关于linux2.6.19版本中SIP协议NAT的处理
本帖最后由 飞机塞进菊花 于 2014-07-07 10:03 编辑最近在研究SIP在nat中的处理 看了比较早期的内核代码2.6.19只支持DUP+IPV4
但找了很久没有找到关于RTCP期待连接的处理。
还有INVINTE和对于call-ID的200OK会导致两条期待连接的建立，表示不解，求指点 一下是内核相关源码
ip_commtrack_sip.c
/* 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/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_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");
#define MAX_PORTS 8
static unsigned short 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 = SIP_TIMEOUT;
module_param(sip_timeout, uint, 0600);
MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session");
unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb,
enum ip_conntrack_info ctinfo,
struct ip_conntrack *ct,
const char **dptr);
EXPORT_SYMBOL_GPL(ip_nat_sip_hook);
unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb,
enum ip_conntrack_info ctinfo,
struct ip_conntrack_expect *exp,
const char *dptr);
EXPORT_SYMBOL_GPL(ip_nat_sdp_hook);
int ct_sip_get_info(const char *dptr, size_t dlen,
unsigned int *matchoff,
unsigned int *matchlen,
struct sip_header_nfo *hnfo);
EXPORT_SYMBOL_GPL(ct_sip_get_info);
static int digits_len(const char *dptr, const char *limit, int *shift);
static int epaddr_len(const char *dptr, const char *limit, int *shift);
static int skp_digits_len(const char *dptr, const char *limit, int *shift);
static int skp_epaddr_len(const char *dptr, const char *limit, int *shift);
struct sip_header_nfo ct_sip_hdrs[] = {
{ /* 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,
},
{ /* 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
},
{ /* 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
},
{ /* SDP media info */
.lname = "\nm=",
.lnlen = sizeof("\nm=") - 1,
.sname = "\rm=",
.snlen = sizeof("\rm=") - 1,
.ln_str = "audio ",
.ln_strlen = sizeof("audio ") - 1,
.match_len = digits_len
},
{ /* SDP owner address*/
.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
},
{ /* SDP connection info */
.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
},
{ /* Requests headers */
.lname = "sip:",
.lnlen = sizeof("sip:") - 1,
.sname = "sip:",
.snlen = sizeof("sip:") - 1, /* yes, i know.. ;) */
.ln_str = "@",
.ln_strlen = sizeof("@") - 1,
.match_len = epaddr_len
},
{ /* SDP version header */
.lname = "\nv=",
.lnlen = sizeof("\nv=") - 1,
.sname = "\rv=",
.snlen = sizeof("\rv=") - 1,
.ln_str = "=",
.ln_strlen = sizeof("=") - 1,
.match_len = digits_len
}
};
EXPORT_SYMBOL_GPL(ct_sip_hdrs);
/* 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)
{
const char *limit = haystack + (haystack_len - needle_len);
while (haystack <= limit) {
if (memcmp(haystack, needle, needle_len) == 0)
return haystack;
haystack++;
}
return NULL;
}
EXPORT_SYMBOL_GPL(ct_sip_search);
static int digits_len(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(const char *dptr, const char *limit, int *shift)
{
for (; dptr <= limit && *dptr == ' '; dptr++)
(*shift)++;
return digits_len(dptr, limit, shift);
}
/* Simple ipaddr parser.. */
static int parse_ipaddr(const char *cp, const char **endp,
__be32 *ipaddr, const char *limit)
{
unsigned long int val;
int i, digit = 0;
for (i = 0, *ipaddr = 0; cp <= limit && i < 4; i++) {
digit = 0;
if (!isdigit(*cp))
break;
val = simple_strtoul(cp, (char **)&cp, 10);
if (val > 0xFF)
return -1;
((u_int8_t *)ipaddr) = val;
digit = 1;
if (*cp != '.')
break;
cp++;
}
if (!digit)
return -1;
if (endp)
*endp = cp;
return 0;
}
/* skip ip address. returns it lenght. */
static int epaddr_len(const char *dptr, const char *limit, int *shift)
{
const char *aux = dptr;
__be32 ip;
if (parse_ipaddr(dptr, &dptr, &ip, limit) < 0) {
DEBUGP("ip: %s parse failed.!\n", dptr);
return 0;
}
/* Port number */
if (*dptr == ':') {
dptr++;
dptr += digits_len(dptr, limit, shift);
}
return dptr - aux;
}
/* get address length, skiping user info. */
static int skp_epaddr_len(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(dptr, limit, shift);
}
/* Returns 0 if not found, -1 error parsing. */
int ct_sip_get_info(const char *dptr, size_t dlen,
unsigned int *matchoff,
unsigned int *matchlen,
struct sip_header_nfo *hnfo)
{
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));
if (!aux) {
DEBUGP("'%s' not found in '%s'.\n", hnfo->ln_str,
hnfo->lname);
return -1;
}
aux += hnfo->ln_strlen;
*matchlen = hnfo->match_len(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;
}
static int set_expected_rtp(struct sk_buff **pskb,
struct ip_conntrack *ct,
enum ip_conntrack_info ctinfo,
__be32 ipaddr, u_int16_t port,
const char *dptr)
{
struct ip_conntrack_expect *exp;
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
int ret;
exp = ip_conntrack_expect_alloc(ct);
if (exp == NULL)
return NF_DROP;
exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip;
exp->tuple.src.u.udp.port = 0;
exp->tuple.dst.ip = ipaddr;
exp->tuple.dst.u.udp.port = htons(port);
exp->tuple.dst.protonum = IPPROTO_UDP;
exp->mask.src.ip = htonl(0xFFFFFFFF);
exp->mask.src.u.udp.port = 0;
exp->mask.dst.ip = htonl(0xFFFFFFFF);
exp->mask.dst.u.udp.port = htons(0xFFFF);
exp->mask.dst.protonum = 0xFF;
exp->expectfn = NULL;
exp->flags = 0;
if (ip_nat_sdp_hook)
ret = ip_nat_sdp_hook(pskb, ctinfo, exp, dptr);
else {
if (ip_conntrack_expect_related(exp) != 0)
ret = NF_DROP;
else
ret = NF_ACCEPT;
}
ip_conntrack_expect_put(exp);
return ret;
}
static int sip_help(struct sk_buff **pskb,
struct ip_conntrack *ct,
enum ip_conntrack_info ctinfo)
{
unsigned int dataoff, datalen;
const char *dptr;
int ret = NF_ACCEPT;
int matchoff, matchlen;
__be32 ipaddr;
u_int16_t port;
/* No Data ? */
dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
if (dataoff >= (*pskb)->len) {
DEBUGP("skb->len = %u\n", (*pskb)->len);
return NF_ACCEPT;
}
ip_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;
}
if (ip_nat_sip_hook) {
if (!ip_nat_sip_hook(pskb, ctinfo, ct, &dptr)) {
ret = NF_DROP;
goto out;
}
}
/* After this point NAT, could have mangled skb, so
we need to recalculate payload lenght. */
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 ip and port address from SDP packet. */
if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen,
&ct_sip_hdrs) > 0) {
/* We'll drop only if there are parse problems. */
if (parse_ipaddr(dptr + matchoff, NULL, &ipaddr,
dptr + datalen) < 0) {
ret = NF_DROP;
goto out;
}
if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen,
&ct_sip_hdrs) > 0) {
port = simple_strtoul(dptr + matchoff, NULL, 10);
if (port < 1024) {
ret = NF_DROP;
goto out;
}
ret = set_expected_rtp(pskb, ct, ctinfo,
ipaddr, port, dptr);
}
}
out:
return ret;
}
static struct ip_conntrack_helper sip;
static char sip_names;
static void fini(void)
{
int i;
for (i = 0; i < ports_c; i++) {
DEBUGP("unregistering helper for port %d\n", ports);
ip_conntrack_helper_unregister(&sip);
}
}
static int __init init(void)
{
int i, ret;
char *tmpname;
if (ports_c == 0)
ports = SIP_PORT;
for (i = 0; i < ports_c; i++) {
/* Create helper structure */
memset(&sip, 0, sizeof(struct ip_conntrack_helper));
sip.tuple.dst.protonum = IPPROTO_UDP;
sip.tuple.src.u.udp.port = htons(ports);
sip.mask.src.u.udp.port = htons(0xFFFF);
sip.mask.dst.protonum = 0xFF;
sip.max_expected = 2;
sip.timeout = 3 * 60; /* 3 minutes */
sip.me = THIS_MODULE;
sip.help = sip_help;
tmpname = &sip_names;
if (ports == SIP_PORT)
sprintf(tmpname, "sip");
else
sprintf(tmpname, "sip-%d", i);
sip.name = tmpname;
DEBUGP("port #%d: %d\n", i, ports);
ret = ip_conntrack_helper_register(&sip);
if (ret) {
printk("ERROR registering helper for port %d\n",
ports);
fini();
return ret;
}
}
return 0;
}
module_init(init);
module_exit(fini);
ip_nat_ip.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 <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;
unsigned int bufflen, dataoff;
__be32 ip;
__be16 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);
return 1;
}
if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
(*pskb)->len - dataoff,
buffer, bufflen, &ct_sip_hdrs))
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);
}
if ((ctinfo) < IP_CT_IS_REPLY) {
if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
(*pskb)->len - dataoff,
buffer, bufflen, &ct_sip_hdrs))
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);
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);
}
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;
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) > 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) > 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,
__be32 newip, u_int16_t port,
const char *dptr)
{
char buffer;
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))
return 0;
if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff,
buffer, bufflen, &ct_sip_hdrs))
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))
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);
__be32 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);
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