udp: Restore UDP sockets

Reuse the TCP socket restore, just add connect() and sanity checks
for protocol.

This is OK, since UDP connect doesn't go to network for connection
and (unlike unix sockets) doesn't require peer to be "online". It
just puts the peer's creds on socket and returns.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

sockets.c

@@ -1188,7 +1188,7 @@ static int open_inet_sk(const struct inet_sk_entry *ie, int *img_fd)
 		return -1;
 	}
 
-	if (ie->type != SOCK_STREAM) {
+	if ((ie->type != SOCK_STREAM) && (ie->type != SOCK_DGRAM)) {
 		pr_err("Unsupported socket type: %d\n", ie->type);
 		return -1;
 	}
@@ -1213,9 +1213,33 @@ static int open_inet_sk(const struct inet_sk_entry *ie, int *img_fd)
 		goto err;
 	}
 
-	if (listen(sk, ie->backlog) == -1) {
-		pr_perror("Can't listen on a socket");
-		goto err;
+	if (ie->state == TCP_LISTEN) {
+		if (ie->proto != IPPROTO_TCP) {
+			pr_err("Wrong socket in listen state %d\n", ie->proto);
+			goto err;
+		}
+
+		if (listen(sk, ie->backlog) == -1) {
+			pr_perror("Can't listen on a socket");
+			goto err;
+		}
+	}
+
+	if (ie->state == TCP_ESTABLISHED) {
+		if (ie->proto != IPPROTO_UDP) {
+			pr_err("Connected TCP socket in image\n");
+			goto err;
+		}
+
+		memset(&addr, 0, sizeof(addr));
+		addr.sin_family = ie->family;
+		addr.sin_port = htons(ie->dst_port);
+		memcpy(&addr.sin_addr.s_addr, ie->dst_addr, sizeof(ie->dst_addr));
+
+		if (connect(sk, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+			pr_perror("Can't connect UDP socket back");
+			goto err;
+		}
 	}
 
 	if (move_img_fd(img_fd, ie->fd))