324 lines
8.4 KiB
C
324 lines
8.4 KiB
C
/* $NetBSD: arp.c,v 1.33 2009/01/17 14:00:36 tsutsui Exp $ */
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/*
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* Copyright (c) 1992 Regents of the University of California.
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* All rights reserved.
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*
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* This software was developed by the Computer Systems Engineering group
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* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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* contributed to Berkeley.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Lawrence Berkeley Laboratory and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL)
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <net/if.h>
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#include <net/if_ether.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#ifdef _STANDALONE
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#include <lib/libkern/libkern.h>
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#else
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#include <string.h>
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#endif
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#include "stand.h"
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#include "net.h"
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/*
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* Ethernet Address Resolution Protocol.
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*
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* See RFC 826 for protocol description. Structure below is adapted
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* to resolving internet addresses. Field names used correspond to
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* RFC 826.
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*/
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struct ether_arp {
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struct arphdr ea_hdr; /* fixed-size header */
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u_int8_t arp_sha[ETHER_ADDR_LEN]; /* sender hardware address */
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u_int8_t arp_spa[4]; /* sender protocol address */
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u_int8_t arp_tha[ETHER_ADDR_LEN]; /* target hardware address */
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u_int8_t arp_tpa[4]; /* target protocol address */
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};
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#define arp_hrd ea_hdr.ar_hrd
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#define arp_pro ea_hdr.ar_pro
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#define arp_hln ea_hdr.ar_hln
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#define arp_pln ea_hdr.ar_pln
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#define arp_op ea_hdr.ar_op
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/* Cache stuff */
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#define ARP_NUM 8 /* need at most 3 arp entries */
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struct arp_list {
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struct in_addr addr;
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u_char ea[6];
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} arp_list[ARP_NUM] = {
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/* XXX - net order `INADDR_BROADCAST' must be a constant */
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{ {0xffffffff}, BA }
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};
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int arp_num = 1;
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/* Local forwards */
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static ssize_t arpsend(struct iodesc *, void *, size_t);
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static ssize_t arprecv(struct iodesc *, void *, size_t, saseconds_t);
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/* Broadcast an ARP packet, asking who has addr on interface d */
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u_char *
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arpwhohas(struct iodesc *d, struct in_addr addr)
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{
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int i;
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struct ether_arp *ah;
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struct arp_list *al;
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struct {
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struct ether_header eh;
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struct {
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struct ether_arp arp;
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u_char pad[18]; /* 60 - sizeof(...) */
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} data;
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} wbuf;
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struct {
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struct ether_header eh;
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struct {
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struct ether_arp arp;
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u_char pad[24]; /* extra space */
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} data;
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} rbuf;
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/* Try for cached answer first */
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for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
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if (addr.s_addr == al->addr.s_addr)
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return al->ea;
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/* Don't overflow cache */
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if (arp_num > ARP_NUM - 1) {
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arp_num = 1; /* recycle */
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printf("arpwhohas: overflowed arp_list!\n");
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}
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#ifdef ARP_DEBUG
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if (debug)
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printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
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#endif
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(void)memset(&wbuf.data, 0, sizeof(wbuf.data));
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ah = &wbuf.data.arp;
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ah->arp_hrd = htons(ARPHRD_ETHER);
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ah->arp_pro = htons(ETHERTYPE_IP);
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ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
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ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
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ah->arp_op = htons(ARPOP_REQUEST);
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MACPY(d->myea, ah->arp_sha);
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(void)memcpy(ah->arp_spa, &d->myip, sizeof(ah->arp_spa));
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/* Leave zeros in arp_tha */
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(void)memcpy(ah->arp_tpa, &addr, sizeof(ah->arp_tpa));
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/* Store ip address in cache (incomplete entry). */
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al->addr = addr;
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i = sendrecv(d,
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arpsend, &wbuf.data, sizeof(wbuf.data),
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arprecv, &rbuf.data, sizeof(rbuf.data));
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if (i == -1) {
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panic("arp: no response for %s",
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inet_ntoa(addr));
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}
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/* Store ethernet address in cache */
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ah = &rbuf.data.arp;
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#ifdef ARP_DEBUG
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if (debug) {
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printf("arp: response from %s\n",
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ether_sprintf(rbuf.eh.ether_shost));
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printf("arp: cacheing %s --> %s\n",
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inet_ntoa(addr), ether_sprintf(ah->arp_sha));
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}
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#endif
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MACPY(ah->arp_sha, al->ea);
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++arp_num;
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return al->ea;
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}
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static ssize_t
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arpsend(struct iodesc *d, void *pkt, size_t len)
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{
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#ifdef ARP_DEBUG
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if (debug)
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printf("arpsend: called\n");
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#endif
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return sendether(d, pkt, len, bcea, ETHERTYPE_ARP);
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}
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/*
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* Returns 0 if this is the packet we're waiting for
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* else -1 (and errno == 0)
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*/
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static ssize_t
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arprecv(struct iodesc *d, void *pkt, size_t len, saseconds_t tleft)
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{
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ssize_t n;
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struct ether_arp *ah;
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u_int16_t etype; /* host order */
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#ifdef ARP_DEBUG
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if (debug)
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printf("arprecv: ");
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#endif
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n = readether(d, pkt, len, tleft, &etype);
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errno = 0; /* XXX */
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if (n == -1 || (size_t)n < sizeof(struct ether_arp)) {
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#ifdef ARP_DEBUG
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if (debug)
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printf("bad len=%ld\n", (signed long) n);
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#endif
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return -1;
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}
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if (etype != ETHERTYPE_ARP) {
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#ifdef ARP_DEBUG
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if (debug)
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printf("not arp type=%d\n", etype);
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#endif
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return -1;
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}
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/* Ethernet address now checked in readether() */
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ah = (struct ether_arp *)pkt;
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if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
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ah->arp_pro != htons(ETHERTYPE_IP) ||
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ah->arp_hln != sizeof(ah->arp_sha) ||
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ah->arp_pln != sizeof(ah->arp_spa) )
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{
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#ifdef ARP_DEBUG
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if (debug)
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printf("bad hrd/pro/hln/pln\n");
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#endif
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return -1;
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}
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if (ah->arp_op == htons(ARPOP_REQUEST)) {
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#ifdef ARP_DEBUG
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if (debug)
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printf("is request\n");
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#endif
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arp_reply(d, ah);
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return -1;
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}
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if (ah->arp_op != htons(ARPOP_REPLY)) {
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#ifdef ARP_DEBUG
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if (debug)
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printf("not ARP reply\n");
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#endif
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return -1;
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}
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/* Is the reply from the source we want? */
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if (memcmp(&arp_list[arp_num].addr,
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ah->arp_spa, sizeof(ah->arp_spa)))
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{
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#ifdef ARP_DEBUG
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if (debug)
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printf("unwanted address\n");
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#endif
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return -1;
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}
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/* We don't care who the reply was sent to. */
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/* We have our answer. */
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#ifdef ARP_DEBUG
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if (debug)
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printf("got it\n");
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#endif
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return n;
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}
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/*
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* Convert an ARP request into a reply and send it.
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* Notes: Re-uses buffer. Pad to length = 46.
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*/
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void
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arp_reply(struct iodesc *d, void *pkt)
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{
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struct ether_arp *arp = pkt;
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if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
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arp->arp_pro != htons(ETHERTYPE_IP) ||
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arp->arp_hln != sizeof(arp->arp_sha) ||
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arp->arp_pln != sizeof(arp->arp_spa) )
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{
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#ifdef ARP_DEBUG
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if (debug)
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printf("arp_reply: bad hrd/pro/hln/pln\n");
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#endif
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return;
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}
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if (arp->arp_op != htons(ARPOP_REQUEST)) {
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#ifdef ARP_DEBUG
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if (debug)
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printf("arp_reply: not request!\n");
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#endif
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return;
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}
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/* If we are not the target, ignore the request. */
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if (memcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
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return;
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#ifdef ARP_DEBUG
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if (debug) {
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printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
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}
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#endif
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arp->arp_op = htons(ARPOP_REPLY);
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/* source becomes target */
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(void)memcpy(arp->arp_tha, arp->arp_sha, sizeof(arp->arp_tha));
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(void)memcpy(arp->arp_tpa, arp->arp_spa, sizeof(arp->arp_tpa));
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/* here becomes source */
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(void)memcpy(arp->arp_sha, d->myea, sizeof(arp->arp_sha));
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(void)memcpy(arp->arp_spa, &d->myip, sizeof(arp->arp_spa));
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/*
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* No need to get fancy here. If the send fails, the
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* requestor will just ask again.
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*/
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(void) sendether(d, pkt, sizeof(*arp) + 18,
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arp->arp_tha, ETHERTYPE_ARP);
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}
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