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/*
* IP_MASQ_RAUDIO - Real Audio masquerading module
*
*
* Version: @(#)$Id: ip_masq_raudio.c,v 1.7 1997/09/16 18:43:40 kuznet Exp $
*
* Author: Nigel Metheringham
* [strongly based on ftp module by Juan Jose Ciarlante & Wouter Gadeyne]
* [Real Audio information taken from Progressive Networks firewall docs]
*
*
*
*
* 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.
*
*
* Limitations
* The IP Masquerading proxies at present do not have access to a processed
* data stream. Hence for a protocol like the Real Audio control protocol,
* which depends on knowing where you are in the data stream, you either
* to keep a *lot* of state in your proxy, or you cheat and simplify the
* problem [needless to say I did the latter].
*
* This proxy only handles data in the first packet. Everything else is
* passed transparently. This means it should work under all normal
* circumstances, but it could be fooled by new data formats or a
* malicious application!
*
* At present the "first packet" is defined as a packet starting with
* the protocol ID string - "PNA".
* When the link is up there appears to be enough control data
* crossing the control link to keep it open even if a long audio
* piece is playing.
*
*/
#include <linux/config.h>
#include <linux/module.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/init.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/ip_masq.h>
#ifndef DEBUG_CONFIG_IP_MASQ_RAUDIO
#define DEBUG_CONFIG_IP_MASQ_RAUDIO 0
#endif
struct raudio_priv_data {
/* Associated data connection - setup but not used at present */
struct ip_masq *data_conn;
/* Have we seen and performed setup */
short seen_start;
};
static int
masq_raudio_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
MOD_INC_USE_COUNT;
if ((ms->app_data = kmalloc(sizeof(struct raudio_priv_data),
GFP_ATOMIC)) == NULL)
printk(KERN_INFO "RealAudio: No memory for application data\n");
else
{
struct raudio_priv_data *priv =
(struct raudio_priv_data *)ms->app_data;
priv->seen_start = 0;
priv->data_conn = NULL;
}
return 0;
}
static int
masq_raudio_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
MOD_DEC_USE_COUNT;
if (ms->app_data)
kfree_s(ms->app_data, sizeof(struct raudio_priv_data));
return 0;
}
int
masq_raudio_out (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, __u32 maddr)
{
struct sk_buff *skb;
struct iphdr *iph;
struct tcphdr *th;
char *p, *data, *data_limit;
struct ip_masq *n_ms;
unsigned short version, msg_id, msg_len, udp_port;
struct raudio_priv_data *priv =
(struct raudio_priv_data *)ms->app_data;
/* Everything running correctly already */
if (priv && priv->seen_start)
return 0;
skb = *skb_p;
iph = skb->nh.iph;
th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
data = (char *)&th[1];
data_limit = skb->h.raw + skb->len - 18;
/* Check to see if this is the first packet with protocol ID */
if (memcmp(data, "PNA", 3)) {
#if DEBUG_CONFIG_IP_MASQ_RAUDIO
printk("RealAudio: not initial protocol packet - ignored\n");
#endif
return(0);
}
data += 3;
memcpy(&version, data, 2);
#if DEBUG_CONFIG_IP_MASQ_RAUDIO
printk("RealAudio: initial seen - protocol version %d\n",
ntohs(version));
#endif
if (priv)
priv->seen_start = 1;
if (ntohs(version) >= 256)
{
printk(KERN_INFO "RealAudio: version (%d) not supported\n",
ntohs(version));
return 0;
}
data += 2;
while (data < data_limit) {
memcpy(&msg_id, data, 2);
data += 2;
memcpy(&msg_len, data, 2);
data += 2;
#if DEBUG_CONFIG_IP_MASQ_RAUDIO
printk("RealAudio: msg %d - %d byte\n",
ntohs(msg_id), ntohs(msg_len));
#endif
p = data;
data += ntohs(msg_len);
if (data > data_limit)
{
printk(KERN_INFO "RealAudio: Packet too short for data\n");
return 0;
}
if (ntohs(msg_id) == 1) {
/* This is a message detailing the UDP port to be used */
memcpy(&udp_port, p, 2);
n_ms = ip_masq_new(maddr, IPPROTO_UDP,
ms->saddr, udp_port,
ms->daddr, 0,
IP_MASQ_F_NO_DPORT);
if (n_ms==NULL)
return 0;
memcpy(p, &(n_ms->mport), 2);
#if DEBUG_CONFIG_IP_MASQ_RAUDIO
printk("RealAudio: rewrote UDP port %d -> %d\n",
ntohs(udp_port), ntohs(n_ms->mport));
#endif
ip_masq_set_expire(n_ms, ip_masq_expire->udp_timeout);
/* Make ref in application data to data connection */
if (priv)
priv->data_conn = n_ms;
/*
* There is nothing else useful we can do
* Maybe a development could do more, but for now
* we exit gracefully!
*/
return 0;
} else if (ntohs(msg_id) == 0)
return 0;
}
return 0;
}
struct ip_masq_app ip_masq_raudio = {
NULL, /* next */
"RealAudio", /* name */
0, /* type */
0, /* n_attach */
masq_raudio_init_1, /* ip_masq_init_1 */
masq_raudio_done_1, /* ip_masq_done_1 */
masq_raudio_out, /* pkt_out */
NULL /* pkt_in */
};
/*
* ip_masq_raudio initialization
*/
__initfunc(int ip_masq_raudio_init(void))
{
return register_ip_masq_app(&ip_masq_raudio, IPPROTO_TCP, 7070);
}
/*
* ip_masq_raudio fin.
*/
int ip_masq_raudio_done(void)
{
return unregister_ip_masq_app(&ip_masq_raudio);
}
#ifdef MODULE
EXPORT_NO_SYMBOLS;
int init_module(void)
{
if (ip_masq_raudio_init() != 0)
return -EIO;
return 0;
}
void cleanup_module(void)
{
if (ip_masq_raudio_done() != 0)
printk(KERN_INFO "ip_masq_raudio: can't remove module");
}
#endif /* MODULE */
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