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1629 |
jcastillo |
/*
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* IP_MASQ_RAUDIO - Real Audio masquerading module
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*
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*
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* Version: @(#)$Id: ip_masq_raudio.c,v 1.1 2005-12-20 10:41:09 jcastillo Exp $
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*
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* Author: Nigel Metheringham
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* [strongly based on ftp module by Juan Jose Ciarlante & Wouter Gadeyne]
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* [Real Audio information taken from Progressive Networks firewall docs]
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* [Kudos to Progressive Networks for making the protocol specs available]
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*
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*
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*
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* Limitations
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* The IP Masquerading proxies at present do not have access to a processed
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* data stream. Hence for a protocol like the Real Audio control protocol,
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* which depends on knowing where you are in the data stream, you either
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* to keep a *lot* of state in your proxy, or you cheat and simplify the
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* problem [needless to say I did the latter].
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*
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* This proxy only handles data in the first packet. Everything else is
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* passed transparently. This means it should work under all normal
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* circumstances, but it could be fooled by new data formats or a
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* malicious application!
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*
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* At present the "first packet" is defined as a packet starting with
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* the protocol ID string - "PNA".
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* When the link is up there appears to be enough control data
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* crossing the control link to keep it open even if a long audio
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* piece is playing.
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*
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* The Robust UDP support added in RealAudio 3.0 is supported, but due
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* to servers/clients not making great use of this has not been greatly
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* tested. RealVideo (as used in the Real client version 4.0beta1) is
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* supported but again is not greatly tested (bandwidth requirements
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* appear to exceed that available at the sites supporting the protocol).
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*
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* Multiple Port Support
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* The helper can be made to handle up to MAX_MASQ_APP_PORTS (normally 12)
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* with the port numbers being defined at module load time. The module
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* uses the symbol "ports" to define a list of monitored ports, which can
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* be specified on the insmod command line as
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* ports=x1,x2,x3...
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* where x[n] are integer port numbers. This option can be put into
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* /etc/conf.modules (or /etc/modules.conf depending on your config)
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* where modload will pick it up should you use modload to load your
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* modules.
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*
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*/
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#include <linux/module.h>
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#include <asm/system.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <net/protocol.h>
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#include <net/tcp.h>
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#include <net/ip_masq.h>
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#ifndef DEBUG_CONFIG_IP_MASQ_RAUDIO
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#define DEBUG_CONFIG_IP_MASQ_RAUDIO 0
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#endif
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struct raudio_priv_data {
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/* Associated data connection - setup but not used at present */
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struct ip_masq *data_conn;
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/* UDP Error correction connection - setup but not used at present */
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struct ip_masq *error_conn;
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/* Have we seen and performed setup */
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short seen_start;
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};
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#ifdef MODULE
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#define STATIC
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#else
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#define STATIC static
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#endif
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/*
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* List of ports (up to MAX_MASQ_APP_PORTS) to be handled by helper
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* First port is set to the default port.
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*/
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STATIC int ports[MAX_MASQ_APP_PORTS] = {7070}; /* I rely on the trailing items being set to zero */
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struct ip_masq_app *masq_incarnations[MAX_MASQ_APP_PORTS];
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static int
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masq_raudio_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
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{
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MOD_INC_USE_COUNT;
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if ((ms->app_data = kmalloc(sizeof(struct raudio_priv_data),
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GFP_ATOMIC)) == NULL)
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printk(KERN_INFO "RealAudio: No memory for application data\n");
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else
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{
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struct raudio_priv_data *priv =
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(struct raudio_priv_data *)ms->app_data;
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priv->seen_start = 0;
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priv->data_conn = NULL;
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priv->error_conn = NULL;
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}
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return 0;
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}
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static int
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masq_raudio_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
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{
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MOD_DEC_USE_COUNT;
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if (ms->app_data)
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kfree_s(ms->app_data, sizeof(struct raudio_priv_data));
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return 0;
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}
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int
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masq_raudio_out (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, struct device *dev)
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{
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struct sk_buff *skb;
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struct iphdr *iph;
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struct tcphdr *th;
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char *p, *data, *data_limit;
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struct ip_masq *n_ms;
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unsigned short version, msg_id, msg_len, udp_port;
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struct raudio_priv_data *priv =
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(struct raudio_priv_data *)ms->app_data;
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/* Everything running correctly already */
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if (priv && priv->seen_start)
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return 0;
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skb = *skb_p;
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iph = skb->h.iph;
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th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
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data = (char *)&th[1];
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data_limit = skb->h.raw + skb->len;
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/* Check to see if this is the first packet with protocol ID */
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if (memcmp(data, "PNA", 3)) {
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: not initial protocol packet - ignored\n");
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#endif
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return(0);
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}
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data += 3;
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memcpy(&version, data, 2);
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: initial seen - protocol version %d\n",
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ntohs(version));
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#endif
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if (priv)
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priv->seen_start = 1;
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if (ntohs(version) >= 256)
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{
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printk(KERN_INFO "RealAudio: version (%d) not supported\n",
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ntohs(version));
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return 0;
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}
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data += 2;
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while (data+4 < data_limit) {
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memcpy(&msg_id, data, 2);
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data += 2;
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memcpy(&msg_len, data, 2);
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data += 2;
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if (ntohs(msg_id) == 0) {
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/* The zero tag indicates the end of options */
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: packet end tag seen\n");
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#endif
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return 0;
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}
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: msg %d - %d byte\n",
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ntohs(msg_id), ntohs(msg_len));
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#endif
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if (ntohs(msg_id) == 0) {
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/* The zero tag indicates the end of options */
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return 0;
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}
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p = data;
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data += ntohs(msg_len);
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if (data > data_limit)
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{
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printk(KERN_INFO "RealAudio: Packet too short for data\n");
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return 0;
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}
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if ((ntohs(msg_id) == 1) || (ntohs(msg_id) == 7)) {
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/*
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* MsgId == 1
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* Audio UDP data port on client
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*
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* MsgId == 7
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* Robust UDP error correction port number on client
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*
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* Since these messages are treated just the same, they
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* are bundled together here....
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*/
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memcpy(&udp_port, p, 2);
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/*
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* Sometimes a server sends a message 7 with a zero UDP port
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* Rather than do anything with this, just ignore it!
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*/
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if (udp_port == 0)
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continue;
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n_ms = ip_masq_new(dev, IPPROTO_UDP,
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ms->saddr, udp_port,
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ms->daddr, 0,
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IP_MASQ_F_NO_DPORT);
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if (n_ms==NULL)
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return 0;
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memcpy(p, &(n_ms->mport), 2);
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: rewrote UDP port %d -> %d in msg %d\n",
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ntohs(udp_port), ntohs(n_ms->mport), ntohs(msg_id));
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#endif
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ip_masq_set_expire(n_ms, ip_masq_expire->udp_timeout);
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/* Make ref in application data to data connection */
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if (priv) {
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if (ntohs(msg_id) == 1)
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priv->data_conn = n_ms;
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else
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priv->error_conn = n_ms;
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}
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}
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}
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return 0;
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}
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struct ip_masq_app ip_masq_raudio = {
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NULL, /* next */
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"RealAudio", /* name */
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0, /* type */
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0, /* n_attach */
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masq_raudio_init_1, /* ip_masq_init_1 */
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masq_raudio_done_1, /* ip_masq_done_1 */
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masq_raudio_out, /* pkt_out */
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NULL /* pkt_in */
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};
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/*
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* ip_masq_raudio initialization
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*/
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int ip_masq_raudio_init(void)
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| 259 |
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{
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int i, j;
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| 262 |
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for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
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if (ports[i]) {
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if ((masq_incarnations[i] = kmalloc(sizeof(struct ip_masq_app),
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GFP_KERNEL)) == NULL)
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return -ENOMEM;
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memcpy(masq_incarnations[i], &ip_masq_raudio, sizeof(struct ip_masq_app));
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if ((j = register_ip_masq_app(masq_incarnations[i],
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IPPROTO_TCP,
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ports[i]))) {
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return j;
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}
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| 273 |
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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printk("RealAudio: loaded support on port[%d] = %d\n",
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i, ports[i]);
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#endif
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} else {
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| 278 |
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/* To be safe, force the incarnation table entry to NULL */
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| 279 |
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masq_incarnations[i] = NULL;
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| 280 |
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}
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| 281 |
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}
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| 282 |
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return 0;
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| 283 |
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}
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| 284 |
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| 285 |
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/*
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| 286 |
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* ip_masq_raudio fin.
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| 287 |
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*/
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| 288 |
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| 289 |
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int ip_masq_raudio_done(void)
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| 290 |
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{
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| 291 |
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int i, j, k;
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| 292 |
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| 293 |
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k=0;
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| 294 |
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for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
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| 295 |
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if (masq_incarnations[i]) {
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| 296 |
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if ((j = unregister_ip_masq_app(masq_incarnations[i]))) {
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| 297 |
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k = j;
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| 298 |
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} else {
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| 299 |
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kfree(masq_incarnations[i]);
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| 300 |
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masq_incarnations[i] = NULL;
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| 301 |
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#if DEBUG_CONFIG_IP_MASQ_RAUDIO
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| 302 |
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printk("RealAudio: unloaded support on port[%d] = %d\n",
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| 303 |
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i, ports[i]);
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| 304 |
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#endif
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| 305 |
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}
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| 306 |
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}
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| 307 |
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}
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| 308 |
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return k;
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| 309 |
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}
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| 310 |
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| 311 |
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#ifdef MODULE
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| 312 |
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| 313 |
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int init_module(void)
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| 314 |
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{
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| 315 |
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if (ip_masq_raudio_init() != 0)
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| 316 |
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return -EIO;
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| 317 |
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register_symtab(0);
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| 318 |
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return 0;
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| 319 |
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}
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| 320 |
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| 321 |
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void cleanup_module(void)
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| 322 |
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{
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| 323 |
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if (ip_masq_raudio_done() != 0)
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| 324 |
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printk("ip_masq_raudio: can't remove module");
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| 325 |
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}
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| 326 |
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| 327 |
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#endif /* MODULE */
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