_send: short write\n");
+		return -EIO;
+	}
+	return ret;
+}
+
+int ipaccess_send_pong(int fd)
+{
+	return ipaccess_send(fd, ipa_pong_msg, sizeof(ipa_pong_msg));
+}
+
+int ipaccess_send_id_ack(int fd)
+{
+	return ipaccess_send(fd, ipa_id_ack_msg, sizeof(ipa_id_ack_msg));
+}
+
+int ipaccess_send_id_req(int fd)
+{
+	return ipaccess_send(fd, ipa_id_req_msg, sizeof(ipa_id_req_msg));
+}
+
+/* base handling of the ip.access protocol */
+int osmo_ipa_rcvmsg_base(struct msgb *msg, struct osmo_fd *bfd)
+{
+	int ipa_ccm = 0;
+	uint8_t msg_type = *(msg->l2h);
+	int ret = 0;
+
+	switch (msg_type) {
+	case IPAC_MSGT_PING:
+		ipa_ccm = 1;
+		ret = ipaccess_send_pong(bfd->fd);
+		break;
+	case IPAC_MSGT_PONG:
+		DEBUGP(DLMI, "PONG!\n");
+		ipa_ccm = 1;
+		break;
+	case IPAC_MSGT_ID_ACK:
+		DEBUGP(DLMI, "ID_ACK? -> ACK!\n");
+		ipa_ccm = 1;
+		ret = ipaccess_send_id_ack(bfd->fd);
+		break;
+	}
+	return ipa_ccm;
+}
+
+int ipaccess_parse_unitid(const char *str, struct ipaccess_unit *unit_data)
+{
+	unsigned long ul;
+	char *endptr;
+	const char *nptr;
+
+	nptr = str;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->site_id = ul & 0xffff;
+
+	if (*endptr++ != '/')
+		return -EINVAL;
+
+	nptr = endptr;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->bts_id = ul & 0xffff;
+
+	if (*endptr++ != '/')
+		return -EINVAL;
+
+	nptr = endptr;
+	ul = strtoul(nptr, &endptr, 10);
+	if (endptr <= nptr)
+		return -EINVAL;
+	unit_data->trx_id = ul & 0xffff;
+
+	return 0;
+}
diff --git a/src/stream.c b/src/stream.c
index c87f999..b32f9b5 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -510,6 +510,13 @@ osmo_stream_server_conn_create(void *ctx, struct osmo_stream_server_link *link,
 	return conn;
 }
 
+void
+osmo_stream_server_conn_set_data(struct osmo_stream_server_conn *conn,
+				 void *data)
+{
+	conn->data = data;
+}
+
 void *osmo_stream_server_conn_get_data(struct osmo_stream_server_conn *link)
 {
 	return link->data;