[PATCH v5 07/11] netlink: allow modification of transit net

[Julian Orth <ju.orth@gmail.com>]

This commit adds two new attributes of which at most one may be
provided:

* WGDEVICE_A_TRANSIT_NETNS_PID: NLA_U32
* WGDEVICE_A_TRANSIT_NETNS_FD: NLA_U32

The transit namespace is then set to this namespace. The caller must
either be in this namespace or have CAP_NET_ADMIN in it.
---
 src/netlink.c        | 48 +++++++++++++++++++++++++++++++-------------
 src/uapi/wireguard.h | 14 +++++++++----
 2 files changed, 44 insertions(+), 18 deletions(-)

diff --git a/src/netlink.c b/src/netlink.c
index e0f3632..f5c3a9e 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -27,6 +27,8 @@ static const struct nla_policy device_policy[WGDEVICE_A_MAX + 1] = {
 	[WGDEVICE_A_PEERS]		= { .type = NLA_NESTED },
 	[WGDEVICE_A_DEV_NETNS_PID]	= { .type = NLA_U32 },
 	[WGDEVICE_A_DEV_NETNS_FD]	= { .type = NLA_U32 },
+	[WGDEVICE_A_TRANSIT_NETNS_PID]	= { .type = NLA_U32 },
+	[WGDEVICE_A_TRANSIT_NETNS_FD]	= { .type = NLA_U32 },
 };
 
 static const struct nla_policy peer_policy[WGPEER_A_MAX + 1] = {
@@ -346,23 +348,44 @@ static int wg_get_device_done(struct netlink_callback *cb)
 	return 0;
 }
 
-static int set_port(struct wg_device *wg, u16 port)
+static int set_socket(struct wg_device *wg, struct nlattr **attrs)
 {
 	struct wg_peer *peer;
-	int ret;
+	struct nlattr *port_attr = attrs[WGDEVICE_A_LISTEN_PORT];
+	u16 port;
+	struct net *net = NULL;
+	int ret = 0;
+
+	net = get_attr_net(attrs[WGDEVICE_A_TRANSIT_NETNS_PID],
+			attrs[WGDEVICE_A_TRANSIT_NETNS_FD]);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+	if (port_attr)
+		port = nla_get_u16(port_attr);
+	else
+		port = wg->incoming_port;
 
-	ret = test_socket_net_capable(wg->transit_net);
+	ret = test_socket_net_capable(net ? : wg->transit_net);
 	if (ret)
-		return ret;
-	if (wg->incoming_port == port)
-		return 0;
+		goto out;
+
+	if (wg->incoming_port == port && (!net || wg->transit_net == net))
+		goto out;
+
 	list_for_each_entry(peer, &wg->peer_list, peer_list)
 		wg_socket_clear_peer_endpoint_src(peer);
 	if (!netif_running(wg->dev)) {
 		wg->incoming_port = port;
-		return 0;
+		if (net)
+			wg_device_set_nets(wg, wg->dev_net, net);
+		goto out;
 	}
-	return wg_socket_init(wg, wg->transit_net, port);
+	ret = wg_socket_init(wg, net ? : wg->transit_net, port);
+
+out:
+	if (net)
+		put_net(net);
+	return ret;
 }
 
 static int set_allowedip(struct wg_peer *peer, struct nlattr **attrs)
@@ -559,12 +582,9 @@ static int wg_set_device(struct sk_buff *skb, struct genl_info *info)
 			wg_socket_clear_peer_endpoint_src(peer);
 	}
 
-	if (info->attrs[WGDEVICE_A_LISTEN_PORT]) {
-		ret = set_port(wg,
-			nla_get_u16(info->attrs[WGDEVICE_A_LISTEN_PORT]));
-		if (ret)
-			goto out;
-	}
+	ret = set_socket(wg, info->attrs);
+	if (ret)
+		goto out;
 
 	if (info->attrs[WGDEVICE_A_FLAGS] &&
 	    nla_get_u32(info->attrs[WGDEVICE_A_FLAGS]) &
diff --git a/src/uapi/wireguard.h b/src/uapi/wireguard.h
index 8b60ad1..5eabe22 100644
--- a/src/uapi/wireguard.h
+++ b/src/uapi/wireguard.h
@@ -88,16 +88,18 @@
  * May only be called via NLM_F_REQUEST. The command must contain the following
  * tree of nested items. Exactly one of WGDEVICE_A_IFINDEX and WGDEVICE_A_IFNAME
  * must be provided. All other top-level items are optional. At most one of
- * WGDEVICE_A_DEV_NETNS_PID and WGDEVICE_A_DEV_NETNS_FD may be provided.
+ * WGDEVICE_A_TRANSIT_NETNS_PID and WGDEVICE_A_TRANSIT_NETNS_FD may be provided.
+ * At most one of WGDEVICE_A_DEV_NETNS_PID and WGDEVICE_A_DEV_NETNS_FD may be
+ * provided.
  *
  * If WGDEVICE_A_DEV_NETNS_PID/FD is provided, the Wireguard device is looked up
  * in this network namespace. Otherwise it is looked up in the network namespace
  * of the netlink socket. The caller must have CAP_NET_ADMIN in the namespace of
  * the Wireguard device.
  *
- * If WGDEVICE_A_LISTEN_PORT is provided and the calling process is not in the
- * transit namespace, then the calling process must have CAP_NET_ADMIN the
- * transit namespace.
+ * If WGDEVICE_A_TRANSIT_NETNS_PID/FD and/or WGDEVICE_A_LISTEN_PORT are provided
+ * and the calling process is not in the transit namespace, then the calling
+ * process must have CAP_NET_ADMIN the transit namespace.
  *
  *    WGDEVICE_A_IFINDEX: NLA_U32
  *    WGDEVICE_A_IFNAME: NLA_NUL_STRING, maxlen IFNAMESIZ - 1
@@ -107,6 +109,8 @@
  *    WGDEVICE_A_LISTEN_PORT: NLA_U16, 0 to choose randomly
  *    WGDEVICE_A_DEV_NETNS_PID: NLA_U32
  *    WGDEVICE_A_DEV_NETNS_FD: NLA_U32
+ *    WGDEVICE_A_TRANSIT_NETNS_PID: NLA_U32
+ *    WGDEVICE_A_TRANSIT_NETNS_FD: NLA_U32
  *    WGDEVICE_A_FWMARK: NLA_U32, 0 to disable
  *    WGDEVICE_A_PEERS: NLA_NESTED
  *        0: NLA_NESTED
@@ -181,6 +185,8 @@ enum wgdevice_attribute {
 	WGDEVICE_A_PEERS,
 	WGDEVICE_A_DEV_NETNS_PID,
 	WGDEVICE_A_DEV_NETNS_FD,
+	WGDEVICE_A_TRANSIT_NETNS_PID,
+	WGDEVICE_A_TRANSIT_NETNS_FD,
 	__WGDEVICE_A_LAST
 };
 #define WGDEVICE_A_MAX (__WGDEVICE_A_LAST - 1)
-- 
2.19.2

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