netfilter: nf_conntrack_sip: pass data offset to NAT functions

When using TCP multiple SIP messages might be present in a single packet.
A following patch will parse them by setting the dptr to the beginning of
each message. The NAT helper needs to reload the dptr value after mangling
the packet however, so it needs to know the offset of the message to the
beginning of the packet.
Signed-off-by: Patrick McHardy <kaber@trash.net>

include/linux/netfilter/nf_conntrack_sip.h

@@ -34,10 +34,10 @@ struct sdp_media_type {
 struct sip_handler {
 	const char	*method;
 	unsigned int	len;
-	int		(*request)(struct sk_buff *skb,
+	int		(*request)(struct sk_buff *skb, unsigned int dataoff,
 				   const char **dptr, unsigned int *datalen,
 				   unsigned int cseq);
-	int		(*response)(struct sk_buff *skb,
+	int		(*response)(struct sk_buff *skb, unsigned int dataoff,
 				    const char **dptr, unsigned int *datalen,
 				    unsigned int cseq, unsigned int code);
 };
@@ -100,33 +100,39 @@ enum sdp_header_types {
 };
 
 extern unsigned int (*nf_nat_sip_hook)(struct sk_buff *skb,
+				       unsigned int dataoff,
 				       const char **dptr,
 				       unsigned int *datalen);
 extern unsigned int (*nf_nat_sip_expect_hook)(struct sk_buff *skb,
+					      unsigned int dataoff,
 					      const char **dptr,
 					      unsigned int *datalen,
 					      struct nf_conntrack_expect *exp,
 					      unsigned int matchoff,
 					      unsigned int matchlen);
 extern unsigned int (*nf_nat_sdp_addr_hook)(struct sk_buff *skb,
-					    const char **dptr,
 					    unsigned int dataoff,
+					    const char **dptr,
 					    unsigned int *datalen,
+					    unsigned int sdpoff,
 					    enum sdp_header_types type,
 					    enum sdp_header_types term,
 					    const union nf_inet_addr *addr);
 extern unsigned int (*nf_nat_sdp_port_hook)(struct sk_buff *skb,
+					    unsigned int dataoff,
 					    const char **dptr,
 					    unsigned int *datalen,
 					    unsigned int matchoff,
 					    unsigned int matchlen,
 					    u_int16_t port);
 extern unsigned int (*nf_nat_sdp_session_hook)(struct sk_buff *skb,
-					       const char **dptr,
 					       unsigned int dataoff,
+					       const char **dptr,
 					       unsigned int *datalen,
+					       unsigned int sdpoff,
 					       const union nf_inet_addr *addr);
 extern unsigned int (*nf_nat_sdp_media_hook)(struct sk_buff *skb,
+					     unsigned int dataoff,
 					     const char **dptr,
 					     unsigned int *datalen,
 					     struct nf_conntrack_expect *rtp_exp,