[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>

6 files changed, 832 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index c3327ac024de..83e83f553ccb 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/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"
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index ef33ff2cdda9..167b65e89aca 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/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
diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
new file mode 100644
index 000000000000..3d524b957310
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -0,0 +1,283 @@
+/* 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);
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 6b2eb26ae03f..e73891194b31 100644
--- a/net/netfilter/Kconfig
+++ b/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
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 897bed4cbd79..86da21700aa3 100644
--- a/net/netfilter/Makefile
+++ b/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
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
new file mode 100644
index 000000000000..e0c06795a943
--- /dev/null
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -0,0 +1,530 @@
+/* SIP extension for IP connection tracking.
+ *
+ * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
+ * based on RR's ip_conntrack_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/ctype.h>
+#include <linux/skbuff.h>
+#include <linux/inet.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <linux/netfilter/nf_conntrack_sip.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
+MODULE_DESCRIPTION("SIP connection tracking helper");
+MODULE_ALIAS("ip_conntrack_sip");
+
+#define MAX_PORTS       8
+static unsigned short ports[MAX_PORTS];
+static int ports_c;
+module_param_array(ports, ushort, &ports_c, 0400);
+MODULE_PARM_DESC(ports, "port numbers of SIP servers");
+
+static unsigned int sip_timeout __read_mostly = SIP_TIMEOUT;
+module_param(sip_timeout, uint, 0600);
+MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session");
+
+unsigned int (*nf_nat_sip_hook)(struct sk_buff **pskb,
+                                enum ip_conntrack_info ctinfo,
+                                struct nf_conn *ct,
+                                const char **dptr) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_sip_hook);
+
+unsigned int (*nf_nat_sdp_hook)(struct sk_buff **pskb,
+                                enum ip_conntrack_info ctinfo,
+                                struct nf_conntrack_expect *exp,
+                                const char *dptr) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_sdp_hook);
+
+static int digits_len(struct nf_conn *, const char *, const char *, int *);
+static int epaddr_len(struct nf_conn *, const char *, const char *, int *);
+static int skp_digits_len(struct nf_conn *, const char *, const char *, int *);
+static int skp_epaddr_len(struct nf_conn *, const char *, const char *, int *);
+
+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             case_sensitive;
+        int             (*match_len)(struct nf_conn *, const char *,
+                                     const char *, int *);
+};
+
+static const struct sip_header_nfo ct_sip_hdrs[] = {
+        [POS_REG_REQ_URI] = {   /* SIP REGISTER request URI */
+                .lname          = "sip:",
+                .lnlen          = sizeof("sip:") - 1,
+                .ln_str         = ":",
+                .ln_strlen      = sizeof(":") - 1,
+                .match_len      = epaddr_len,
+        },
+        [POS_REQ_URI] = {       /* SIP request URI */
+                .lname          = "sip:",
+                .lnlen          = sizeof("sip:") - 1,
+                .ln_str         = "@",
+                .ln_strlen      = sizeof("@") - 1,
+                .match_len      = epaddr_len,
+        },
+        [POS_FROM] = {          /* SIP From header */
+                .lname          = "From:",
+                .lnlen          = sizeof("From:") - 1,
+                .sname          = "\r\nf:",
+                .snlen          = sizeof("\r\nf:") - 1,
+                .ln_str         = "sip:",
+                .ln_strlen      = sizeof("sip:") - 1,
+                .match_len      = skp_epaddr_len,
+        },
+        [POS_TO] = {            /* SIP To header */
+                .lname          = "To:",
+                .lnlen          = sizeof("To:") - 1,
+                .sname          = "\r\nt:",
+                .snlen          = sizeof("\r\nt:") - 1,
+                .ln_str         = "sip:",
+                .ln_strlen      = sizeof("sip:") - 1,
+                .match_len      = skp_epaddr_len
+        },
+        [POS_VIA] = {           /* SIP Via header */
+                .lname          = "Via:",
+                .lnlen          = sizeof("Via:") - 1,
+                .sname          = "\r\nv:",
+                .snlen          = sizeof("\r\nv:") - 1, /* rfc3261 "\r\n" */
+                .ln_str         = "UDP ",
+                .ln_strlen      = sizeof("UDP ") - 1,
+                .match_len      = epaddr_len,
+        },
+        [POS_CONTACT] = {       /* SIP Contact header */
+                .lname          = "Contact:",
+                .lnlen          = sizeof("Contact:") - 1,
+                .sname          = "\r\nm:",
+                .snlen          = sizeof("\r\nm:") - 1,
+                .ln_str         = "sip:",
+                .ln_strlen      = sizeof("sip:") - 1,
+                .match_len      = skp_epaddr_len
+        },
+        [POS_CONTENT] = {       /* SIP Content length header */
+                .lname          = "Content-Length:",
+                .lnlen          = sizeof("Content-Length:") - 1,
+                .sname          = "\r\nl:",
+                .snlen          = sizeof("\r\nl:") - 1,
+                .ln_str         = ":",
+                .ln_strlen      = sizeof(":") - 1,
+                .match_len      = skp_digits_len
+        },
+        [POS_MEDIA] = {         /* SDP media info */
+                .case_sensitive = 1,
+                .lname          = "\nm=",
+                .lnlen          = sizeof("\nm=") - 1,
+                .sname          = "\rm=",
+                .snlen          = sizeof("\rm=") - 1,
+                .ln_str         = "audio ",
+                .ln_strlen      = sizeof("audio ") - 1,
+                .match_len      = digits_len
+        },
+        [POS_OWNER_IP4] = {     /* SDP owner address*/
+                .case_sensitive = 1,
+                .lname          = "\no=",
+                .lnlen          = sizeof("\no=") - 1,
+                .sname          = "\ro=",
+                .snlen          = sizeof("\ro=") - 1,
+                .ln_str         = "IN IP4 ",
+                .ln_strlen      = sizeof("IN IP4 ") - 1,
+                .match_len      = epaddr_len
+        },
+        [POS_CONNECTION_IP4] = {/* SDP connection info */
+                .case_sensitive = 1,
+                .lname          = "\nc=",
+                .lnlen          = sizeof("\nc=") - 1,
+                .sname          = "\rc=",
+                .snlen          = sizeof("\rc=") - 1,
+                .ln_str         = "IN IP4 ",
+                .ln_strlen      = sizeof("IN IP4 ") - 1,
+                .match_len      = epaddr_len
+        },
+        [POS_OWNER_IP6] = {     /* SDP owner address*/
+                .case_sensitive = 1,
+                .lname          = "\no=",
+                .lnlen          = sizeof("\no=") - 1,
+                .sname          = "\ro=",
+                .snlen          = sizeof("\ro=") - 1,
+                .ln_str         = "IN IP6 ",
+                .ln_strlen      = sizeof("IN IP6 ") - 1,
+                .match_len      = epaddr_len
+        },
+        [POS_CONNECTION_IP6] = {/* SDP connection info */
+                .case_sensitive = 1,
+                .lname          = "\nc=",
+                .lnlen          = sizeof("\nc=") - 1,
+                .sname          = "\rc=",
+                .snlen          = sizeof("\rc=") - 1,
+                .ln_str         = "IN IP6 ",
+                .ln_strlen      = sizeof("IN IP6 ") - 1,
+                .match_len      = epaddr_len
+        },
+        [POS_SDP_HEADER] = {    /* SDP version header */
+                .case_sensitive = 1,
+                .lname          = "\nv=",
+                .lnlen          = sizeof("\nv=") - 1,
+                .sname          = "\rv=",
+                .snlen          = sizeof("\rv=") - 1,
+                .ln_str         = "=",
+                .ln_strlen      = sizeof("=") - 1,
+                .match_len      = digits_len
+        }
+};
+
+/* get line lenght until first CR or LF seen. */
+int ct_sip_lnlen(const char *line, const char *limit)
+{
+        const char *k = line;
+
+        while ((line <= limit) && (*line == '\r' || *line == '\n'))
+                line++;
+
+        while (line <= limit) {
+                if (*line == '\r' || *line == '\n')
+                        break;
+                line++;
+        }
+        return line - k;
+}
+EXPORT_SYMBOL_GPL(ct_sip_lnlen);
+
+/* Linear string search, case sensitive. */
+const char *ct_sip_search(const char *needle, const char *haystack,
+                          size_t needle_len, size_t haystack_len,
+                          int case_sensitive)
+{
+        const char *limit = haystack + (haystack_len - needle_len);
+
+        while (haystack <= limit) {
+                if (case_sensitive) {
+                        if (strncmp(haystack, needle, needle_len) == 0)
+                                return haystack;
+                } else {
+                        if (strnicmp(haystack, needle, needle_len) == 0)
+                                return haystack;
+                }
+                haystack++;
+        }
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(ct_sip_search);
+
+static int digits_len(struct nf_conn *ct, const char *dptr,
+                      const char *limit, int *shift)
+{
+        int len = 0;
+        while (dptr <= limit && isdigit(*dptr)) {
+                dptr++;
+                len++;
+        }
+        return len;
+}
+
+/* get digits lenght, skiping blank spaces. */
+static int skp_digits_len(struct nf_conn *ct, const char *dptr,
+                          const char *limit, int *shift)
+{
+        for (; dptr <= limit && *dptr == ' '; dptr++)
+                (*shift)++;
+
+        return digits_len(ct, dptr, limit, shift);
+}
+
+static int parse_addr(struct nf_conn *ct, const char *cp, const char **endp,
+                      union nf_conntrack_address *addr, const char *limit)
+{
+        const char *end;
+        int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
+        int ret = 0;
+
+        switch (family) {
+        case AF_INET:
+                ret = in4_pton(cp, limit - cp, (u8 *)&addr->ip, -1, &end);
+                break;
+        case AF_INET6:
+                ret = in6_pton(cp, limit - cp, (u8 *)&addr->ip6, -1, &end);
+                break;
+        default:
+                BUG();
+        }
+
+        if (ret == 0 || end == cp)
+                return 0;
+        if (endp)
+                *endp = end;
+        return 1;
+}
+
+/* skip ip address. returns its length. */
+static int epaddr_len(struct nf_conn *ct, const char *dptr,
+                      const char *limit, int *shift)
+{
+        union nf_conntrack_address addr;
+        const char *aux = dptr;
+
+        if (!parse_addr(ct, dptr, &dptr, &addr, limit)) {
+                DEBUGP("ip: %s parse failed.!\n", dptr);
+                return 0;
+        }
+
+        /* Port number */
+        if (*dptr == ':') {
+                dptr++;
+                dptr += digits_len(ct, dptr, limit, shift);
+        }
+        return dptr - aux;
+}
+
+/* get address length, skiping user info. */
+static int skp_epaddr_len(struct nf_conn *ct, const char *dptr,
+                          const char *limit, int *shift)
+{
+        int s = *shift;
+
+        for (; dptr <= limit && *dptr != '@'; dptr++)
+                (*shift)++;
+
+        if (*dptr == '@') {
+                dptr++;
+                (*shift)++;
+        } else
+                *shift = s;
+
+        return epaddr_len(ct, dptr, limit, shift);
+}
+
+/* Returns 0 if not found, -1 error parsing. */
+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)
+{
+        const struct sip_header_nfo *hnfo = &ct_sip_hdrs[pos];
+        const char *limit, *aux, *k = dptr;
+        int shift = 0;
+
+        limit = dptr + (dlen - hnfo->lnlen);
+
+        while (dptr <= limit) {
+                if ((strncmp(dptr, hnfo->lname, hnfo->lnlen) != 0) &&
+                    (strncmp(dptr, hnfo->sname, hnfo->snlen) != 0)) {
+                        dptr++;
+                        continue;
+                }
+                aux = ct_sip_search(hnfo->ln_str, dptr, hnfo->ln_strlen,
+                                    ct_sip_lnlen(dptr, limit),
+                                    hnfo->case_sensitive);
+                if (!aux) {
+                        DEBUGP("'%s' not found in '%s'.\n", hnfo->ln_str,
+                               hnfo->lname);
+                        return -1;
+                }
+                aux += hnfo->ln_strlen;
+
+                *matchlen = hnfo->match_len(ct, aux, limit, &shift);
+                if (!*matchlen)
+                        return -1;
+
+                *matchoff = (aux - k) + shift;
+
+                DEBUGP("%s match succeeded! - len: %u\n", hnfo->lname,
+                       *matchlen);
+                return 1;
+        }
+        DEBUGP("%s header not found.\n", hnfo->lname);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(ct_sip_get_info);
+
+static int set_expected_rtp(struct sk_buff **pskb,
+                            struct nf_conn *ct,
+                            enum ip_conntrack_info ctinfo,
+                            union nf_conntrack_address *addr,
+                            __be16 port,
+                            const char *dptr)
+{
+        struct nf_conntrack_expect *exp;
+        enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+        int family = ct->tuplehash[!dir].tuple.src.l3num;
+        int ret;
+        typeof(nf_nat_sdp_hook) nf_nat_sdp;
+
+        exp = nf_conntrack_expect_alloc(ct);
+        if (exp == NULL)
+                return NF_DROP;
+        nf_conntrack_expect_init(exp, family,
+                                 &ct->tuplehash[!dir].tuple.src.u3, addr,
+                                 IPPROTO_UDP, NULL, &port);
+
+        nf_nat_sdp = rcu_dereference(nf_nat_sdp_hook);
+        if (nf_nat_sdp && ct->status & IPS_NAT_MASK)
+                ret = nf_nat_sdp(pskb, ctinfo, exp, dptr);
+        else {
+                if (nf_conntrack_expect_related(exp) != 0)
+                        ret = NF_DROP;
+                else
+                        ret = NF_ACCEPT;
+        }
+        nf_conntrack_expect_put(exp);
+
+        return ret;
+}
+
+static int sip_help(struct sk_buff **pskb,
+                    unsigned int protoff,
+                    struct nf_conn *ct,
+                    enum ip_conntrack_info ctinfo)
+{
+        int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
+        union nf_conntrack_address addr;
+        unsigned int dataoff, datalen;
+        const char *dptr;
+        int ret = NF_ACCEPT;
+        int matchoff, matchlen;
+        u_int16_t port;
+        enum sip_header_pos pos;
+        typeof(nf_nat_sip_hook) nf_nat_sip;
+
+        /* No Data ? */
+        dataoff = protoff + sizeof(struct udphdr);
+        if (dataoff >= (*pskb)->len)
+                return NF_ACCEPT;
+
+        nf_ct_refresh(ct, *pskb, sip_timeout * HZ);
+
+        if (!skb_is_nonlinear(*pskb))
+                dptr = (*pskb)->data + dataoff;
+        else {
+                DEBUGP("Copy of skbuff not supported yet.\n");
+                goto out;
+        }
+
+        nf_nat_sip = rcu_dereference(nf_nat_sip_hook);
+        if (nf_nat_sip && ct->status & IPS_NAT_MASK) {
+                if (!nf_nat_sip(pskb, ctinfo, ct, &dptr)) {
+                        ret = NF_DROP;
+                        goto out;
+                }
+        }
+
+        datalen = (*pskb)->len - dataoff;
+        if (datalen < sizeof("SIP/2.0 200") - 1)
+                goto out;
+
+        /* RTP info only in some SDP pkts */
+        if (memcmp(dptr, "INVITE", sizeof("INVITE") - 1) != 0 &&
+            memcmp(dptr, "SIP/2.0 200", sizeof("SIP/2.0 200") - 1) != 0) {
+                goto out;
+        }
+        /* Get address and port from SDP packet. */
+        pos = family == AF_INET ? POS_CONNECTION_IP4 : POS_CONNECTION_IP6;
+        if (ct_sip_get_info(ct, dptr, datalen, &matchoff, &matchlen, pos) > 0) {
+
+                /* We'll drop only if there are parse problems. */
+                if (!parse_addr(ct, dptr + matchoff, NULL, &addr,
+                                dptr + datalen)) {
+                        ret = NF_DROP;
+                        goto out;
+                }
+                if (ct_sip_get_info(ct, dptr, datalen, &matchoff, &matchlen,
+                                    POS_MEDIA) > 0) {
+
+                        port = simple_strtoul(dptr + matchoff, NULL, 10);
+                        if (port < 1024) {
+                                ret = NF_DROP;
+                                goto out;
+                        }
+                        ret = set_expected_rtp(pskb, ct, ctinfo, &addr,
+                                               htons(port), dptr);
+                }
+        }
+out:
+        return ret;
+}
+
+static struct nf_conntrack_helper sip[MAX_PORTS][2] __read_mostly;
+static char sip_names[MAX_PORTS][2][sizeof("sip-65535")] __read_mostly;
+
+static void nf_conntrack_sip_fini(void)
+{
+        int i, j;
+
+        for (i = 0; i < ports_c; i++) {
+                for (j = 0; j < 2; j++) {
+                        if (sip[i][j].me == NULL)
+                                continue;
+                        nf_conntrack_helper_unregister(&sip[i][j]);
+                }
+        }
+}
+
+static int __init nf_conntrack_sip_init(void)
+{
+        int i, j, ret;
+        char *tmpname;
+
+        if (ports_c == 0)
+                ports[ports_c++] = SIP_PORT;
+
+        for (i = 0; i < ports_c; i++) {
+                memset(&sip[i], 0, sizeof(sip[i]));
+
+                sip[i][0].tuple.src.l3num = AF_INET;
+                sip[i][1].tuple.src.l3num = AF_INET6;
+                for (j = 0; j < 2; j++) {
+                        sip[i][j].tuple.dst.protonum = IPPROTO_UDP;
+                        sip[i][j].tuple.src.u.udp.port = htons(ports[i]);
+                        sip[i][j].mask.src.l3num = 0xFFFF;
+                        sip[i][j].mask.src.u.udp.port = htons(0xFFFF);
+                        sip[i][j].mask.dst.protonum = 0xFF;
+                        sip[i][j].max_expected = 2;
+                        sip[i][j].timeout = 3 * 60; /* 3 minutes */
+                        sip[i][j].me = THIS_MODULE;
+                        sip[i][j].help = sip_help;
+
+                        tmpname = &sip_names[i][j][0];
+                        if (ports[i] == SIP_PORT)
+                                sprintf(tmpname, "sip");
+                        else
+                                sprintf(tmpname, "sip-%u", i);
+                        sip[i][j].name = tmpname;
+
+                        DEBUGP("port #%u: %u\n", i, ports[i]);
+
+                        ret = nf_conntrack_helper_register(&sip[i][j]);
+                        if (ret) {
+                                printk("nf_ct_sip: failed to register helper "
+                                       "for pf: %u port: %u\n",
+                                       sip[i][j].tuple.src.l3num, ports[i]);
+                                nf_conntrack_sip_fini();
+                                return ret;
+                        }
+                }
+        }
+        return 0;
+}
+
+module_init(nf_conntrack_sip_init);
+module_exit(nf_conntrack_sip_fini);