1 /* $OpenBSD: arptab.c,v 1.28 2016/08/27 01:42:37 guenther 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/file.h> 41 #include <sys/socket.h> 42 #include <sys/sysctl.h> 43 #include <sys/time.h> 44 45 #include <net/if.h> 46 #include <net/if_dl.h> 47 #include <net/if_types.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/if_ether.h> 52 53 #include <arpa/inet.h> 54 55 #include <netdb.h> 56 #include <errno.h> 57 #include <stdio.h> 58 #include <unistd.h> 59 #include <stdlib.h> 60 #include <paths.h> 61 #include <syslog.h> 62 #include <string.h> 63 #include <err.h> 64 65 /* ROUNDUP() is nasty, but it is identical to what's in the kernel. */ 66 #define ROUNDUP(a) \ 67 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long)) 68 69 static pid_t pid; 70 static int s = -1; 71 72 int rtget(struct sockaddr_inarp **, struct sockaddr_dl **); 73 74 void 75 arptab_init(void) 76 { 77 s = socket(PF_ROUTE, SOCK_RAW, 0); 78 if (s < 0) 79 err(1, "arp: socket"); 80 } 81 82 struct sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}}; 83 struct sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m; 84 struct sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m; 85 struct sockaddr_dl ifp_m = {sizeof(&ifp_m), AF_LINK}; 86 time_t expire_time; 87 int flags, export_only, doing_proxy; 88 89 struct { 90 struct rt_msghdr m_rtm; 91 char m_space[512]; 92 } m_rtmsg; 93 94 int arptab_set(u_char *, u_int32_t); 95 int rtmsg(int); 96 97 /* 98 * Set an individual arp entry 99 */ 100 int 101 arptab_set(u_char *eaddr, u_int32_t host) 102 { 103 struct sockaddr_inarp *sin = &sin_m; 104 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 105 struct sockaddr_dl *sdl; 106 struct timeval now; 107 int rt; 108 109 pid = getpid(); 110 111 sdl_m = blank_sdl; 112 sin_m = blank_sin; 113 sin->sin_addr.s_addr = host; 114 memcpy((u_char *)LLADDR(&sdl_m), (char *)eaddr, 6); 115 sdl_m.sdl_alen = 6; 116 expire_time = 0; 117 doing_proxy = flags = export_only = 0; 118 gettimeofday(&now, 0); 119 expire_time = now.tv_sec + 20 * 60; 120 121 tryagain: 122 if (rtget(&sin, &sdl)) { 123 syslog(LOG_ERR,"%s: %m", inet_ntoa(sin->sin_addr)); 124 return (1); 125 } 126 127 if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 128 if (sdl->sdl_family == AF_LINK && 129 (rtm->rtm_flags & RTF_LLINFO) && 130 !(rtm->rtm_flags & RTF_GATEWAY)) 131 switch (sdl->sdl_type) { 132 case IFT_ETHER: 133 case IFT_FDDI: 134 case IFT_ISO88023: 135 case IFT_ISO88024: 136 case IFT_ISO88025: 137 goto overwrite; 138 default: 139 break; 140 } 141 if (doing_proxy == 0) { 142 syslog(LOG_ERR, "arptab_set: can only proxy for %s", 143 inet_ntoa(sin->sin_addr)); 144 return (1); 145 } 146 if (sin_m.sin_other & SIN_PROXY) { 147 syslog(LOG_ERR, 148 "arptab_set: proxy entry exists for non 802 device"); 149 return(1); 150 } 151 sin_m.sin_other = SIN_PROXY; 152 export_only = 1; 153 goto tryagain; 154 } 155 overwrite: 156 if (sdl->sdl_family != AF_LINK) { 157 syslog(LOG_ERR, 158 "arptab_set: cannot intuit interface index and type for %s", 159 inet_ntoa(sin->sin_addr)); 160 return (1); 161 } 162 sdl_m.sdl_type = sdl->sdl_type; 163 sdl_m.sdl_index = sdl->sdl_index; 164 rt = rtmsg(RTM_ADD); 165 return (rt); 166 } 167 168 int 169 rtmsg(int cmd) 170 { 171 static int seq; 172 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 173 char *cp = m_rtmsg.m_space; 174 int l; 175 176 retry: 177 errno = 0; 178 if (cmd == RTM_DELETE) 179 goto doit; 180 memset((char *)&m_rtmsg, 0, sizeof(m_rtmsg)); 181 rtm->rtm_flags = flags; 182 rtm->rtm_version = RTM_VERSION; 183 184 switch (cmd) { 185 default: 186 syslog(LOG_ERR, "arptab_set: internal wrong cmd"); 187 exit(1); 188 case RTM_ADD: 189 rtm->rtm_addrs |= RTA_GATEWAY; 190 rtm->rtm_rmx.rmx_expire = expire_time; 191 rtm->rtm_inits = RTV_EXPIRE; 192 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 193 sin_m.sin_other = 0; 194 if (doing_proxy) { 195 if (export_only) 196 sin_m.sin_other = SIN_PROXY; 197 else { 198 rtm->rtm_addrs |= RTA_NETMASK; 199 rtm->rtm_flags &= ~RTF_HOST; 200 } 201 } 202 /* FALLTHROUGH */ 203 case RTM_GET: 204 rtm->rtm_addrs |= (RTA_DST | RTA_IFP); 205 } 206 #define NEXTADDR(w, s) \ 207 if (rtm->rtm_addrs & (w)) { \ 208 memcpy(cp, (char *)&s, sizeof(s)); \ 209 cp += sizeof(s); \ 210 } 211 212 NEXTADDR(RTA_DST, sin_m); 213 NEXTADDR(RTA_GATEWAY, sdl_m); 214 NEXTADDR(RTA_NETMASK, so_mask); 215 NEXTADDR(RTA_IFP, ifp_m); 216 217 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 218 doit: 219 l = rtm->rtm_msglen; 220 rtm->rtm_seq = ++seq; 221 rtm->rtm_type = cmd; 222 if (write(s, (char *)&m_rtmsg, l) < 0) { 223 if (errno != ESRCH && errno != EEXIST) { 224 syslog(LOG_ERR, "writing to routing socket: %m"); 225 return (-1); 226 } 227 } 228 do { 229 l = recv(s, (char *)&m_rtmsg, sizeof(m_rtmsg), MSG_DONTWAIT); 230 } while (l > 0 && (rtm->rtm_version != RTM_VERSION || 231 rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 232 if (l < 0) { 233 if (errno == EAGAIN || errno == EINTR) 234 goto retry; 235 syslog(LOG_ERR, "arptab_set: read from routing socket: %m"); 236 } 237 return (0); 238 } 239 240 int 241 rtget(struct sockaddr_inarp **sinp, struct sockaddr_dl **sdlp) 242 { 243 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 244 struct sockaddr_inarp *sin = NULL; 245 struct sockaddr_dl *sdl = NULL; 246 struct sockaddr *sa; 247 char *cp; 248 unsigned int i; 249 250 if (rtmsg(RTM_GET) < 0) 251 return (1); 252 253 if (rtm->rtm_addrs) { 254 cp = ((char *)rtm + rtm->rtm_hdrlen); 255 for (i = 1; i; i <<= 1) { 256 if (i & rtm->rtm_addrs) { 257 sa = (struct sockaddr *)cp; 258 switch (i) { 259 case RTA_DST: 260 sin = (struct sockaddr_inarp *)sa; 261 break; 262 case RTA_IFP: 263 sdl = (struct sockaddr_dl *)sa; 264 break; 265 default: 266 break; 267 } 268 cp += ROUNDUP(sa->sa_len); 269 } 270 } 271 } 272 273 if (sin == NULL || sdl == NULL) 274 return (1); 275 276 *sinp = sin; 277 *sdlp = sdl; 278 279 return (0); 280 } 281