feat: zombie connection check

This commit adds the check that verifies if the connection is dead, AKA zombie. Without this, once internet was unavailable for a certain time, Discord would stop responding to the heartbeats and wouldn't send any events, causing to the bot be offline, while the process would be still alive.

Author: ThePedroo

include/discord-internal.h

@@ -749,6 +749,11 @@ struct discord_gateway {
          * @note obtained at `HELLO`
          */
         int64_t hbeat_interval;
+        /**
+         * boolean that indicates if the last heartbeat was answered
+         * @note used to detect zombie connections
+        */
+        bool hbeat_acknowledged;
         /**
          * Gateway's concept of "now"
          * @note updated at discord_gateway_perform()

src/discord-gateway.c

@@ -319,6 +319,7 @@ _discord_on_heartbeat_ack(struct discord_gateway *gw)
     /* get request / response interval in milliseconds */
     pthread_rwlock_wrlock(&gw->timer->rwlock);
     gw->timer->ping_ms = (int)(gw->timer->now - gw->timer->hbeat_last);
+    gw->timer->hbeat_acknowledged = true;
     pthread_rwlock_unlock(&gw->timer->rwlock);
 
     logconf_trace(&gw->conf, "PING: %d ms", gw->timer->ping_ms);
@@ -551,6 +552,9 @@ discord_gateway_init(struct discord_gateway *gw,
     ASSERT_S(!pthread_rwlock_init(&gw->timer->rwlock, NULL),
              "Couldn't initialize Gateway's rwlock");
 
+    /* mark true to not get reconnected each reconnect */
+    gw->timer->hbeat_acknowledged = true;
+
     /* client connection status */
     gw->session = calloc(1, sizeof *gw->session);
     gw->session->retry.enable = true;

src/discord-gateway_dispatch.c

@@ -264,6 +264,16 @@ discord_gateway_send_heartbeat(struct discord_gateway *gw, int seq)
         jsonb_object_pop(&b, buf, sizeof(buf));
     }
 
+    if (!gw->timer->hbeat_acknowledged) {
+        logconf_warn(&gw->conf, "Heartbeat ACK not received, marked as zombie");
+
+        gw->timer->hbeat_acknowledged = true;
+
+        discord_gateway_reconnect(gw, false);
+
+        return;
+    }
+
     if (ws_send_text(gw->ws, &info, buf, b.pos)) {
         io_poller_curlm_enable_perform(CLIENT(gw, gw)->io_poller, gw->mhandle);
         logconf_info(
@@ -273,6 +283,8 @@ discord_gateway_send_heartbeat(struct discord_gateway *gw, int seq)
                 ANSI_FG_BRIGHT_GREEN) " HEARTBEAT (%d bytes) [@@@_%zu_@@@]",
             b.pos, info.loginfo.counter + 1);
 
+        gw->timer->hbeat_acknowledged = false;
+
         /* update heartbeat timestamp */
         gw->timer->hbeat_last = gw->timer->now;
         if (!gw->timer->hbeat_timer)