FreeBSD/Linux Kernel Cross Reference
sys/netinet/libalias/alias_dummy.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2005 Paolo Pisati <piso@FreeBSD.org>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * Alias_dummy is just an empty skeleton used to demostrate how to write
     * a module for libalias, that will run unalterated in userland or in
     * kernel land.
     */
    
    #ifdef _KERNEL
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/module.h>
    #else
    #include <errno.h>
    #include <sys/types.h>
    #include <stdio.h>
    #endif
    
    #include <netinet/in_systm.h>
    #include <netinet/in.h>
    #include <netinet/ip.h>
    #include <netinet/udp.h>
    
    #ifdef _KERNEL
    #include <netinet/libalias/alias_local.h>
    #include <netinet/libalias/alias_mod.h>
    #else
    #include "alias_local.h"
    #include "alias_mod.h"
    #endif
    
    static void
    AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah);
    
    static int
    fingerprint(struct libalias *la, struct alias_data *ah)
    {
            /*
             * Check here all the data that will be used later, if any field
             * is empy/NULL, return a -1 value.
             */
            if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL ||
                ah->maxpktsize == 0)
                    return (-1);
            /*
             * Fingerprint the incoming packet, if it matches any conditions
             * return an OK value.
             */
            if (ntohs(*ah->dport) == 123 || ntohs(*ah->sport) == 456)
                    return (0);     /* I know how to handle it. */
            return (-1);            /* I don't recognize this packet. */
    }
    
    /*
     * Wrap in this general purpose function, the real function used to alias the
     * packets.
     */
    
    static int
    protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
    {
            AliasHandleDummy(la, pip, ah);
            return (0);
    }
    
    /*
     * NOTA BENE: the next variable MUST NOT be renamed in any case if you want
     * your module to work in userland, cause it's used to find and use all
     * the protocol handlers present in every module.
     * So WATCH OUT, your module needs this variables and it needs it with
    * ITS EXACT NAME: handlers.
    */
   
   struct proto_handler handlers [] = {
           {
             .pri = 666,
             .dir = IN|OUT,
             .proto = UDP|TCP,
             .fingerprint = &fingerprint,
             .protohandler = &protohandler
           },
           { EOH }
   };
   
   static int
   mod_handler(module_t mod, int type, void *data)
   {
           int error;
   
           switch (type) {
           case MOD_LOAD:
                   error = 0;
                   LibAliasAttachHandlers(handlers);
                   break;
           case MOD_UNLOAD:
                   error = 0;
                   LibAliasDetachHandlers(handlers);
                   break;
           default:
                   error = EINVAL;
           }
           return (error);
   }
   
   #ifdef _KERNEL
   static
   #endif
   moduledata_t alias_mod = {
          "alias_dummy", mod_handler, NULL
   };
   
   #ifdef _KERNEL
   DECLARE_MODULE(alias_dummy, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
   MODULE_VERSION(alias_dummy, 1);
   MODULE_DEPEND(alias_dummy, libalias, 1, 1, 1);
   #endif
   
   static void
   AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah)
   {
           ; /* Dummy. */
   }

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