freebsd-dev/usr.sbin/rarpd/rarpd.c
1995-05-30 03:57:47 +00:00

753 lines
18 KiB
C

/*
* 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[] =
"@(#) $Header: /home/ncvs/src/usr.sbin/rarpd/rarpd.c,v 1.3 1995/04/02 01:35:54 wpaul Exp $ (LBL)";
#endif
/*
* rarpd - Reverse ARP Daemon
*
* Usage: rarpd -a [ -f ] [ hostname ]
* rarpd [ -f ] interface [ hostname ]
*
* 'hostname' is optional solely for backwards compatibility with Sun's rarpd.
* Currently, the argument is ignored.
*/
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
/* SunOS 4.x defines this while 3.x does not. */
#ifdef __sys_types_h
#define SUNOS4
#endif
#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>
#ifdef SUNOS4
#include <dirent.h>
#else
#include <sys/dir.h>
#endif
/*
* Map field names in ether_arp struct. What a pain in the neck.
*/
#if !defined(SUNOS4) && !defined(__FreeBSD__)
#undef arp_sha
#undef arp_spa
#undef arp_tha
#undef arp_tpa
#define arp_sha arp_xsha
#define arp_spa arp_xspa
#define arp_tha arp_xtha
#define arp_tpa arp_xtpa
#endif
#ifndef __GNUC__
#define inline
#endif
extern int errno;
extern int ether_ntohost __P((char *, struct ether_addr *));
/*
* 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;
extern char *malloc();
extern void exit();
u_long ipaddrtonetmask();
void init_one();
void init_all();
void rarp_loop();
void lookup_eaddr();
void lookup_ipaddr();
void
main(argc, argv)
int argc;
char **argv;
{
int op, pid;
char *ifname, *hostname, *name;
int aflag = 0; /* listen on "all" interfaces */
int fflag = 0; /* don't fork */
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_DAEMON);
opterr = 0;
while ((op = getopt(argc, argv, "af")) != EOF) {
switch (op) {
case 'a':
++aflag;
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) {
pid = fork();
if (pid > 0)
/* Parent exits, leaving child in background. */
exit(0);
else if (pid == -1) {
syslog(LOG_ERR, "cannot fork");
exit(1);
}
}
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));
p->ii_next = iflist;
iflist = p;
p->ii_fd = rarp_open(ifname);
lookup_eaddr(p->ii_fd, 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 ifflags;
struct ifreq ibuf[8], tmp_ibuf, *ifptr, *n;
struct ifconf ifc;
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
syslog(LOG_ERR, "socket: %m");
exit(1);
}
ifc.ifc_len = sizeof ibuf;
ifc.ifc_buf = (caddr_t)ibuf;
if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
ifc.ifc_len < sizeof(struct ifreq)) {
syslog(LOG_ERR, "SIOCGIFCONF: %m");
exit(1);
}
ifptr = ifc.ifc_req;
ifflags = ifptr->ifr_flags;
n = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
while (ifptr < n) {
bcopy((char *)ifptr, (char *)&tmp_ibuf, sizeof(struct ifreq));
if (ioctl(fd, SIOCGIFFLAGS, (char *)&tmp_ibuf) < 0) {
syslog(LOG_ERR, "SIOCGIFFLAGS: %m");
exit(1);
}
if (ifptr->ifr_flags == ifflags && (tmp_ibuf.ifr_flags &
(IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) == IFF_UP)
init_one(ifptr->ifr_name);
if(ifptr->ifr_addr.sa_len) /* Dohw! */
ifptr = (struct ifreq *) ((caddr_t) ifptr +
ifptr->ifr_addr.sa_len -
sizeof(struct sockaddr));
ifptr++;
}
(void)close(fd);
}
usage()
{
(void)fprintf(stderr, "usage: rarpd [ -af ] [ 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) {
syslog(LOG_ERR, "%s: %m", device);
exit(-1);
}
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;
int immediate, link_type;
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]),
(struct bpf_insn *)&insns
};
fd = bpf_open();
/*
* Set immediate mode so packets are processed as they arrive.
*/
immediate = 1;
if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) {
syslog(LOG_ERR, "BIOCIMMEDIATE: %m");
exit(1);
}
(void)strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
syslog(LOG_ERR, "BIOCSETIF: %m");
exit(1);
}
/*
* Check that the data link layer is an Ethernet; this code won't
* work with anything else.
*/
if (ioctl(fd, BIOCGDLT, &link_type) < 0) {
syslog(LOG_ERR, "BIOCGDLP: %m");
exit(1);
}
if (link_type != DLT_EN10MB) {
syslog(LOG_ERR, "%s not on ethernet", device);
exit(1);
}
/*
* Set filter program.
*/
if (ioctl(fd, BIOCSETF, (caddr_t)&filter) < 0) {
syslog(LOG_ERR, "BIOCSETF: %m");
exit(1);
}
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));
if (len < sizeof(*ep) + sizeof(*ap)) {
syslog(LOG_ERR, "truncated request");
return 0;
}
/*
* XXX This test might be better off broken out...
*/
if (ep->ether_type != htons(ETHERTYPE_REVARP) ||
ap->arp_hrd != htons(ARPHRD_ETHER) ||
ap->arp_op != htons(ARPOP_REVREQUEST) ||
ap->arp_pro != htons(ETHERTYPE_IP) ||
ap->arp_hln != 6 || ap->arp_pln != 4) {
syslog(LOG_DEBUG, "request fails sanity check");
return 0;
}
if (bcmp((char *)&ep->ether_shost, (char *)&ap->arp_sha, 6) != 0) {
syslog(LOG_DEBUG, "ether/arp sender address mismatch");
return 0;
}
if (bcmp((char *)&ap->arp_sha, (char *)&ap->arp_tha, 6) != 0) {
syslog(LOG_DEBUG, "ether/arp target address mismatch");
return 0;
}
return 1;
}
#ifndef FD_SETSIZE
#define FD_SET(n, fdp) ((fdp)->fds_bits[0] |= (1 << (n)))
#define FD_ISSET(n, fdp) ((fdp)->fds_bits[0] & (1 << (n)))
#define FD_ZERO(fdp) ((fdp)->fds_bits[0] = 0)
#endif
/*
* Loop indefinitely listening for RARP requests on the
* interfaces in 'iflist'.
*/
void
rarp_loop()
{
struct bpf_hdr *bhp;
u_char *pkt;
int cc, fd;
fd_set fds, listeners;
int bufsize, maxfd = 0;
struct if_info *ii;
if (iflist == 0) {
syslog(LOG_ERR, "no interfaces");
exit(1);
}
if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t)&bufsize) < 0) {
syslog(LOG_ERR, "BIOCGBLEN: %m");
exit(1);
}
bhp = (struct bpf_hdr *)malloc((unsigned)bufsize);
/*
* 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) {
syslog(LOG_ERR, "select: %m");
exit(1);
}
for (ii = iflist; ii; ii = ii->ii_next) {
fd = ii->ii_fd;
if (FD_ISSET(fd, &listeners)) {
again:
cc = read(fd, (char *)bhp, bufsize);
/*
* 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;
}
syslog(LOG_ERR, "read: %m");
exit(1);
}
pkt = (u_char *)bhp + bhp->bh_hdrlen;
if (rarp_check(pkt, (int)bhp->bh_datalen))
rarp_process(ii, pkt);
}
}
}
}
#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.
*/
rarp_bootable(addr)
u_long addr;
{
#ifdef SUNOS4
register struct dirent *dent;
#else
register struct direct *dent;
#endif
register DIR *d;
char ipname[9];
static DIR *dd = 0;
/*
* XXX Need to htonl() the IP address or it'll
* come out backwards.
*/
(void)sprintf(ipname, "%08X", htonl(addr));
/*
* If directory is already open, rewind it. Otherwise, open it.
*/
if (d = dd)
rewinddir(d);
else {
if (chdir(TFTP_DIR) == -1) {
syslog(LOG_ERR, "chdir: %m");
exit(1);
}
d = opendir(".");
if (d == 0) {
syslog(LOG_ERR, "opendir: %m");
exit(1);
}
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;
}
/*
* A one entry ip/ethernet address cache.
*/
static u_long cache_ipaddr;
static u_char cache_eaddr[6];
/*
* Answer the RARP request in 'pkt', on the interface 'ii'. 'pkt' has
* already been checked for validity. The reply is overlaid on the request.
*/
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];
ep = (struct ether_header *)pkt;
/*
* If the address in the one element cache, don't bother
* looking up names.
*/
if (bcmp((char *)cache_eaddr, (char *)&ep->ether_shost, 6) == 0)
target_ipaddr = cache_ipaddr;
else {
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) {
syslog(LOG_ERR, "cannot handle non IP addresses");
exit(1);
}
target_ipaddr = choose_ipaddr((u_long **)hp->h_addr_list,
ii->ii_ipaddr & ii->ii_netmask,
ii->ii_netmask);
if (target_ipaddr == 0) {
syslog(LOG_ERR, "cannot find %s on %08x",
ename, ii->ii_ipaddr & ii->ii_netmask);
return;
}
bcopy((char *)&ep->ether_shost, (char *)cache_eaddr, 6);
cache_ipaddr = target_ipaddr;
}
if (rarp_bootable(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(fd, eaddr)
int fd;
u_char *eaddr;
{
struct ifreq ifr;
/* Use BPF descriptor to get ethernet address. */
if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
syslog(LOG_ERR, "SIOCGIFADDR: %m");
exit(1);
}
bcopy((char *)&ifr.ifr_addr.sa_data[0], (char *)eaddr, 6);
}
/*
* 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 data gram socket to get IP address. */
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
syslog(LOG_ERR, "socket: %m");
exit(1);
}
(void)strncpy(ifr.ifr_name, ifname, sizeof ifr.ifr_name);
if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
syslog(LOG_ERR, "SIOCGIFADDR: %m");
exit(1);
}
*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).
*/
update_arptab(ep, ipaddr)
u_char *ep;
u_long ipaddr;
{
#ifdef SIOCSARP
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;
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)
syslog(LOG_ERR, "SIOCSARP: %m");
(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.
*/
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, raw_sock;
update_arptab((u_char *)&ap->arp_sha, ipaddr);
/*
* Build the rarp reply by modifying the rarp request in place.
*/
ap->arp_op = htons(ARPOP_REVREPLY);
/*
* XXX Using htons(ETHERTYPE_REVARP) doesn't work: you wind
* up transmitting 0x3580 instead of the correct value of
* 0x8035. What makes no sense is that the NetBSD people
* do in fact use htons(ETHERTYPE_REVARP) in their rarpd.
* (Thank god for tcpdump or I would never have figured this
* out.)
*/
ep->ether_type = ETHERTYPE_REVARP;
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) {
syslog(LOG_ERR, "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;
syslog(LOG_DEBUG, "unknown IP address class: %08X", addr);
exit(1);
/* NOTREACHED */
}