qapi: Add InetSocketAddress member keep-alive

It's needed to provide keepalive for nbd client to track server
availability.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190725094937.32454-1-vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
[eblake: Fix error message typo]
Signed-off-by: Eric Blake <eblake@redhat.com>

qapi/sockets.json

@@ -53,6 +53,9 @@
 #
 # @ipv6: whether to accept IPv6 addresses, default try both IPv4 and IPv6
 #
+# @keep-alive: enable keep-alive when connecting to this socket. Not supported
+#              for passive sockets. (Since 4.2)
+#
 # Since: 1.3
 ##
 { 'struct': 'InetSocketAddress',
@@ -61,7 +64,8 @@
     '*numeric':  'bool',
     '*to': 'uint16',
     '*ipv4': 'bool',
-    '*ipv6': 'bool' } }
+    '*ipv6': 'bool',
+    '*keep-alive': 'bool' } }
 
 ##
 # @UnixSocketAddress:

util/qemu-sockets.c

@@ -219,6 +219,12 @@ static int inet_listen_saddr(InetSocketAddress *saddr,
     bool socket_created = false;
     Error *err = NULL;
 
+    if (saddr->keep_alive) {
+        error_setg(errp, "keep-alive option is not supported for passive "
+                   "sockets");
+        return -1;
+    }
+
     memset(&ai,0, sizeof(ai));
     ai.ai_flags = AI_PASSIVE;
     if (saddr->has_numeric && saddr->numeric) {
@@ -458,6 +464,19 @@ int inet_connect_saddr(InetSocketAddress *saddr, Error **errp)
     }
 
     freeaddrinfo(res);
+
+    if (saddr->keep_alive) {
+        int val = 1;
+        int ret = qemu_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
+                                  &val, sizeof(val));
+
+        if (ret < 0) {
+            error_setg_errno(errp, errno, "Unable to set KEEPALIVE");
+            close(sock);
+            return -1;
+        }
+    }
+
     return sock;
 }
 
@@ -653,6 +672,15 @@ int inet_parse(InetSocketAddress *addr, const char *str, Error **errp)
         }
         addr->has_ipv6 = true;
     }
+    begin = strstr(optstr, ",keep-alive");
+    if (begin) {
+        if (inet_parse_flag("keep-alive", begin + strlen(",keep-alive"),
+                            &addr->keep_alive, errp) < 0)
+        {
+            return -1;
+        }
+        addr->has_keep_alive = true;
+    }
     return 0;
 }