4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
9 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
11 * Extricated from iputils by Nick Bowler (2023-07).
26 #include <arpa/inet.h>
27 #include <netinet/in.h>
29 #include <linux/if_arp.h>
30 #include <linux/if_packet.h>
31 #include <linux/filter.h>
32 #include <sys/ioctl.h>
33 #include <sys/socket.h>
49 char *tftp_dir = "/etc/tftpboot";
51 extern int ether_ntohost(char *name, unsigned char *ea);
52 void usage(void) __attribute__((noreturn));
59 unsigned char lladdr[16];
61 struct ifaddr *ifa_list;
74 struct rarp_map *next;
79 unsigned char lladdr[16];
87 " rarpd [options] [interface]\n"
89 " -A listen also arp messages\n"
90 " -a listen on all the interfaces\n"
91 " -b <dir> tftpd boot directory\n"
93 " -e /etc/ethers markup alone is fine\n"
95 " -V print version and exit\n"
96 "\nFor more details see rarpd(8).\n"
101 static void print_version(void)
103 printf("rarpd (%s) %s\n", PACKAGE, PACKAGE_VERSION);
104 puts("License GPLv2+: GNU GPL version 2 or any later version");
105 puts("This is free software: you are free to change and redistribute it.");
106 puts("There is NO WARRANTY, to the extent permitted by law.");
116 struct ifreq *ifrp, *ifend;
120 struct ifreq ibuf[256];
122 if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
123 syslog(LOG_ERR, "socket: %s", strerror(errno));
127 ifc.ifc_len = sizeof ibuf;
128 ifc.ifc_buf = (char *)ibuf;
129 if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
130 ifc.ifc_len < (int)sizeof(struct ifreq)) {
131 syslog(LOG_ERR, "SIOCGIFCONF: %s", strerror(errno));
136 while ((ifl = ifl_list) != NULL) {
137 while ((ifa = ifl->ifa_list) != NULL) {
138 ifl->ifa_list = ifa->next;
141 ifl_list = ifl->next;
145 ifend = (struct ifreq *)((char *)ibuf + ifc.ifc_len);
146 for (ifrp = ibuf; ifrp < ifend; ifrp++) {
151 if (ifrp->ifr_addr.sa_family != AF_INET)
153 addr = ((struct sockaddr_in*)&ifrp->ifr_addr)->sin_addr.s_addr;
156 if (ioctl(fd, SIOCGIFINDEX, ifrp)) {
157 syslog(LOG_ERR, "ioctl(SIOCGIFNAME): %s", strerror(errno));
160 if (ifidx && ifrp->ifr_ifindex != ifidx)
162 for (ifl = ifl_list; ifl; ifl = ifl->next)
163 if (ifl->index == ifrp->ifr_ifindex)
167 int index = ifrp->ifr_ifindex;
169 if (ioctl(fd, SIOCGIFHWADDR, ifrp)) {
170 syslog(LOG_ERR, "ioctl(SIOCGIFHWADDR): %s", strerror(errno));
174 ifl = (struct iflink*)malloc(sizeof(*ifl));
177 memset(ifl, 0, sizeof(*ifl));
178 ifl->next = ifl_list;
181 ifl->hatype = ifrp->ifr_hwaddr.sa_family;
182 memcpy(ifl->lladdr, ifrp->ifr_hwaddr.sa_data, 14);
183 strncpy(ifl->name, ifrp->ifr_name, IFNAMSIZ);
184 p = strchr(ifl->name, ':');
188 syslog(LOG_INFO, "link %s", ifl->name);
190 if (ioctl(fd, SIOCGIFNETMASK, ifrp)) {
191 syslog(LOG_ERR, "ioctl(SIOCGIFMASK): %s", strerror(errno));
194 mask = ((struct sockaddr_in*)&ifrp->ifr_netmask)->sin_addr.s_addr;
195 if (ioctl(fd, SIOCGIFDSTADDR, ifrp)) {
196 syslog(LOG_ERR, "ioctl(SIOCGIFDSTADDR): %s", strerror(errno));
199 prefix = ((struct sockaddr_in*)&ifrp->ifr_dstaddr)->sin_addr.s_addr;
200 for (ifa = ifl->ifa_list; ifa; ifa = ifa->next) {
201 if (ifa->local == addr &&
202 ifa->prefix == prefix &&
207 if (mask == 0 || prefix == 0)
209 ifa = (struct ifaddr*)malloc(sizeof(*ifa));
210 memset(ifa, 0, sizeof(*ifa));
212 ifa->prefix = prefix;
214 ifa->next = ifl->ifa_list;
220 for (i=32; i>=0; i--) {
221 if (htonl(m) == mask)
225 if (addr == prefix) {
226 syslog(LOG_INFO, " addr %s/%d on %s\n",
227 inet_ntoa(*(struct in_addr*)&addr), i, ifl->name);
230 sprintf(tmpa, "%s", inet_ntoa(*(struct in_addr*)&addr));
231 syslog(LOG_INFO, " addr %s %s/%d on %s\n", tmpa,
232 inet_ntoa(*(struct in_addr*)&prefix), i, ifl->name);
245 int bootable(uint32_t addr)
251 sprintf(name, "%08X", (uint32_t)ntohl(addr));
252 d = opendir(tftp_dir);
254 syslog(LOG_ERR, "opendir: %s", strerror(errno));
257 while ((dent = readdir(d)) != NULL) {
258 if (strncmp(dent->d_name, name, 8) == 0)
265 struct ifaddr *select_ipaddr(int ifindex, uint32_t *sel_addr, uint32_t **alist)
273 for (ifl=ifl_list; ifl; ifl=ifl->next)
274 if (ifl->index == ifindex)
276 if (ifl == NULL && !retry) {
284 for (i=0; alist[i]; i++) {
285 uint32_t addr = *(alist[i]);
286 for (ifa=ifl->ifa_list; ifa; ifa=ifa->next) {
287 if (!((ifa->prefix^addr)&ifa->mask)) {
292 if (ifa == NULL && retry==0) {
298 if (i==1 && allow_offlink) {
299 *sel_addr = *(alist[0]);
300 return ifl->ifa_list;
302 syslog(LOG_ERR, "Off-link request on %s", ifl->name);
306 struct rarp_map *rarp_lookup(int ifindex, int hatype,
307 int halen, unsigned char *lladdr)
311 for (r=rarp_db; r; r=r->next) {
312 if (r->arp_type != hatype && r->arp_type != -1)
314 if (r->lladdr_len != halen)
316 if (r->ifindex != ifindex && r->ifindex != 0)
318 if (memcmp(r->lladdr, lladdr, halen) == 0)
323 if (hatype == ARPHRD_ETHER && halen == 6) {
327 static struct rarp_map emap = {
328 .arp_type = ARPHRD_ETHER,
332 if (ether_ntohost(ename, lladdr) != 0 ||
333 (hp = gethostbyname(ename)) == NULL) {
335 syslog(LOG_INFO, "not found in /etc/ethers");
338 if (hp->h_addrtype != AF_INET) {
339 syslog(LOG_ERR, "no IP address");
342 ifa = select_ipaddr(ifindex, &emap.ipaddr, (uint32_t **)hp->h_addr_list);
344 memcpy(emap.lladdr, lladdr, 6);
345 if (only_ethers || bootable(emap.ipaddr))
348 syslog(LOG_INFO, "not bootable");
355 static int load_arp_bpflet(int fd)
357 static struct sock_filter insns[] = {
358 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
359 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, ARPOP_RREQUEST, 0, 1),
360 BPF_STMT(BPF_RET|BPF_K, 1024),
361 BPF_STMT(BPF_RET|BPF_K, 0),
363 static struct sock_fprog filter = {
364 sizeof insns / sizeof(insns[0]),
368 return setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
371 int put_mylladdr(unsigned char **ptr_p, int ifindex, int alen)
375 for (ifl=ifl_list; ifl; ifl = ifl->next)
376 if (ifl->index == ifindex)
382 memcpy(*ptr_p, ifl->lladdr, alen);
387 int put_myipaddr(unsigned char **ptr_p, int ifindex, uint32_t hisipaddr)
393 for (ifl=ifl_list; ifl; ifl = ifl->next)
394 if (ifl->index == ifindex)
400 for (ifa=ifl->ifa_list; ifa; ifa=ifa->next) {
401 if (!((ifa->prefix^hisipaddr)&ifa->mask)) {
406 memcpy(*ptr_p, &laddr, 4);
411 void arp_advise(int ifindex, unsigned char *lladdr, int lllen, uint32_t ipaddr)
415 struct sockaddr_in *sin;
418 for (ifl=ifl_list; ifl; ifl = ifl->next)
419 if (ifl->index == ifindex)
425 fd = socket(AF_INET, SOCK_DGRAM, 0);
426 memset(&req, 0, sizeof(req));
427 req.arp_flags = ATF_COM;
428 sin = (struct sockaddr_in *)&req.arp_pa;
429 sin->sin_family = AF_INET;
430 sin->sin_addr.s_addr = ipaddr;
431 req.arp_ha.sa_family = ifl->hatype;
432 memcpy(req.arp_ha.sa_data, lladdr, lllen);
433 memcpy(req.arp_dev, ifl->name, IFNAMSIZ);
435 if (ioctl(fd, SIOCSARP, &req))
436 syslog(LOG_ERR, "SIOCSARP: %s", strerror(errno));
440 void serve_it(int fd)
442 unsigned char buf[1024];
443 struct sockaddr_ll sll = { 0 };
444 socklen_t sll_len = sizeof(sll);
445 struct arphdr *a = (struct arphdr*)buf;
446 struct rarp_map *rmap;
450 n = recvfrom(fd, buf, sizeof(buf), MSG_DONTWAIT, (struct sockaddr*)&sll, &sll_len);
452 if (errno != EINTR && errno != EAGAIN)
453 syslog(LOG_ERR, "recvfrom: %s", strerror(errno));
457 /* Do not accept packets for other hosts and our own ones */
458 if (sll.sll_pkttype != PACKET_BROADCAST &&
459 sll.sll_pkttype != PACKET_MULTICAST &&
460 sll.sll_pkttype != PACKET_HOST)
463 if (ifidx && sll.sll_ifindex != ifidx)
466 if ((size_t)n<sizeof(*a)) {
467 syslog(LOG_ERR, "truncated arp packet; len=%zu", n);
471 /* Accept only RARP requests */
472 if (a->ar_op != htons(ARPOP_RREQUEST))
479 for (i=0; i<sll.sll_halen; i++) {
481 sprintf(p, ":%02x", sll.sll_addr[i]);
484 sprintf(p, "%02x", sll.sll_addr[i]);
487 syslog(LOG_INFO, "RARP request from %s on if%d", tmpbuf, sll.sll_ifindex);
492 /* 1. IP only -> pln==4 */
493 if (a->ar_pln != 4) {
494 syslog(LOG_ERR, "interesting rarp_req plen=%d", a->ar_pln);
497 /* 2. ARP protocol must be IP */
498 if (a->ar_pro != htons(ETH_P_IP)) {
499 syslog(LOG_ERR, "rarp protocol is not IP %04x", ntohs(a->ar_pro));
502 /* 3. ARP types must match */
503 if (htons(sll.sll_hatype) != a->ar_hrd) {
504 switch (sll.sll_hatype) {
506 if (a->ar_hrd == htons(ARPHRD_ETHER) ||
507 a->ar_hrd == htons(ARPHRD_IEEE802))
511 syslog(LOG_ERR, "rarp htype mismatch");
515 /* 3. LL address lengths must be equal */
516 if (a->ar_hln != sll.sll_halen) {
517 syslog(LOG_ERR, "rarp hlen mismatch");
520 /* 4. Check packet length */
521 if (sizeof(*a) + 2*4 + 2*a->ar_hln > (size_t) n) {
522 syslog(LOG_ERR, "truncated rarp request; len=%zu", n);
525 /* 5. Silly check: if this guy set different source
526 addresses in MAC header and in ARP, he is insane
528 if (memcmp(sll.sll_addr, a+1, sll.sll_halen)) {
529 syslog(LOG_ERR, "this guy set different his lladdrs in arp and header");
532 /* End of sanity checks */
534 /* Lookup requested target in our database */
535 rmap = rarp_lookup(sll.sll_ifindex, sll.sll_hatype,
536 sll.sll_halen, (unsigned char*)(a+1) + sll.sll_halen + 4);
540 /* Prepare reply. It is almost ready, we only
541 replace ARP packet type, put our lladdr and
542 IP address to source fields,
543 and fill target IP address.
545 a->ar_op = htons(ARPOP_RREPLY);
546 ptr = (unsigned char*)(a+1);
547 if (put_mylladdr(&ptr, sll.sll_ifindex, rmap->lladdr_len))
549 if (put_myipaddr(&ptr, sll.sll_ifindex, rmap->ipaddr))
551 /* It is already filled */
552 ptr += rmap->lladdr_len;
553 memcpy(ptr, &rmap->ipaddr, 4);
556 /* Update our ARP cache. Probably, this guy
557 will not able to make ARP (if it is broken)
559 arp_advise(sll.sll_ifindex, rmap->lladdr, rmap->lladdr_len, rmap->ipaddr);
561 /* Sendto is blocking, but with 5sec timeout */
563 sendto(fd, buf, ptr - buf, 0, (struct sockaddr*)&sll, sizeof(sll));
567 void catch_signal(int sig, void (*handler)(int))
571 memset(&sa, 0, sizeof(sa));
572 sa.sa_handler = handler;
573 sigaction(sig, &sa, NULL);
576 void sig_alarm(int signo __attribute__((__unused__)))
580 void sig_hup(int signo __attribute__((__unused__)))
585 int main(int argc, char **argv)
587 struct pollfd pset[2];
592 while ((opt = getopt(argc, argv, "aAb:dvoeV")) != EOF) {
631 ifname = argv[optind];
635 pset[0].fd = socket(PF_PACKET, SOCK_DGRAM, 0);
639 memset(&ifr, 0, sizeof(ifr));
640 strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
641 if (ioctl(pset[0].fd, SIOCGIFINDEX, &ifr)) {
642 error(0, errno, "ioctl(SIOCGIFINDEX)");
645 ifidx = ifr.ifr_ifindex;
650 pset[1].fd = socket(PF_PACKET, SOCK_DGRAM, 0);
651 if (pset[1].fd >= 0) {
652 load_arp_bpflet(pset[1].fd);
657 if (pset[1].fd >= 0) {
658 struct sockaddr_ll sll;
659 memset(&sll, 0, sizeof(sll));
660 sll.sll_family = AF_PACKET;
661 sll.sll_protocol = htons(ETH_P_ARP);
662 sll.sll_ifindex = all_ifaces ? 0 : ifidx;
663 if (bind(pset[1].fd, (struct sockaddr*)&sll, sizeof(sll)) < 0) {
669 if (pset[0].fd >= 0) {
670 struct sockaddr_ll sll;
671 memset(&sll, 0, sizeof(sll));
672 sll.sll_family = AF_PACKET;
673 sll.sll_protocol = htons(ETH_P_RARP);
674 sll.sll_ifindex = all_ifaces ? 0 : ifidx;
675 if (bind(pset[0].fd, (struct sockaddr*)&sll, sizeof(sll)) < 0) {
680 if (pset[0].fd < 0) {
685 error(1, errno, "failed to bind any socket");
688 if (daemon(0, 0) < 0)
689 error(1, errno, "failed to daemon()");
692 openlog("rarpd", LOG_PID | LOG_CONS, LOG_DAEMON);
693 catch_signal(SIGALRM, sig_alarm);
694 catch_signal(SIGHUP, sig_hup);
704 #define EVENTS (POLLIN|POLLPRI|POLLERR|POLLHUP)
705 pset[0].events = EVENTS;
707 pset[1].events = EVENTS;
710 i = poll(pset, psize, -1);
712 if (errno != EINTR && i<0) {
713 syslog(LOG_ERR, "poll returned some crap: %s\n", strerror(errno));
718 for (i=0; i<psize; i++) {
719 if (pset[i].revents&EVENTS)
720 serve_it(pset[i].fd);