arp.c revision 21673 
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 * $FreeBSD: head/usr.sbin/ppp/arp.c 21673 1997-01-14 07:20:47Z jkh $
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 __P((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("Cannot determine ethernet address for proxy ARP\n");
100	return 0;
101    }
102
103    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
104	logprintf("sifproxyarp: opening routing socket: \n");
105	return 0;
106    }
107
108    arpmsg.hdr.rtm_type = RTM_ADD;
109    arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
110    arpmsg.hdr.rtm_version = RTM_VERSION;
111    arpmsg.hdr.rtm_seq = ++rtm_seq;
112    arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
113    arpmsg.hdr.rtm_inits = RTV_EXPIRE;
114    arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
115    arpmsg.dst.sin_family = AF_INET;
116    arpmsg.dst.sin_addr.s_addr = hisaddr;
117    arpmsg.dst.sin_other = SIN_PROXY;
118
119    arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
120	+ arpmsg.hwa.sdl_len;
121    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
122	logprintf("add proxy arp entry: \n");
123	close(routes);
124	return 0;
125    }
126
127    close(routes);
128    arpmsg_valid = 1;
129    return 1;
130}
131
132/*
133 * cifproxyarp - Delete the proxy ARP entry for the peer.
134 */
135int
136cifproxyarp(unit, hisaddr)
137    int unit;
138    u_long hisaddr;
139{
140    int routes;
141
142    if (!arpmsg_valid)
143	return 0;
144    arpmsg_valid = 0;
145
146    arpmsg.hdr.rtm_type = RTM_DELETE;
147    arpmsg.hdr.rtm_seq = ++rtm_seq;
148
149    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
150	logprintf("sifproxyarp: opening routing socket: \n");
151	return 0;
152    }
153
154    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
155	logprintf("delete proxy arp entry: \n");
156	close(routes);
157	return 0;
158    }
159
160    close(routes);
161    return 1;
162}
163
164#else	/* RTM_VERSION */
165
166/*
167 * sifproxyarp - Make a proxy ARP entry for the peer.
168 */
169int
170sifproxyarp(unit, hisaddr)
171    int unit;
172    u_long hisaddr;
173{
174    struct arpreq arpreq;
175    struct {
176	struct sockaddr_dl	sdl;
177	char			space[128];
178    } dls;
179
180    BZERO(&arpreq, sizeof(arpreq));
181
182    /*
183     * Get the hardware address of an interface on the same subnet
184     * as our local address.
185     */
186    if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
187	LogPrintf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
188	return 0;
189    }
190
191    arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
192    arpreq.arp_ha.sa_family = AF_UNSPEC;
193    BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
194    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
195    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
196    arpreq.arp_flags = ATF_PERM | ATF_PUBL;
197    if (ioctl(unit, SIOCSARP, (caddr_t)&arpreq) < 0) {
198	fprintf(stderr, "ioctl(SIOCSARP): \n");
199	return 0;
200    }
201
202    return 1;
203}
204
205/*
206 * cifproxyarp - Delete the proxy ARP entry for the peer.
207 */
208int
209cifproxyarp(unit, hisaddr)
210    int unit;
211    u_long hisaddr;
212{
213    struct arpreq arpreq;
214
215    BZERO(&arpreq, sizeof(arpreq));
216    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
217    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
218    if (ioctl(unit, SIOCDARP, (caddr_t)&arpreq) < 0) {
219	fprintf(stderr, "ioctl(SIOCDARP): \n");
220	return 0;
221    }
222    return 1;
223}
224#endif	/* RTM_VERSION */
225
226
227/*
228 * get_ether_addr - get the hardware address of an interface on the
229 * the same subnet as ipaddr.
230 */
231#define MAX_IFS		32
232
233int
234get_ether_addr(s, ipaddr, hwaddr)
235    int    s;
236    u_long ipaddr;
237    struct sockaddr_dl *hwaddr;
238{
239    struct ifreq *ifr, *ifend, *ifp;
240    u_long ina, mask;
241    struct sockaddr_dl *dla;
242    struct ifreq ifreq;
243    struct ifconf ifc;
244    struct ifreq ifs[MAX_IFS];
245
246    ifc.ifc_len = sizeof(ifs);
247    ifc.ifc_req = ifs;
248    if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
249	fprintf(stderr, "ioctl(SIOCGIFCONF): \n");
250	return 0;
251    }
252
253    /*
254     * Scan through looking for an interface with an Internet
255     * address on the same subnet as `ipaddr'.
256     */
257    ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
258    for (ifr = ifc.ifc_req; ifr < ifend; ) {
259	if (ifr->ifr_addr.sa_family == AF_INET) {
260	    ina = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr;
261	    strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
262	    ifreq.ifr_name[sizeof(ifreq.ifr_name)-1]='\0';
263	    /*
264	     * Check that the interface is up, and not point-to-point
265	     * or loopback.
266	     */
267	    if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
268		continue;
269	    if ((ifreq.ifr_flags &
270		 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|IFF_LOOPBACK|IFF_NOARP))
271		 != (IFF_UP|IFF_BROADCAST))
272		goto nextif;
273	    /*
274	     * Get its netmask and check that it's on the right subnet.
275	     */
276	    if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
277		continue;
278	    mask = ((struct sockaddr_in *) &ifreq.ifr_addr)->sin_addr.s_addr;
279	    if ((ipaddr & mask) != (ina & mask))
280		goto nextif;
281
282	    break;
283	}
284nextif:
285	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
286    }
287
288    if (ifr >= ifend)
289	return 0;
290    LogPrintf(LOG_PHASE_BIT, "found interface %s for proxy arp\n", ifr->ifr_name);
291
292    /*
293     * Now scan through again looking for a link-level address
294     * for this interface.
295     */
296    ifp = ifr;
297    for (ifr = ifc.ifc_req; ifr < ifend; ) {
298	if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
299	    && ifr->ifr_addr.sa_family == AF_LINK) {
300	    /*
301	     * Found the link-level address - copy it out
302	     */
303	    dla = (struct sockaddr_dl *) &ifr->ifr_addr;
304#ifdef __bsdi__
305	    if (dla->sdl_alen == 0)
306	      kmemgetether(ifr->ifr_name, dla);
307#endif
308	    BCOPY(dla, hwaddr, dla->sdl_len);
309	    return 1;
310	}
311	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
312    }
313
314    return 0;
315}
316
317#ifdef __bsdi__
318#include <nlist.h>
319
320struct nlist nl[] = {
321#define N_IFNET		0
322	{ "_ifnet" },
323	"",
324};
325
326
327kvm_t *kvmd;
328
329/*
330 * Read kernel memory, return 0 on success.
331 */
332int
333kread(addr, buf, size)
334  u_long addr;
335  char *buf;
336  int size;
337{
338
339	if (kvm_read(kvmd, addr, buf, size) != size) {
340		/* XXX this duplicates kvm_read's error printout */
341		(void)fprintf(stderr, "kvm_read %s\n",
342			kvm_geterr(kvmd));
343		return (-1);
344	}
345	return (0);
346}
347
348kmemgetether(ifname, dlo)
349char *ifname;
350struct sockaddr_dl *dlo;
351{
352  struct ifnet ifnet;
353  int n;
354  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
355  char name[16+32];
356  struct sockaddr *sa;
357  char *cp;
358  struct sockaddr_dl *sdl;
359  union {
360	  struct ifaddr ifa;
361	  struct in_ifaddr in;
362  } ifaddr;
363  struct arpcom ac;
364
365  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
366  if (kvmd) {
367    n = kvm_nlist(kvmd, nl);
368    if (n >= 0) {
369      addr = nl[N_IFNET].n_value;
370      kread(addr, (char *)&addr, sizeof(addr));
371      ifaddraddr = ifnetfound = 0;
372      while (addr || ifaddraddr) {
373	ifnetfound = addr;
374	if (ifaddraddr == 0) {
375	  if (kread(addr, (char *)&ifnet, sizeof(ifnet)) ||
376	      kread((u_long)ifnet.if_name, name, 16))
377		return;
378	  name[15] = 0;
379	  addr = (u_long) ifnet.if_next;
380	  cp = (char *)index(name, '\0');
381	  cp += sprintf(cp, "%d", ifnet.if_unit);
382	  *cp = '\0';
383	  ifaddraddr = (u_long)ifnet.if_addrlist;
384	}
385	ifaddrfound = ifaddraddr;
386	if (ifaddraddr) {
387	  if (kread(ifaddraddr, (char *)&ifaddr, sizeof ifaddr)) {
388	    ifaddraddr = 0;
389	    continue;
390	  }
391#define CP(x) ((char *)(x))
392	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
393	  sa = (struct sockaddr *)cp;
394	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
395	    sdl = (struct sockaddr_dl *)sa;
396	    cp = (char *)LLADDR(sdl);
397	    n = sdl->sdl_alen;
398	    if (ifnet.if_type == IFT_ETHER) {
399		if (n == 0) {
400		  kread(ifnetfound, (char *)&ac, sizeof(ac));
401	    	  cp = (char *)LLADDR(sdl);
402		  bcopy((char *)ac.ac_enaddr, cp, 6);
403		  sdl->sdl_alen = 6;
404		}
405		bcopy(sdl, dlo, sizeof(*sdl));
406		return;
407	    }
408	  }
409	  ifaddraddr = (u_long)ifaddr.ifa.ifa_next;
410	}
411      }
412    }
413  }
414}
415#endif
416
417#ifdef DEBUG
418main()
419{
420    u_long ipaddr;
421    int s;
422
423    s = socket(AF_INET, SOCK_DGRAM, 0);
424    ipaddr = inet_addr("192.168.1.32");
425    sifproxyarp(s, ipaddr);
426    close(s);
427}
428#endif
429