net: sockets: Monitor TCP transmit state with semaphore

Utilize the TCP semaphore monitoring transmit status at the socket
layer. This allows to resume transfer as soon as possible instead of
waiting blindly.

Signed-off-by: Robert Lubos <[email protected]>

Author: rlubos

subsys/net/lib/sockets/sockets.c

@@ -28,6 +28,7 @@ LOG_MODULE_REGISTER(net_sock, CONFIG_NET_SOCKETS_LOG_LEVEL);
 #include "../../ip/net_stats.h"
 
 #include "sockets_internal.h"
+#include "../../ip/tcp_internal.h"
 
 #define SET_ERRNO(x) \
 	{ int _err = x; if (_err < 0) { errno = -_err; return -1; } }
@@ -653,6 +654,65 @@ static inline int z_vrfy_zsock_accept(int sock, struct sockaddr *addr,
 #define WAIT_BUFS K_MSEC(100)
 #define MAX_WAIT_BUFS K_SECONDS(10)
 
+static int send_check_and_wait(struct net_context *ctx, int status,
+			       uint64_t buf_timeout, k_timeout_t timeout)
+{
+	int64_t remaining;
+
+	if (!K_TIMEOUT_EQ(timeout, K_FOREVER)) {
+		goto out;
+	}
+
+	if (status != -ENOBUFS && status != -EAGAIN) {
+		goto out;
+	}
+
+	/* If we cannot get any buffers in reasonable
+	 * amount of time, then do not wait forever as
+	 * there might be some bigger issue.
+	 * If we get -EAGAIN and cannot recover, then
+	 * it means that the sending window is blocked
+	 * and we just cannot send anything.
+	 */
+	remaining = buf_timeout - sys_clock_tick_get();
+	if (remaining <= 0) {
+		if (status == -ENOBUFS) {
+			status = -ENOMEM;
+		} else {
+			status = -ENOBUFS;
+		}
+
+		goto out;
+	}
+
+	if (status == -ENOBUFS) {
+		/* We can monitor net_pkt/net_buf avaialbility, so just wait. */
+		k_sleep(WAIT_BUFS);
+	}
+
+	if (status == -EAGAIN) {
+		if (IS_ENABLED(CONFIG_NET_NATIVE_TCP) &&
+		    net_context_get_type(ctx) == SOCK_STREAM) {
+			struct k_poll_event event;
+
+			k_poll_event_init(&event,
+					  K_POLL_TYPE_SEM_AVAILABLE,
+					  K_POLL_MODE_NOTIFY_ONLY,
+					  net_tcp_tx_sem_get(ctx));
+
+			k_poll(&event, 1, WAIT_BUFS);
+		} else {
+			k_sleep(WAIT_BUFS);
+		}
+	}
+
+	return 0;
+
+out:
+	errno = -status;
+	return -1;
+}
+
 ssize_t zsock_sendto_ctx(struct net_context *ctx, const void *buf, size_t len,
 			 int flags,
 			 const struct sockaddr *dest_addr, socklen_t addrlen)
@@ -689,33 +749,13 @@ ssize_t zsock_sendto_ctx(struct net_context *ctx, const void *buf, size_t len,
 		}
 
 		if (status < 0) {
-			if (((status == -ENOBUFS) || (status == -EAGAIN)) &&
-			    K_TIMEOUT_EQ(timeout, K_FOREVER)) {
-				/* If we cannot get any buffers in reasonable
-				 * amount of time, then do not wait forever as
-				 * there might be some bigger issue.
-				 * If we get -EAGAIN and cannot recover, then
-				 * it means that the sending window is blocked
-				 * and we just cannot send anything.
-				 */
-				int64_t remaining = buf_timeout - sys_clock_tick_get();
-
-				if (remaining <= 0) {
-					if (status == -ENOBUFS) {
-						errno = ENOMEM;
-					} else {
-						errno = ENOBUFS;
-					}
-
-					return -1;
-				}
-
-				k_sleep(WAIT_BUFS);
-				continue;
-			} else {
-				errno = -status;
-				return -1;
+			status = send_check_and_wait(ctx, status, buf_timeout,
+						     timeout);
+			if (status < 0) {
+				return status;
 			}
+
+			continue;
 		}
 
 		break;
@@ -767,32 +807,15 @@ ssize_t zsock_sendmsg_ctx(struct net_context *ctx, const struct msghdr *msg,
 	while (1) {
 		status = net_context_sendmsg(ctx, msg, flags, NULL, timeout, NULL);
 		if (status < 0) {
-			if (((status == -ENOBUFS) || (status == -EAGAIN)) &&
-			    K_TIMEOUT_EQ(timeout, K_FOREVER)) {
-				/* If we cannot get any buffers in reasonable
-				 * amount of time, then do not wait forever as
-				 * there might be some bigger issue.
-				 * If we get -EAGAIN and cannot recover, then
-				 * it means that the sending window is blocked
-				 * and we just cannot send anything.
-				 */
-				int64_t remaining = buf_timeout - sys_clock_tick_get();
-
-				if (remaining <= 0) {
-					if (status == -ENOBUFS) {
-						errno = ENOMEM;
-					} else {
-						errno = ENOBUFS;
-					}
-
-					return -1;
+			if (status < 0) {
+				status = send_check_and_wait(ctx, status,
+							     buf_timeout,
+							     timeout);
+				if (status < 0) {
+					return status;
 				}
 
-				k_sleep(WAIT_BUFS);
 				continue;
-			} else {
-				errno = -status;
-				return -1;
 			}
 		}