/*      $NetBSD: arp.c,v 1.35 2019/03/31 20:08:45 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 <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <net/if_ether.h>
#include <netinet/in.h>

#include <netinet/in_systm.h>

#ifdef _STANDALONE
#include <lib/libkern/libkern.h>
#else
#include <arpa/inet.h>
#include <string.h>
#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[ETHER_ADDR_LEN];
} 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(struct iodesc *, void *, size_t);
static  ssize_t arprecv(struct iodesc *, void *, size_t, saseconds_t);

/* Broadcast an ARP packet, asking who has addr on interface d */
u_char *
arpwhohas(struct iodesc *d, struct in_addr addr)
{
       int i;
       ssize_t ns;
       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("%s: overflowed arp_list!\n", __func__);
       }

#ifdef ARP_DEBUG
       if (debug)
               printf("%s: send request for %s\n", __func__, 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;

       ns = sendrecv(d,
           arpsend, &wbuf.data, sizeof(wbuf.data),
           arprecv, &rbuf.data, sizeof(rbuf.data));
       if (ns == -1) {
               panic("%s: no response for %s", __func__, inet_ntoa(addr));
       }

       /* Store ethernet address in cache */
       ah = &rbuf.data.arp;
#ifdef ARP_DEBUG
       if (debug) {
               printf("%s: response from %s\n", __func__,
                   ether_sprintf(rbuf.eh.ether_shost));
               printf("%s: cacheing %s --> %s\n", __func__,
                   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("%s: called\n", __func__);
#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, saseconds_t tleft)
{
       ssize_t n;
       struct ether_arp *ah;
       u_int16_t etype;        /* host order */

#ifdef ARP_DEBUG
       if (debug)
               printf("%s: ", __func__);
#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=%zd\n", 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("%s: bad hrd/pro/hln/pln\n", __func__);
#endif
               return;
       }

       if (arp->arp_op != htons(ARPOP_REQUEST)) {
#ifdef ARP_DEBUG
               if (debug)
                       printf("%s: not request!\n", __func__);
#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("%s: to %s\n", __func__, 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);
}