netfilter: ctnetlink: allow to set expectfn for expectations

This patch allows you to set expectfn which is specifically used
by the NAT side of most of the existing conntrack helpers.

I have added a symbol map that uses a string as key to look up for
the function that is attached to the expectation object. This is
the best solution I came out with to solve this issue.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index d0319f9..57932c4 100644
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -526,6 +526,11 @@ err1:
 	return NF_DROP;
 }
 
+static struct nf_ct_helper_expectfn sip_nat = {
+        .name           = "sip",
+        .expectfn       = ip_nat_sip_expected,
+};
+
 static void __exit nf_nat_sip_fini(void)
 {
 	RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
@@ -535,6 +540,7 @@ static void __exit nf_nat_sip_fini(void)
 	RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
 	RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
 	RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
+	nf_ct_helper_expectfn_unregister(&sip_nat);
 	synchronize_rcu();
 }
 
@@ -554,6 +560,7 @@ static int __init nf_nat_sip_init(void)
 	RCU_INIT_POINTER(nf_nat_sdp_port_hook, ip_nat_sdp_port);
 	RCU_INIT_POINTER(nf_nat_sdp_session_hook, ip_nat_sdp_session);
 	RCU_INIT_POINTER(nf_nat_sdp_media_hook, ip_nat_sdp_media);
+	nf_ct_helper_expectfn_register(&sip_nat);
 	return 0;
 }