ip_masq_app.c

GNU Hurd 源代码

/*
 *		IP_MASQ_APP application masquerading module
 *
 *
 * 	$Id: ip_masq_app.c,v 1.16 1998/08/29 23:51:14 davem Exp $
 *
 * Author:	Juan Jose Ciarlante, <[e-mail]>
 *
 *
 *	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.
 *
 * Fixes:
 *	JJC			: Implemented also input pkt hook
 *	Miquel van Smoorenburg	: Copy more stuff when resizing skb
 *
 *
 * FIXME:
 *	- ip_masq_skb_replace(): use same skb if space available.
 *
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.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/udp.h>
#include <asm/system.h>
#include <linux/stat.h>
#include <linux/proc_fs.h>
#include <net/ip_masq.h>

#define IP_MASQ_APP_TAB_SIZE  16 /* must be power of 2 */

#define IP_MASQ_APP_HASH(proto, port) ((port^proto) & (IP_MASQ_APP_TAB_SIZE-1))
#define IP_MASQ_APP_TYPE(proto, port) ( proto<<16 | port )
#define IP_MASQ_APP_PORT(type)        ( type & 0xffff )
#define IP_MASQ_APP_PROTO(type)       ( (type>>16) & 0x00ff )


EXPORT_SYMBOL(register_ip_masq_app);
EXPORT_SYMBOL(unregister_ip_masq_app);
EXPORT_SYMBOL(ip_masq_skb_replace);

/*
 * 	will hold masq app. hashed list heads
 */

struct ip_masq_app *ip_masq_app_base[IP_MASQ_APP_TAB_SIZE];

/*
 * 	ip_masq_app registration routine
 *	port: host byte order.
 */

int register_ip_masq_app(struct ip_masq_app *mapp, unsigned short proto, __u16 port)
{
        unsigned long flags;
        unsigned hash;
        if (!mapp) {
                IP_MASQ_ERR("register_ip_masq_app(): NULL arg\n");
                return -EINVAL;
        }
        mapp->type = IP_MASQ_APP_TYPE(proto, port);
        mapp->n_attach = 0;
        hash = IP_MASQ_APP_HASH(proto, port);

        save_flags(flags);
        cli();
        mapp->next = ip_masq_app_base[hash];
        ip_masq_app_base[hash] = mapp;
        restore_flags(flags);

        return 0;
}

/*
 * 	ip_masq_app unreg. routine.
 */

int unregister_ip_masq_app(struct ip_masq_app *mapp)
{
        struct ip_masq_app **mapp_p;
        unsigned hash;
        unsigned long flags;
        if (!mapp) {
                IP_MASQ_ERR("unregister_ip_masq_app(): NULL arg\n");
                return -EINVAL;
        }
        /*
         * only allow unregistration if it has no attachments
         */
        if (mapp->n_attach)  {
                IP_MASQ_ERR("unregister_ip_masq_app(): has %d attachments. failed\n",
                       mapp->n_attach);
                return -EINVAL;
        }
        hash = IP_MASQ_APP_HASH(IP_MASQ_APP_PROTO(mapp->type), IP_MASQ_APP_PORT(mapp->type));

        save_flags(flags);
        cli();
        for (mapp_p = &ip_masq_app_base[hash]; *mapp_p ; mapp_p = &(*mapp_p)->next)
                if (mapp == (*mapp_p))  {
                        *mapp_p = mapp->next;
                        restore_flags(flags);
                        return 0;
                }

        restore_flags(flags);
        IP_MASQ_ERR("unregister_ip_masq_app(proto=%s,port=%u): not hashed!\n",
               masq_proto_name(IP_MASQ_APP_PROTO(mapp->type)), IP_MASQ_APP_PORT(mapp->type));
        return -EINVAL;
}

/*
 *	get ip_masq_app object by its proto and port (net byte order).
 */

struct ip_masq_app * ip_masq_app_get(unsigned short proto, __u16 port)
{
        struct ip_masq_app *mapp;
        unsigned hash;
        unsigned type;

        port = ntohs(port);
        type = IP_MASQ_APP_TYPE(proto,port);
        hash = IP_MASQ_APP_HASH(proto,port);
        for(mapp = ip_masq_app_base[hash]; mapp ; mapp = mapp->next) {
                if (type == mapp->type) return mapp;
        }
        return NULL;
}

/*
 *	ip_masq_app object binding related funcs.
 */

/*
 * 	change ip_masq_app object's number of bindings
 */

static __inline__ int ip_masq_app_bind_chg(struct ip_masq_app *mapp, int delta)
{
        unsigned long flags;
        int n_at;
        if (!mapp) return -1;
        save_flags(flags);
        cli();
        n_at = mapp->n_attach + delta;
        if (n_at < 0) {
                restore_flags(flags);
                IP_MASQ_ERR("ip_masq_app: tried to set n_attach < 0 for (proto=%s,port==%d) ip_masq_app object.\n",
                       masq_proto_name(IP_MASQ_APP_PROTO(mapp->type)),
                       IP_MASQ_APP_PORT(mapp->type));
                return -1;
        }
        mapp->n_attach = n_at;
        restore_flags(flags);
        return 0;
}

/*
 *	Bind ip_masq to its ip_masq_app based on proto and dport ALREADY
 *	set in ip_masq struct. Also calls constructor.
 */

struct ip_masq_app * ip_masq_bind_app(struct ip_masq *ms)
{
        struct ip_masq_app * mapp;

	if (ms->protocol != IPPROTO_TCP && ms->protocol != IPPROTO_UDP)
		return NULL;

        mapp = ip_masq_app_get(ms->protocol, ms->dport);

#if 0000
/* #ifdef CONFIG_IP_MASQUERADE_IPAUTOFW */
	if (mapp == NULL)
		mapp = ip_masq_app_get(ms->protocol, ms->sport);
/* #endif */
#endif

        if (mapp != NULL) {
                /*
                 *	don't allow binding if already bound
                 */

                if (ms->app != NULL) {
                        IP_MASQ_ERR("ip_masq_bind_app() called for already bound object.\n");
                        return ms->app;
                }

                ms->app = mapp;
                if (mapp->masq_init_1) mapp->masq_init_1(mapp, ms);
                ip_masq_app_bind_chg(mapp, +1);
        }
        return mapp;
}

/*
 * 	Unbind ms from type object and call ms destructor (does not kfree()).
 */

int ip_masq_unbind_app(struct ip_masq *ms)
{
        struct ip_masq_app * mapp;
        mapp = ms->app;

	if (ms->protocol != IPPROTO_TCP && ms->protocol != IPPROTO_UDP)
		return 0;

        if (mapp != NULL) {
                if (mapp->masq_done_1) mapp->masq_done_1(mapp, ms);
                ms->app = NULL;
                ip_masq_app_bind_chg(mapp, -1);
        }
        return (mapp != NULL);
}

/*
 *	Fixes th->seq based on ip_masq_seq info.
 */

static __inline__ void masq_fix_seq(const struct ip_masq_seq *ms_seq, struct tcphdr *th)
{
        __u32 seq;

        seq = ntohl(th->seq);

	/*
	 * 	Adjust seq with delta-offset for all packets after
         * 	the most recent resized pkt seq and with previous_delta offset
         *	for all packets	before most recent resized pkt seq.
	 */

	if (ms_seq->delta || ms_seq->previous_delta) {
		if(after(seq,ms_seq->init_seq) ) {
			th->seq = htonl(seq + ms_seq->delta);
			IP_MASQ_DEBUG(1, "masq_fix_seq() : added delta (%d) to seq\n",ms_seq->delta);
		} else {
			th->seq = htonl(seq + ms_seq->previous_delta);
			IP_MASQ_DEBUG(1, "masq_fix_seq() : added previous_delta (%d) to seq\n",ms_seq->previous_delta);
		}
	}


}

/*
 *	Fixes th->ack_seq based on ip_masq_seq info.
 */

static __inline__ void masq_fix_ack_seq(const struct ip_masq_seq *ms_seq, struct tcphdr *th)
{
        __u32 ack_seq;

        ack_seq=ntohl(th->ack_seq);

        /*
         * Adjust ack_seq with delta-offset for
         * the packets AFTER most recent resized pkt has caused a shift
         * for packets before most recent resized pkt, use previous_delta
         */

        if (ms_seq->delta || ms_seq->previous_delta) {
                if(after(ack_seq,ms_seq->init_seq)) {
                        th->ack_seq = htonl(ack_seq-ms_seq->delta);
                        IP_MASQ_DEBUG(1, "masq_fix_ack_seq() : subtracted delta (%d) from ack_seq\n",ms_seq->delta);

                } else {
                        th->ack_seq = htonl(ack_seq-ms_seq->previous_delta);
                        IP_MASQ_DEBUG(1, "masq_fix_ack_seq() : subtracted previous_delta (%d) from ack_seq\n",ms_seq->previous_delta);
                }
        }

}

/*
 *	Updates ip_masq_seq if pkt has been resized
 *	Assumes already checked proto==IPPROTO_TCP and diff!=0.
 */

static __inline__ void masq_seq_update(struct ip_masq *ms, struct ip_masq_seq *ms_seq, unsigned mflag, __u32 seq, int diff)
{
        /* if (diff == 0) return; */

        if ( !(ms->flags & mflag) || after(seq, ms_seq->init_seq))
        {
                ms_seq->previous_delta=ms_seq->delta;
                ms_seq->delta+=diff;
                ms_seq->init_seq=seq;
                ms->flags |= mflag;
        }