net: sockets: Make use of the status field reported by TCP

Make use of the status field, reported by TCP, in the socket receive
callback. This allows to differentiate a graceful connection shutdown
from actual errors at TCP level (transmission timeout or RST received).
In case of error reported from TCP layer, set a new SOCK_ERROR flag on
the socket, and store the error code in the net_context user_data.

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

Author: rlubos

subsys/net/lib/sockets/sockets.c

@@ -372,6 +372,11 @@ static void zsock_received_cb(struct net_context *ctx,
 	NET_DBG("ctx=%p, pkt=%p, st=%d, user_data=%p", ctx, pkt, status,
 		user_data);
 
+	if (status < 0) {
+		ctx->user_data = INT_TO_POINTER(-status);
+		sock_set_error(ctx);
+	}
+
 	/* if pkt is NULL, EOF */
 	if (!pkt) {
 		struct net_pkt *last_pkt = k_fifo_peek_tail(&ctx->recv_q);
@@ -1188,7 +1193,7 @@ static inline ssize_t zsock_recv_stream(struct net_context *ctx,
 
 	if ((flags & ZSOCK_MSG_DONTWAIT) || sock_is_nonblock(ctx)) {
 		timeout = K_NO_WAIT;
-	} else if (!sock_is_eof(ctx)) {
+	} else if (!sock_is_eof(ctx) && !sock_is_error(ctx)) {
 		net_context_get_option(ctx, NET_OPT_RCVTIMEO, &timeout, NULL);
 	}
 
@@ -1199,6 +1204,11 @@ static inline ssize_t zsock_recv_stream(struct net_context *ctx,
 		size_t data_len, read_len;
 		bool release_pkt = true;
 
+		if (sock_is_error(ctx)) {
+			errno = POINTER_TO_INT(ctx->user_data);
+			return -1;
+		}
+
 		if (sock_is_eof(ctx)) {
 			return 0;
 		}
@@ -1220,6 +1230,9 @@ static inline ssize_t zsock_recv_stream(struct net_context *ctx,
 
 			if (waitall && (recv_len > 0)) {
 				return recv_len;
+			} else if (sock_is_error(ctx)) {
+				errno = POINTER_TO_INT(ctx->user_data);
+				return -1;
 			} else if (sock_is_eof(ctx)) {
 				return 0;
 			} else {
@@ -1400,10 +1413,10 @@ static int zsock_poll_prepare_ctx(struct net_context *ctx,
 		return -EALREADY;
 	}
 
-	/* If socket is already in EOF, it can be reported
+	/* If socket is already in EOF or error, it can be reported
 	 * immediately, so we tell poll() to short-circuit wait.
 	 */
-	if (sock_is_eof(ctx)) {
+	if (sock_is_eof(ctx) || sock_is_error(ctx)) {
 		return -EALREADY;
 	}
 
@@ -1428,6 +1441,10 @@ static int zsock_poll_update_ctx(struct net_context *ctx,
 		(*pev)++;
 	}
 
+	if (sock_is_error(ctx)) {
+		pfd->revents |= ZSOCK_POLLERR;
+	}
+
 	if (sock_is_eof(ctx)) {
 		pfd->revents |= ZSOCK_POLLHUP;
 	}

subsys/net/lib/sockets/sockets_internal.h

@@ -11,6 +11,7 @@
 
 #define SOCK_EOF 1
 #define SOCK_NONBLOCK 2
+#define SOCK_ERROR 4
 
 int zsock_close_ctx(struct net_context *ctx);
 int zsock_poll_internal(struct zsock_pollfd *fds, int nfds, k_timeout_t timeout);
@@ -47,6 +48,8 @@ static inline bool net_socket_is_tls(void *obj)
 #define sock_is_eof(ctx) sock_get_flag(ctx, SOCK_EOF)
 #define sock_set_eof(ctx) sock_set_flag(ctx, SOCK_EOF, SOCK_EOF)
 #define sock_is_nonblock(ctx) sock_get_flag(ctx, SOCK_NONBLOCK)
+#define sock_is_error(ctx) sock_get_flag(ctx, SOCK_ERROR)
+#define sock_set_error(ctx) sock_set_flag(ctx, SOCK_ERROR, SOCK_ERROR)
 
 struct socket_op_vtable {
 	struct fd_op_vtable fd_vtable;