/*
 *              IP_MASQ_IRC irc masquerading module
 *
 *
 * Version:     @(#)ip_masq_irc.c 0.03   97/11/30
 *
 * Author:      Juan Jose Ciarlante
 *              
 * Additions:
 *  - recognize a few non-irc-II DCC requests (Oliver Wagner)
 *     DCC MOVE (AmIRC/DCC.MOVE; SEND with resuming)
 *     DCC SCHAT (AmIRC IDEA encrypted CHAT)
 *     DCC TSEND (AmIRC/PIRCH SEND without ACKs)
 * Fixes:
 *      Juan Jose Ciarlante     :  set NO_DADDR flag in ip_masq_new()
 *      Nigel Metheringham      :  Added multiple port support 
 *      Juan Jose Ciarlante     :  litl bits for 2.1
 *      Oliver Wagner           :  more IRC cmds processing
 *        <winmute@lucifer.gv.kotnet.org>
 *      Juan Jose Ciarlante     :  put new ms entry to listen()
 *
 * FIXME:
 *      - detect also previous "PRIVMSG" string ?.
 *
 *      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 <linux/types.h>
#include <linux/kernel.h>
#include <asm/system.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>


/* 
 * List of ports (up to MAX_MASQ_APP_PORTS) to be handled by helper
 * First port is set to the default port.
 */
int ports[MAX_MASQ_APP_PORTS] = {6667}; /* 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");


/*
 * List of supported DCC protocols
 */

#define NUM_DCCPROTO 5

struct dccproto 
{
  char *match;
  int matchlen;
  int xtra_args;
};

struct dccproto dccprotos[NUM_DCCPROTO] = {
 { "SEND ", 5, 1 },
 { "CHAT ", 5, 0, },
 { "MOVE ", 5, 1 },
 { "TSEND ", 6, 1, },
 { "SCHAT ", 6, 0, }
};
#define MAXMATCHLEN 6

static int
masq_irc_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
        MOD_INC_USE_COUNT;
        return 0;
}

static int
masq_irc_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
        MOD_DEC_USE_COUNT;
        return 0;
}

int
masq_irc_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 *data, *data_limit;
        __u32 s_addr;
        __u16 s_port;
        struct ip_masq *n_ms;
        char buf[20];           /* "m_addr m_port" (dec base)*/
        unsigned buf_len;
        int diff;
        int xtra_args = 0;      /* extra int args wanted after addr */
        char *dcc_p, *addr_beg_p, *addr_end_p;

        skb = *skb_p;
        iph = skb->nh.iph;
        th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
        data = (char *)&th[1];

        /*
         *      Hunt irc DCC string, the _shortest_:
         *
         *      strlen("DCC CHAT chat AAAAAAAA P\x01\n")=26
         *      strlen("DCC SCHAT chat AAAAAAAA P\x01\n")=27
         *      strlen("DCC SEND F AAAAAAAA P S\x01\n")=25
         *      strlen("DCC MOVE F AAAAAAAA P S\x01\n")=25
         *      strlen("DCC TSEND F AAAAAAAA P S\x01\n")=26
         *      strlen("DCC MOVE F AAAAAAAA P S\x01\n")=25
         *              AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits)
         *              P:         bound port (min 1 d )
         *              F:         filename   (min 1 d )
         *              S:         size       (min 1 d ) 
         *              0x01, \n:  terminators
         */

        data_limit = skb->h.raw + skb->len;
        
        while (data < (data_limit - ( 21 + MAXMATCHLEN ) ) )
        {
                int i;
                if (memcmp(data,"DCC ",4))  {
                        data ++;
                        continue;
                }

                dcc_p = data;
                data += 4;     /* point to DCC cmd */

                for(i=0; i<NUM_DCCPROTO; i++)
                {
                        /*
                         * go through the table and hunt a match string
                         */

                        if( memcmp(data, dccprotos[i].match, dccprotos[i].matchlen ) == 0 )
                        {
                                xtra_args = dccprotos[i].xtra_args;
                                data += dccprotos[i].matchlen;

                                /*
                                 *      skip next string.
                                 */

                                while( *data++ != ' ')

                                        /*
                                         *      must still parse, at least, "AAAAAAAA P\x01\n",
                                         *      12 bytes left.
                                         */
                                        if (data > (data_limit-12)) return 0;


                                addr_beg_p = data;

                                /*
                                 *      client bound address in dec base
                                 */

                                s_addr = simple_strtoul(data,&data,10);
                                if (*data++ !=' ')
                                        continue;

                                /*
                                 *      client bound port in dec base
                                 */

                                s_port = simple_strtoul(data,&data,10);
                                addr_end_p = data;

                                /*
                                 *      should check args consistency?
                                 */

                                while(xtra_args) {
                                        if (*data != ' ')
                                                break;
                                        data++;
                                        simple_strtoul(data,&data,10);
                                        xtra_args--;
                                }

                                if (xtra_args != 0) continue;

                                /*
                                 *      terminators.
                                 */

                                if (data[0] != 0x01)
                                        continue;
                                if (data[1]!='\r' && data[1]!='\n')
                                        continue;

                                /*
                                 *      Now create an masquerade entry for it
                                 *      must set NO_DPORT and NO_DADDR because
                                 *      connection is requested by another client.
                                 */

                                n_ms = ip_masq_new(IPPROTO_TCP,
                                                maddr, 0,
                                                htonl(s_addr),htons(s_port),
                                                0, 0,
                                                IP_MASQ_F_NO_DPORT|IP_MASQ_F_NO_DADDR);
                                if (n_ms==NULL)
                                        return 0;

                                /*
                                 * Replace the old "address port" with the new one
                                 */

                                buf_len = sprintf(buf,"%lu %u",
                                                ntohl(n_ms->maddr),ntohs(n_ms->mport));

                                /*
                                 * Calculate required delta-offset to keep TCP happy
                                 */

                                diff = buf_len - (addr_end_p-addr_beg_p);

                                *addr_beg_p = '\0';
                                IP_MASQ_DEBUG(1-debug, "masq_irc_out(): '%s' %X:%X detected (diff=%d)\n", dcc_p, s_addr,s_port, diff);

                                /*
                                 *      No shift.
                                 */

                                if (diff==0) {
                                        /*
                                         * simple case, just copy.
                                         */
                                        memcpy(addr_beg_p,buf,buf_len);
                                } else {

                                        *skb_p = ip_masq_skb_replace(skb, GFP_ATOMIC,
                                                        addr_beg_p, addr_end_p-addr_beg_p,
                                                        buf, buf_len);
                                }
                                ip_masq_listen(n_ms);
                                ip_masq_put(n_ms);
                                return diff;
                        }
                }
        }
        return 0;

}

/*
 *      Main irc object
 *      You need 1 object per port in case you need
 *      to offer also other used irc ports (6665,6666,etc),
 *      they will share methods but they need own space for
 *      data. 
 */

struct ip_masq_app ip_masq_irc = {
        NULL,                   /* next */
        "irc",                  /* name */
        0,                      /* type */
        0,                      /* n_attach */
        masq_irc_init_1,        /* init_1 */
        masq_irc_done_1,        /* done_1 */
        masq_irc_out,           /* pkt_out */
        NULL                    /* pkt_in */
};

/*
 *      ip_masq_irc initialization
 */

__initfunc(int ip_masq_irc_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_irc, sizeof(struct ip_masq_app));
                        if ((j = register_ip_masq_app(masq_incarnations[i], 
                                                      IPPROTO_TCP, 
                                                      ports[i]))) {
                                return j;
                        }
                        IP_MASQ_DEBUG(1-debug,
                                        "Irc: loaded support on port[%d] = %d\n",
                               i, ports[i]);
                } else {
                        /* To be safe, force the incarnation table entry to NULL */
                        masq_incarnations[i] = NULL;
                }
        }
        return 0;
}

/*
 *      ip_masq_irc fin.
 */

int ip_masq_irc_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, "Irc: unloaded support on port[%d] = %d\n",
                                       i, ports[i]);
                        }
                }
        }
        return k;
}


#ifdef MODULE
EXPORT_NO_SYMBOLS;

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

void cleanup_module(void)
{
        if (ip_masq_irc_done() != 0)
                printk(KERN_INFO "ip_masq_irc: can't remove module");
}

#endif /* MODULE */