netfilter: ctnetlink: fix dump of the expect mask attribute

Before this change, the mask is never included in the netlink message, so
"conntrack -E expect" always prints 0.0.0.0.

In older kernels the l3num callback struct was passed as argument, based
on tuple->src.l3num. After the l3num indirection got removed, the call
chain is based on m.src.l3num, but this value is 0xffff.

Init l3num to the correct value.

Fixes: f957be9d ("netfilter: conntrack: remove ctnetlink callbacks from l3 protocol trackers")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_netlink.c

@@ -2962,6 +2962,7 @@ static int ctnetlink_exp_dump_mask(struct sk_buff *skb,
 	memset(&m, 0xFF, sizeof(m));
 	memcpy(&m.src.u3, &mask->src.u3, sizeof(m.src.u3));
 	m.src.u.all = mask->src.u.all;
+	m.src.l3num = tuple->src.l3num;
 	m.dst.protonum = tuple->dst.protonum;
 
 	nest_parms = nla_nest_start(skb, CTA_EXPECT_MASK);