From 3ac4722a92d2c88a667d8a8e90a68362e41f4dda Mon Sep 17 00:00:00 2001
From: Susant Sahani <ssahani@gmail.com>
Date: Wed, 22 May 2024 19:00:11 +0530
Subject: [PATCH] TCP: Reconnect to remote server after a reset/closed
 connection by remote server

closes https://github.com/systemd/systemd-netlogd/issues/104
---
 src/netlog/netlog-manager.h |  1 +
 src/netlog/netlog-network.c | 38 ++++++++++++++++++++++++++-----------
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/src/netlog/netlog-manager.h b/src/netlog/netlog-manager.h
index a922aff..9cb1058 100644
--- a/src/netlog/netlog-manager.h
+++ b/src/netlog/netlog-manager.h
@@ -78,6 +78,7 @@ struct Manager {
 
         bool keep_alive;
         bool no_delay;
+        bool connected;
 
         unsigned keep_alive_cnt;
 
diff --git a/src/netlog/netlog-network.c b/src/netlog/netlog-network.c
index db4e0c4..c0cacb1 100644
--- a/src/netlog/netlog-network.c
+++ b/src/netlog/netlog-network.c
@@ -86,6 +86,13 @@ static int protocol_send(Manager *m, struct iovec *iovec, unsigned n_iovec) {
                                 return r;
                         }
                         break;
+               case SYSLOG_TRANSMISSION_PROTOCOL_TCP:
+                       r = network_send(m, iovec, n_iovec);
+                        if (r < 0 && r != -EAGAIN) {
+                                manager_close_network_socket(m);
+                                return r;
+                        }
+                        break;
                 default:
                         return network_send(m, iovec, n_iovec);
         }
@@ -297,9 +304,6 @@ int manager_push_to_network(Manager *m,
 
         assert(m);
 
-        if (!message)
-                return 0;
-
         switch (m->protocol) {
                 case SYSLOG_TRANSMISSION_PROTOCOL_DTLS:
                         if (!m->dtls->connected) {
@@ -316,6 +320,13 @@ int manager_push_to_network(Manager *m,
                                         return r;
                         }
                         break;
+                case SYSLOG_TRANSMISSION_PROTOCOL_TCP:
+                        if (!m->connected) {
+                                r = manager_open_network_socket(m);
+                                if (r < 0)
+                                        return r;
+                        }
+                        break;
                 default:
                         break;
         }
@@ -340,6 +351,7 @@ void manager_close_network_socket(Manager *m) {
                         log_error_errno(errno, "Failed to shutdown netlog socket: %m");
         }
 
+        m->connected = false;
         m->socket = safe_close(m->socket);
 }
 
@@ -377,11 +389,16 @@ int manager_network_connect_socket(Manager *m) {
         if (r < 0)
                 return r;
 
+        log_debug("Connecting to remote server: '%s'", pretty);
+
         r = connect(m->socket, &m->address.sockaddr.sa, salen);
         if (r < 0 && errno != EINPROGRESS)
-                return log_error_errno(errno, "Failed to connect to remote server='%s'", pretty);
+                return log_error_errno(errno, "Failed to connect to remote server='%s': %m", pretty);
 
-        log_debug("Connected to remote server: '%s'", pretty);
+        if (errno != EINPROGRESS)
+                log_debug("Connected to remote server: '%s'", pretty);
+        else
+                log_debug("Connection in progress to remote server: '%s'", pretty);
 
         return 0;
 }
@@ -407,6 +424,8 @@ int manager_open_network_socket(Manager *m) {
         if (m->socket < 0)
                 return log_error_errno(errno, "Failed to create socket: %m");;
 
+        log_debug("Successfully created socket with fd='%d'", m->socket);
+
         switch (m->protocol) {
                 case SYSLOG_TRANSMISSION_PROTOCOL_UDP: {
                         r = setsockopt_int(m->socket, IPPROTO_IP, IP_MULTICAST_LOOP, true);
@@ -462,17 +481,14 @@ int manager_open_network_socket(Manager *m) {
         }
 
         r = fd_nonblock(m->socket, true);
-        if (r < 0) {
-                log_error_errno(errno, "Failed to set socket nonblock: %m");
-                goto fail;
-        }
+        if (r < 0)
+                log_debug_errno(errno, "Failed to set socket='%d' nonblock: %m", m->socket);
 
         r = manager_network_connect_socket(m);
         if (r < 0)
                 goto fail;
 
-        log_debug("Successfully created socket with fd='%d'", m->socket);
-
+        m->connected = true;
         return m->socket;
 
  fail: