ipcomp: assign if_id to child tunnel from parent tunnel

The child tunnel if_id will be used for xfrm interface's lookup
when processing the IP(6)IP(6) packets in the next patches.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/ipcomp.c

@@ -72,6 +72,7 @@ static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 	t->props.flags = x->props.flags;
 	t->props.extra_flags = x->props.extra_flags;
 	memcpy(&t->mark, &x->mark, sizeof(t->mark));
+	t->if_id = x->if_id;
 
 	if (xfrm_init_state(t))
 		goto error;

net/ipv6/ipcomp6.c

@@ -91,6 +91,7 @@ static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
 	t->props.mode = x->props.mode;
 	memcpy(t->props.saddr.a6, x->props.saddr.a6, sizeof(struct in6_addr));
 	memcpy(&t->mark, &x->mark, sizeof(t->mark));
+	t->if_id = x->if_id;
 
 	if (xfrm_init_state(t))
 		goto error;