client rpc: Send keepalive requests from IO event loop

In addition to keepalive responses, we also need to send keepalive
requests from client IO loop to properly detect dead connection in case
a libvirt API is called from the main loop, which prevents any timers to
be called.
(cherry picked from commit 4d971dc7)

src/rpc/virnetclient.c

@@ -1272,6 +1272,7 @@ static int virNetClientIOEventLoop(virNetClientPtr client,
         char ignore;
         sigset_t oldmask, blockedsigs;
         int timeout = -1;
+        virNetMessagePtr msg = NULL;
 
         /* If we have existing SASL decoded data we don't want to sleep in
          * the poll(), just check if any other FDs are also ready.
@@ -1285,6 +1286,10 @@ static int virNetClientIOEventLoop(virNetClientPtr client,
         if (thiscall->nonBlock)
             timeout = 0;
 
+        /* Limit timeout so that we can send keepalive request in time */
+        if (timeout == -1)
+            timeout = virKeepAliveTimeout(client->keepalive);
+
         fds[0].events = fds[0].revents = 0;
         fds[1].events = fds[1].revents = 0;
 
@@ -1330,6 +1335,13 @@ static int virNetClientIOEventLoop(virNetClientPtr client,
 
         virNetClientLock(client);
 
+        if (virKeepAliveTrigger(client->keepalive, &msg)) {
+            client->wantClose = true;
+        } else if (msg && virNetClientQueueNonBlocking(client, msg) < 0) {
+            VIR_WARN("Could not queue keepalive request");
+            virNetMessageFree(msg);
+        }
+
         /* If we have existing SASL decoded data, pretend
          * the socket became readable so we consume it
          */