The nat_rtp_rtcp hook takes two separate parameters port and rtp_port. port is expected to be the real h245 address(found inside the packet).rtp_port is the even number closest to port (RTP ports are even and RTCP ports are odd)
However currently, both port and rtp_port are having same value(both are rounded to nearest even numbers).
This works well in case of openlogicalchannel with media (RTP/even) port.But in case of openlogicalchannel for media control (RTCP/odd) port, h245 address in the packet is wrongly modified to have an even port.
I am attaching a pcap demonstrating the problem, for any further analysis. This behavior was introduced around v2.6.19 while rewriting the helper. Signed-off-by: Jagdish Motwani <jagdish.motwani@xxxxxxxxxxxxx> Signed-off-by: Sanket Shah <sanket.shah@xxxxxxxxxxxxx> --diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
index 46d69d7..7f0de36 100644 --- a/net/netfilter/nf_conntrack_h323_main.c +++ b/net/netfilter/nf_conntrack_h323_main.c@@ -270,9 +270,8 @@ static int expect_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
return 0;
/* RTP port is even */
- port &= htons(~1);
- rtp_port = port;
- rtcp_port = htons(ntohs(port) + 1);
+ rtp_port = port & htons(~1);
+ rtcp_port = htons(ntohs(rtp_port) + 1);
/* Create expect for RTP */
if ((rtp_exp = nf_ct_expect_alloc(ct)) == NULL)
Attachment:
rtcp_nat_bug.pcap
Description: application/pcap
