net: Treat venet device as a separate complete device

When restoring venet device we need to restore its
index as well, which actually possible with new iproute2
package but the problem is that the index itself lays
inside image file. We could use crit tool to extract
it but this would slowdon procedure signifantly (need
to run python which would parse the image, or need
to pass the index into environmnet from inside of
the CRIU itself).

So lets do a trick and simply created venet device
inside container by criu itself (thanks we support
creating venet via netlink interface now).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@odin.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

net.c

@@ -256,12 +256,7 @@ static int dump_one_voiddev(struct ifinfomsg *ifi, char *kind,
 		struct rtattr **tb, struct cr_imgset *fds)
 {
 	if (!strcmp(kind, "venet"))
-		/*
-		 * If we meet a link we know about, such as
-		 * OpenVZ's venet, save general parameters of
-		 * it as external link.
-		 */
-		return dump_one_netdev(ND_TYPE__EXTLINK, ifi, tb, fds, NULL);
+		return dump_one_netdev(ND_TYPE__VENET, ifi, tb, fds, NULL);
 
 	return dump_unknown_device(ifi, kind, tb, fds);
 }
@@ -454,6 +449,21 @@ static int veth_link_info(NetDeviceEntry *nde, struct newlink_req *req)
 	return 0;
 }
 
+static int venet_link_info(NetDeviceEntry *nde, struct newlink_req *req)
+{
+	struct rtattr *venet_data;
+
+	BUG_ON(ns_fd < 0);
+
+	venet_data = NLMSG_TAIL(&req->h);
+	addattr_l(&req->h, sizeof(*req), IFLA_INFO_KIND, "venet", 5);
+	addattr_l(&req->h, sizeof(*req), IFLA_INFO_DATA, NULL, 0);
+	addattr_l(&req->h, sizeof(*req), IFLA_NET_NS_FD, &ns_fd, sizeof(ns_fd));
+	venet_data->rta_len = (void *)NLMSG_TAIL(&req->h) - (void *)venet_data;
+
+	return 0;
+}
+
 static int restore_link(NetDeviceEntry *nde, int nlsk)
 {
 	pr_info("Restoring link %s type %d\n", nde->name, nde->type);
@@ -462,6 +472,8 @@ static int restore_link(NetDeviceEntry *nde, int nlsk)
 	case ND_TYPE__LOOPBACK: /* fallthrough */
 	case ND_TYPE__EXTLINK:  /* see comment in protobuf/netdev.proto */
 		return restore_link_parms(nde, nlsk);
+	case ND_TYPE__VENET:
+		return restore_one_link(nde, nlsk, venet_link_info);
 	case ND_TYPE__VETH:
 		return restore_one_link(nde, nlsk, veth_link_info);
 	case ND_TYPE__TUN:

protobuf/netdev.proto

@@ -12,6 +12,10 @@ enum nd_type {
 	 * by the setup-namespaces script.
 	 */
 	EXTLINK		= 4;
+	/*
+	 * Virtuozzo specific device.
+	 */
+	VENET		= 5;
 }
 
 message net_device_entry {