/* $NetBSD: arp.c,v 1.31 2008/03/25 22:55:25 christos Exp $ */ /* * Copyright (c) 1992 Regents of the University of California. * All rights reserved. * * This software was developed by the Computer Systems Engineering group * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and * contributed to Berkeley. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Lawrence Berkeley Laboratory and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL) */ #include #include #include #include #include #include #ifdef _STANDALONE #include #else #include #endif #include "stand.h" #include "net.h" /* * Ethernet Address Resolution Protocol. * * See RFC 826 for protocol description. Structure below is adapted * to resolving internet addresses. Field names used correspond to * RFC 826. */ struct ether_arp { struct arphdr ea_hdr; /* fixed-size header */ u_int8_t arp_sha[ETHER_ADDR_LEN]; /* sender hardware address */ u_int8_t arp_spa[4]; /* sender protocol address */ u_int8_t arp_tha[ETHER_ADDR_LEN]; /* target hardware address */ u_int8_t arp_tpa[4]; /* target protocol address */ }; #define arp_hrd ea_hdr.ar_hrd #define arp_pro ea_hdr.ar_pro #define arp_hln ea_hdr.ar_hln #define arp_pln ea_hdr.ar_pln #define arp_op ea_hdr.ar_op /* Cache stuff */ #define ARP_NUM 8 /* need at most 3 arp entries */ struct arp_list { struct in_addr addr; u_char ea[6]; } arp_list[ARP_NUM] = { /* XXX - net order `INADDR_BROADCAST' must be a constant */ { {0xffffffff}, BA } }; int arp_num = 1; /* Local forwards */ static ssize_t arpsend __P((struct iodesc *, void *, size_t)); static ssize_t arprecv __P((struct iodesc *, void *, size_t, time_t)); /* Broadcast an ARP packet, asking who has addr on interface d */ u_char * arpwhohas(struct iodesc *d, struct in_addr addr) { int i; struct ether_arp *ah; struct arp_list *al; struct { struct ether_header eh; struct { struct ether_arp arp; u_char pad[18]; /* 60 - sizeof(...) */ } data; } wbuf; struct { struct ether_header eh; struct { struct ether_arp arp; u_char pad[24]; /* extra space */ } data; } rbuf; /* Try for cached answer first */ for (i = 0, al = arp_list; i < arp_num; ++i, ++al) if (addr.s_addr == al->addr.s_addr) return al->ea; /* Don't overflow cache */ if (arp_num > ARP_NUM - 1) { arp_num = 1; /* recycle */ printf("arpwhohas: overflowed arp_list!\n"); } #ifdef ARP_DEBUG if (debug) printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); #endif (void)memset(&wbuf.data, 0, sizeof(wbuf.data)); ah = &wbuf.data.arp; ah->arp_hrd = htons(ARPHRD_ETHER); ah->arp_pro = htons(ETHERTYPE_IP); ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ ah->arp_op = htons(ARPOP_REQUEST); MACPY(d->myea, ah->arp_sha); (void)memcpy(ah->arp_spa, &d->myip, sizeof(ah->arp_spa)); /* Leave zeros in arp_tha */ (void)memcpy(ah->arp_tpa, &addr, sizeof(ah->arp_tpa)); /* Store ip address in cache (incomplete entry). */ al->addr = addr; i = sendrecv(d, arpsend, &wbuf.data, sizeof(wbuf.data), arprecv, &rbuf.data, sizeof(rbuf.data)); if (i == -1) { panic("arp: no response for %s", inet_ntoa(addr)); } /* Store ethernet address in cache */ ah = &rbuf.data.arp; #ifdef ARP_DEBUG if (debug) { printf("arp: response from %s\n", ether_sprintf(rbuf.eh.ether_shost)); printf("arp: cacheing %s --> %s\n", inet_ntoa(addr), ether_sprintf(ah->arp_sha)); } #endif MACPY(ah->arp_sha, al->ea); ++arp_num; return al->ea; } static ssize_t arpsend(struct iodesc *d, void *pkt, size_t len) { #ifdef ARP_DEBUG if (debug) printf("arpsend: called\n"); #endif return sendether(d, pkt, len, bcea, ETHERTYPE_ARP); } /* * Returns 0 if this is the packet we're waiting for * else -1 (and errno == 0) */ static ssize_t arprecv(struct iodesc *d, void *pkt, size_t len, time_t tleft) { ssize_t n; struct ether_arp *ah; u_int16_t etype; /* host order */ #ifdef ARP_DEBUG if (debug) printf("arprecv: "); #endif n = readether(d, pkt, len, tleft, &etype); errno = 0; /* XXX */ if (n == -1 || (size_t)n < sizeof(struct ether_arp)) { #ifdef ARP_DEBUG if (debug) printf("bad len=%ld\n", (signed long) n); #endif return -1; } if (etype != ETHERTYPE_ARP) { #ifdef ARP_DEBUG if (debug) printf("not arp type=%d\n", etype); #endif return -1; } /* Ethernet address now checked in readether() */ ah = (struct ether_arp *)pkt; if (ah->arp_hrd != htons(ARPHRD_ETHER) || ah->arp_pro != htons(ETHERTYPE_IP) || ah->arp_hln != sizeof(ah->arp_sha) || ah->arp_pln != sizeof(ah->arp_spa) ) { #ifdef ARP_DEBUG if (debug) printf("bad hrd/pro/hln/pln\n"); #endif return -1; } if (ah->arp_op == htons(ARPOP_REQUEST)) { #ifdef ARP_DEBUG if (debug) printf("is request\n"); #endif arp_reply(d, ah); return -1; } if (ah->arp_op != htons(ARPOP_REPLY)) { #ifdef ARP_DEBUG if (debug) printf("not ARP reply\n"); #endif return -1; } /* Is the reply from the source we want? */ if (memcmp(&arp_list[arp_num].addr, ah->arp_spa, sizeof(ah->arp_spa))) { #ifdef ARP_DEBUG if (debug) printf("unwanted address\n"); #endif return -1; } /* We don't care who the reply was sent to. */ /* We have our answer. */ #ifdef ARP_DEBUG if (debug) printf("got it\n"); #endif return n; } /* * Convert an ARP request into a reply and send it. * Notes: Re-uses buffer. Pad to length = 46. */ void arp_reply(struct iodesc *d, void *pkt) { struct ether_arp *arp = pkt; if (arp->arp_hrd != htons(ARPHRD_ETHER) || arp->arp_pro != htons(ETHERTYPE_IP) || arp->arp_hln != sizeof(arp->arp_sha) || arp->arp_pln != sizeof(arp->arp_spa) ) { #ifdef ARP_DEBUG if (debug) printf("arp_reply: bad hrd/pro/hln/pln\n"); #endif return; } if (arp->arp_op != htons(ARPOP_REQUEST)) { #ifdef ARP_DEBUG if (debug) printf("arp_reply: not request!\n"); #endif return; } /* If we are not the target, ignore the request. */ if (memcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) return; #ifdef ARP_DEBUG if (debug) { printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); } #endif arp->arp_op = htons(ARPOP_REPLY); /* source becomes target */ (void)memcpy(arp->arp_tha, arp->arp_sha, sizeof(arp->arp_tha)); (void)memcpy(arp->arp_tpa, arp->arp_spa, sizeof(arp->arp_tpa)); /* here becomes source */ (void)memcpy(arp->arp_sha, d->myea, sizeof(arp->arp_sha)); (void)memcpy(arp->arp_spa, &d->myip, sizeof(arp->arp_spa)); /* * No need to get fancy here. If the send fails, the * requestor will just ask again. */ (void) sendether(d, pkt, sizeof(*arp) + 18, arp->arp_tha, ETHERTYPE_ARP); }