arp.c revision 6735 
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 * $Id:$
21 *
22 */
23
24/*
25 * TODO:
26 */
27
28#include <sys/ioctl.h>
29#include <sys/types.h>
30#include <sys/socket.h>
31#include <sys/time.h>
32#include <sys/errno.h>
33
34#include <net/if.h>
35#include <net/route.h>
36#include <net/if_dl.h>
37#include <netinet/in.h>
38#include <stdio.h>
39#include <fcntl.h>
40#ifdef __bsdi__
41#include <kvm.h>
42#endif
43#include <net/if_types.h>
44#include <netinet/in_var.h>
45#include <netinet/if_ether.h>
46#include "log.h"
47
48#if RTM_VERSION >= 3
49#include <netinet/if_ether.h>
50#endif
51
52static int rtm_seq;
53
54#define BCOPY(s, d, l)		memcpy(d, s, l)
55#define BZERO(s, n)		memset(s, 0, n)
56/*
57 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
58 * if it exists.
59 */
60#define SET_SA_FAMILY(addr, family)		\
61    BZERO((char *) &(addr), sizeof(addr));	\
62    addr.sa_family = (family); 			\
63    addr.sa_len = sizeof(addr);
64
65
66#if RTM_VERSION >= 3
67
68/*
69 * sifproxyarp - Make a proxy ARP entry for the peer.
70 */
71static struct {
72    struct rt_msghdr		hdr;
73    struct sockaddr_inarp	dst;
74    struct sockaddr_dl		hwa;
75    char			extra[128];
76} arpmsg;
77
78static int arpmsg_valid;
79
80int
81sifproxyarp(unit, hisaddr)
82    int unit;
83    u_long hisaddr;
84{
85    int routes;
86    int l;
87
88    /*
89     * Get the hardware address of an interface on the same subnet
90     * as our local address.
91     */
92    memset(&arpmsg, 0, sizeof(arpmsg));
93    if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
94	logprintf("Cannot determine ethernet address for proxy ARP\n");
95	return 0;
96    }
97
98    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
99	logprintf("sifproxyarp: opening routing socket: \n");
100	return 0;
101    }
102
103    arpmsg.hdr.rtm_type = RTM_ADD;
104    arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
105    arpmsg.hdr.rtm_version = RTM_VERSION;
106    arpmsg.hdr.rtm_seq = ++rtm_seq;
107    arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
108    arpmsg.hdr.rtm_inits = RTV_EXPIRE;
109    arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
110    arpmsg.dst.sin_family = AF_INET;
111    arpmsg.dst.sin_addr.s_addr = hisaddr;
112    arpmsg.dst.sin_other = SIN_PROXY;
113
114    arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
115	+ arpmsg.hwa.sdl_len;
116    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
117	logprintf("add proxy arp entry: \n");
118	close(routes);
119	return 0;
120    }
121
122    close(routes);
123    arpmsg_valid = 1;
124    return 1;
125}
126
127/*
128 * cifproxyarp - Delete the proxy ARP entry for the peer.
129 */
130int
131cifproxyarp(unit, hisaddr)
132    int unit;
133    u_long hisaddr;
134{
135    int routes;
136
137    if (!arpmsg_valid)
138	return 0;
139    arpmsg_valid = 0;
140
141    arpmsg.hdr.rtm_type = RTM_DELETE;
142    arpmsg.hdr.rtm_seq = ++rtm_seq;
143
144    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
145	logprintf("sifproxyarp: opening routing socket: \n");
146	return 0;
147    }
148
149    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
150	logprintf("delete proxy arp entry: \n");
151	close(routes);
152	return 0;
153    }
154
155    close(routes);
156    return 1;
157}
158
159#else	/* RTM_VERSION */
160
161/*
162 * sifproxyarp - Make a proxy ARP entry for the peer.
163 */
164int
165sifproxyarp(unit, hisaddr)
166    int unit;
167    u_long hisaddr;
168{
169    struct arpreq arpreq;
170    struct {
171	struct sockaddr_dl	sdl;
172	char			space[128];
173    } dls;
174
175    BZERO(&arpreq, sizeof(arpreq));
176
177    /*
178     * Get the hardware address of an interface on the same subnet
179     * as our local address.
180     */
181    if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
182	LogPrintf(LOG_PHASE, "Cannot determine ethernet address for proxy ARP\n");
183	return 0;
184    }
185
186    arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
187    arpreq.arp_ha.sa_family = AF_UNSPEC;
188    BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
189    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
190    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
191    arpreq.arp_flags = ATF_PERM | ATF_PUBL;
192    if (ioctl(unit, SIOCSARP, (caddr_t)&arpreq) < 0) {
193	fprintf(stderr, "ioctl(SIOCSARP): \n");
194	return 0;
195    }
196
197    return 1;
198}
199
200/*
201 * cifproxyarp - Delete the proxy ARP entry for the peer.
202 */
203int
204cifproxyarp(unit, hisaddr)
205    int unit;
206    u_long hisaddr;
207{
208    struct arpreq arpreq;
209
210    BZERO(&arpreq, sizeof(arpreq));
211    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
212    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
213    if (ioctl(unit, SIOCDARP, (caddr_t)&arpreq) < 0) {
214	fprintf(stderr, "ioctl(SIOCDARP): \n");
215	return 0;
216    }
217    return 1;
218}
219#endif	/* RTM_VERSION */
220
221
222/*
223 * get_ether_addr - get the hardware address of an interface on the
224 * the same subnet as ipaddr.
225 */
226#define MAX_IFS		32
227
228int
229get_ether_addr(s, ipaddr, hwaddr)
230    int    s;
231    u_long ipaddr;
232    struct sockaddr_dl *hwaddr;
233{
234    struct ifreq *ifr, *ifend, *ifp;
235    u_long ina, mask;
236    struct sockaddr_dl *dla;
237    struct ifreq ifreq;
238    struct ifconf ifc;
239    struct ifreq ifs[MAX_IFS];
240    struct ifreq ifx;
241
242    ifc.ifc_len = sizeof(ifs);
243    ifc.ifc_req = ifs;
244    if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
245	fprintf(stderr, "ioctl(SIOCGIFCONF): \n");
246	return 0;
247    }
248
249    /*
250     * Scan through looking for an interface with an Internet
251     * address on the same subnet as `ipaddr'.
252     */
253    ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
254    for (ifr = ifc.ifc_req; ifr < ifend; ) {
255	if (ifr->ifr_addr.sa_family == AF_INET) {
256	    ina = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr;
257	    strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
258	    /*
259	     * Check that the interface is up, and not point-to-point
260	     * or loopback.
261	     */
262	    if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
263		continue;
264	    if ((ifreq.ifr_flags &
265		 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|IFF_LOOPBACK|IFF_NOARP))
266		 != (IFF_UP|IFF_BROADCAST))
267		goto nextif;
268	    /*
269	     * Get its netmask and check that it's on the right subnet.
270	     */
271	    if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
272		continue;
273	    mask = ((struct sockaddr_in *) &ifreq.ifr_addr)->sin_addr.s_addr;
274	    if ((ipaddr & mask) != (ina & mask))
275		goto nextif;
276
277	    break;
278	}
279nextif:
280	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
281    }
282
283    if (ifr >= ifend)
284	return 0;
285    LogPrintf(LOG_PHASE, "found interface %s for proxy arp\n", ifr->ifr_name);
286
287    /*
288     * Now scan through again looking for a link-level address
289     * for this interface.
290     */
291    ifp = ifr;
292    for (ifr = ifc.ifc_req; ifr < ifend; ) {
293	if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
294	    && ifr->ifr_addr.sa_family == AF_LINK) {
295	    /*
296	     * Found the link-level address - copy it out
297	     */
298	    dla = (struct sockaddr_dl *) &ifr->ifr_addr;
299#ifdef __bsdi__
300	    if (dla->sdl_alen == 0)
301	      kmemgetether(ifr->ifr_name, dla);
302#endif
303	    BCOPY(dla, hwaddr, dla->sdl_len);
304	    return 1;
305	}
306	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
307    }
308
309    return 0;
310}
311
312#ifdef __bsdi__
313#include <nlist.h>
314
315struct nlist nl[] = {
316#define N_IFNET		0
317	{ "_ifnet" },
318	"",
319};
320
321
322kvm_t *kvmd;
323
324/*
325 * Read kernel memory, return 0 on success.
326 */
327int
328kread(addr, buf, size)
329  u_long addr;
330  char *buf;
331  int size;
332{
333
334	if (kvm_read(kvmd, addr, buf, size) != size) {
335		/* XXX this duplicates kvm_read's error printout */
336		(void)fprintf(stderr, "kvm_read %s\n",
337			kvm_geterr(kvmd));
338		return (-1);
339	}
340	return (0);
341}
342
343kmemgetether(ifname, dlo)
344char *ifname;
345struct sockaddr_dl *dlo;
346{
347  struct ifnet ifnet;
348  int n;
349  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
350  char name[32];
351  struct sockaddr *sa;
352  char *cp;
353  struct sockaddr_dl *sdl;
354  union {
355	  struct ifaddr ifa;
356	  struct in_ifaddr in;
357  } ifaddr;
358  struct arpcom ac;
359
360  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
361  if (kvmd) {
362    n = kvm_nlist(kvmd, nl);
363    if (n >= 0) {
364      addr = nl[N_IFNET].n_value;
365      kread(addr, (char *)&addr, sizeof(addr));
366      ifaddraddr = ifnetfound = 0;
367      while (addr || ifaddraddr) {
368	ifnetfound = addr;
369	if (ifaddraddr == 0) {
370	  if (kread(addr, (char *)&ifnet, sizeof(ifnet)) ||
371	      kread((u_long)ifnet.if_name, name, 16))
372		return;
373	  name[15] = 0;
374	  addr = (u_long) ifnet.if_next;
375	  cp = (char *)index(name, '\0');
376	  cp += sprintf(cp, "%d", ifnet.if_unit);
377	  *cp = '\0';
378	  ifaddraddr = (u_long)ifnet.if_addrlist;
379	}
380	ifaddrfound = ifaddraddr;
381	if (ifaddraddr) {
382	  if (kread(ifaddraddr, (char *)&ifaddr, sizeof ifaddr)) {
383	    ifaddraddr = 0;
384	    continue;
385	  }
386#define CP(x) ((char *)(x))
387	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
388	  sa = (struct sockaddr *)cp;
389	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
390	    sdl = (struct sockaddr_dl *)sa;
391	    cp = (char *)LLADDR(sdl);
392	    n = sdl->sdl_alen;
393	    if (ifnet.if_type == IFT_ETHER) {
394		if (n == 0) {
395		  kread(ifnetfound, (char *)&ac, sizeof(ac));
396	    	  cp = (char *)LLADDR(sdl);
397		  bcopy((char *)ac.ac_enaddr, cp, 6);
398		  sdl->sdl_alen = 6;
399		}
400		bcopy(sdl, dlo, sizeof(*sdl));
401		return;
402	    }
403	  }
404	  ifaddraddr = (u_long)ifaddr.ifa.ifa_next;
405	}
406      }
407    }
408  }
409}
410#endif
411
412#ifdef DEBUG
413main()
414{
415    u_long ipaddr;
416    int s;
417
418    s = socket(AF_INET, SOCK_DGRAM, 0);
419    ipaddr = inet_addr("192.168.1.32");
420    sifproxyarp(s, ipaddr);
421    close(s);
422}
423#endif
424