--- /dev/null
+/* 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);
git://git.onelab.eu / linux-2.6.git / blobdiff