NetBSD/usr.sbin/rarpd/rarpd.c

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/*
* 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[] =
"@(#) $Id: rarpd.c,v 1.4 1994/03/01 06:46:42 cgd Exp $";
#endif
/*
* rarpd - Reverse ARP Daemon
*
* Usage: rarpd -a [ -d -f ]
* rarpd [ -d -f ] interface
*/
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/time.h>
#include <net/bpf.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <sys/errno.h>
#include <sys/file.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <dirent.h>
#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 */
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 *));
int rarp_bootable __P((u_long));
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));
int aflag = 0; /* listen on "all" interfaces */
int dflag = 0; /* print debugging messages */
int fflag = 0; /* don't fork */
void
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")) != EOF) {
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();
}
/*
* 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;
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);
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()
{
int fd;
int i, len;
struct ifreq ibuf[8], *ifrp;
struct ifconf ifc;
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
err(FATAL, "socket: %s", strerror(errno));
/* NOTREACHED */
}
ifc.ifc_len = sizeof ibuf;
ifc.ifc_buf = (caddr_t) ibuf;
if (ioctl(fd, SIOCGIFCONF, (char *) &ifc) < 0 ||
ifc.ifc_len < sizeof(struct ifreq)) {
err(FATAL, "SIOCGIFCONF: %s", strerror(errno));
/* NOTREACHED */
}
ifrp = ibuf;
ifrp = ifc.ifc_req;
for(i=0; i<ifc.ifc_len; i+=len, ifrp=(struct ifreq *)((caddr_t)ifrp+len)) {
len = sizeof ifrp->ifr_name + ifrp->ifr_addr.sa_len;
if (ioctl(fd, SIOCGIFFLAGS, (char *) ifrp) < 0) {
err(FATAL, "SIOCGIFFLAGS: %s", strerror(errno));
/* NOTREACHED */
}
if ((ifrp->ifr_flags & IFF_UP) == 0 ||
ifrp->ifr_flags & IFF_LOOPBACK ||
ifrp->ifr_flags & IFF_POINTOPOINT)
continue;
init_one(ifrp->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, REVARP_REQUEST, 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) != REVARP_REQUEST ||
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 &&
(long) (lseek(fd, 0L, 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);
}
}
}
}
#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;
}
/*
* 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, &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;
}
if (rarp_bootable(htonl(target_ipaddr)))
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 in_addr in;
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, &ifc) < 0) {
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;
if (!strncmp (ifr->ifr_name, ifname, sizeof (ifr->ifr_name))) {
bcopy((char *) &ifr->ifr_addr.sa_data[0],
(char *) eaddr, 6);
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);
}
/*
* 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;
{
int s;
struct arpreq request;
struct sockaddr_in *sin;
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);
}
/*
* Build a reverse ARP packet and sent it out on the interface.
* 'ep' points to a valid REVARP_REQUEST. The REVARP_REPLY 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.
*
* REVARP_REQUEST
*
* 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.
*
* REVARP_REPLY
*
* 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(REVARP_REPLY);
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 <stdarg.h>
#else
#include <varargs.h>
#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");
}
}