usr.sbin/vknetd/filter.c

   1 /*
   2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/usr.sbin/vknetd/filter.c,v 1.2 2008/05/27 22:47:16 dillon Exp $
  35  */
  36 /*
  37  * Bridging code (serialized)
  38  */
  39 #include "vknetd.h"
  40 #include <netinet/ip.h>
  41
  42 /*
  43  * Return on-zero if the packet should be passed through, zero if it should
  44  * be discarded.
  45  */
  46 int
  47 filter_ok(u_int8_t *pkt, int bytes)
  48 {
  49         struct ip *ip;
  50         u_int16_t ether_type;
  51
  52         if (bytes < 12 + 2 + 20)
  53                 return(0);
  54
  55         /*
  56          * Allow only ARP and IP packetes
  57          */
  58         ether_type = ntohs(*(u_int16_t *)(pkt + 12));
  59         if (ether_type == ETHERTYPE_ARP)
  60                 return(1);
  61         if (ether_type != ETHERTYPE_IP)
  62                 return(0);
  63
  64         /*
  65          * Allow only ICMP, TCP, and UDP protocols.
  66          */
  67         ip = (void *)(pkt + 14);
  68
  69         switch(ip->ip_p) {
  70         case 1:         /* ICMP */
  71                 /* XXX fix me */
  72                 break;
  73         case 6:         /* TCP */
  74         case 17:        /* UDP */
  75                 /*
  76                  * ip_src must represent our network.
  77                  */
  78                 if ((ip->ip_src.s_addr & NetMask.s_addr) !=
  79                     (NetAddress.s_addr & NetMask.s_addr)) {
  80                         fprintf(stderr, "Filtered Address: %08x\n",
  81                                 ntohl(ip->ip_src.s_addr));
  82                         return(0);
  83                 }
  84                 break;
  85         default:
  86                 return(0);
  87         }
  88         return(1);
  89 }
  90