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)
34 // Does it match our address?
35 if(memcmp(&in->sin_addr.s_addr, arp.arp_tpa, 4))
39 memcpy(buf, buf + 6, 6);
40 memcpy(buf + 6, mymac, 6);
42 arp.arp_op = htons(ARPOP_REPLY);
43 memcpy(arp.arp_tpa, arp.arp_spa, sizeof arp.arp_tpa);
44 memcpy(arp.arp_tha, arp.arp_sha, sizeof arp.arp_tha);
45 memcpy(arp.arp_spa, &in->sin_addr.s_addr, sizeof in->sin_addr.s_addr);
46 memcpy(arp.arp_sha, mymac, 6);
48 memcpy(buf + 14, &arp, sizeof arp);
53 static ssize_t do_ipv4(uint8_t *buf, ssize_t len, struct sockaddr_in *in) {
57 // Does it match our address?
58 if(memcmp(buf, mymac, 6))
61 memcpy(&ip, buf + 14, sizeof ip);
62 if(memcmp(&ip.ip_dst, &in->sin_addr.s_addr, 4))
65 // Is it an ICMP echo request?
66 if(ip.ip_p != IPPROTO_ICMP)
69 memcpy(&icmp, buf + 14 + sizeof ip, sizeof icmp);
70 if(icmp.icmp_type != ICMP_ECHO)
73 // Return an echo reply
74 memcpy(buf, buf + 6, 6);
75 memcpy(buf + 6, mymac, 6);
77 ip.ip_dst = ip.ip_src;
78 memcpy(&ip.ip_src, &in->sin_addr.s_addr, 4);
80 icmp.icmp_type = ICMP_ECHOREPLY;
82 memcpy(buf + 14, &ip, sizeof ip);
83 memcpy(buf + 14 + sizeof ip, &icmp, sizeof icmp);
88 static ssize_t do_ipv6(uint8_t *buf, ssize_t len, struct sockaddr_in6 *in) {
92 int main(int argc, char *argv[]) {
94 fprintf(stderr, "Usage: %s <multicast address> <port> <ping address>\n", argv[0]);
98 struct addrinfo hints = {}, *ai = NULL;
99 hints.ai_socktype = SOCK_DGRAM;
100 hints.ai_flags = AI_ADDRCONFIG;
103 if(getaddrinfo(argv[1], argv[2], &hints, &ai) || !ai) {
104 fprintf(stderr, "Could not resolve %s port %s: %s\n", argv[1], argv[2], strerror(errno));
109 fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
111 fprintf(stderr, "Could not create socket: %s\n", strerror(errno));
115 static const int one = 1;
116 setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (void *)&one, sizeof one);
118 if(bind(fd, ai->ai_addr, ai->ai_addrlen)) {
119 fprintf(stderr, "Could not bind socket: %s\n", strerror(errno));
123 switch(ai->ai_family) {
126 struct sockaddr_in in;
127 memcpy(&in, ai->ai_addr, sizeof in);
128 mreq.imr_multiaddr.s_addr = in.sin_addr.s_addr;
129 mreq.imr_interface.s_addr = htonl(INADDR_ANY);
130 if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *)&mreq, sizeof mreq)) {
131 fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
134 #ifdef IP_MULTICAST_LOOP
135 setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, (const void *)&one, sizeof one);
139 #ifdef IPV6_JOIN_GROUP
141 struct ipv6_mreq mreq;
142 struct sockaddr_in6 in6;
143 memcpy(&in6, ai->ai_addr, sizeof in6);
144 memcpy(&mreq.ipv6mr_multiaddr, &in6.sin6_addr, sizeof mreq.ipv6mr_multiaddr);
145 mreq.ipv6mr_interface = in6.sin6_scope_id;
146 if(setsockopt(fd, IPPROTO_IPV6, IPV6_JOIN_GROUP, (void *)&mreq, sizeof mreq)) {
147 fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
150 #ifdef IPV6_MULTICAST_LOOP
151 setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, (const void *)&one, sizeof one);
157 fprintf(stderr, "Multicast for address family %x unsupported\n", ai->ai_family);
162 struct addrinfo *ai2 = NULL;
163 if(getaddrinfo(argv[3], NULL, &hints, &ai2) || !ai2) {
164 fprintf(stderr, "Could not resolve %s: %s\n", argv[3], strerror(errno));
172 ssize_t len = recvfrom(fd, buf, sizeof buf, 0, &src, &srclen);
176 // Ignore short packets.
180 uint16_t type = buf[12] << 8 | buf[13];
182 if(ai2->ai_family == AF_INET && type == ETH_P_IP)
183 len = do_ipv4(buf, len, (struct sockaddr_in *)ai2->ai_addr);
184 else if(ai2->ai_family == AF_INET && type == ETH_P_ARP)
185 len = do_arp(buf, len, (struct sockaddr_in *)ai2->ai_addr);
186 else if(ai2->ai_family == AF_INET6 && type == ETH_P_IPV6)
187 len = do_ipv6(buf, len, (struct sockaddr_in6 *)ai2->ai_addr);
192 sendto(fd, buf, len, 0, ai->ai_addr, ai->ai_addrlen);