/* $OpenBSD: rarpd.c,v 1.6 1997/01/15 23:44:15 millert Exp $ */ /* $NetBSD: rarpd.c,v 1.12 1996/03/21 18:28:23 jtc Exp $ */ /* * Copyright (c) 1990 The Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that: (1) source code distributions * retain the above copyright notice and this paragraph in its entirety, (2) * distributions including binary code include the above copyright notice and * this paragraph in its entirety in the documentation or other materials * provided with the distribution, and (3) all advertising materials mentioning * features or use of this software display the following acknowledgement: * ``This product includes software developed by the University of California, * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of * the University nor the names of its contributors may be used to endorse * or promote products derived from this software without specific prior * written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. */ #ifndef lint char copyright[] = "@(#) Copyright (c) 1990 The Regents of the University of California.\n\ All rights reserved.\n"; #endif /* not lint */ #ifndef lint static char rcsid[] = "$OpenBSD: rarpd.c,v 1.6 1997/01/15 23:44:15 millert Exp $"; #endif /* * rarpd - Reverse ARP Daemon * * Usage: rarpd -a [ -d -f ] * rarpd [ -d -f ] interface */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define FATAL 1 /* fatal error occurred */ #define NONFATAL 0 /* non fatal error occurred */ /* * The structure for each interface. */ struct if_info { int ii_fd; /* BPF file descriptor */ char ii_name[IFNAMSIZ]; /* if name, e.g. "en0" */ u_char ii_eaddr[6]; /* Ethernet address of this interface */ u_long ii_ipaddr; /* IP address of this interface */ u_long ii_netmask; /* subnet or net mask */ struct if_info *ii_next; }; /* * The list of all interfaces that are being listened to. rarp_loop() * "selects" on the descriptors in this list. */ struct if_info *iflist; int rarp_open __P((char *)); void init_one __P((char *)); void init_all __P((void)); void rarp_loop __P((void)); void lookup_eaddr __P((char *, u_char *)); void lookup_ipaddr __P((char *, u_long *, u_long *)); void usage __P((void)); void rarp_process __P((struct if_info *, u_char *)); void rarp_reply __P((struct if_info *, struct ether_header *, u_long)); void update_arptab __P((u_char *, u_long)); void err __P((int, const char *,...)); void debug __P((const char *,...)); u_long ipaddrtonetmask __P((u_long)); #ifdef REQUIRE_TFTPBOOT int rarp_bootable __P((u_long)); #endif int aflag = 0; /* listen on "all" interfaces */ int dflag = 0; /* print debugging messages */ int fflag = 0; /* don't fork */ int main(argc, argv) int argc; char **argv; { int op, pid, devnull, f; char *ifname, *hostname, *name; extern char *optarg; extern int optind, opterr; if ((name = strrchr(argv[0], '/'))) ++name; else name = argv[0]; if (*name == '-') ++name; /* All error reporting is done through syslogs. */ openlog(name, LOG_PID | LOG_CONS, LOG_DAEMON); opterr = 0; while ((op = getopt(argc, argv, "adf")) != -1) { switch (op) { case 'a': ++aflag; break; case 'd': ++dflag; break; case 'f': ++fflag; break; default: usage(); /* NOTREACHED */ } } ifname = argv[optind++]; hostname = ifname ? argv[optind] : 0; if ((aflag && ifname) || (!aflag && ifname == 0)) usage(); if (aflag) init_all(); else init_one(ifname); if ((!fflag) && (!dflag)) { pid = fork(); if (pid > 0) /* Parent exits, leaving child in background. */ exit(0); else if (pid == -1) { err(FATAL, "cannot fork"); /* NOTREACHED */ } /* Fade into the background */ f = open("/dev/tty", O_RDWR); if (f >= 0) { if (ioctl(f, TIOCNOTTY, 0) < 0) { err(FATAL, "TIOCNOTTY: %s", strerror(errno)); /* NOTREACHED */ } (void) close(f); } (void) chdir("/"); (void) setpgrp(0, getpid()); devnull = open("/dev/null", O_RDWR); if (devnull >= 0) { (void) dup2(devnull, 0); (void) dup2(devnull, 1); (void) dup2(devnull, 2); if (devnull > 2) (void) close(devnull); } } rarp_loop(); exit(0); } /* * Add 'ifname' to the interface list. Lookup its IP address and network * mask and Ethernet address, and open a BPF file for it. */ void init_one(ifname) char *ifname; { struct if_info *p; /* first check to see if this "if" was already opened? */ for(p = iflist; p; p = p->ii_next) if (!strncmp(p->ii_name, ifname, IFNAMSIZ)) return; p = (struct if_info *)malloc(sizeof(*p)); if (p == 0) { err(FATAL, "malloc: %s", strerror(errno)); /* NOTREACHED */ } p->ii_next = iflist; iflist = p; p->ii_fd = rarp_open(ifname); strncpy(p->ii_name, ifname, IFNAMSIZ); lookup_eaddr(ifname, p->ii_eaddr); lookup_ipaddr(ifname, &p->ii_ipaddr, &p->ii_netmask); } /* * Initialize all "candidate" interfaces that are in the system * configuration list. A "candidate" is up, not loopback and not * point to point. */ void init_all() { char inbuf[8192]; struct ifconf ifc; struct ifreq *ifr; int fd; int i, len; if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { err(FATAL, "socket: %s", strerror(errno)); /* NOTREACHED */ } ifc.ifc_len = sizeof(inbuf); ifc.ifc_buf = inbuf; if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 || ifc.ifc_len < sizeof(struct ifreq)) { err(FATAL, "init_all: SIOCGIFCONF: %s", strerror(errno)); /* NOTREACHED */ } ifr = ifc.ifc_req; for (i = 0; i < ifc.ifc_len; i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) { len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len; if (ioctl(fd, SIOCGIFFLAGS, (caddr_t)ifr) < 0) { err(FATAL, "init_all: SIOCGIFFLAGS: %s", strerror(errno)); /* NOTREACHED */ } if ((ifr->ifr_flags & (IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) != IFF_UP) continue; init_one(ifr->ifr_name); } (void) close(fd); } void usage() { (void) fprintf(stderr, "usage: rarpd -a [ -d -f ]\n"); (void) fprintf(stderr, " rarpd [ -d -f ] interface\n"); exit(1); } static int bpf_open() { int fd; int n = 0; char device[sizeof "/dev/bpf000"]; /* Go through all the minors and find one that isn't in use. */ do { (void) sprintf(device, "/dev/bpf%d", n++); fd = open(device, O_RDWR); } while (fd < 0 && errno == EBUSY); if (fd < 0) { err(FATAL, "%s: %s", device, strerror(errno)); /* NOTREACHED */ } return fd; } /* * Open a BPF file and attach it to the interface named 'device'. * Set immediate mode, and set a filter that accepts only RARP requests. */ int rarp_open(device) char *device; { int fd; struct ifreq ifr; u_int dlt; int immediate; static struct bpf_insn insns[] = { BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 12), BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_REVARP, 0, 3), BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 20), BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ARPOP_REVREQUEST, 0, 1), BPF_STMT(BPF_RET | BPF_K, sizeof(struct ether_arp) + sizeof(struct ether_header)), BPF_STMT(BPF_RET | BPF_K, 0), }; static struct bpf_program filter = { sizeof insns / sizeof(insns[0]), insns }; fd = bpf_open(); /* Set immediate mode so packets are processed as they arrive. */ immediate = 1; if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) { err(FATAL, "BIOCIMMEDIATE: %s", strerror(errno)); /* NOTREACHED */ } (void) strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name); if (ioctl(fd, BIOCSETIF, (caddr_t) & ifr) < 0) { err(FATAL, "BIOCSETIF: %s", strerror(errno)); /* NOTREACHED */ } /* Check that the data link layer is an Ethernet; this code won't work * with anything else. */ if (ioctl(fd, BIOCGDLT, (caddr_t) & dlt) < 0) { err(FATAL, "BIOCGDLT: %s", strerror(errno)); /* NOTREACHED */ } if (dlt != DLT_EN10MB) { err(FATAL, "%s is not an ethernet", device); /* NOTREACHED */ } /* Set filter program. */ if (ioctl(fd, BIOCSETF, (caddr_t) & filter) < 0) { err(FATAL, "BIOCSETF: %s", strerror(errno)); /* NOTREACHED */ } return fd; } /* * Perform various sanity checks on the RARP request packet. Return * false on failure and log the reason. */ static int rarp_check(p, len) u_char *p; int len; { struct ether_header *ep = (struct ether_header *) p; struct ether_arp *ap = (struct ether_arp *) (p + sizeof(*ep)); (void) debug("got a packet"); if (len < sizeof(*ep) + sizeof(*ap)) { err(NONFATAL, "truncated request"); return 0; } /* XXX This test might be better off broken out... */ if (ntohs (ep->ether_type) != ETHERTYPE_REVARP || ntohs (ap->arp_hrd) != ARPHRD_ETHER || ntohs (ap->arp_op) != ARPOP_REVREQUEST || ntohs (ap->arp_pro) != ETHERTYPE_IP || ap->arp_hln != 6 || ap->arp_pln != 4) { err(NONFATAL, "request fails sanity check"); return 0; } if (bcmp((char *) &ep->ether_shost, (char *) &ap->arp_sha, 6) != 0) { err(NONFATAL, "ether/arp sender address mismatch"); return 0; } if (bcmp((char *) &ap->arp_sha, (char *) &ap->arp_tha, 6) != 0) { err(NONFATAL, "ether/arp target address mismatch"); return 0; } return 1; } /* * Loop indefinitely listening for RARP requests on the * interfaces in 'iflist'. */ void rarp_loop() { u_char *buf, *bp, *ep; int cc, fd; fd_set fds, listeners; int bufsize, maxfd = 0; struct if_info *ii; if (iflist == 0) { err(FATAL, "no interfaces"); /* NOTREACHED */ } if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t) & bufsize) < 0) { err(FATAL, "BIOCGBLEN: %s", strerror(errno)); /* NOTREACHED */ } buf = (u_char *) malloc((unsigned) bufsize); if (buf == 0) { err(FATAL, "malloc: %s", strerror(errno)); /* NOTREACHED */ } /* * Find the highest numbered file descriptor for select(). * Initialize the set of descriptors to listen to. */ FD_ZERO(&fds); for (ii = iflist; ii; ii = ii->ii_next) { FD_SET(ii->ii_fd, &fds); if (ii->ii_fd > maxfd) maxfd = ii->ii_fd; } while (1) { listeners = fds; if (select(maxfd + 1, &listeners, (struct fd_set *) 0, (struct fd_set *) 0, (struct timeval *) 0) < 0) { err(FATAL, "select: %s", strerror(errno)); /* NOTREACHED */ } for (ii = iflist; ii; ii = ii->ii_next) { fd = ii->ii_fd; if (!FD_ISSET(fd, &listeners)) continue; again: cc = read(fd, (char *) buf, bufsize); /* Don't choke when we get ptraced */ if (cc < 0 && errno == EINTR) goto again; /* Due to a SunOS bug, after 2^31 bytes, the file * offset overflows and read fails with EINVAL. The * lseek() to 0 will fix things. */ if (cc < 0) { if (errno == EINVAL && (lseek(fd, 0, SEEK_CUR) + bufsize) < 0) { (void) lseek(fd, 0, 0); goto again; } err(FATAL, "read: %s", strerror(errno)); /* NOTREACHED */ } /* Loop through the packet(s) */ #define bhp ((struct bpf_hdr *)bp) bp = buf; ep = bp + cc; while (bp < ep) { register int caplen, hdrlen; caplen = bhp->bh_caplen; hdrlen = bhp->bh_hdrlen; if (rarp_check(bp + hdrlen, caplen)) rarp_process(ii, bp + hdrlen); bp += BPF_WORDALIGN(hdrlen + caplen); } } } } #ifdef REQUIRE_TFTPBOOT #ifndef TFTP_DIR #define TFTP_DIR "/tftpboot" #endif /* * True if this server can boot the host whose IP address is 'addr'. * This check is made by looking in the tftp directory for the * configuration file. */ int rarp_bootable(addr) u_long addr; { register struct dirent *dent; register DIR *d; char ipname[9]; static DIR *dd = 0; (void) sprintf(ipname, "%08X", addr); /* If directory is already open, rewind it. Otherwise, open it. */ if (d = dd) rewinddir(d); else { if (chdir(TFTP_DIR) == -1) { err(FATAL, "chdir: %s", strerror(errno)); /* NOTREACHED */ } d = opendir("."); if (d == 0) { err(FATAL, "opendir: %s", strerror(errno)); /* NOTREACHED */ } dd = d; } while (dent = readdir(d)) if (strncmp(dent->d_name, ipname, 8) == 0) return 1; return 0; } #endif /* REQUIRE_TFTPBOOT */ /* * Given a list of IP addresses, 'alist', return the first address that * is on network 'net'; 'netmask' is a mask indicating the network portion * of the address. */ u_long choose_ipaddr(alist, net, netmask) u_long **alist; u_long net; u_long netmask; { for (; *alist; ++alist) { if ((**alist & netmask) == net) return **alist; } return 0; } /* * Answer the RARP request in 'pkt', on the interface 'ii'. 'pkt' has * already been checked for validity. The reply is overlaid on the request. */ void rarp_process(ii, pkt) struct if_info *ii; u_char *pkt; { struct ether_header *ep; struct hostent *hp; u_long target_ipaddr; char ename[256]; struct in_addr in; ep = (struct ether_header *) pkt; if (ether_ntohost(ename, (struct ether_addr *)&ep->ether_shost) != 0 || (hp = gethostbyname(ename)) == 0) return; /* Choose correct address from list. */ if (hp->h_addrtype != AF_INET) { err(FATAL, "cannot handle non IP addresses"); /* NOTREACHED */ } target_ipaddr = choose_ipaddr((u_long **) hp->h_addr_list, ii->ii_ipaddr & ii->ii_netmask, ii->ii_netmask); if (target_ipaddr == 0) { in.s_addr = ii->ii_ipaddr & ii->ii_netmask; err(NONFATAL, "cannot find %s on net %s\n", ename, inet_ntoa(in)); return; } #ifdef REQUIRE_TFTPBOOT if (rarp_bootable(htonl(target_ipaddr))) #endif rarp_reply(ii, ep, target_ipaddr); } /* * Lookup the ethernet address of the interface attached to the BPF * file descriptor 'fd'; return it in 'eaddr'. */ void lookup_eaddr(ifname, eaddr) char *ifname; u_char *eaddr; { char inbuf[8192]; struct ifconf ifc; struct ifreq *ifr; struct sockaddr_dl *sdl; int fd; int i, len; /* We cannot use SIOCGIFADDR on the BPF descriptor. We must instead get all the interfaces with SIOCGIFCONF and find the right one. */ /* Use datagram socket to get Ethernet address. */ if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { err(FATAL, "socket: %s", strerror(errno)); /* NOTREACHED */ } ifc.ifc_len = sizeof(inbuf); ifc.ifc_buf = inbuf; if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 || ifc.ifc_len < sizeof(struct ifreq)) { err(FATAL, "lookup_eaddr: SIOGIFCONF: %s", strerror(errno)); /* NOTREACHED */ } ifr = ifc.ifc_req; for (i = 0; i < ifc.ifc_len; i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) { len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len; sdl = (struct sockaddr_dl *)&ifr->ifr_addr; if (sdl->sdl_family != AF_LINK || sdl->sdl_type != IFT_ETHER || sdl->sdl_alen != 6) continue; if (!strncmp(ifr->ifr_name, ifname, sizeof(ifr->ifr_name))) { bcopy((caddr_t)LLADDR(sdl), (caddr_t)eaddr, 6); if (dflag) fprintf(stderr, "%s: %x:%x:%x:%x:%x:%x\n", ifr->ifr_name, eaddr[0], eaddr[1], eaddr[2], eaddr[3], eaddr[4], eaddr[5]); return; } } err(FATAL, "lookup_eaddr: Never saw interface `%s'!", ifname); } /* * Lookup the IP address and network mask of the interface named 'ifname'. */ void lookup_ipaddr(ifname, addrp, netmaskp) char *ifname; u_long *addrp; u_long *netmaskp; { int fd; struct ifreq ifr; /* Use datagram socket to get IP address. */ if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { err(FATAL, "socket: %s", strerror(errno)); /* NOTREACHED */ } (void) strncpy(ifr.ifr_name, ifname, sizeof ifr.ifr_name); if (ioctl(fd, SIOCGIFADDR, (char *) &ifr) < 0) { err(FATAL, "SIOCGIFADDR: %s", strerror(errno)); /* NOTREACHED */ } *addrp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr; if (ioctl(fd, SIOCGIFNETMASK, (char *) &ifr) < 0) { perror("SIOCGIFNETMASK"); exit(1); } *netmaskp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr; /* If SIOCGIFNETMASK didn't work, figure out a mask from the IP * address class. */ if (*netmaskp == 0) *netmaskp = ipaddrtonetmask(*addrp); (void) close(fd); } int arptab_set __P((u_char *eaddr, u_long host)); /* * Poke the kernel arp tables with the ethernet/ip address combinataion * given. When processing a reply, we must do this so that the booting * host (i.e. the guy running rarpd), won't try to ARP for the hardware * address of the guy being booted (he cannot answer the ARP). */ void update_arptab(ep, ipaddr) u_char *ep; u_long ipaddr; { #ifdef SIOCSARP int s; struct arpreq request; struct sockaddr_in *sin; u_char *eaddr; u_long host; request.arp_flags = 0; sin = (struct sockaddr_in *) & request.arp_pa; sin->sin_family = AF_INET; sin->sin_addr.s_addr = ipaddr; request.arp_ha.sa_family = AF_UNSPEC; /* This is needed #if defined(COMPAT_43) && BYTE_ORDER != BIG_ENDIAN, because AF_UNSPEC is zero and the kernel assumes that a zero sa_family means that the real sa_family value is in sa_len. */ request.arp_ha.sa_len = 16; /* XXX */ bcopy((char *) ep, (char *) request.arp_ha.sa_data, 6); s = socket(AF_INET, SOCK_DGRAM, 0); if (ioctl(s, SIOCSARP, (caddr_t) & request) < 0) { err(NONFATAL, "SIOCSARP: %s", strerror(errno)); } (void) close(s); #else if (arptab_set(ep, ipaddr) > 0) syslog(LOG_ERR, "couldn't update arp table"); #endif } /* * Build a reverse ARP packet and sent it out on the interface. * 'ep' points to a valid ARPOP_REVREQUEST. The ARPOP_REVREPLY is built * on top of the request, then written to the network. * * RFC 903 defines the ether_arp fields as follows. The following comments * are taken (more or less) straight from this document. * * ARPOP_REVREQUEST * * arp_sha is the hardware address of the sender of the packet. * arp_spa is undefined. * arp_tha is the 'target' hardware address. * In the case where the sender wishes to determine his own * protocol address, this, like arp_sha, will be the hardware * address of the sender. * arp_tpa is undefined. * * ARPOP_REVREPLY * * arp_sha is the hardware address of the responder (the sender of the * reply packet). * arp_spa is the protocol address of the responder (see the note below). * arp_tha is the hardware address of the target, and should be the same as * that which was given in the request. * arp_tpa is the protocol address of the target, that is, the desired address. * * Note that the requirement that arp_spa be filled in with the responder's * protocol is purely for convenience. For instance, if a system were to use * both ARP and RARP, then the inclusion of the valid protocol-hardware * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent * ARP request. */ void rarp_reply(ii, ep, ipaddr) struct if_info *ii; struct ether_header *ep; u_long ipaddr; { int n; struct ether_arp *ap = (struct ether_arp *) (ep + 1); int len; update_arptab((u_char *) & ap->arp_sha, ipaddr); /* Build the rarp reply by modifying the rarp request in place. */ ep->ether_type = htons(ETHERTYPE_REVARP); ap->ea_hdr.ar_hrd = htons(ARPHRD_ETHER); ap->ea_hdr.ar_pro = htons(ETHERTYPE_IP); ap->arp_op = htons(ARPOP_REVREPLY); bcopy((char *) &ap->arp_sha, (char *) &ep->ether_dhost, 6); bcopy((char *) ii->ii_eaddr, (char *) &ep->ether_shost, 6); bcopy((char *) ii->ii_eaddr, (char *) &ap->arp_sha, 6); bcopy((char *) &ipaddr, (char *) ap->arp_tpa, 4); /* Target hardware is unchanged. */ bcopy((char *) &ii->ii_ipaddr, (char *) ap->arp_spa, 4); len = sizeof(*ep) + sizeof(*ap); n = write(ii->ii_fd, (char *) ep, len); if (n != len) { err(NONFATAL, "write: only %d of %d bytes written", n, len); } } /* * Get the netmask of an IP address. This routine is used if * SIOCGIFNETMASK doesn't work. */ u_long ipaddrtonetmask(addr) u_long addr; { if (IN_CLASSA(addr)) return IN_CLASSA_NET; if (IN_CLASSB(addr)) return IN_CLASSB_NET; if (IN_CLASSC(addr)) return IN_CLASSC_NET; err(FATAL, "unknown IP address class: %08X", addr); /* NOTREACHED */ } #if __STDC__ #include #else #include #endif void #if __STDC__ err(int fatal, const char *fmt,...) #else err(fmt, va_alist) int fatal; char *fmt; va_dcl #endif { va_list ap; #if __STDC__ va_start(ap, fmt); #else va_start(ap); #endif if (dflag) { if (fatal) (void) fprintf(stderr, "rarpd: error: "); else (void) fprintf(stderr, "rarpd: warning: "); (void) vfprintf(stderr, fmt, ap); (void) fprintf(stderr, "\n"); } vsyslog(LOG_ERR, fmt, ap); va_end(ap); if (fatal) exit(1); /* NOTREACHED */ } void #if __STDC__ debug(const char *fmt,...) #else debug(fmt, va_alist) char *fmt; va_dcl #endif { va_list ap; if (dflag) { #if __STDC__ va_start(ap, fmt); #else va_start(ap); #endif (void) fprintf(stderr, "rarpd: "); (void) vfprintf(stderr, fmt, ap); va_end(ap); (void) fprintf(stderr, "\n"); } }