/*
 *              IP_MASQ_FTP CUSeeMe masquerading module
 *
 *
 * Version:     @(#)$Id: ip_masq_cuseeme.c,v 1.4 1998/10/06 04:48:57 davem Exp $
 *
 * Author:      Richard Lynch
 *              
 *
 * Fixes:
 *      Richard Lynch           :       Updated patch to conform to new module
 *                                      specifications
 *      Nigel Metheringham      :       Multiple port support
 *      Michael Owings          :       Fixed broken init code
 *                                      Added code to update inbound
 *                                      packets with correct local addresses.
 *                                      Fixes audio and "chat" problems
 *                                      Thanx to the CU-SeeMe Consortium for
 *                                      technical docs
 *      Steven Clarke           :       Small changes for 2.1   
 *
 *
 *
 *      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.
 *      
 * Multiple Port Support
 *      The helper can be made to handle up to MAX_MASQ_APP_PORTS (normally 12)
 *      with the port numbers being defined at module load time.  The module
 *      uses the symbol "ports" to define a list of monitored ports, which can
 *      be specified on the insmod command line as
 *              ports=x1,x2,x3...
 *      where x[n] are integer port numbers.  This option can be put into
 *      /etc/conf.modules (or /etc/modules.conf depending on your config)
 *      where modload will pick it up should you use modload to load your
 *      modules.
 *      
 */

#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/udp.h>

/* #define IP_MASQ_NDEBUG */
#include <net/ip_masq.h>

#pragma pack(1)
/* CU-SeeMe Data Header */
typedef struct {
        u_short         dest_family;
        u_short         dest_port;
        u_long          dest_addr;
        short           family;
        u_short         port;
        u_long          addr;
        u_long          seq;
        u_short         msg;
        u_short         data_type;
        u_short         packet_len;
} cu_header;

/* Open Continue Header */
typedef struct  {
        cu_header       cu_head;
        u_short         client_count; /* Number of client info structs */
        u_long          seq_no;
        char            user_name[20];
        char            stuff[4]; /* flags,  version stuff,  etc */
}oc_header;

/* client info structures */
typedef struct {
        u_long          address; /* Client address */
        char            stuff[8]; /* Flags, pruning bitfield,  packet counts etc */
} client_info;
#pragma pack()

/*
 * List of ports (up to MAX_MASQ_APP_PORTS) to be handled by helper
 * First port is set to the default port.
 */
static int ports[MAX_MASQ_APP_PORTS] = {7648}; /* I rely on the trailing items being set to zero */
struct ip_masq_app *masq_incarnations[MAX_MASQ_APP_PORTS];

/*
 *     Debug level
 */
#ifdef CONFIG_IP_MASQ_DEBUG
static int debug=0;
MODULE_PARM(debug, "i");
#endif

MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_MASQ_APP_PORTS) "i");

static int
masq_cuseeme_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
        MOD_INC_USE_COUNT;
        return 0;
}

static int
masq_cuseeme_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
        MOD_DEC_USE_COUNT;
        return 0;
}

int
masq_cuseeme_out (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, __u32 maddr)
{
        struct sk_buff *skb = *skb_p;
        struct iphdr *iph = skb->nh.iph;
        struct udphdr *uh = (struct udphdr *)&(((char *)iph)[iph->ihl*4]);
        cu_header *cu_head;
        char *data=(char *)&uh[1];

        if (skb->len - ((unsigned char *) data - skb->h.raw) >= sizeof(cu_header))
        {
                cu_head         = (cu_header *) data;
                /* cu_head->port   = ms->mport; */
                if( cu_head->addr )
                cu_head->addr = (u_long) maddr;
                if(ntohs(cu_head->data_type) == 257)
                        IP_MASQ_DEBUG(1-debug, "Sending talk packet!\n");
        }
        return 0;
}

int
masq_cuseeme_in (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, __u32 maddr)
{
        struct sk_buff *skb = *skb_p;
        struct iphdr *iph = skb->nh.iph;
        struct udphdr *uh = (struct udphdr *)&(((char *)iph)[iph->ihl*4]);
        cu_header *cu_head;
        oc_header       *oc;
        client_info     *ci;
        char *data=(char *)&uh[1];
        u_short len = skb->len - ((unsigned char *) data - skb->h.raw);
        int             i, off;

        if (len >= sizeof(cu_header))
        {
                cu_head         = (cu_header *) data;
                if(cu_head->dest_addr) /* Correct destination address */
                        cu_head->dest_addr = (u_long) ms->saddr;
                if(ntohs(cu_head->data_type)==101 && len > sizeof(oc_header))
                {
                        oc = (oc_header * ) data;
                        /* Spin (grovel) thru client_info structs till we find our own */
                        off=sizeof(oc_header);
                        for(i=0;
                            (i < oc->client_count && off+sizeof(client_info) <= len);
                            i++)                    
                        {
                                ci=(client_info *)(data+off);
                                if(ci->address==(u_long) maddr)
                                {
                                        /* Update w/ our real ip address and exit */
                                        ci->address = (u_long) ms->saddr;
                                        break;
                                }
                                else
                                   off+=sizeof(client_info);
                        }
                }
        }
        return 0;
}

struct ip_masq_app ip_masq_cuseeme = {
        NULL,                   /* next */
        "cuseeme",
        0,                      /* type */
        0,                      /* n_attach */
        masq_cuseeme_init_1,    /* ip_masq_init_1 */
        masq_cuseeme_done_1,    /* ip_masq_done_1 */
        masq_cuseeme_out,       /* pkt_out */
        masq_cuseeme_in         /* pkt_in */
};


/*
 *      ip_masq_cuseeme initialization
 */

__initfunc(int ip_masq_cuseeme_init(void))
{
        int i, j;

        for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
                if (ports[i]) {
                        if ((masq_incarnations[i] = kmalloc(sizeof(struct ip_masq_app),
                                                            GFP_KERNEL)) == NULL)
                                return -ENOMEM;
                        memcpy(masq_incarnations[i], &ip_masq_cuseeme, sizeof(struct ip_masq_app));
                        if ((j = register_ip_masq_app(masq_incarnations[i], 
                                                      IPPROTO_UDP,
                                                      ports[i]))) {
                                return j;
                        }
#if DEBUG_CONFIG_IP_MASQ_CUSEEME
                        IP_MASQ_DEBUG(1-debug, "CuSeeMe: loaded support on port[%d] = %d\n",
                               i, ports[i]);
#endif
                } else {
                        /* To be safe, force the incarnation table entry to NULL */
                        masq_incarnations[i] = NULL;
                }
        }
        return 0;
}

/*
 *      ip_masq_cuseeme fin.
 */

int ip_masq_cuseeme_done(void)
{
        int i, j, k;

        k=0;
        for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
                if (masq_incarnations[i]) {
                        if ((j = unregister_ip_masq_app(masq_incarnations[i]))) {
                                k = j;
                        } else {
                                kfree(masq_incarnations[i]);
                                masq_incarnations[i] = NULL;
                                IP_MASQ_DEBUG(1-debug, "CuSeeMe: unloaded support on port[%d] = %d\n", i, ports[i]);
                        }
                }
        }
        return k;
}

#ifdef MODULE
EXPORT_NO_SYMBOLS;

int init_module(void)
{
        if (ip_masq_cuseeme_init() != 0)
                return -EIO;
        return 0;
}

void cleanup_module(void)
{
        if (ip_masq_cuseeme_done() != 0)
                IP_MASQ_DEBUG(1-debug, "ip_masq_cuseeme: can't remove module");
}

#endif /* MODULE */