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 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 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 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 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