--- /dev/null
+/*
+ pong.c -- ICMP echo reply generator
+ Copyright (C) 2013 Guus Sliepen <guus@tinc-vpn.org>
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along
+ with this program; if not, write to the Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "../src/system.h"
+
+uint8_t mymac[6] = {6, 5, 5, 6, 5, 5};
+
+static ssize_t do_arp(uint8_t *buf, ssize_t len, struct sockaddr_in *in) {
+ struct ether_arp arp;
+ memcpy(&arp, buf + 14, sizeof arp);
+
+ // Is it a valid ARP request?
+ 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)
+ return 0;
+
+ // Does it match our address?
+ if(memcmp(&in->sin_addr.s_addr, arp.arp_tpa, 4))
+ return 0;
+
+ // Swap addresses
+ memcpy(buf, buf + 6, 6);
+ memcpy(buf + 6, mymac, 6);
+
+ arp.arp_op = htons(ARPOP_REPLY);
+ memcpy(arp.arp_tpa, arp.arp_spa, sizeof arp.arp_tpa);
+ memcpy(arp.arp_tha, arp.arp_sha, sizeof arp.arp_tha);
+ memcpy(arp.arp_spa, &in->sin_addr.s_addr, sizeof in->sin_addr.s_addr);
+ memcpy(arp.arp_sha, mymac, 6);
+
+ memcpy(buf + 14, &arp, sizeof arp);
+
+ return len;
+}
+
+static ssize_t do_ipv4(uint8_t *buf, ssize_t len, struct sockaddr_in *in) {
+ struct ip ip;
+ struct icmp icmp;
+
+ // Does it match our address?
+ if(memcmp(buf, mymac, 6))
+ return 0;
+
+ memcpy(&ip, buf + 14, sizeof ip);
+ if(memcmp(&ip.ip_dst, &in->sin_addr.s_addr, 4))
+ return 0;
+
+ // Is it an ICMP echo request?
+ if(ip.ip_p != IPPROTO_ICMP)
+ return 0;
+
+ memcpy(&icmp, buf + 14 + sizeof ip, sizeof icmp);
+ if(icmp.icmp_type != ICMP_ECHO)
+ return 0;
+
+ // Return an echo reply
+ memcpy(buf, buf + 6, 6);
+ memcpy(buf + 6, mymac, 6);
+
+ ip.ip_dst = ip.ip_src;
+ memcpy(&ip.ip_src, &in->sin_addr.s_addr, 4);
+
+ icmp.icmp_type = ICMP_ECHOREPLY;
+
+ memcpy(buf + 14, &ip, sizeof ip);
+ memcpy(buf + 14 + sizeof ip, &icmp, sizeof icmp);
+
+ return len;
+}
+
+static ssize_t do_ipv6(uint8_t *buf, ssize_t len, struct sockaddr_in6 *in) {
+ return 0;
+}
+
+int main(int argc, char *argv[]) {
+ if(argc != 4) {
+ fprintf(stderr, "Usage: %s <multicast address> <port> <ping address>\n", argv[0]);
+ return 1;
+ }
+
+ struct addrinfo hints = {}, *ai = NULL;
+ hints.ai_socktype = SOCK_DGRAM;
+ hints.ai_flags = AI_ADDRCONFIG;
+
+ errno = ENOENT;
+ if(getaddrinfo(argv[1], argv[2], &hints, &ai) || !ai) {
+ fprintf(stderr, "Could not resolve %s port %s: %s\n", argv[1], argv[2], strerror(errno));
+ return 1;
+ }
+
+ int fd;
+ fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+ if(!fd) {
+ fprintf(stderr, "Could not create socket: %s\n", strerror(errno));
+ return 1;
+ }
+
+ static const int one = 1;
+ setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (void *)&one, sizeof one);
+
+ if(bind(fd, ai->ai_addr, ai->ai_addrlen)) {
+ fprintf(stderr, "Could not bind socket: %s\n", strerror(errno));
+ return 1;
+ }
+
+ switch(ai->ai_family) {
+ case AF_INET: {
+ struct ip_mreq mreq;
+ struct sockaddr_in in;
+ memcpy(&in, ai->ai_addr, sizeof in);
+ mreq.imr_multiaddr.s_addr = in.sin_addr.s_addr;
+ mreq.imr_interface.s_addr = htonl(INADDR_ANY);
+ if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *)&mreq, sizeof mreq)) {
+ fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
+ return 1;
+ }
+#ifdef IP_MULTICAST_LOOP
+ setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, (const void *)&one, sizeof one);
+#endif
+ } break;
+
+#ifdef IPV6_JOIN_GROUP
+ case AF_INET6: {
+ struct ipv6_mreq mreq;
+ struct sockaddr_in6 in6;
+ memcpy(&in6, ai->ai_addr, sizeof in6);
+ memcpy(&mreq.ipv6mr_multiaddr, &in6.sin6_addr, sizeof mreq.ipv6mr_multiaddr);
+ mreq.ipv6mr_interface = in6.sin6_scope_id;
+ if(setsockopt(fd, IPPROTO_IPV6, IPV6_JOIN_GROUP, (void *)&mreq, sizeof mreq)) {
+ fprintf(stderr, "Cannot join multicast group: %s\n", strerror(errno));
+ return 1;
+ }
+#ifdef IPV6_MULTICAST_LOOP
+ setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, (const void *)&one, sizeof one);
+#endif
+ } break;
+#endif
+
+ default:
+ fprintf(stderr, "Multicast for address family %hx unsupported\n", ai->ai_family);
+ return 1;
+ }
+
+ errno = ENOENT;
+ struct addrinfo *ai2 = NULL;
+ if(getaddrinfo(argv[3], NULL, &hints, &ai2) || !ai2) {
+ fprintf(stderr, "Could not resolve %s: %s\n", argv[3], strerror(errno));
+ return 1;
+ }
+
+ while(true) {
+ uint8_t buf[10000];
+ struct sockaddr src;
+ socklen_t srclen;
+ ssize_t len = recvfrom(fd, buf, sizeof buf, 0, &src, &srclen);
+ if(len <= 0)
+ break;
+
+ // Ignore short packets.
+ if(len < 14)
+ continue;
+
+ uint16_t type = buf[12] << 8 | buf[13];
+
+ if(ai2->ai_family == AF_INET && type == ETH_P_IP)
+ len = do_ipv4(buf, len, (struct sockaddr_in *)ai2->ai_addr);
+ else if(ai2->ai_family == AF_INET && type == ETH_P_ARP)
+ len = do_arp(buf, len, (struct sockaddr_in *)ai2->ai_addr);
+ else if(ai2->ai_family == AF_INET6 && type == ETH_P_IPV6)
+ len = do_ipv6(buf, len, (struct sockaddr_in6 *)ai2->ai_addr);
+ else
+ continue;
+
+ if(len > 0)
+ sendto(fd, buf, len, 0, ai->ai_addr, ai->ai_addrlen);
+ }
+
+ return 0;
+}
projects / meshlink / commitdiff