[NETFILTER]: nf_conntrack/nf_nat: add SIP helper port

Add IPv4 and IPv6 capable nf_conntrack port of the SIP conntrack/NAT helper.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter/nf_conntrack_sip.h

+#ifndef __NF_CONNTRACK_SIP_H__
+#define __NF_CONNTRACK_SIP_H__
+#ifdef __KERNEL__
+
+#define SIP_PORT	5060
+#define SIP_TIMEOUT	3600
+
+enum sip_header_pos {
+	POS_REG_REQ_URI,
+	POS_REQ_URI,
+	POS_FROM,
+	POS_TO,
+	POS_VIA,
+	POS_CONTACT,
+	POS_CONTENT,
+	POS_MEDIA,
+	POS_OWNER_IP4,
+	POS_CONNECTION_IP4,
+	POS_OWNER_IP6,
+	POS_CONNECTION_IP6,
+	POS_SDP_HEADER,
+};
+
+extern unsigned int (*nf_nat_sip_hook)(struct sk_buff **pskb,
+				       enum ip_conntrack_info ctinfo,
+				       struct nf_conn *ct,
+				       const char **dptr);
+extern unsigned int (*nf_nat_sdp_hook)(struct sk_buff **pskb,
+				       enum ip_conntrack_info ctinfo,
+				       struct nf_conntrack_expect *exp,
+				       const char *dptr);
+
+extern int ct_sip_get_info(struct nf_conn *ct, const char *dptr, size_t dlen,
+			   unsigned int *matchoff, unsigned int *matchlen,
+			   enum sip_header_pos pos);
+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,
+				 int case_sensitive);
+#endif /* __KERNEL__ */
+#endif /* __NF_CONNTRACK_SIP_H__ */

net/ipv4/netfilter/Kconfig

@@ -555,6 +555,11 @@ config IP_NF_NAT_SIP
 	default IP_NF_NAT if IP_NF_SIP=y
 	default m if IP_NF_SIP=m
 
+config NF_NAT_SIP
+	tristate
+	depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+	default NF_NAT && NF_CONNTRACK_SIP
+
 # mangle + specific targets
 config IP_NF_MANGLE
 	tristate "Packet mangling"

net/ipv4/netfilter/Makefile

@@ -55,6 +55,7 @@ obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
 obj-$(CONFIG_NF_NAT_H323) += nf_nat_h323.o
 obj-$(CONFIG_NF_NAT_IRC) += nf_nat_irc.o
 obj-$(CONFIG_NF_NAT_PPTP) += nf_nat_pptp.o
+obj-$(CONFIG_NF_NAT_SIP) += nf_nat_sip.o
 
 # NAT protocols (nf_nat)
 obj-$(CONFIG_NF_NAT_PROTO_GRE) += nf_nat_proto_gre.o

net/ipv4/netfilter/nf_nat_sip.c

+/* SIP extension for UDP NAT alteration.
+ *
+ * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
+ * based on RR's ip_nat_ftp.c and other modules.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_sip.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
+MODULE_DESCRIPTION("SIP NAT helper");
+MODULE_ALIAS("ip_nat_sip");
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+struct addr_map {
+	struct {
+		char		src[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
+		char		dst[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
+		unsigned int	srclen, srciplen;
+		unsigned int	dstlen, dstiplen;
+	} addr[IP_CT_DIR_MAX];
+};
+
+static void addr_map_init(struct nf_conn *ct, struct addr_map *map)
+{
+	struct nf_conntrack_tuple *t;
+	enum ip_conntrack_dir dir;
+	unsigned int n;
+
+	for (dir = 0; dir < IP_CT_DIR_MAX; dir++) {
+		t = &ct->tuplehash[dir].tuple;
+
+		n = sprintf(map->addr[dir].src, "%u.%u.%u.%u",
+			    NIPQUAD(t->src.u3.ip));
+		map->addr[dir].srciplen = n;
+		n += sprintf(map->addr[dir].src + n, ":%u",
+			     ntohs(t->src.u.udp.port));
+		map->addr[dir].srclen = n;
+
+		n = sprintf(map->addr[dir].dst, "%u.%u.%u.%u",
+			    NIPQUAD(t->dst.u3.ip));
+		map->addr[dir].dstiplen = n;
+		n += sprintf(map->addr[dir].dst + n, ":%u",
+			     ntohs(t->dst.u.udp.port));
+		map->addr[dir].dstlen = n;
+	}
+}
+
+static int map_sip_addr(struct sk_buff **pskb, enum ip_conntrack_info ctinfo,
+			struct nf_conn *ct, const char **dptr, size_t dlen,
+			enum sip_header_pos pos, struct addr_map *map)
+{
+	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+	unsigned int matchlen, matchoff, addrlen;
+	char *addr;
+
+	if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0)
+		return 1;
+
+	if ((matchlen == map->addr[dir].srciplen ||
+	     matchlen == map->addr[dir].srclen) &&
+	    memcmp(*dptr + matchoff, map->addr[dir].src, matchlen) == 0) {
+		addr    = map->addr[!dir].dst;
+		addrlen = map->addr[!dir].dstlen;
+	} else if ((matchlen == map->addr[dir].dstiplen ||
+		    matchlen == map->addr[dir].dstlen) &&
+		   memcmp(*dptr + matchoff, map->addr[dir].dst, matchlen) == 0) {
+		addr    = map->addr[!dir].src;
+		addrlen = map->addr[!dir].srclen;
+	} else
+		return 1;
+
+	if (!nf_nat_mangle_udp_packet(pskb, ct, ctinfo,
+	                              matchoff, matchlen, addr, addrlen))
+		return 0;
+	*dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+	return 1;
+
+}
+
+static unsigned int ip_nat_sip(struct sk_buff **pskb,
+			       enum ip_conntrack_info ctinfo,
+			       struct nf_conn *ct,
+			       const char **dptr)
+{
+	enum sip_header_pos pos;
+	struct addr_map map;
+	int dataoff, datalen;
+
+	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+	datalen = (*pskb)->len - dataoff;
+	if (datalen < sizeof("SIP/2.0") - 1)
+		return NF_DROP;
+
+	addr_map_init(ct, &map);
+
+	/* Basic rules: requests and responses. */
+	if (strncmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) {
+		/* 10.2: Constructing the REGISTER Request:
+		 *
+		 * The "userinfo" and "@" components of the SIP URI MUST NOT
+		 * be present.
+		 */
+		if (datalen >= sizeof("REGISTER") - 1 &&
+		    strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0)
+			pos = POS_REG_REQ_URI;
+		else
+			pos = POS_REQ_URI;
+
+		if (!map_sip_addr(pskb, ctinfo, ct, dptr, datalen, pos, &map))
+			return NF_DROP;
+	}
+
+	if (!map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_FROM, &map) ||
+	    !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_TO, &map) ||
+	    !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_VIA, &map) ||
+	    !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_CONTACT, &map))
+		return NF_DROP;
+	return NF_ACCEPT;
+}
+
+static unsigned int mangle_sip_packet(struct sk_buff **pskb,
+				      enum ip_conntrack_info ctinfo,
+				      struct nf_conn *ct,
+				      const char **dptr, size_t dlen,
+				      char *buffer, int bufflen,
+				      enum sip_header_pos pos)
+{
+	unsigned int matchlen, matchoff;
+
+	if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0)
+		return 0;
+
+	if (!nf_nat_mangle_udp_packet(pskb, ct, ctinfo,
+	                              matchoff, matchlen, buffer, bufflen))
+		return 0;
+
+	/* We need to reload this. Thanks Patrick. */
+	*dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+	return 1;
+}
+
+static int mangle_content_len(struct sk_buff **pskb,
+			      enum ip_conntrack_info ctinfo,
+			      struct nf_conn *ct,
+			      const char *dptr)
+{
+	unsigned int dataoff, matchoff, matchlen;
+	char buffer[sizeof("65536")];
+	int bufflen;
+
+	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+
+	/* Get actual SDP lenght */
+	if (ct_sip_get_info(ct, dptr, (*pskb)->len - dataoff, &matchoff,
+	                    &matchlen, POS_SDP_HEADER) > 0) {
+
+		/* since ct_sip_get_info() give us a pointer passing 'v='
+		   we need to add 2 bytes in this count. */
+		int c_len = (*pskb)->len - dataoff - matchoff + 2;
+
+		/* Now, update SDP length */
+		if (ct_sip_get_info(ct, dptr, (*pskb)->len - dataoff, &matchoff,
+		                    &matchlen, POS_CONTENT) > 0) {
+
+			bufflen = sprintf(buffer, "%u", c_len);
+			return nf_nat_mangle_udp_packet(pskb, ct, ctinfo,
+							matchoff, matchlen,
+							buffer, bufflen);
+		}
+	}
+	return 0;
+}
+
+static unsigned int mangle_sdp(struct sk_buff **pskb,
+			       enum ip_conntrack_info ctinfo,
+			       struct nf_conn *ct,
+			       __be32 newip, u_int16_t port,
+			       const char *dptr)
+{
+	char buffer[sizeof("nnn.nnn.nnn.nnn")];
+	unsigned int dataoff, bufflen;
+
+	dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+
+	/* Mangle owner and contact info. */
+	bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip));
+	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
+	                       buffer, bufflen, POS_OWNER_IP4))
+		return 0;
+
+	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
+	                       buffer, bufflen, POS_CONNECTION_IP4))
+		return 0;
+
+	/* Mangle media port. */
+	bufflen = sprintf(buffer, "%u", port);
+	if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
+	                       buffer, bufflen, POS_MEDIA))
+		return 0;
+
+	return mangle_content_len(pskb, ctinfo, ct, dptr);
+}
+
+/* So, this packet has hit the connection tracking matching code.
+   Mangle it, and change the expectation to match the new version. */
+static unsigned int ip_nat_sdp(struct sk_buff **pskb,
+			       enum ip_conntrack_info ctinfo,
+			       struct nf_conntrack_expect *exp,
+			       const char *dptr)
+{
+	struct nf_conn *ct = exp->master;
+	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+	__be32 newip;
+	u_int16_t port;
+
+	DEBUGP("ip_nat_sdp():\n");
+
+	/* Connection will come from reply */
+	newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
+
+	exp->tuple.dst.u3.ip = newip;
+	exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
+	exp->dir = !dir;
+
+	/* When you see the packet, we need to NAT it the same as the
+	   this one. */
+	exp->expectfn = nf_nat_follow_master;
+
+	/* Try to get same port: if not, try to change it. */
+	for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) {
+		exp->tuple.dst.u.udp.port = htons(port);
+		if (nf_conntrack_expect_related(exp) == 0)
+			break;
+	}
+
+	if (port == 0)
+		return NF_DROP;
+
+	if (!mangle_sdp(pskb, ctinfo, ct, newip, port, dptr)) {
+		nf_conntrack_unexpect_related(exp);
+		return NF_DROP;
+	}
+	return NF_ACCEPT;
+}
+
+static void __exit nf_nat_sip_fini(void)
+{
+	rcu_assign_pointer(nf_nat_sip_hook, NULL);
+	rcu_assign_pointer(nf_nat_sdp_hook, NULL);
+	synchronize_rcu();
+}
+
+static int __init nf_nat_sip_init(void)
+{
+	BUG_ON(rcu_dereference(nf_nat_sip_hook));
+	BUG_ON(rcu_dereference(nf_nat_sdp_hook));
+	rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip);
+	rcu_assign_pointer(nf_nat_sdp_hook, ip_nat_sdp);
+	return 0;
+}
+
+module_init(nf_nat_sip_init);
+module_exit(nf_nat_sip_fini);

net/netfilter/Kconfig

@@ -236,6 +236,18 @@ config NF_CONNTRACK_PPTP
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NF_CONNTRACK_SIP
+	tristate "SIP protocol support (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && NF_CONNTRACK
+	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 nf_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 N.
+
 config NF_CT_NETLINK
 	tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
 	depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK

net/netfilter/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
 obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
 obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
 obj-$(CONFIG_NF_CONNTRACK_PPTP) += nf_conntrack_pptp.o
+obj-$(CONFIG_NF_CONNTRACK_SIP) += nf_conntrack_sip.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o