chan_sip: in case of tcp/tls, be less annoying about tx errors.

chan_sip.c:3782 __sip_xmit: sip_xmit of 0x7f1478069230 (len 600) to
213.150.203.60:1492 returned -2: Interrupted system call

returned -2 implies this wasn't actually an OS error, so errno makes no
sense either.  Internal error was already logged higher up, and -2
generally means that either there isn't a valid connection available, or
the pipe notification failed, and that is already correctly logged.

ASTERISK-28651 #close

Change-Id: I46eb82924beeff9dfd86fa6c7eb87d2651b950f2
Signed-off-by: Jaco Kroon <jaco@uls.co.za>

channels/chan_sip.c

@@ -2619,12 +2619,16 @@ static int sip_tcptls_write(struct ast_tcptls_session_instance *tcptls_session,
 	ao2_lock(tcptls_session);
 
 	if (!tcptls_session->stream ||
-		!(th = ao2_t_find(threadt, &tmp, OBJ_POINTER, "ao2_find, getting sip_threadinfo in tcp helper thread")) ||
 		!(packet = ao2_alloc(sizeof(*packet), tcptls_packet_destructor)) ||
 		!(packet->data = ast_str_create(len))) {
 		goto tcptls_write_setup_error;
 	}
 
+	if (!(th = ao2_t_find(threadt, &tmp, OBJ_POINTER, "ao2_find, getting sip_threadinfo in tcp helper thread"))) {
+		ast_log(LOG_ERROR, "Unable to locate tcptls_session helper thread.\n");
+		goto tcptls_write_setup_error;
+	}
+
 	/* goto tcptls_write_error should _NOT_ be used beyond this point */
 	ast_str_set(&packet->data, 0, "%s", (char *) buf);
 	packet->len = len;
@@ -3808,6 +3812,9 @@ static int __sip_xmit(struct sip_pvt *p, struct ast_str *data)
 		res = ast_sendto(p->socket.fd, ast_str_buffer(data), ast_str_strlen(data), 0, dst);
 	} else if (p->socket.tcptls_session) {
 		res = sip_tcptls_write(p->socket.tcptls_session, ast_str_buffer(data), ast_str_strlen(data));
+		if (res < -1) {
+			return res;
+		}
 	} else if (p->socket.ws_session) {
 		if (!(res = ast_websocket_write_string(p->socket.ws_session, ast_str_buffer(data)))) {
 			/* The WebSocket API just returns 0 on success and -1 on failure, while this code expects the payload length to be returned */
@@ -30383,6 +30390,9 @@ static int sip_send_keepalive(const void *data)
 	} else if ((peer->socket.type & (AST_TRANSPORT_TCP | AST_TRANSPORT_TLS)) &&
 		   peer->socket.tcptls_session) {
 		res = sip_tcptls_write(peer->socket.tcptls_session, keepalive, count);
+		if (res < -1) {
+			return 0;
+		}
 	} else if (peer->socket.type == AST_TRANSPORT_UDP) {
 		res = ast_sendto(sipsock, keepalive, count, 0, &peer->addr);
 	}