On 05/06/15 at 11:58am, Nicolas Dichtel wrote:

More accurately, listen all netns that have a nsid assigned into the netns
where the netlink socket is opened.
For this purpose, a netlink socket option is added:
NETLINK_LISTEN_ALL_NSID. When this option is set on a netlink socket, this
socket will receive netlink notifications from all netns that have a nsid
assigned into the netns where the socket has been opened. The nsid is sent
to userland via an anscillary data.

With this patch, a daemon needs only one socket to listen many netns. This
is useful when the number of netns is high.

Signed-off-by: Nicolas Dichtel <redacted>

[...]

+/* This function returns true is the peer netns has an id assigned into the
+ * current netns.
+ */
+bool peernet_has_id(struct net *net, struct net *peer)
+{
+	return peernet2id(net, peer) >= 0;
+}

Missing export?

Maybe name this NETLINK_LISTEN_ALL_NSID just to make it clear?

+		if (!file_ns_capable(sk->sk_socket->file, p->net->user_ns,
+				     CAP_NET_BROADCAST))
+			return;
+	}
+	NETLINK_CB(p->skb).net = p->net;

Does this need a get_net()? The netns could disappear while the skb is
queued, right?