Ok, after finding out rather late that the rtsp patch did not work with 2.6.22, I downloaded 2.6.23-rc2 and ported it yet again. As always you can find the code here. I really hope that this patch will survive 2.6.23-final.

NB: As always, this code works for me, if you find any bugs or have fixes please contact me.


Gravatar
Fri Sep 7 17:08:49 2007
LORAND Benoit says:
hi,

  i have used your two rtsp's patches and notice they don't work with mythtv (on freebox in france). I can't change url (channel in this case) since i have opened one first.

The last patche i know to work is this one for 2.6.19.2 :

diff -Naur linux-2.6.19.2/include/linux/netfilter_ipv4/ip_conntrack_rtsp.h linux-2.6.19.2-rtsp/include/linux/netfilter_ipv4/ip_conntrack_rtsp.h
--- linux-2.6.19.2/include/linux/netfilter_ipv4/ip_conntrack_rtsp.h 1970-01-01 01:00:00.000000000  0100
  linux-2.6.19.2-rtsp/include/linux/netfilter_ipv4/ip_conntrack_rtsp.h 2007-01-27 18:18:35.000000000  0100
@@ -0,0  1,60 @@
/*
  * RTSP extension for IP connection tracking.
  * (C) 2003 by Tom Marshall <tmarshall@real.com>
  * based on ip_conntrack_irc.h
  *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  as published by the Free Software Foundation; either version
  *  2 of the License, or (at your option) any later version.
  */
#ifndef _IP_CONNTRACK_RTSP_H
#define _IP_CONNTRACK_RTSP_H

//#define IP_NF_RTSP_DEBUG 1
#define IP_NF_RTSP_VERSION "0.6.21"

#ifdef _KERNEL_
/* port block types */
typedef enum {
  pb_single,  /* client_port=x */
  pb_range,  /* client_port=x-y */
  pb_discon  /* client_port=x/y (rtspbis) */
} portblock_t;

/* We record seq number and length of rtsp headers here, all in host order. */

/*
  * This structure is per expected connection.  It is a member of struct
  * ip_conntrack_expect.  The TCP SEQ for the conntrack expect is stored
  * there and we are expected to only store the length of the data which
  * needs replaced.  If a packet contains multiple RTSP messages, we create
  * one expected connection per message.
  *
  * We use these variables to mark the entire header block.  This may seem
  * like overkill, but the nature of RTSP requires it.  A header may appear
  * multiple times in a message.  We must treat two Transport headers the
  * same as one Transport header with two entries.
  */
struct ip_ct_rtsp_expect
{
  u_int32_t  len;  /* length of header block */
  portblock_t pbtype;  /* Type of port block that was requested */
  u_int16_t  loport;  /* Port that was requested, low or first */
  u_int16_t  hiport;  /* Port that was requested, high or second */
#if 0
  uint  method;  /* RTSP method */
  uint  cseq;  /* CSeq from request */
#endif
};

extern unsigned int (ip_nat_rtsp_hook)(struct sk_buff *pskb,
enum ip_conntrack_info ctinfo,
unsigned int matchoff, unsigned int matchlen,
struct ip_ct_rtsp_expect *expinfo,
struct ip_conntrack_expect *exp);
#define RTSP_PORT  554

#endif /* _KERNEL_ */

#endif /* _IP_CONNTRACK_RTSP_H */
diff -Naur linux-2.6.19.2/net/ipv4/netfilter/ip_conntrack_rtsp.c linux-2.6.19.2-rtsp/net/ipv4/netfilter/ip_conntrack_rtsp.c
--- linux-2.6.19.2/net/ipv4/netfilter/ip_conntrack_rtsp.c 1970-01-01 01:00:00.000000000  0100
  linux-2.6.19.2-rtsp/net/ipv4/netfilter/ip_conntrack_rtsp.c 2007-01-27 18:22:32.000000000  0100
@@ -0,0  1,537 @@
/*
  * RTSP extension for IP connection tracking
  * (C) 2003 by Tom Marshall <tmarshall@real.com>
  * based on ip_conntrack_irc.c
  *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  as published by the Free Software Foundation; either version
  *  2 of the License, or (at your option) any later version.
  *
  * Module load syntax:
  *  insmod ip_conntrack_rtsp.o ports=port1,port2,...port<MAX_PORTS>
  *  max_outstanding=n setup_timeout=secs
  *
  * If no ports are specified, the default will be port 554.
  *
  * With max_outstanding you can define the maximum number of not yet
  * answered SETUP requests per RTSP session (default 8).
  * With setup_timeout you can specify how long the system waits for
  * an expected data channel (default 300 seconds).
  *
  * 2005-02-13: Harald Welte <laforge@netfilter.org>
  * - port to 2.6
  * - update to recent post-2.6.11 api changes
  */

  /* #include <linux/config.h>
  */
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/inet.h>
#include <net/checksum.h>
#include <net/tcp.h>

#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_conntrack_rtsp.h>

#include <linux/ctype.h>
#define NF_NEED_STRNCASECMP
#define NF_NEED_STRTOU16
#define NF_NEED_STRTOU32
#define NF_NEED_NEXTLINE
#include <linux/netfilter_helpers.h>
#define NF_NEED_MIME_NEXTLINE
#include <linux/netfilter_mime.h>

#define MAX_SIMUL_SETUP 8 /* XXX: use max_outstanding */
#define IP_NF_RTSP_DEBUG
#define INFOP(fmt, args...) printk(KERN_INFO "%s: %s: " fmt, _FILE_, _FUNCTION_ , ## args)
#ifdef IP_NF_RTSP_DEBUG
#define DEBUGP(fmt, args...) printk(KERN_DEBUG "%s: %s: " fmt, _FILE_, _FUNCTION_ , ## args)
#else
#define DEBUGP(fmt, args...)
#endif

#define MAX_PORTS 8
static int ports[MAX_PORTS];
static int num_ports = 0;
static int max_outstanding = 8;
static unsigned int setup_timeout = 300;

MODULE_AUTHOR("Tom Marshall <tmarshall@real.com>");
MODULE_DESCRIPTION("RTSP connection tracking module");
MODULE_LICENSE("GPL");
module_param_array(ports, int, &num_ports, 0400);
MODULE_PARM_DESC(ports, "port numbers of RTSP servers");
module_param(max_outstanding, int, 0400);
MODULE_PARM_DESC(max_outstanding, "max number of outstanding SETUP requests per RTSP session");
module_param(setup_timeout, int, 0400);
MODULE_PARM_DESC(setup_timeout, "timeout on for unestablished data channels");

static char *rtsp_buffer;
static DEFINE_SPINLOCK(rtsp_buffer_lock);

unsigned int (ip_nat_rtsp_hook)(struct sk_buff *pskb,
enum ip_conntrack_info ctinfo,
unsigned int matchoff, unsigned int matchlen,struct ip_ct_rtsp_expect* prtspexp,
struct ip_conntrack_expect *exp);
EXPORT_SYMBOL_GPL(ip_nat_rtsp_hook);

/*
  * Max mappings we will allow for one RTSP connection (for RTP, the number
  * of allocated ports is twice this value).  Note that SMIL burns a lot of
  * ports so keep this reasonably high.  If this is too low, you will see a
  * lot of "no free client map entries" messages.
  */
#define MAX_PORT_MAPS 16

/*** default port list was here in the masq code: 554, 3030, 4040 ***/

#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr off))) { off  ; }

/*
  * Parse an RTSP packet.
  *
  * Returns zero if parsing failed.
  *
  * Parameters:
  *  IN  ptcp  tcp data pointer
  *  IN  tcplen  tcp data len
  *  IN/OUT  ptcpoff  points to current tcp offset
  *  OUT  phdrsoff  set to offset of rtsp headers
  *  OUT  phdrslen  set to length of rtsp headers
  *  OUT  pcseqoff  set to offset of CSeq header
  *  OUT  pcseqlen  set to length of CSeq header
  */
static int
rtsp_parse_message(char* ptcp, uint tcplen, uint* ptcpoff,
  uint* phdrsoff, uint* phdrslen,
  uint* pcseqoff, uint* pcseqlen,
  uint* transoff, uint* translen)
{
uint  entitylen = 0;
uint  lineoff;
uint  linelen;

if (!nf_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen))
return 0;

phdrsoff = ptcpoff;
while (nf_mime_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen)) {
if (linelen == 0) {
if (entitylen > 0)
ptcpoff  = min(entitylen, tcplen - ptcpoff);
break;
}
if (lineoff linelen > tcplen) {
INFOP("!! overrun !!\n");
break;
}

if (nf_strncasecmp(ptcp lineoff, "CSeq:", 5) == 0) {
*pcseqoff = lineoff;
*pcseqlen = linelen;
}

if (nf_strncasecmp(ptcp lineoff, "Transport:", 10) == 0) {
*transoff = lineoff;
*translen = linelen;
}

if (nf_strncasecmp(ptcp lineoff, "Content-Length:", 15) == 0) {
uint off = lineoff 15;
SKIP_WSPACE(ptcp lineoff, linelen, off);
nf_strtou32(ptcp off, &entitylen);
}
}
phdrslen = (ptcpoff) - (*phdrsoff);

return 1;
}

/*
  * Find lo/hi client ports (if any) in transport header
  * In:
  *  ptcp, tcplen = packet
  *  tranoff, tranlen = buffer to search
  *
  * Out:
  *  pport_lo, pport_hi = lo/hi ports (host endian)
  *
  * Returns nonzero if any client ports found
  *
  * Note: it is valid (and expected) for the client to request multiple
  * transports, so we need to parse the entire line.
  */
static int
rtsp_parse_transport(char* ptran, uint tranlen,
  struct ip_ct_rtsp_expect* prtspexp)
{
int  rc = 0;
uint  off = 0;

if (tranlen < 10 || !iseol(ptran[tranlen-1]) ||
  nf_strncasecmp(ptran, "Transport:", 10) != 0) {
INFOP("sanity check failed\n");
return 0;
}

DEBUGP("tran='%.*s'\n", (int)tranlen, ptran);
off  = 10;
SKIP_WSPACE(ptran, tranlen, off);

/* Transport: tran;field;field=val,tran;field;field=val,... */
while (off < tranlen) {
const char* pparamend;
uint  nextparamoff;

pparamend = memchr(ptran off, ',', tranlen-off);
pparamend = (pparamend == NULL) ? ptran tranlen : pparamend 1;
nextparamoff = pparamend-ptran;

while (off < nextparamoff) {
const char* pfieldend;
uint  nextfieldoff;

pfieldend = memchr(ptran off, ';', nextparamoff-off);
nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran 1;
 
if (strncmp(ptran off, "client_port=", 12) == 0) {
u_int16_t  port;
uint  numlen;
 
off  = 12;
numlen = nf_strtou16(ptran off, &port);
off  = numlen;
if (prtspexp->loport != 0 && prtspexp->loport != port)
DEBUGP("multiple ports found, port %hu ignored\n", port);
else {
DEBUGP("lo port found : %hu\n", port);
prtspexp->loport = prtspexp->hiport = port;
if (ptran[off] == '-') {
off  ;
numlen = nf_strtou16(ptran off, &port);
off  = numlen;
prtspexp->pbtype = pb_range;
prtspexp->hiport = port;

// If we have a range, assume rtp:
// loport must be even, hiport must be loport 1
if ((prtspexp->loport & 0x0001) != 0 ||
  prtspexp->hiport != prtspexp->loport 1) {
DEBUGP("incorrect range: %hu-%hu, correcting\n",
  prtspexp->loport, prtspexp->hiport);
prtspexp->loport &= 0xfffe;
prtspexp->hiport = prtspexp->loport 1;
}
} else if (ptran[off] == '/') {
off  ;
numlen = nf_strtou16(ptran off, &port);
off  = numlen;
prtspexp->pbtype = pb_discon;
prtspexp->hiport = port;
}
rc = 1;
}
}

/*
* Note we don't look for the destination parameter here.
* If we are using NAT, the NAT module will handle it.  If not,
* and the client is sending packets elsewhere, the expectation
* will quietly time out.
*/

off = nextfieldoff;
}

off = nextparamoff;
}

return rc;
}

void expected(struct ip_conntrack* ct, struct ip_conntrack_expect *exp)
{
  struct ip_nat_multi_range_compat mr;
  u_int32_t newdstip, newsrcip, newip;

  struct ip_conntrack *master = master_ct(ct);

  newdstip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
  newsrcip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
  //FIXME (how to port that ?)
  //code from 2.4 : newip = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC) ? newsrcip : newdstip;
  newip = newdstip;

  DEBUGP("newsrcip=%u.%u.%u.%u, newdstip=%u.%u.%u.%u, newip=%u.%u.%u.%u\n",
  NIPQUAD(newsrcip), NIPQUAD(newdstip), NIPQUAD(newip));

  mr.rangesize = 1;
  // We don't want to manip the per-protocol, just the IPs.
  mr.range[0].flags = IP_NAT_RANGE_MAP_IPS;
  mr.range[0].min_ip = mr.range[0].max_ip = newip;

  ip_nat_setup_info(ct, &mr.range[0], NF_IP_PRE_ROUTING);
}

/*** conntrack functions ***/

/* outbound packet: client->server */
static inline int
help_out(struct sk_buff *pskb, unsigned char rb_ptr, unsigned int datalen,
  struct ip_conntrack* ct, enum ip_conntrack_info ctinfo)
{
struct ip_ct_rtsp_expect expinfo;

int dir = CTINFO2DIR(ctinfo);  /* = IP_CT_DIR_ORIGINAL */
//struct  tcphdr* tcph = (void*)iph  iph->ihl * 4;
//uint  tcplen = pktlen - iph->ihl * 4;
char*  pdata = rb_ptr;
//uint  datalen = tcplen - tcph->doff * 4;
uint  dataoff = 0;
int ret = NF_ACCEPT;

struct ip_conntrack_expect *exp;

memset(&expinfo, 0, sizeof(expinfo));

while (dataoff < datalen) {
uint  cmdoff = dataoff;
uint  hdrsoff = 0;
uint  hdrslen = 0;
uint  cseqoff = 0;
uint  cseqlen = 0;
uint  transoff = 0;
uint  translen = 0;
uint  off;

if (!rtsp_parse_message(pdata, datalen, &dataoff,
&hdrsoff, &hdrslen,
&cseqoff, &cseqlen,
&transoff, &translen))
break;  /* not a valid message */

if (strncmp(pdata cmdoff, "SETUP ", 6) != 0)
continue;  /* not a SETUP message */
DEBUGP("found a setup message\n");

off = 0;
if(translen) {
rtsp_parse_transport(pdata transoff, translen, &expinfo);
}

if (expinfo.loport == 0) {
DEBUGP("no udp transports found\n");
continue;  /* no udp transports found */
}

DEBUGP("udp transport found, ports=(%d,%hu,%hu)\n",
  (int)expinfo.pbtype, expinfo.loport, expinfo.hiport);

exp = ip_conntrack_expect_alloc(ct);
if (!exp) {
ret = NF_DROP;
goto out;
}

exp->master = ct;

exp->expectfn = expected;
exp->flags = 0;

exp->tuple = ((struct ip_conntrack_tuple)
{
{ ct->tuplehash[!dir].tuple.src.ip,
{ 0 }
},
{
ct->tuplehash[!dir].tuple.dst.ip,
{ .udp = { htons(expinfo.loport) } },
IPPROTO_UDP
}
});
exp->mask = ((struct ip_conntrack_tuple)
{
{ 0,
{ 0 }
},
{
0xFFFFFFFF,
{ .udp = { 0xFFFF } }, 0xFF
}
});
if (expinfo.pbtype == pb_range) {
DEBUGP("Changing expectation mask to handle multiple ports\n");
exp->mask.dst.u.udp.port  = 0xfffe;
}

DEBUGP("expect_related %u.%u.%u.%u:%u-%u.%u.%u.%u:%u\n",
  NIPQUAD(exp->tuple.src.ip),
  ntohs(exp->tuple.src.u.udp.port),
  NIPQUAD(exp->tuple.dst.ip),
  ntohs(exp->tuple.dst.u.udp.port));

if (ip_nat_rtsp_hook)
/* pass the request off to the nat helper */
ret = ip_nat_rtsp_hook(pskb, ctinfo, hdrsoff, hdrslen, &expinfo, exp);
else if (ip_conntrack_expect_related(exp) != 0) {
INFOP("ip_conntrack_expect_related failed\n");
ret  = NF_DROP;
}
ip_conntrack_expect_put(exp);
goto out;
}
out:

return ret;
}

/* inbound packet: server->client */
static inline int
help_in(struct sk_buff **pskb, size_t pktlen,
struct ip_conntrack* ct, enum ip_conntrack_info ctinfo)
{
return NF_ACCEPT;
}

static int help(struct sk_buff *pskb, struct ip_conntrack ct, enum
ip_conntrack_info ctinfo)
{
struct tcphdr _tcph, *th;
unsigned int dataoff, datalen;
char *rb_ptr;
int ret = NF_DROP;

/* Until there's been traffic both ways, don't look in packets. */
if (ctinfo != IP_CT_ESTABLISHED &&
  ctinfo != IP_CT_ESTABLISHED  IP_CT_IS_REPLY) {
DEBUGP("conntrackinfo = %u\n", ctinfo);
return NF_ACCEPT;
}

/* Not whole TCP header? */
th = skb_header_pointer(pskb, (pskb)->nh.iph->ihl*4,
sizeof(_tcph), &_tcph);
if (!th)
return NF_ACCEPT;
 
/* No data ? */
dataoff = (pskb)->nh.iph->ihl4  th->doff*4;
datalen = (*pskb)->len - dataoff;
if (dataoff >= (*pskb)->len)
return NF_ACCEPT;

spin_lock_bh(&rtsp_buffer_lock);
rb_ptr = skb_header_pointer(*pskb, dataoff,
  (*pskb)->len - dataoff, rtsp_buffer);
BUG_ON(rb_ptr == NULL);

#if 0
/* Checksum invalid?  Ignore. */
/* FIXME: Source route IP option packets --RR */
if (tcp_v4_check(tcph, tcplen, iph->saddr, iph->daddr,
csum_partial((char*)tcph, tcplen, 0)))
{
DEBUGP("bad csum: %p %u %u.%u.%u.%u %u.%u.%u.%u\n",
  tcph, tcplen, NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
return NF_ACCEPT;
}
#endif

switch (CTINFO2DIR(ctinfo)) {
case IP_CT_DIR_ORIGINAL:
ret = help_out(pskb, rb_ptr, datalen, ct, ctinfo);
break;
case IP_CT_DIR_REPLY:
DEBUGP("IP_CT_DIR_REPLY\n");
/* inbound packet: server->client */
ret = NF_ACCEPT;
break;
}

spin_unlock_bh(&rtsp_buffer_lock);

return ret;
}

static struct ip_conntrack_helper rtsp_helpers[MAX_PORTS];
static char rtsp_names[MAX_PORTS][10];

/* This function is intentionally NOT defined as __exit */
static void
fini(void)
{
int i;
for (i = 0; i < num_ports; i  ) {
DEBUGP("unregistering port %d\n", ports[i]);
ip_conntrack_helper_unregister(&rtsp_helpers[i]);
}
kfree(rtsp_buffer);
}

static int __init
init(void)
{
int i, ret;
struct ip_conntrack_helper *hlpr;
char *tmpname;

printk("ip_conntrack_rtsp v" IP_NF_RTSP_VERSION " loading\n");

if (max_outstanding < 1) {
printk("ip_conntrack_rtsp: max_outstanding must be a positive integer\n");
return -EBUSY;
}
if (setup_timeout < 0) {
printk("ip_conntrack_rtsp: setup_timeout must be a positive integer\n");
return -EBUSY;
}

rtsp_buffer = kmalloc(65536, GFP_KERNEL);
if (!rtsp_buffer)
return -ENOMEM;

/* If no port given, default to standard rtsp port */
if (ports[0] == 0) {
ports[0] = RTSP_PORT;
}

for (i = 0; (i < MAX_PORTS) && ports[i]; i  ) {
hlpr = &rtsp_helpers[i];
memset(hlpr, 0, sizeof(struct ip_conntrack_helper));
hlpr->tuple.src.u.tcp.port = htons(ports[i]);
hlpr->tuple.dst.protonum = IPPROTO_TCP;
hlpr->mask.src.u.tcp.port = 0xFFFF;
hlpr->mask.dst.protonum = 0xFF;
hlpr->max_expected = max_outstanding;
hlpr->timeout = setup_timeout;
hlpr->me = THIS_MODULE;
hlpr->help = help;

tmpname = &rtsp_names[i][0];
if (ports[i] == RTSP_PORT) {
sprintf(tmpname, "rtsp");
} else {
sprintf(tmpname, "rtsp-%d", i);
}
hlpr->name = tmpname;

DEBUGP("port #%d: %d\n", i, ports[i]);

ret = ip_conntrack_helper_register(hlpr);

if (ret) {
printk("ip_conntrack_rtsp: ERROR registering port %d\n", ports[i]);
fini();
return -EBUSY;
}
num_ports  ;
}
return 0;
}

module_init(init);
module_exit(fini);
diff -Naur linux-2.6.19.2/net/ipv4/netfilter/ip_nat_rtsp.c linux-2.6.19.2-rtsp/net/ipv4/netfilter/ip_nat_rtsp.c
--- linux-2.6.19.2/net/ipv4/netfilter/ip_nat_rtsp.c 1970-01-01 01:00:00.000000000  0100
  linux-2.6.19.2-rtsp/net/ipv4/netfilter/ip_nat_rtsp.c 2007-01-27 18:18:35.000000000  0100
@@ -0,0  1,475 @@
/*
  * RTSP extension for TCP NAT alteration
  * (C) 2003 by Tom Marshall <tmarshall@real.com>
  * based on ip_nat_irc.c
  *
  *  This program is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public License
  *  as published by the Free Software Foundation; either version
  *  2 of the License, or (at your option) any later version.
  *
  * Module load syntax:
  *  insmod ip_nat_rtsp.o ports=port1,port2,...port<MAX_PORTS>
  *  stunaddr=<address>
  *  destaction=[auto|strip|none]
  *
  * If no ports are specified, the default will be port 554 only.
  *
  * stunaddr specifies the address used to detect that a client is using STUN.
  * If this address is seen in the destination parameter, it is assumed that
  * the client has already punched a UDP hole in the firewall, so we don't
  * mangle the client_port.  If none is specified, it is autodetected.  It
  * only needs to be set if you have multiple levels of NAT.  It should be
  * set to the external address that the STUN clients detect.  Note that in
  * this case, it will not be possible for clients to use UDP with servers
  * between the NATs.
  *
  * If no destaction is specified, auto is used.
  *  destaction=auto:  strip destination parameter if it is not stunaddr.
  *  destaction=strip: always strip destination parameter (not recommended).
  *  destaction=none:  do not touch destination parameter (not recommended).
  */

#include <linux/module.h>
#include <linux/netfilter_ipv4.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/kernel.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_nat_helper.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
#include <linux/netfilter_ipv4/ip_conntrack_rtsp.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>

#include <linux/inet.h>
#include <linux/ctype.h>
#define NF_NEED_STRNCASECMP
#define NF_NEED_STRTOU16
#include <linux/netfilter_helpers.h>
#define NF_NEED_MIME_NEXTLINE
#include <linux/netfilter_mime.h>

#define INFOP(fmt, args...) printk(KERN_INFO "%s: %s: " fmt, _FILE_, _FUNCTION_ , ## args)
#define IP_NF_RTSP_DEBUG
#ifdef IP_NF_RTSP_DEBUG
#define DEBUGP(fmt, args...) printk(KERN_DEBUG "%s: %s: " fmt, _FILE_, _FUNCTION_ , ## args)
#else
#define DEBUGP(fmt, args...)
#endif

#define MAX_PORTS  8
#define DSTACT_AUTO  0
#define DSTACT_STRIP  1
#define DSTACT_NONE  2

static char*  stunaddr = NULL;
static char*  destaction = NULL;

static u_int32_t extip = 0;
static int  dstact = 0;

MODULE_AUTHOR("Tom Marshall <tmarshall@real.com>");
MODULE_DESCRIPTION("RTSP network address translation module");
MODULE_LICENSE("GPL");
module_param(stunaddr, charp, 0644);
MODULE_PARM_DESC(stunaddr, "Address for detecting STUN");
module_param(destaction, charp, 0644);
MODULE_PARM_DESC(destaction, "Action for destination parameter (auto/strip/none)");

#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr off))) { off  ; }

/*** helper functions ***/

static void
get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen)
{
  struct iphdr*  iph  = (struct iphdr*)skb->nh.iph;
  struct tcphdr*  tcph = (struct tcphdr*)((char*)iph  iph->ihl*4);

  pptcpdata = (char)tcph  tcph->doff*4;
  ptcpdatalen = ((char)skb->h.raw  skb->len) - *pptcpdata;
}

/*** nat functions ***/

/*
  * Mangle the "Transport:" header:
  *  - Replace all occurences of "client_port=<spec>"
  *  - Handle destination parameter
  *
  * In:
  *  ct, ctinfo = conntrack context
  *  pskb  = packet
  *  tranoff  = Transport header offset from TCP data
  *  tranlen  = Transport header length (incl. CRLF)
  *  rport_lo  = replacement low  port (host endian)
  *  rport_hi  = replacement high port (host endian)
  *
  * Returns packet size difference.
  *
  * Assumes that a complete transport header is present, ending with CR or LF
  */
static int
rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
  struct ip_conntrack_expect* exp,
  struct ip_ct_rtsp_expect* prtspexp,
  struct sk_buff** pskb, uint tranoff, uint tranlen)
{
  char*  ptcp;
  uint  tcplen;
  char*  ptran;
  char  rbuf1[16];  /* Replacement buffer (one port) */
  uint  rbuf1len;  /* Replacement len (one port) */
  char  rbufa[16];  /* Replacement buffer (all ports) */
  uint  rbufalen;  /* Replacement len (all ports) */
  u_int32_t  newip;
  u_int16_t  loport, hiport;
  uint  off = 0;
  uint  diff;  /* Number of bytes we removed */

  struct ip_conntrack *ct = exp->master;
  struct ip_conntrack_tuple t;

  char  szextaddr[15 1];
  uint  extaddrlen;
  int  is_stun;

  get_skb_tcpdata(*pskb, &ptcp, &tcplen);
  ptran = ptcp tranoff;

  if (tranoff tranlen > tcplen || tcplen-tranoff < tranlen ||
  tranlen < 10 || !iseol(ptran[tranlen-1]) ||
  nf_strncasecmp(ptran, "Transport:", 10) != 0)
  {
  INFOP("sanity check failed\n");
  return 0;
  }
  off  = 10;
  SKIP_WSPACE(ptcp tranoff, tranlen, off);

  newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
  t = exp->tuple;
  t.dst.ip = newip;

  extaddrlen = extip ? sprintf(szextaddr, "%u.%u.%u.%u", NIPQUAD(extip))
  : sprintf(szextaddr, "%u.%u.%u.%u", NIPQUAD(newip));
  DEBUGP("stunaddr=%s (%s)\n", szextaddr, (extip?"forced":"auto"));

  rbuf1len = rbufalen = 0;
  switch (prtspexp->pbtype)
  {
  case pb_single:
  for (loport = prtspexp->loport; loport != 0; loport  ) /* XXX: improper wrap? */
  {
  t.dst.u.udp.port = htons(loport);
  if (ip_conntrack_expect_related(exp) == 0)
  {
  DEBUGP("using port %hu\n", loport);
  break;
  }
  }
  if (loport != 0)
  {
  rbuf1len = sprintf(rbuf1, "%hu", loport);
  rbufalen = sprintf(rbufa, "%hu", loport);
  }
  break;
  case pb_range:
  for (loport = prtspexp->loport; loport != 0; loport  = 2) /* XXX: improper wrap? */
  {
  t.dst.u.udp.port = htons(loport);
  if (ip_conntrack_expect_related(exp) == 0)
  {
  hiport = loport  ~exp->mask.dst.u.udp.port;
  DEBUGP("using ports %hu-%hu\n", loport, hiport);
  break;
  }
  }
  if (loport != 0)
  {
  rbuf1len = sprintf(rbuf1, "%hu", loport);
  rbufalen = sprintf(rbufa, "%hu-%hu", loport, loport 1);
  }
  break;
  case pb_discon:
  for (loport = prtspexp->loport; loport != 0; loport  ) /* XXX: improper wrap? */
  {
  t.dst.u.udp.port = htons(loport);
  if (ip_conntrack_expect_related(exp) == 0)
  {
  DEBUGP("using port %hu (1 of 2)\n", loport);
  break;
  }
  }
  for (hiport = prtspexp->hiport; hiport != 0; hiport  ) /* XXX: improper wrap? */
  {
  t.dst.u.udp.port = htons(hiport);
  if (ip_conntrack_expect_related(exp) == 0)
  {
  DEBUGP("using port %hu (2 of 2)\n", hiport);
  break;
  }
  }
  if (loport != 0 && hiport != 0)
  {
  rbuf1len = sprintf(rbuf1, "%hu", loport);
  if (hiport == loport 1)
  {
  rbufalen = sprintf(rbufa, "%hu-%hu", loport, hiport);
  }
  else
  {
  rbufalen = sprintf(rbufa, "%hu/%hu", loport, hiport);
  }
  }
  break;
  }

  if (rbuf1len == 0)
  {
  return 0;  /* cannot get replacement port(s) */
  }

  /* Transport: tran;field;field=val,tran;field;field=val,... */
  while (off < tranlen)
  {
  uint  saveoff;
  const char* pparamend;
  uint  nextparamoff;

  pparamend = memchr(ptran off, ',', tranlen-off);
  pparamend = (pparamend == NULL) ? ptran tranlen : pparamend 1;
  nextparamoff = pparamend-ptcp;

  /*
  * We pass over each param twice.  On the first pass, we look for a
  * destination= field.  It is handled by the security policy.  If it
  * is present, allowed, and equal to our external address, we assume
  * that STUN is being used and we leave the client_port= field alone.
  */
  is_stun = 0;
  saveoff = off;
  while (off < nextparamoff)
  {
  const char* pfieldend;
  uint  nextfieldoff;

  pfieldend = memchr(ptran off, ';', nextparamoff-off);
  nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran 1;

  if (dstact != DSTACT_NONE && strncmp(ptran off, "destination=", 12) == 0)
  {
  if (strncmp(ptran off 12, szextaddr, extaddrlen) == 0)
  {
  is_stun = 1;
  }
  if (dstact == DSTACT_STRIP || (dstact == DSTACT_AUTO && !is_stun))
  {
  diff = nextfieldoff-off;
  if (!ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
  off, diff, NULL, 0))
  {
  /* mangle failed, all we can do is bail */
ip_conntrack_unexpect_related(exp);
  return 0;
  }
  get_skb_tcpdata(*pskb, &ptcp, &tcplen);
  ptran = ptcp tranoff;
  tranlen -= diff;
  nextparamoff -= diff;
  nextfieldoff -= diff;
  }
  }

  off = nextfieldoff;
  }
  if (is_stun)
  {
  continue;
  }
  off = saveoff;
  while (off < nextparamoff)
  {
  const char* pfieldend;
  uint  nextfieldoff;

  pfieldend = memchr(ptran off, ';', nextparamoff-off);
  nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran 1;

  if (strncmp(ptran off, "client_port=", 12) == 0)
  {
  u_int16_t  port;
  uint  numlen;
  uint  origoff;
  uint  origlen;
  char*  rbuf  = rbuf1;
  uint  rbuflen = rbuf1len;

  off  = 12;
  origoff = (ptran-ptcp) off;
  origlen = 0;
  numlen = nf_strtou16(ptran off, &port);
  off  = numlen;
  origlen  = numlen;
  if (port != prtspexp->loport)
  {
  DEBUGP("multiple ports found, port %hu ignored\n", port);
  }
  else
  {
  if (ptran[off] == '-' || ptran[off] == '/')
  {
  off  ;
  origlen  ;
  numlen = nf_strtou16(ptran off, &port);
  off  = numlen;
  origlen  = numlen;
  rbuf = rbufa;
  rbuflen = rbufalen;
  }

  /*
  * note we cannot just memcpy() if the sizes are the same.
  * the mangle function does skb resizing, checks for a
  * cloned skb, and updates the checksums.
  *
  * parameter 4 below is offset from start of tcp data.
  */
  diff = origlen-rbuflen;
  if (!ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
  origoff, origlen, rbuf, rbuflen))
  {
  /* mangle failed, all we can do is bail */
ip_conntrack_unexpect_related(exp);
  return 0;
  }
  get_skb_tcpdata(*pskb, &ptcp, &tcplen);
  ptran = ptcp tranoff;
  tranlen -= diff;
  nextparamoff -= diff;
  nextfieldoff -= diff;
  }
  }

  off = nextfieldoff;
  }

  off = nextparamoff;
  }

  return 1;
}

static uint
help_out(struct sk_buff **pskb, enum ip_conntrack_info ctinfo,
unsigned int matchoff, unsigned int matchlen,struct ip_ct_rtsp_expect* prtspexp,
  struct ip_conntrack_expect* exp)
{
  char*  ptcp;
  uint  tcplen;
  uint  hdrsoff;
  uint  hdrslen;
  uint  lineoff;
  uint  linelen;
  uint  off;

  struct iphdr* iph = (struct iphdr*)(*pskb)->nh.iph;
  struct tcphdr* tcph = (struct tcphdr*)((void*)iph  iph->ihl*4);

  get_skb_tcpdata(*pskb, &ptcp, &tcplen);
  hdrsoff = matchoff;//exp->seq - ntohl(tcph->seq);
  hdrslen = matchlen;
  off = hdrsoff;
  DEBUGP("NAT rtsp help_out\n");

  while (nf_mime_nextline(ptcp, hdrsoff hdrslen, &off, &lineoff, &linelen))
  {
  if (linelen == 0)
  {
  break;
  }
  if (off > hdrsoff hdrslen)
  {
  INFOP("!! overrun !!");
  break;
  }
  DEBUGP("hdr: len=%u, %.*s", linelen, (int)linelen, ptcp lineoff);

  if (nf_strncasecmp(ptcp lineoff, "Transport:", 10) == 0)
  {
  uint oldtcplen = tcplen;
  DEBUGP("hdr: Transport\n");
  if (!rtsp_mangle_tran(ctinfo, exp, prtspexp, pskb, lineoff, linelen))
  {
DEBUGP("hdr: Transport mangle failed");
  break;
  }
  get_skb_tcpdata(*pskb, &ptcp, &tcplen);
  hdrslen -= (oldtcplen-tcplen);
  off -= (oldtcplen-tcplen);
  lineoff -= (oldtcplen-tcplen);
  linelen -= (oldtcplen-tcplen);
  DEBUGP("rep: len=%u, %.*s", linelen, (int)linelen, ptcp lineoff);
  }
  }

  return NF_ACCEPT;
}

static unsigned int
help(struct sk_buff **pskb, enum ip_conntrack_info ctinfo,
  unsigned int matchoff, unsigned int matchlen,struct ip_ct_rtsp_expect* prtspexp,
  struct ip_conntrack_expect* exp)
{
  int dir = CTINFO2DIR(ctinfo);
  int rc = NF_ACCEPT;

  switch (dir)
  {
  case IP_CT_DIR_ORIGINAL:
  rc = help_out(pskb, ctinfo, matchoff, matchlen, prtspexp, exp);
  break;
  case IP_CT_DIR_REPLY:
DEBUGP("unmangle ! %u\n", ctinfo);
  /* XXX: unmangle */
rc = NF_ACCEPT;
  break;
  }
  //UNLOCK_BH(&ip_rtsp_lock);

  return rc;
}

static void __exit fini(void)
{
ip_nat_rtsp_hook = NULL;
synchronize_net();
}

static int __init init(void)
{
printk("ip_nat_rtsp v" IP_NF_RTSP_VERSION " loading\n");

BUG_ON(ip_nat_rtsp_hook);
ip_nat_rtsp_hook = help;

if (stunaddr != NULL)
extip = in_aton(stunaddr);

if (destaction != NULL) {
  if (strcmp(destaction, "auto") == 0)
dstact = DSTACT_AUTO;

if (strcmp(destaction, "strip") == 0)
dstact = DSTACT_STRIP;

if (strcmp(destaction, "none") == 0)
dstact = DSTACT_NONE;
}

return 0;
}

module_init(init);
module_exit(fini);
diff -Naur linux-2.6.19.2/net/ipv4/netfilter/Kconfig linux-2.6.19.2-rtsp/net/ipv4/netfilter/Kconfig
--- linux-2.6.19.2/net/ipv4/netfilter/Kconfig 2007-01-10 20:10:37.000000000  0100
  linux-2.6.19.2-rtsp/net/ipv4/netfilter/Kconfig 2007-09-05 20:44:49.000000000  0200
@@ -623,5  623,21 @@
  Allows altering the ARP packet payload: source and destination
  hardware and network addresses.

config IP_NF_NAT_RTSP
tristate
depends on IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
default IP_NF_NAT if IP_NF_RTSP=y
default m if IP_NF_RTSP=m

config IP_NF_RTSP
tristate  ' RTSP protocol support'
depends on IP_NF_CONNTRACK
help
  Support the RTSP protocol.  This allows UDP transports to be setup
  properly, including RTP and RDT.

  If you want to compile it as a module, say 'M' here and read
  Documentation/modules.txt.  If unsure, say 'Y'.

endmenu

diff -Naur linux-2.6.19.2/net/ipv4/netfilter/Makefile linux-2.6.19.2-rtsp/net/ipv4/netfilter/Makefile
--- linux-2.6.19.2/net/ipv4/netfilter/Makefile 2007-01-10 20:10:37.000000000  0100
  linux-2.6.19.2-rtsp/net/ipv4/netfilter/Makefile 2007-09-05 20:44:48.000000000  0200
@@ -26,6  26,11 @@

# connection tracking helpers
obj-$(CONFIG_IP_NF_H323)  = ip_conntrack_h323.o

# rtsp protocol support
obj-$(CONFIG_IP_NF_RTSP)  = ip_conntrack_rtsp.o
obj-$(CONFIG_IP_NF_NAT_RTSP)  = ip_nat_rtsp.o

obj-$(CONFIG_IP_NF_PPTP)  = ip_conntrack_pptp.o
obj-$(CONFIG_IP_NF_AMANDA)  = ip_conntrack_amanda.o
obj-$(CONFIG_IP_NF_TFTP)  = ip_conntrack_tftp.o
Gravatar
Wed Sep 12 05:27:43 2007
Mike says:
Just a heads up for the people reading this. The patch actually works it was a mythtv related problem according to Lorand.