Add osmo_stream_{cli,srv_link}_set_nodelay() function

Using this function, the user can configure if sockets related to the
respective stream client or server should have the NODELAY socket
option set in order to avoid Nagle algorithm or related algorithms
that may introduce packet delay on the transmitter side.

Change-Id: Ibeb9ba227bab18f7f4f16518c0022c4f003cc8e9

1 files changed, 60 insertions, 0 deletions

diff --git a/src/stream.c b/src/stream.c
index f5ead17..3bc36a3 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -9,6 +9,7 @@
 #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>
@@ -63,6 +64,27 @@ static int sctp_sock_activate_events(int fd)
 #endif
 }
 
+static int setsockopt_nodelay(int fd, int proto, int on)
+{
+	int rc;
+
+	switch (proto) {
+	case IPPROTO_SCTP:
+		rc = setsockopt(fd, IPPROTO_SCTP, SCTP_NODELAY, &on, sizeof(on));
+		break;
+	case IPPROTO_TCP:
+		rc = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
+		break;
+	default:
+		rc = -1;
+		LOGP(DLINP, LOGL_ERROR, "Unknown protocol %u, cannot set NODELAY\n",
+		     proto);
+		break;
+	}
+	return rc;
+}
+
+
 /*
  * Client side.
  */
@@ -75,6 +97,7 @@ enum osmo_stream_cli_state {
 };
 
 #define OSMO_STREAM_CLI_F_RECONF	(1 << 0)
+#define OSMO_STREAM_CLI_F_NODELAY	(1 << 1)
 
 struct osmo_stream_cli {
 	struct osmo_fd			ofd;
@@ -400,6 +423,9 @@ int osmo_stream_cli_open2(struct osmo_stream_cli *cli, int reconnect)
 		return ret;
 	}
 
+	if (cli->flags & OSMO_STREAM_CLI_F_NODELAY)
+		setsockopt_nodelay(cli->ofd.fd, cli->proto, 1);
+
 	cli->ofd.fd = ret;
 	if (osmo_fd_register(&cli->ofd) < 0) {
 		close(ret);
@@ -409,6 +435,21 @@ int osmo_stream_cli_open2(struct osmo_stream_cli *cli, int reconnect)
 	return 0;
 }
 
+/*! \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
  *  \param[in] cli Stream Client to connect */
@@ -473,6 +514,7 @@ int osmo_stream_cli_recv(struct osmo_stream_cli *cli, struct msgb *msg)
  */
 
 #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;
@@ -503,6 +545,9 @@ static int osmo_stream_srv_fd_cb(struct osmo_fd *ofd, unsigned int what)
 	if (link->proto == IPPROTO_SCTP)
 		sctp_sock_activate_events(ret);
 
+	if (link->flags & OSMO_STREAM_SRV_F_NODELAY)
+		setsockopt_nodelay(ret, link->proto, 1);
+
 	if (link->accept_cb)
 		link->accept_cb(link, ret);
 
@@ -532,6 +577,21 @@ struct osmo_stream_srv_link *osmo_stream_srv_link_create(void *ctx)
 	return link;
 }
 
+/*! \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