arp.c revision 26516 
1/*
2 * sys-bsd.c - System-dependent procedures for setting up
3 * PPP interfaces on bsd-4.4-ish systems (including 386BSD, NetBSD, etc.)
4 *
5 * Copyright (c) 1989 Carnegie Mellon University.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms are permitted
9 * provided that the above copyright notice and this paragraph are
10 * duplicated in all such forms and that any documentation,
11 * advertising materials, and other materials related to such
12 * distribution and use acknowledge that the software was developed
13 * by Carnegie Mellon University.  The name of the
14 * University may not be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
18 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * $Id: arp.c,v 1.11 1997/04/15 00:03:35 brian Exp $
21 *
22 */
23
24/*
25 * TODO:
26 */
27
28#include <sys/ioctl.h>
29#include <sys/types.h>
30#include <sys/uio.h>
31#include <sys/socket.h>
32#include <sys/time.h>
33#include <sys/errno.h>
34#include <unistd.h>
35#include <string.h>
36
37#include <net/if.h>
38#include <net/if_var.h>
39#include <net/route.h>
40#include <net/if_dl.h>
41#include <netinet/in.h>
42#include <stdio.h>
43#include <fcntl.h>
44#ifdef __bsdi__
45#include <kvm.h>
46#endif
47#include <net/if_types.h>
48#include <netinet/in_var.h>
49#include <netinet/if_ether.h>
50#include "log.h"
51
52#if RTM_VERSION >= 3
53#include <netinet/if_ether.h>
54#endif
55
56static int rtm_seq;
57
58static int get_ether_addr(int, u_long, struct sockaddr_dl *);
59
60#define BCOPY(s, d, l)		memcpy(d, s, l)
61#define BZERO(s, n)		memset(s, 0, n)
62/*
63 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
64 * if it exists.
65 */
66#define SET_SA_FAMILY(addr, family)		\
67    BZERO((char *) &(addr), sizeof(addr));	\
68    addr.sa_family = (family); 			\
69    addr.sa_len = sizeof(addr);
70
71
72#if RTM_VERSION >= 3
73
74/*
75 * sifproxyarp - Make a proxy ARP entry for the peer.
76 */
77static struct {
78    struct rt_msghdr		hdr;
79    struct sockaddr_inarp	dst;
80    struct sockaddr_dl		hwa;
81    char			extra[128];
82} arpmsg;
83
84static int arpmsg_valid;
85
86int
87sifproxyarp(unit, hisaddr)
88    int unit;
89    u_long hisaddr;
90{
91    int routes;
92
93    /*
94     * Get the hardware address of an interface on the same subnet
95     * as our local address.
96     */
97    memset(&arpmsg, 0, sizeof(arpmsg));
98    if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
99	LogPrintf(LogERROR, "Cannot determine ethernet address"
100		 " for proxy ARP\n");
101	return 0;
102    }
103
104    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
105	LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
106		  strerror(errno));
107	return 0;
108    }
109
110    arpmsg.hdr.rtm_type = RTM_ADD;
111    arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
112    arpmsg.hdr.rtm_version = RTM_VERSION;
113    arpmsg.hdr.rtm_seq = ++rtm_seq;
114    arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
115    arpmsg.hdr.rtm_inits = RTV_EXPIRE;
116    arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
117    arpmsg.dst.sin_family = AF_INET;
118    arpmsg.dst.sin_addr.s_addr = hisaddr;
119    arpmsg.dst.sin_other = SIN_PROXY;
120
121    arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
122	+ arpmsg.hwa.sdl_len;
123    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
124	LogPrintf(LogERROR, "Add proxy arp entry: %s\n", strerror(errno));
125	close(routes);
126	return 0;
127    }
128
129    close(routes);
130    arpmsg_valid = 1;
131    return 1;
132}
133
134/*
135 * cifproxyarp - Delete the proxy ARP entry for the peer.
136 */
137int
138cifproxyarp(unit, hisaddr)
139    int unit;
140    u_long hisaddr;
141{
142    int routes;
143
144    if (!arpmsg_valid)
145	return 0;
146    arpmsg_valid = 0;
147
148    arpmsg.hdr.rtm_type = RTM_DELETE;
149    arpmsg.hdr.rtm_seq = ++rtm_seq;
150
151    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
152	LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
153		  strerror(errno));
154	return 0;
155    }
156
157    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
158	LogPrintf(LogERROR, "Delete proxy arp entry: %s\n", strerror(errno));
159	close(routes);
160	return 0;
161    }
162
163    close(routes);
164    return 1;
165}
166
167#else	/* RTM_VERSION */
168
169/*
170 * sifproxyarp - Make a proxy ARP entry for the peer.
171 */
172int
173sifproxyarp(unit, hisaddr)
174    int unit;
175    u_long hisaddr;
176{
177    struct arpreq arpreq;
178    struct {
179	struct sockaddr_dl	sdl;
180	char			space[128];
181    } dls;
182
183    BZERO(&arpreq, sizeof(arpreq));
184
185    /*
186     * Get the hardware address of an interface on the same subnet
187     * as our local address.
188     */
189    if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
190	LogPrintf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
191	return 0;
192    }
193
194    arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
195    arpreq.arp_ha.sa_family = AF_UNSPEC;
196    BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
197    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
198    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
199    arpreq.arp_flags = ATF_PERM | ATF_PUBL;
200    if (ioctl(unit, SIOCSARP, (caddr_t)&arpreq) < 0) {
201	LogPrintf(LogERROR, "sifproxyarp: ioctl(SIOCSARP): \n");
202	return 0;
203    }
204
205    return 1;
206}
207
208/*
209 * cifproxyarp - Delete the proxy ARP entry for the peer.
210 */
211int
212cifproxyarp(unit, hisaddr)
213    int unit;
214    u_long hisaddr;
215{
216    struct arpreq arpreq;
217
218    BZERO(&arpreq, sizeof(arpreq));
219    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
220    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
221    if (ioctl(unit, SIOCDARP, (caddr_t)&arpreq) < 0) {
222	LogPrintf(LogERROR, "cifproxyarp: ioctl(SIOCDARP): \n");
223	return 0;
224    }
225    return 1;
226}
227#endif	/* RTM_VERSION */
228
229
230/*
231 * get_ether_addr - get the hardware address of an interface on the
232 * the same subnet as ipaddr.
233 */
234#define MAX_IFS		32
235
236int
237get_ether_addr(s, ipaddr, hwaddr)
238    int    s;
239    u_long ipaddr;
240    struct sockaddr_dl *hwaddr;
241{
242    struct ifreq *ifr, *ifend, *ifp;
243    u_long ina, mask;
244    struct sockaddr_dl *dla;
245    struct ifreq ifreq;
246    struct ifconf ifc;
247    struct ifreq ifs[MAX_IFS];
248
249    ifc.ifc_len = sizeof(ifs);
250    ifc.ifc_req = ifs;
251    if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
252	LogPrintf(LogERROR, "get_ether_addr: ioctl(SIOCGIFCONF): \n");
253	return 0;
254    }
255
256    /*
257     * Scan through looking for an interface with an Internet
258     * address on the same subnet as `ipaddr'.
259     */
260    ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
261    for (ifr = ifc.ifc_req; ifr < ifend; ) {
262	if (ifr->ifr_addr.sa_family == AF_INET) {
263	    ina = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr;
264	    strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
265	    ifreq.ifr_name[sizeof(ifreq.ifr_name)-1]='\0';
266	    /*
267	     * Check that the interface is up, and not point-to-point
268	     * or loopback.
269	     */
270	    if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
271		continue;
272	    if ((ifreq.ifr_flags &
273		 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|IFF_LOOPBACK|IFF_NOARP))
274		 != (IFF_UP|IFF_BROADCAST))
275		goto nextif;
276	    /*
277	     * Get its netmask and check that it's on the right subnet.
278	     */
279	    if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
280		continue;
281	    mask = ((struct sockaddr_in *) &ifreq.ifr_addr)->sin_addr.s_addr;
282	    if ((ipaddr & mask) != (ina & mask))
283		goto nextif;
284
285	    break;
286	}
287nextif:
288	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
289    }
290
291    if (ifr >= ifend)
292	return 0;
293    LogPrintf(LogPHASE, "Found interface %s for proxy arp\n", ifr->ifr_name);
294
295    /*
296     * Now scan through again looking for a link-level address
297     * for this interface.
298     */
299    ifp = ifr;
300    for (ifr = ifc.ifc_req; ifr < ifend; ) {
301	if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
302	    && ifr->ifr_addr.sa_family == AF_LINK) {
303	    /*
304	     * Found the link-level address - copy it out
305	     */
306	    dla = (struct sockaddr_dl *) &ifr->ifr_addr;
307#ifdef __bsdi__
308	    if (dla->sdl_alen == 0)
309	      kmemgetether(ifr->ifr_name, dla);
310#endif
311	    BCOPY(dla, hwaddr, dla->sdl_len);
312	    return 1;
313	}
314	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
315    }
316
317    return 0;
318}
319
320#ifdef __bsdi__
321#include <nlist.h>
322
323struct nlist nl[] = {
324#define N_IFNET		0
325	{ "_ifnet" },
326	"",
327};
328
329
330kvm_t *kvmd;
331
332/*
333 * Read kernel memory, return 0 on success.
334 */
335int
336kread(addr, buf, size)
337  u_long addr;
338  char *buf;
339  int size;
340{
341  if (kvm_read(kvmd, addr, buf, size) != size) {
342    /* XXX this duplicates kvm_read's error printout */
343    LogPrintf(LogERROR, "kvm_read %s\n", kvm_geterr(kvmd));
344    return -1;
345  }
346  return 0;
347}
348
349kmemgetether(ifname, dlo)
350char *ifname;
351struct sockaddr_dl *dlo;
352{
353  struct ifnet ifnet;
354  int n;
355  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
356  char name[16+32];
357  struct sockaddr *sa;
358  char *cp;
359  struct sockaddr_dl *sdl;
360  union {
361	  struct ifaddr ifa;
362	  struct in_ifaddr in;
363  } ifaddr;
364  struct arpcom ac;
365
366  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
367  if (kvmd) {
368    n = kvm_nlist(kvmd, nl);
369    if (n >= 0) {
370      addr = nl[N_IFNET].n_value;
371      kread(addr, (char *)&addr, sizeof(addr));
372      ifaddraddr = ifnetfound = 0;
373      while (addr || ifaddraddr) {
374	ifnetfound = addr;
375	if (ifaddraddr == 0) {
376	  if (kread(addr, (char *)&ifnet, sizeof(ifnet)) ||
377	      kread((u_long)ifnet.if_name, name, 16))
378		return;
379	  name[15] = 0;
380	  addr = (u_long) ifnet.if_next;
381	  cp = (char *)index(name, '\0');
382	  cp += sprintf(cp, "%d", ifnet.if_unit);
383	  *cp = '\0';
384	  ifaddraddr = (u_long)ifnet.if_addrlist;
385	}
386	ifaddrfound = ifaddraddr;
387	if (ifaddraddr) {
388	  if (kread(ifaddraddr, (char *)&ifaddr, sizeof ifaddr)) {
389	    ifaddraddr = 0;
390	    continue;
391	  }
392#define CP(x) ((char *)(x))
393	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
394	  sa = (struct sockaddr *)cp;
395	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
396	    sdl = (struct sockaddr_dl *)sa;
397	    cp = (char *)LLADDR(sdl);
398	    n = sdl->sdl_alen;
399	    if (ifnet.if_type == IFT_ETHER) {
400		if (n == 0) {
401		  kread(ifnetfound, (char *)&ac, sizeof(ac));
402	    	  cp = (char *)LLADDR(sdl);
403		  bcopy((char *)ac.ac_enaddr, cp, 6);
404		  sdl->sdl_alen = 6;
405		}
406		bcopy(sdl, dlo, sizeof(*sdl));
407		return;
408	    }
409	  }
410	  ifaddraddr = (u_long)ifaddr.ifa.ifa_next;
411	}
412      }
413    }
414  }
415}
416#endif
417
418#ifdef DEBUG
419main()
420{
421    u_long ipaddr;
422    int s;
423
424    s = socket(AF_INET, SOCK_DGRAM, 0);
425    ipaddr = inet_addr("192.168.1.32");
426    sifproxyarp(s, ipaddr);
427    close(s);
428}
429#endif
430