--- /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 <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv4/ip_nat.h>
+#include <linux/netfilter_ipv4/ip_nat_helper.h>
+#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
+#include <linux/netfilter_ipv4/ip_conntrack_sip.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
+MODULE_DESCRIPTION("SIP NAT helper");
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+extern struct sip_header_nfo ct_sip_hdrs[];
+
+static unsigned int mangle_sip_packet(struct sk_buff **pskb,
+ enum ip_conntrack_info ctinfo,
+ struct ip_conntrack *ct,
+ const char **dptr, size_t dlen,
+ char *buffer, int bufflen,
+ struct sip_header_nfo *hnfo)
+{
+ unsigned int matchlen, matchoff;
+
+ if (ct_sip_get_info(*dptr, dlen, &matchoff, &matchlen, hnfo) <= 0)
+ return 0;
+
+ if (!ip_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 unsigned int ip_nat_sip(struct sk_buff **pskb,
+ enum ip_conntrack_info ctinfo,
+ struct ip_conntrack *ct,
+ const char **dptr)
+{
+ enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+ char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
+ unsigned int bufflen, dataoff;
+ u_int32_t ip;
+ u_int16_t port;
+
+ dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+
+ ip = ct->tuplehash[!dir].tuple.dst.ip;
+ port = ct->tuplehash[!dir].tuple.dst.u.udp.port;
+ bufflen = sprintf(buffer, "%u.%u.%u.%u:%u", NIPQUAD(ip), ntohs(port));
+
+ /* short packet ? */
+ if (((*pskb)->len - dataoff) < (sizeof("SIP/2.0") - 1))
+ return 0;
+
+ /* Basic rules: requests and responses. */
+ if (memcmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) == 0) {
+ const char *aux;
+
+ if ((ctinfo) < IP_CT_IS_REPLY) {
+ mangle_sip_packet(pskb, ctinfo, ct, dptr,
+ (*pskb)->len - dataoff,
+ buffer, bufflen,
+ &ct_sip_hdrs[POS_CONTACT]);
+ return 1;
+ }
+
+ if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
+ (*pskb)->len - dataoff,
+ buffer, bufflen, &ct_sip_hdrs[POS_VIA]))
+ return 0;
+
+ /* This search should ignore case, but later.. */
+ aux = ct_sip_search("CSeq:", *dptr, sizeof("CSeq:") - 1,
+ (*pskb)->len - dataoff);
+ if (!aux)
+ return 0;
+
+ if (!ct_sip_search("REGISTER", aux, sizeof("REGISTER"),
+ ct_sip_lnlen(aux, *dptr + (*pskb)->len - dataoff)))
+ return 1;
+
+ return mangle_sip_packet(pskb, ctinfo, ct, dptr,
+ (*pskb)->len - dataoff,
+ buffer, bufflen,
+ &ct_sip_hdrs[POS_CONTACT]);
+ }
+ if ((ctinfo) < IP_CT_IS_REPLY) {
+ if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
+ (*pskb)->len - dataoff,
+ buffer, bufflen, &ct_sip_hdrs[POS_VIA]))
+ return 0;
+
+ /* Mangle Contact if exists only. - watch udp_nat_mangle()! */
+ mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff,
+ buffer, bufflen, &ct_sip_hdrs[POS_CONTACT]);
+ return 1;
+ }
+ /* This mangle requests headers. */
+ return mangle_sip_packet(pskb, ctinfo, ct, dptr,
+ ct_sip_lnlen(*dptr,
+ *dptr + (*pskb)->len - dataoff),
+ buffer, bufflen, &ct_sip_hdrs[POS_REQ_HEADER]);
+}
+
+static int mangle_content_len(struct sk_buff **pskb,
+ enum ip_conntrack_info ctinfo,
+ struct ip_conntrack *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(dptr, (*pskb)->len - dataoff, &matchoff,
+ &matchlen, &ct_sip_hdrs[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 lenght */
+ if (ct_sip_get_info(dptr, (*pskb)->len - dataoff, &matchoff,
+ &matchlen, &ct_sip_hdrs[POS_CONTENT]) > 0) {
+
+ bufflen = sprintf(buffer, "%u", c_len);
+
+ return ip_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 ip_conntrack *ct,
+ u_int32_t 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, &ct_sip_hdrs[POS_OWNER]))
+ return 0;
+
+ if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
+ buffer, bufflen, &ct_sip_hdrs[POS_CONNECTION]))
+ return 0;
+
+ /* Mangle media port. */
+ bufflen = sprintf(buffer, "%u", port);
+ if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
+ buffer, bufflen, &ct_sip_hdrs[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 ip_conntrack_expect *exp,
+ const char *dptr)
+{
+ struct ip_conntrack *ct = exp->master;
+ enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+ u_int32_t newip;
+ u_int16_t port;
+
+ DEBUGP("ip_nat_sdp():\n");
+
+ /* Connection will come from reply */
+ newip = ct->tuplehash[!dir].tuple.dst.ip;
+
+ exp->tuple.dst.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 = ip_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 (ip_conntrack_expect_related(exp) == 0)
+ break;
+ }
+
+ if (port == 0)
+ return NF_DROP;
+
+ if (!mangle_sdp(pskb, ctinfo, ct, newip, port, dptr)) {
+ ip_conntrack_unexpect_related(exp);
+ return NF_DROP;
+ }
+ return NF_ACCEPT;
+}
+
+static void __exit fini(void)
+{
+ ip_nat_sip_hook = NULL;
+ ip_nat_sdp_hook = NULL;
+ /* Make sure noone calls it, meanwhile. */
+ synchronize_net();
+}
+
+static int __init init(void)
+{
+ BUG_ON(ip_nat_sip_hook);
+ BUG_ON(ip_nat_sdp_hook);
+ ip_nat_sip_hook = ip_nat_sip;
+ ip_nat_sdp_hook = ip_nat_sdp;
+ return 0;
+}
+
+module_init(init);
+module_exit(fini);
git://git.onelab.eu / linux-2.6.git / blobdiff