1 /* $OpenBSD: arptab.c,v 1.31 2019/06/28 13:32:50 deraadt Exp $ */
2
3 /*
4 * Copyright (c) 1984, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Sun Microsystems, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 /*
36 * set arp table entries
37 */
38
39
40 #include <sys/socket.h>
41 #include <sys/time.h>
42
43 #include <net/if.h>
44 #include <net/if_dl.h>
45 #include <net/if_types.h>
46 #include <net/route.h>
47
48 #include <netinet/in.h>
49 #include <netinet/if_ether.h>
50
51 #include <arpa/inet.h>
52
53 #include <netdb.h>
54 #include <errno.h>
55 #include <fcntl.h>
56 #include <stdio.h>
57 #include <unistd.h>
58 #include <stdlib.h>
59 #include <syslog.h>
60 #include <string.h>
61 #include <err.h>
62
63 /* ROUNDUP() is nasty, but it is identical to what's in the kernel. */
64 #define ROUNDUP(a) \
65 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
66
67 static pid_t pid;
68 static int s = -1;
69
70 int rtget(struct sockaddr_inarp **, struct sockaddr_dl **);
71
72 void
arptab_init(void)73 arptab_init(void)
74 {
75 s = socket(AF_ROUTE, SOCK_RAW, 0);
76 if (s == -1)
77 err(1, "arp: socket");
78 }
79
80 struct sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}};
81 struct sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m;
82 struct sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m;
83 struct sockaddr_dl ifp_m = {sizeof(&ifp_m), AF_LINK};
84 time_t expire_time;
85 int flags, export_only, doing_proxy;
86
87 struct {
88 struct rt_msghdr m_rtm;
89 char m_space[512];
90 } m_rtmsg;
91
92 int arptab_set(u_char *, u_int32_t);
93 int rtmsg(int);
94
95 /*
96 * Set an individual arp entry
97 */
98 int
arptab_set(u_char * eaddr,u_int32_t host)99 arptab_set(u_char *eaddr, u_int32_t host)
100 {
101 struct sockaddr_inarp *sin = &sin_m;
102 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
103 struct sockaddr_dl *sdl;
104 struct timeval now;
105 int rt;
106
107 pid = getpid();
108
109 sdl_m = blank_sdl;
110 sin_m = blank_sin;
111 sin->sin_addr.s_addr = host;
112 memcpy((u_char *)LLADDR(&sdl_m), (char *)eaddr, 6);
113 sdl_m.sdl_alen = 6;
114 expire_time = 0;
115 doing_proxy = flags = export_only = 0;
116 gettimeofday(&now, 0);
117 expire_time = now.tv_sec + 20 * 60;
118
119 tryagain:
120 if (rtget(&sin, &sdl)) {
121 syslog(LOG_ERR,"%s: %m", inet_ntoa(sin->sin_addr));
122 return (1);
123 }
124
125 if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
126 if (sdl->sdl_family == AF_LINK &&
127 (rtm->rtm_flags & RTF_LLINFO) &&
128 !(rtm->rtm_flags & RTF_GATEWAY))
129 switch (sdl->sdl_type) {
130 case IFT_ETHER:
131 case IFT_FDDI:
132 case IFT_ISO88023:
133 case IFT_ISO88024:
134 case IFT_ISO88025:
135 goto overwrite;
136 default:
137 break;
138 }
139 if (doing_proxy == 0) {
140 syslog(LOG_ERR, "arptab_set: can only proxy for %s",
141 inet_ntoa(sin->sin_addr));
142 return (1);
143 }
144 if (sin_m.sin_other & SIN_PROXY) {
145 syslog(LOG_ERR,
146 "arptab_set: proxy entry exists for non 802 device");
147 return(1);
148 }
149 sin_m.sin_other = SIN_PROXY;
150 export_only = 1;
151 goto tryagain;
152 }
153 overwrite:
154 if (sdl->sdl_family != AF_LINK) {
155 syslog(LOG_ERR,
156 "arptab_set: cannot intuit interface index and type for %s",
157 inet_ntoa(sin->sin_addr));
158 return (1);
159 }
160 sdl_m.sdl_type = sdl->sdl_type;
161 sdl_m.sdl_index = sdl->sdl_index;
162 rt = rtmsg(RTM_ADD);
163 return (rt);
164 }
165
166 int
rtmsg(int cmd)167 rtmsg(int cmd)
168 {
169 static int seq;
170 struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
171 char *cp = m_rtmsg.m_space;
172 int l;
173
174 retry:
175 errno = 0;
176 if (cmd == RTM_DELETE)
177 goto doit;
178 memset((char *)&m_rtmsg, 0, sizeof(m_rtmsg));
179 rtm->rtm_flags = flags;
180 rtm->rtm_version = RTM_VERSION;
181
182 switch (cmd) {
183 default:
184 syslog(LOG_ERR, "arptab_set: internal wrong cmd");
185 exit(1);
186 case RTM_ADD:
187 rtm->rtm_addrs |= RTA_GATEWAY;
188 rtm->rtm_rmx.rmx_expire = expire_time;
189 rtm->rtm_inits = RTV_EXPIRE;
190 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
191 sin_m.sin_other = 0;
192 if (doing_proxy) {
193 if (export_only)
194 sin_m.sin_other = SIN_PROXY;
195 else {
196 rtm->rtm_addrs |= RTA_NETMASK;
197 rtm->rtm_flags &= ~RTF_HOST;
198 }
199 }
200 /* FALLTHROUGH */
201 case RTM_GET:
202 rtm->rtm_addrs |= (RTA_DST | RTA_IFP);
203 }
204 #define NEXTADDR(w, s) \
205 if (rtm->rtm_addrs & (w)) { \
206 memcpy(cp, (char *)&s, sizeof(s)); \
207 cp += sizeof(s); \
208 }
209
210 NEXTADDR(RTA_DST, sin_m);
211 NEXTADDR(RTA_GATEWAY, sdl_m);
212 NEXTADDR(RTA_NETMASK, so_mask);
213 NEXTADDR(RTA_IFP, ifp_m);
214
215 rtm->rtm_msglen = cp - (char *)&m_rtmsg;
216 doit:
217 l = rtm->rtm_msglen;
218 rtm->rtm_seq = ++seq;
219 rtm->rtm_type = cmd;
220 if (write(s, (char *)&m_rtmsg, l) == -1) {
221 if (errno != ESRCH && errno != EEXIST) {
222 syslog(LOG_ERR, "writing to routing socket: %m");
223 return (-1);
224 }
225 }
226 do {
227 l = recv(s, (char *)&m_rtmsg, sizeof(m_rtmsg), MSG_DONTWAIT);
228 } while (l > 0 && (rtm->rtm_version != RTM_VERSION ||
229 rtm->rtm_seq != seq || rtm->rtm_pid != pid));
230 if (l == -1) {
231 if (errno == EAGAIN || errno == EINTR)
232 goto retry;
233 syslog(LOG_ERR, "arptab_set: read from routing socket: %m");
234 }
235 return (0);
236 }
237
238 int
rtget(struct sockaddr_inarp ** sinp,struct sockaddr_dl ** sdlp)239 rtget(struct sockaddr_inarp **sinp, struct sockaddr_dl **sdlp)
240 {
241 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
242 struct sockaddr_inarp *sin = NULL;
243 struct sockaddr_dl *sdl = NULL;
244 struct sockaddr *sa;
245 char *cp;
246 unsigned int i;
247
248 if (rtmsg(RTM_GET) < 0)
249 return (1);
250
251 if (rtm->rtm_addrs) {
252 cp = ((char *)rtm + rtm->rtm_hdrlen);
253 for (i = 1; i; i <<= 1) {
254 if (i & rtm->rtm_addrs) {
255 sa = (struct sockaddr *)cp;
256 switch (i) {
257 case RTA_DST:
258 sin = (struct sockaddr_inarp *)sa;
259 break;
260 case RTA_IFP:
261 sdl = (struct sockaddr_dl *)sa;
262 break;
263 default:
264 break;
265 }
266 cp += ROUNDUP(sa->sa_len);
267 }
268 }
269 }
270
271 if (sin == NULL || sdl == NULL)
272 return (1);
273
274 *sinp = sin;
275 *sdlp = sdl;
276
277 return (0);
278 }
279