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 #include <unistd.h> 36 #include <stdlib.h> 37 #include <strings.h> 38 39 #include <pcap-int.h> 40 #include <pcap.h> 41 #include <net/ethernet.h> 42 43 #define ETHER_TYPE_TEST "0x8822" 44 #define SNAPLEN 96 45 #define MAXPROG 128 46 47 char errbuf[PCAP_ERRBUF_SIZE]; 48 49 void usage(char* message) { 50 if (message != NULL) 51 printf ("error: %s\n", message); 52 printf("usage: ether_reflect -i interface -e ethertype " 53 "-a address -t timeout -p -d\n"); 54 exit(1); 55 } 56 57 int main(int argc, char **argv) 58 { 59 int ch; 60 int debug = 0, promisc = 0; 61 int timeout = 100; 62 bpf_u_int32 localnet=0, netmask=0; 63 unsigned int error = 0; 64 char *interface = NULL; 65 char *proto = ETHER_TYPE_TEST; 66 char in_string[MAXPROG]; 67 char tmp[ETHER_ADDR_LEN]; 68 char addr[ETHER_ADDR_LEN]; 69 char *user_addr = NULL; 70 pcap_t *capture; 71 struct bpf_program program; 72 struct pcap_pkthdr *header; 73 unsigned char *packet = NULL; 74 75 while ((ch = getopt(argc, argv, "a:e:i:t:pd")) != -1) { 76 switch (ch) { 77 case 'a': 78 user_addr = optarg; 79 break; 80 case 'e': 81 proto = optarg; 82 break; 83 case 'i': 84 interface = optarg; 85 break; 86 case 'p': 87 promisc = 1; 88 break; 89 case 't': 90 timeout = atoi(optarg); 91 break; 92 case 'd': 93 debug = 1; 94 break; 95 case '?': 96 default: 97 usage("invalid arguments"); 98 } 99 } 100 argc -= optind; 101 argv += optind; 102 103 if (interface == NULL) 104 usage("You must specify an interface"); 105 106 if (user_addr != NULL) 107 ether_aton_r(user_addr, (struct ether_addr *)&tmp); 108 109 if ((capture = pcap_open_live(interface, SNAPLEN, promisc, timeout, 110 &errbuf[0])) == NULL) 111 usage(errbuf); 112 113 snprintf(&in_string[0], MAXPROG, "ether proto %s\n", proto); 114 115 if (pcap_lookupnet(interface, &localnet, &netmask, errbuf) < 0) 116 usage(errbuf); 117 118 if (pcap_compile(capture, &program, in_string, 1, netmask) < 0) 119 usage(errbuf); 120 121 if (pcap_setfilter(capture, &program) < 0) 122 usage(errbuf); 123 124 if (pcap_setdirection(capture, PCAP_D_IN) < 0) 125 usage(errbuf); 126 127 while (1) { 128 error = pcap_next_ex(capture, &header, 129 (const unsigned char **)&packet); 130 if (error == 0) 131 continue; 132 if (error == -1) 133 usage("packet read error"); 134 if (error == -2) 135 usage("savefile? invalid!"); 136 137 if (debug) { 138 printf ("got packet of %d length\n", header->len); 139 printf ("header %s\n", 140 ether_ntoa((const struct ether_addr*) 141 &packet[0])); 142 printf ("header %s\n", 143 ether_ntoa((const struct ether_addr*) 144 &packet[ETHER_ADDR_LEN])); 145 } 146 147 /* 148 * If the user did not supply an address then we simply 149 * reverse the source and destination addresses. 150 */ 151 if (user_addr == NULL) { 152 bcopy(packet, &tmp, ETHER_ADDR_LEN); 153 bcopy(&packet[ETHER_ADDR_LEN], packet, ETHER_ADDR_LEN); 154 bcopy(&tmp, &packet[ETHER_ADDR_LEN], ETHER_ADDR_LEN); 155 } else { 156 bcopy(&tmp, packet, ETHER_ADDR_LEN); 157 } 158 if (pcap_inject(capture, packet, header->len) < 0) 159 if (debug) 160 pcap_perror(capture, "pcap_inject"); 161 } 162 } 163