1 /* 2 * Copyright (c) 2008, Neville-Neil Consulting 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 15 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 16 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 17 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 18 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 19 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 20 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * Author: George V. Neville-Neil 27 * 28 * Purpose: This program uses libpcap to read packets from the network 29 * of a specific ethertype (default is 0x8822) and reflects them back 30 * out the same interface with their destination and source mac 31 * addresses reversed. 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include <unistd.h> 38 #include <stdlib.h> 39 #include <strings.h> 40 41 #include <pcap-int.h> 42 #include <pcap.h> 43 #include <net/ethernet.h> 44 45 #define ETHER_TYPE_TEST "0x8822" 46 #define SNAPLEN 96 47 #define MAXPROG 128 48 49 char errbuf[PCAP_ERRBUF_SIZE]; 50 51 void usage(char* message) { 52 if (message != NULL) 53 printf ("error: %s\n", message); 54 printf("usage: ether_reflect -i interface -e ethertype " 55 "-a address -t timeout -p -d\n"); 56 exit(1); 57 } 58 59 int main(int argc, char **argv) 60 { 61 int ch; 62 int debug = 0, promisc = 0; 63 int timeout = 100; 64 bpf_u_int32 localnet=0, netmask=0; 65 unsigned int error = 0; 66 char *interface = NULL; 67 char *proto = ETHER_TYPE_TEST; 68 char in_string[MAXPROG]; 69 char tmp[ETHER_ADDR_LEN]; 70 char addr[ETHER_ADDR_LEN]; 71 char *user_addr = NULL; 72 pcap_t *capture; 73 struct bpf_program program; 74 struct pcap_pkthdr *header; 75 unsigned char *packet = NULL; 76 77 while ((ch = getopt(argc, argv, "a:e:i:t:pd")) != -1) { 78 switch (ch) { 79 case 'a': 80 user_addr = optarg; 81 break; 82 case 'e': 83 proto = optarg; 84 break; 85 case 'i': 86 interface = optarg; 87 break; 88 case 'p': 89 promisc = 1; 90 break; 91 case 't': 92 timeout = atoi(optarg); 93 break; 94 case 'd': 95 debug = 1; 96 break; 97 case '?': 98 default: 99 usage("invalid arguments"); 100 } 101 } 102 argc -= optind; 103 argv += optind; 104 105 if (interface == NULL) 106 usage("You must specify an interface"); 107 108 if (user_addr != NULL) 109 ether_aton_r(user_addr, (struct ether_addr *)&tmp); 110 111 if ((capture = pcap_open_live(interface, SNAPLEN, promisc, timeout, 112 &errbuf[0])) == NULL) 113 usage(errbuf); 114 115 snprintf(&in_string[0], MAXPROG, "ether proto %s\n", proto); 116 117 if (pcap_lookupnet(interface, &localnet, &netmask, errbuf) < 0) 118 usage(errbuf); 119 120 if (pcap_compile(capture, &program, in_string, 1, netmask) < 0) 121 usage(errbuf); 122 123 if (pcap_setfilter(capture, &program) < 0) 124 usage(errbuf); 125 126 if (pcap_setdirection(capture, PCAP_D_IN) < 0) 127 usage(errbuf); 128 129 while (1) { 130 error = pcap_next_ex(capture, &header, 131 (const unsigned char **)&packet); 132 if (error == 0) 133 continue; 134 if (error == -1) 135 usage("packet read error"); 136 if (error == -2) 137 usage("savefile? invalid!"); 138 139 if (debug) { 140 printf ("got packet of %d length\n", header->len); 141 printf ("header %s\n", 142 ether_ntoa((const struct ether_addr*) 143 &packet[0])); 144 printf ("header %s\n", 145 ether_ntoa((const struct ether_addr*) 146 &packet[ETHER_ADDR_LEN])); 147 } 148 149 /* 150 * If the user did not supply an address then we simply 151 * reverse the source and destination addresses. 152 */ 153 if (user_addr == NULL) { 154 bcopy(packet, &tmp, ETHER_ADDR_LEN); 155 bcopy(&packet[ETHER_ADDR_LEN], packet, ETHER_ADDR_LEN); 156 bcopy(&tmp, &packet[ETHER_ADDR_LEN], ETHER_ADDR_LEN); 157 } else { 158 bcopy(&tmp, packet, ETHER_ADDR_LEN); 159 } 160 if (pcap_inject(capture, packet, header->len) < 0) 161 if (debug) 162 pcap_perror(capture, "pcap_inject"); 163 } 164 } 165