--- /dev/null
+/*
+ * icmpdnd - ICMP Domain Name responder daemon for Linux
+ * Copyright (C) 2005 Fredrik Tolf <fredrik@dolda2000.com>
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <syslog.h>
+#include <time.h>
+#include <sys/socket.h>
+#include <sys/poll.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <sys/types.h>
+
+struct icmphdr {
+ u_int8_t type;
+ u_int8_t code;
+ u_int16_t checksum;
+};
+
+struct reqhdr {
+ u_int8_t type;
+ u_int8_t code;
+ u_int16_t checksum;
+ u_int16_t id;
+ u_int16_t seq;
+};
+
+struct rephdr {
+ u_int8_t type;
+ u_int8_t code;
+ u_int16_t checksum;
+ u_int16_t id;
+ u_int16_t seq;
+ int32_t ttl;
+};
+
+#define ICMP_NAMEREQ 37
+#define ICMP_NAMEREP 38
+
+volatile int alive;
+
+size_t filldn(char *dst)
+{
+ char *p, *p2, *dp;
+ char namebuf[1024];
+ int hl;
+
+ if(gethostname(namebuf, sizeof(namebuf)) < 0) {
+ perror("gethostname");
+ exit(1);
+ }
+ hl = strlen(namebuf);
+ namebuf[hl++] = '.';
+ if(getdomainname(namebuf + hl, sizeof(namebuf) - hl) < 0) {
+ perror("getdomainname");
+ exit(1);
+ }
+ if(strlen(namebuf + hl) != 0) {
+ hl = strlen(namebuf);
+ namebuf[hl++] = '.';
+ }
+ namebuf[hl] = 0;
+
+ p = namebuf;
+ dp = dst;
+ while((p2 = strchr(p, '.')) != NULL) {
+ *p2 = 0;
+ *(dp++) = p2 - p;
+ memcpy(dp, p, p2 - p);
+ dp += p2 - p;
+ p = p2 + 1;
+ }
+ *(dp++) = 0;
+
+ return(dp - dst);
+}
+
+void cksum(void *hdr, size_t len)
+{
+ struct icmphdr *ih;
+ u_int8_t *cb;
+ int i;
+ int b1, b2;
+
+ ih = (struct icmphdr *)hdr;
+ cb = (u_int8_t *)hdr;
+ ih->checksum = 0;
+ b1 = b2 = 0;
+ for(i = 0; i < (len & ~1); i += 2) {
+ b1 += cb[i];
+ b2 += cb[i + 1];
+ }
+ if(i & 1)
+ b1 += cb[len - 1];
+ while(1) {
+ if(b1 >= 256) {
+ b2 += b1 >> 8;
+ b1 &= 0xff;
+ continue;
+ }
+ if(b2 >= 256) {
+ b1 += b2 >> 8;
+ b2 &= 0xff;
+ continue;
+ }
+ break;
+ }
+ cb = (u_int8_t *)&ih->checksum;
+ cb[0] = ~(u_int8_t)b1;
+ cb[1] = ~(u_int8_t)b2;
+}
+
+int main(int argc, char **argv)
+{
+ int i, n, ret;
+ int c, cs, s4, s6, datalen;
+ int daemonize, ttl;
+ unsigned char buf[65536];
+ struct sockaddr_storage name;
+ struct reqhdr req;
+ struct rephdr rep;
+ struct iphdr iphdr;
+ struct msghdr mhdr;
+ struct iovec iov;
+ char cmsgbuf[CMSG_SPACE(sizeof(struct in6_pktinfo))];
+ size_t hdrlen;
+ struct pollfd pfd[2];
+ time_t curtime, lasterr;
+
+ daemonize = 1;
+ ttl = 3600;
+ while((c = getopt(argc, argv, "nht:")) != -1) {
+ switch(c) {
+ case 't':
+ ttl = atoi(optarg);
+ break;
+ case 'n':
+ daemonize = 0;
+ break;
+ case 'h':
+ case '?':
+ case ':':
+ default:
+ fprintf(stderr, "usage: icmpdnd [-n]");
+ exit((c == 'h')?0:1);
+ }
+ }
+
+ s4 = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP);
+ s6 = socket(PF_INET6, SOCK_RAW, IPPROTO_ICMP);
+ if((s4 < 0) && (s6 < 0)) {
+ perror("could not open raw socket");
+ exit(1);
+ }
+ if(s6 >= 0) {
+ i = 1;
+ if(setsockopt(s6, IPPROTO_IPV6, IPV6_PKTINFO, &i, sizeof(i))) {
+ perror("could not set IPV6_PKTINFO sockopt");
+ exit(1);
+ }
+ }
+
+ if(daemonize)
+ daemon(0, 0);
+
+ openlog("icmpdnd", LOG_PID | LOG_NDELAY, LOG_DAEMON);
+
+ alive = 1;
+ lasterr = 0;
+ while(alive) {
+ n = 0;
+ if(s4 >= 0) {
+ pfd[n].fd = s4;
+ pfd[n].events = POLLIN;
+ n++;
+ }
+ if(s6 >= 0) {
+ pfd[n].fd = s6;
+ pfd[n].events = POLLIN;
+ n++;
+ }
+ ret = poll(pfd, n, -1);
+
+ curtime = time(NULL);
+ if(ret < 0) {
+ if(errno == EINTR)
+ continue;
+ syslog(LOG_ERR, "error while polling sockets: %m");
+ if(lasterr == curtime) {
+ syslog(LOG_CRIT, "exiting due to repeated errors");
+ exit(1);
+ }
+ lasterr = curtime;
+ }
+
+ for(i = 0; i < n; i++) {
+ if((pfd[i].revents & POLLIN) == 0)
+ continue;
+ cs = pfd[i].fd;
+ memset(&name, 0, sizeof(name));
+
+ iov.iov_len = sizeof(buf);
+ iov.iov_base = buf;
+ mhdr.msg_name = &name;
+ mhdr.msg_namelen = sizeof(name);
+ mhdr.msg_iov = &iov;
+ mhdr.msg_iovlen = 1;
+ mhdr.msg_control = cmsgbuf;
+ mhdr.msg_controllen = sizeof(cmsgbuf);
+
+ ret = recvmsg(cs, &mhdr, 0);
+ if(ret < 0) {
+ syslog(LOG_WARNING, "error while receiving datagram: %m");
+ continue;
+ }
+
+ if(cs == s4) {
+ if(ret < sizeof(iphdr) + sizeof(req))
+ continue;
+ hdrlen = sizeof(iphdr);
+ memcpy(&iphdr, buf, sizeof(iphdr));
+ if(iphdr.protocol != IPPROTO_ICMP)
+ continue;
+ mhdr.msg_control = NULL;
+ mhdr.msg_controllen = 0;
+ } else if(cs == s6) {
+ if(ret < sizeof(req))
+ continue;
+ ((struct sockaddr_in6 *)&name)->sin6_port = 0;
+ hdrlen = 0;
+ /* Just keep mhdr.msg_control. */
+ } else {
+ syslog(LOG_CRIT, "strangeness!");
+ abort();
+ }
+ memcpy(&req, buf + hdrlen, sizeof(req));
+ if(req.type != ICMP_NAMEREQ)
+ continue;
+ rep.type = ICMP_NAMEREP;
+ rep.code = 0;
+ rep.id = req.id;
+ rep.seq = req.seq;
+ rep.ttl = htonl(ttl);
+ memcpy(buf, &rep, sizeof(rep));
+ datalen = filldn(buf + sizeof(rep));
+
+ cksum(buf, datalen + sizeof(rep));
+
+ iov.iov_len = sizeof(rep) + datalen;
+ iov.iov_base = buf;
+ mhdr.msg_iov = &iov;
+ mhdr.msg_iovlen = 1;
+ ret = sendmsg(cs, &mhdr, 0);
+ if(ret < 0)
+ syslog(LOG_WARNING, "error in sending reply: %m");
+ }
+ }
+
+ close(s4);
+ close(s6);
+ return(0);
+}
+
+/*
+ * Local Variables:
+ * compile-command: "gcc -Wall -g -o icmpdnd icmpdnd.c"
+ * End:
+ */
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