2 pong.c -- ICMP echo reply generator
3 Copyright (C) 2013-2017 Guus Sliepen <guus@tinc-vpn.org>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
20 #include "../src/system.h"
22 #include "../src/ethernet.h"
24 uint8_t mymac[6] = {6, 5, 5, 6, 5, 5};
26 static ssize_t do_arp(uint8_t *buf, ssize_t len, struct sockaddr_in *in) {
28 memcpy(&arp, buf + 14, sizeof(arp));
30 // Is it a valid ARP request?
31 if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP || arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(in->sin_addr.s_addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
35 // Does it match our address?
36 if(memcmp(&in->sin_addr.s_addr, arp.arp_tpa, 4)) {
41 memcpy(buf, buf + 6, 6);
42 memcpy(buf + 6, mymac, 6);
44 arp.arp_op = htons(ARPOP_REPLY);
45 memcpy(arp.arp_tpa, arp.arp_spa, sizeof(arp.arp_tpa));
46 memcpy(arp.arp_tha, arp.arp_sha, sizeof(arp.arp_tha));
47 memcpy(arp.arp_spa, &in->sin_addr.s_addr, sizeof(in->sin_addr.s_addr));
48 memcpy(arp.arp_sha, mymac, 6);
50 memcpy(buf + 14, &arp, sizeof(arp));
55 static ssize_t do_ipv4(uint8_t *buf, ssize_t len, struct sockaddr_in *in) {
59 // Does it match our address?
60 if(memcmp(buf, mymac, 6)) {
64 memcpy(&ip, buf + 14, sizeof(ip));
66 if(memcmp(&ip.ip_dst, &in->sin_addr.s_addr, 4)) {
70 // Is it an ICMP echo request?
71 if(ip.ip_p != IPPROTO_ICMP) {
75 memcpy(&icmp, buf + 14 + sizeof(ip), sizeof icmp);
77 if(icmp.icmp_type != ICMP_ECHO) {
81 // Return an echo reply
82 memcpy(buf, buf + 6, 6);
83 memcpy(buf + 6, mymac, 6);
85 ip.ip_dst = ip.ip_src;
86 memcpy(&ip.ip_src, &in->sin_addr.s_addr, 4);
88 icmp.icmp_type = ICMP_ECHOREPLY;
90 memcpy(buf + 14, &ip, sizeof(ip));
91 memcpy(buf + 14 + sizeof(ip), &icmp, sizeof icmp);
96 static ssize_t do_ipv6(uint8_t *buf, ssize_t len, struct sockaddr_in6 *in) {
100 int main(int argc, char *argv[]) {
102 fprintf(stderr, "Usage: %s <multicast address> <port> <ping address>\n", argv[0]);
106 struct addrinfo hints = {}, *ai = NULL;
107 hints.ai_socktype = SOCK_DGRAM;
108 hints.ai_flags = AI_ADDRCONFIG;
112 if(getaddrinfo(argv[1], argv[2], &hints, &ai) || !ai) {
113 fprintf(stderr, "Could not resolve %s port %s: %s\n", argv[1], argv[2], strerror(errno));
118 fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
121 fprintf(stderr, "Could not create socket: %s\n", strerror(errno));
125 static const int one = 1;
126 setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (void *)&one, sizeof(one));
128 if(bind(fd, ai->ai_addr, ai->ai_addrlen)) {
129 fprintf(stderr, "Could not bind socket: %s\n", strerror(errno));
133 switch(ai->ai_family) {
136 struct sockaddr_in in;
137 memcpy(&in, ai->ai_addr, sizeof(in));
138 mreq.imr_multiaddr.s_addr = in.sin_addr.s_addr;
139 mreq.imr_interface.s_addr = htonl(INADDR_ANY);
141 if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *)&mreq, sizeof(mreq))) {
142 fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
146 #ifdef IP_MULTICAST_LOOP
147 setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, (const void *)&one, sizeof(one));
152 #ifdef IPV6_JOIN_GROUP
155 struct ipv6_mreq mreq;
156 struct sockaddr_in6 in6;
157 memcpy(&in6, ai->ai_addr, sizeof(in6));
158 memcpy(&mreq.ipv6mr_multiaddr, &in6.sin6_addr, sizeof(mreq.ipv6mr_multiaddr));
159 mreq.ipv6mr_interface = in6.sin6_scope_id;
161 if(setsockopt(fd, IPPROTO_IPV6, IPV6_JOIN_GROUP, (void *)&mreq, sizeof(mreq))) {
162 fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
166 #ifdef IPV6_MULTICAST_LOOP
167 setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, (const void *)&one, sizeof(one));
174 fprintf(stderr, "Multicast for address family %x unsupported\n", ai->ai_family);
179 struct addrinfo *ai2 = NULL;
181 if(getaddrinfo(argv[3], NULL, &hints, &ai2) || !ai2) {
182 fprintf(stderr, "Could not resolve %s: %s\n", argv[3], strerror(errno));
190 ssize_t len = recvfrom(fd, buf, sizeof(buf), 0, &src, &srclen);
196 // Ignore short packets.
201 uint16_t type = buf[12] << 8 | buf[13];
203 if(ai2->ai_family == AF_INET && type == ETH_P_IP) {
204 len = do_ipv4(buf, len, (struct sockaddr_in *)ai2->ai_addr);
205 } else if(ai2->ai_family == AF_INET && type == ETH_P_ARP) {
206 len = do_arp(buf, len, (struct sockaddr_in *)ai2->ai_addr);
207 } else if(ai2->ai_family == AF_INET6 && type == ETH_P_IPV6) {
208 len = do_ipv6(buf, len, (struct sockaddr_in6 *)ai2->ai_addr);
214 sendto(fd, buf, len, 0, ai->ai_addr, ai->ai_addrlen);