/*      $NetBSD: mkarp.c,v 1.12 2017/04/12 16:57:14 roy Exp $ */

/*
* Copyright (c) 1984, 1993
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Sun Microsystems, Inc.
*
* 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. 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.
*/

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1984, 1993\
The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)arp.c       8.3 (Berkeley) 4/28/95";
#else
__RCSID("$NetBSD: mkarp.c,v 1.12 2017/04/12 16:57:14 roy Exp $");
#endif
#endif /* not lint */

/*
* mkarp - set an arp table entry
*/

#include <sys/param.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_ether.h>
#include <net/if_types.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/if_inarp.h>
#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <netdb.h>
#include <nlist.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "mkarp.h"

/* Roundup the same way rt_xaddrs does */
#define ROUNDUP(a) \
      ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))

int     rtmsg(int, int, struct rt_msghdr *, struct sockaddr_inarp *,
             struct sockaddr_dl *);
static struct {
       struct  rt_msghdr m_rtm;
       char    m_space[512];
}       m_rtmsg;

static int
is_llinfo(const struct sockaddr_dl *sdl, int rtflags)
{
       if (sdl->sdl_family != AF_LINK ||
           (rtflags & (RTF_LLDATA|RTF_GATEWAY)) != RTF_LLDATA)
               return 0;

       switch (sdl->sdl_type) {
       case IFT_ETHER:
       case IFT_FDDI:
       case IFT_ISO88023:
       case IFT_ISO88024:
       case IFT_ISO88025:
       case IFT_ARCNET:
               return 1;
       default:
               return 0;
       }
}

/*
* Set an individual arp entry
*/
int
mkarp(u_char *haddr, u_int32_t ipaddr)
{
       static struct sockaddr_inarp blank_sin = {
               .sin_len = sizeof(blank_sin),
               .sin_family = AF_INET,
       };
       static struct sockaddr_dl blank_sdl = {
               .sdl_len = sizeof(blank_sdl),
               .sdl_family = AF_LINK,
       };

       struct sockaddr_inarp *sin;
       struct sockaddr_dl *sdl;
       struct rt_msghdr *rtm;
       u_int8_t *p, *endp;
       int result;
       int s;

       struct sockaddr_inarp sin_m;
       struct sockaddr_dl sdl_m;

#ifdef RO_MSGFILTER
       unsigned char msgfilter[] = { RTM_GET, RTM_ADD };
#endif

       sin = &sin_m;
       rtm = &(m_rtmsg.m_rtm);

       sdl_m = blank_sdl;              /* struct copy */
       sin_m = blank_sin;              /* struct copy */

       sin->sin_addr.s_addr = ipaddr;

       p = LLADDR(&sdl_m);
       endp = ((caddr_t)&sdl_m) + sdl_m.sdl_len;
       if (endp > (p + ETHER_ADDR_LEN))
               endp = p + ETHER_ADDR_LEN;

       while (p < endp) {
               *p++ = *haddr++;
       }
       sdl_m.sdl_alen = ETHER_ADDR_LEN;

       /*
        * We need to close and open the socket to prevent routing updates
        * building up such that when we send our message we never see our
        * reply (and hang)
        */
       s = socket(PF_ROUTE, SOCK_RAW, 0);
       if (s < 0)
               err(1, "socket");
#ifdef RO_MSGFILTER
       if (setsockopt(s, PF_ROUTE, RO_MSGFILTER,
           &msgfilter, sizeof(msgfilter)) < 0)
               warn("RO_MSGFILTER");
#endif

       rtm->rtm_flags = 0;

       if (rtmsg(RTM_GET, s, rtm, &sin_m, &sdl_m) < 0) {
#if 0
               warn("%s", host);
#endif
               close(s);
               return (1);
       }
       sin = (struct sockaddr_inarp *)(rtm + 1);
       sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
       if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
               if (is_llinfo(sdl, rtm->rtm_flags))
                       goto overwrite;
#if 0
               (void)printf("set: can only proxy for %s\n", host);
#endif
               close(s);
               return (1);
       }
overwrite:
       if (sdl->sdl_family != AF_LINK) {
#if 0
               (void)printf("cannot intuit interface index and type for %s\n",
                   host);
#endif
               close(s);
               return (1);
       }
       sdl_m.sdl_type = sdl->sdl_type;
       sdl_m.sdl_index = sdl->sdl_index;
       result = rtmsg(RTM_ADD, s, rtm, &sin_m, &sdl_m);
       close(s);
       return (result);
}

int
rtmsg(int cmd, int s, struct rt_msghdr *rtm, struct sockaddr_inarp *sin_m,
     struct sockaddr_dl *sdl_m)
{
       static int seq;
       int rlen;
       char *cp;
       int l;
       pid_t pid;
       struct timeval tv;

       rtm = &m_rtmsg.m_rtm;
       cp = m_rtmsg.m_space;
       errno = 0;

       pid = getpid();

       (void)memset(&m_rtmsg, 0, sizeof(m_rtmsg));
       rtm->rtm_version = RTM_VERSION;

       switch (cmd) {
       default:
               errx(1, "internal wrong cmd");
               /*NOTREACHED*/
       case RTM_ADD:
               rtm->rtm_addrs |= RTA_GATEWAY;
               (void)gettimeofday(&tv, 0);
               rtm->rtm_rmx.rmx_expire = tv.tv_sec + 20 * 60;
               rtm->rtm_inits = RTV_EXPIRE;
               rtm->rtm_flags |= (RTF_HOST | RTF_STATIC | RTF_LLDATA);
               sin_m->sin_other = 0;

               /* FALLTHROUGH */
       case RTM_GET:
               rtm->rtm_addrs |= RTA_DST;
       }
#define NEXTADDR(w, s) \
       if (rtm->rtm_addrs & (w)) { \
               (void)memcpy(cp, s, ((struct sockaddr *)s)->sa_len); \
               cp += ROUNDUP(((struct sockaddr *)s)->sa_len);}

       NEXTADDR(RTA_DST, sin_m);
       NEXTADDR(RTA_GATEWAY, sdl_m);

       rtm->rtm_msglen = cp - (char *)&m_rtmsg;

       l = rtm->rtm_msglen;
       rtm->rtm_seq = ++seq;
       rtm->rtm_type = cmd;
       if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
               if (errno != ESRCH && errno != EEXIST) {
                       warn("writing to routing socket");
                       return (-1);
               }
       }
       do {
               l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
       } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
       if (l < 0)
               warn("read from routing socket");
       return (0);
}

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