[NETFILTER]: Add SIP connection tracking helper

Add SIP connection tracking helper. Originally written by
Christian Hentschel <chentschel@arnet.com.ar>, some cleanup, minor
fixes and bidirectional SIP support added by myself.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ip_conntrack_sip.h

@@ -0,0 +1,44 @@
+#ifndef __IP_CONNTRACK_SIP_H__
+#define __IP_CONNTRACK_SIP_H__
+#ifdef __KERNEL__
+
+#define SIP_PORT	5060
+#define SIP_TIMEOUT	3600
+
+#define POS_VIA		0
+#define POS_CONTACT	1
+#define POS_CONTENT	2
+#define POS_MEDIA	3
+#define POS_OWNER	4
+#define POS_CONNECTION	5
+#define POS_REQ_HEADER	6
+#define POS_SDP_HEADER	7
+
+struct sip_header_nfo {
+	const char	*lname;
+	const char	*sname;
+	const char	*ln_str;
+	size_t		lnlen;
+	size_t		snlen;
+	size_t		ln_strlen;
+	int		(*match_len)(const char *, const char *, int *);
+};
+
+extern unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb,
+				       enum ip_conntrack_info ctinfo,
+				       struct ip_conntrack *ct,
+				       const char **dptr);
+extern unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb,
+				       enum ip_conntrack_info ctinfo,
+				       struct ip_conntrack_expect *exp,
+				       const char *dptr);
+
+extern int ct_sip_get_info(const char *dptr, size_t dlen,
+			   unsigned int *matchoff,
+			   unsigned int *matchlen,
+			   struct sip_header_nfo *hnfo);
+extern int ct_sip_lnlen(const char *line, const char *limit);
+extern const char *ct_sip_search(const char *needle, const char *haystack,
+                                 size_t needle_len, size_t haystack_len);
+#endif /* __KERNEL__ */
+#endif /* __IP_CONNTRACK_SIP_H__ */

net/ipv4/netfilter/Kconfig

@@ -191,6 +191,18 @@ config IP_NF_H323
 	  If you want to compile it as a module, say 'M' here and read
 	  Documentation/modules.txt.  If unsure, say 'N'.
 
+config IP_NF_SIP
+	tristate "SIP protocol support (EXPERIMENTAL)"
+	depends on IP_NF_CONNTRACK && EXPERIMENTAL
+	help
+	  SIP is an application-layer control protocol that can establish,
+	  modify, and terminate multimedia sessions (conferences) such as
+	  Internet telephony calls. With the ip_conntrack_sip and
+	  the ip_nat_sip modules you can support the protocol on a connection
+	  tracking/NATing firewall.
+
+	  To compile it as a module, choose M here.  If unsure, say Y.
+
 config IP_NF_QUEUE
 	tristate "IP Userspace queueing via NETLINK (OBSOLETE)"
 	help
@@ -503,6 +515,12 @@ config IP_NF_NAT_H323
 	default IP_NF_NAT if IP_NF_H323=y
 	default m if IP_NF_H323=m
 
+config IP_NF_NAT_SIP
+	tristate
+	depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
+	default IP_NF_NAT if IP_NF_SIP=y
+	default m if IP_NF_SIP=m
+
 # mangle + specific targets
 config IP_NF_MANGLE
 	tristate "Packet mangling"

net/ipv4/netfilter/Makefile

@@ -31,6 +31,7 @@ obj-$(CONFIG_IP_NF_AMANDA) += ip_conntrack_amanda.o
 obj-$(CONFIG_IP_NF_TFTP) += ip_conntrack_tftp.o
 obj-$(CONFIG_IP_NF_FTP) += ip_conntrack_ftp.o
 obj-$(CONFIG_IP_NF_IRC) += ip_conntrack_irc.o
+obj-$(CONFIG_IP_NF_SIP) += ip_conntrack_sip.o
 obj-$(CONFIG_IP_NF_NETBIOS_NS) += ip_conntrack_netbios_ns.o
 
 # NAT helpers 
@@ -40,6 +41,7 @@ obj-$(CONFIG_IP_NF_NAT_AMANDA) += ip_nat_amanda.o
 obj-$(CONFIG_IP_NF_NAT_TFTP) += ip_nat_tftp.o
 obj-$(CONFIG_IP_NF_NAT_FTP) += ip_nat_ftp.o
 obj-$(CONFIG_IP_NF_NAT_IRC) += ip_nat_irc.o
+obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o
 
 # generic IP tables 
 obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o