[NETFILTER]: sip conntrack: better NAT handling

The NAT handling of the SIP helper has a few problems:

- Request headers are only mangled in the reply direction, From/To headers
  not at all, which can lead to authentication failures with DNAT in case
  the authentication domain is the IP address

- Contact headers in responses are only mangled for REGISTER responses

- Headers may be mangled even though they contain addresses not
  participating in the connection, like alternative addresses

- Packets are droppen when domain names are used where the helper expects
  IP addresses

This patch takes a different approach, instead of fixed rules what field
to mangle to what content, it adds symetric mapping of From/To/Via/Contact
headers, which allows to deal properly with echoed addresses in responses
and foreign addresses not belonging to the connection.

Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/netfilter_ipv4/ip_conntrack_sip.h b/include/linux/netfilter_ipv4/ip_conntrack_sip.h
index 51c65ac18c57..bef6c646defa 100644
--- a/include/linux/netfilter_ipv4/ip_conntrack_sip.h
+++ b/include/linux/netfilter_ipv4/ip_conntrack_sip.h
@@ -6,7 +6,10 @@
 #define SIP_TIMEOUT     3600
 
 enum sip_header_pos {
-        POS_REQ_HEADER,
+        POS_REG_REQ_URI,
+        POS_REQ_URI,
+        POS_FROM,
+        POS_TO,
         POS_VIA,
         POS_CONTACT,
         POS_CONTENT,