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 #include <netinet/udp.h>
42
43 /*
44 * Return on-zero if the packet should be passed through, zero if it should
45 * be discarded.
46 */
47 int
filter_ok(u_int8_t * pkt,int bytes)48 filter_ok(u_int8_t *pkt, int bytes)
49 {
50 struct ip *ip;
51 u_int16_t ether_type;
52
53 if (bytes < 12 + 2 + 20)
54 return(0);
55
56 /*
57 * Allow only ARP and IP packetes
58 */
59 ether_type = ntohs(*(u_int16_t *)(pkt + 12));
60 if (ether_type == ETHERTYPE_ARP)
61 return(1);
62 if (ether_type != ETHERTYPE_IP)
63 return(0);
64
65 /*
66 * Allow only ICMP, TCP, and UDP protocols.
67 */
68 ip = (void *)(pkt + 14);
69
70 switch(ip->ip_p) {
71 case 1: /* ICMP */
72 /* XXX fix me */
73 break;
74 case 17: /* UDP */
75 case 6: /* TCP */
76 /*
77 * ip_src must represent our network or be 0.
78 * 0 is a special case, mainly so bootp (dhclient) gets
79 * through.
80 */
81 if (ip->ip_src.s_addr == 0)
82 break;
83 if (SecureOpt &&
84 (ip->ip_src.s_addr & NetMask.s_addr) !=
85 (NetAddress.s_addr & NetMask.s_addr)) {
86 fprintf(stderr, "Filtered Address: %08x\n",
87 ntohl(ip->ip_src.s_addr));
88 return(0);
89 }
90 break;
91 default:
92 if (SecureOpt)
93 return(0);
94 break;
95 }
96 return(1);
97 }
98
99