/*      $OpenBSD: arptab.c,v 1.31 2019/06/28 13:32:50 deraadt 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.
 */

/*
 * set arp table entries
 */


#include <sys/socket.h>
#include <sys/time.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>

#include <arpa/inet.h>

#include <netdb.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <syslog.h>
#include <string.h>
#include <err.h>

/* ROUNDUP() is nasty, but it is identical to what's in the kernel. */
#define ROUNDUP(a)                                      \
        ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))

static pid_t pid;
static int s = -1;

int rtget(struct sockaddr_inarp **, struct sockaddr_dl **);

void
arptab_init(void)
{
        s = socket(AF_ROUTE, SOCK_RAW, 0);
        if (s == -1)
                err(1, "arp: socket");
}

struct  sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}};
struct  sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m;
struct  sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m;
struct  sockaddr_dl ifp_m = {sizeof(&ifp_m), AF_LINK};
time_t  expire_time;
int     flags, export_only, doing_proxy;

struct  {
        struct  rt_msghdr m_rtm;
        char    m_space[512];
} m_rtmsg;

int     arptab_set(u_char *, u_int32_t);
int     rtmsg(int);

/*
 * Set an individual arp entry
 */
int
arptab_set(u_char *eaddr, u_int32_t host)
{
        struct sockaddr_inarp *sin = &sin_m;
        struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
        struct sockaddr_dl *sdl;
        struct timeval now;
        int rt;

        pid = getpid();

        sdl_m = blank_sdl;
        sin_m = blank_sin;
        sin->sin_addr.s_addr = host;
        memcpy((u_char *)LLADDR(&sdl_m), (char *)eaddr, 6);
        sdl_m.sdl_alen = 6;
        expire_time = 0;
        doing_proxy = flags = export_only = 0;
        gettimeofday(&now, 0);
        expire_time = now.tv_sec + 20 * 60;

tryagain:
        if (rtget(&sin, &sdl)) {
                syslog(LOG_ERR,"%s: %m", inet_ntoa(sin->sin_addr));
                return (1);
        }

        if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
                if (sdl->sdl_family == AF_LINK &&
                    (rtm->rtm_flags & RTF_LLINFO) &&
                    !(rtm->rtm_flags & RTF_GATEWAY))
                        switch (sdl->sdl_type) {
                        case IFT_ETHER:
                        case IFT_FDDI:
                        case IFT_ISO88023:
                        case IFT_ISO88024:
                        case IFT_ISO88025:
                                goto overwrite;
                        default:
                                break;
                }
                if (doing_proxy == 0) {
                        syslog(LOG_ERR, "arptab_set: can only proxy for %s",
                            inet_ntoa(sin->sin_addr));
                        return (1);
                }
                if (sin_m.sin_other & SIN_PROXY) {
                        syslog(LOG_ERR,
                            "arptab_set: proxy entry exists for non 802 device");
                        return(1);
                }
                sin_m.sin_other = SIN_PROXY;
                export_only = 1;
                goto tryagain;
        }
overwrite:
        if (sdl->sdl_family != AF_LINK) {
                syslog(LOG_ERR,
                    "arptab_set: cannot intuit interface index and type for %s",
                    inet_ntoa(sin->sin_addr));
                return (1);
        }
        sdl_m.sdl_type = sdl->sdl_type;
        sdl_m.sdl_index = sdl->sdl_index;
        rt = rtmsg(RTM_ADD);
        return (rt);
}

int
rtmsg(int cmd)
{
        static int seq;
        struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
        char *cp = m_rtmsg.m_space;
        int l;

retry:
        errno = 0;
        if (cmd == RTM_DELETE)
                goto doit;
        memset((char *)&m_rtmsg, 0, sizeof(m_rtmsg));
        rtm->rtm_flags = flags;
        rtm->rtm_version = RTM_VERSION;

        switch (cmd) {
        default:
                syslog(LOG_ERR, "arptab_set: internal wrong cmd");
                exit(1);
        case RTM_ADD:
                rtm->rtm_addrs |= RTA_GATEWAY;
                rtm->rtm_rmx.rmx_expire = expire_time;
                rtm->rtm_inits = RTV_EXPIRE;
                rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
                sin_m.sin_other = 0;
                if (doing_proxy) {
                        if (export_only)
                                sin_m.sin_other = SIN_PROXY;
                        else {
                                rtm->rtm_addrs |= RTA_NETMASK;
                                rtm->rtm_flags &= ~RTF_HOST;
                        }
                }
                /* FALLTHROUGH */
        case RTM_GET:
                rtm->rtm_addrs |= (RTA_DST | RTA_IFP);
        }
#define NEXTADDR(w, s) \
        if (rtm->rtm_addrs & (w)) { \
                memcpy(cp, (char *)&s, sizeof(s)); \
                cp += sizeof(s); \
        }

        NEXTADDR(RTA_DST, sin_m);
        NEXTADDR(RTA_GATEWAY, sdl_m);
        NEXTADDR(RTA_NETMASK, so_mask);
        NEXTADDR(RTA_IFP, ifp_m);

        rtm->rtm_msglen = cp - (char *)&m_rtmsg;
doit:
        l = rtm->rtm_msglen;
        rtm->rtm_seq = ++seq;
        rtm->rtm_type = cmd;
        if (write(s, (char *)&m_rtmsg, l) == -1) {
                if (errno != ESRCH && errno != EEXIST) {
                        syslog(LOG_ERR, "writing to routing socket: %m");
                        return (-1);
                }
        }
        do {
                l = recv(s, (char *)&m_rtmsg, sizeof(m_rtmsg), MSG_DONTWAIT);
        } while (l > 0 && (rtm->rtm_version != RTM_VERSION ||
            rtm->rtm_seq != seq || rtm->rtm_pid != pid));
        if (l == -1) {
                if (errno == EAGAIN || errno == EINTR)
                        goto retry;
                syslog(LOG_ERR, "arptab_set: read from routing socket: %m");
        }
        return (0);
}

int
rtget(struct sockaddr_inarp **sinp, struct sockaddr_dl **sdlp)
{
        struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
        struct sockaddr_inarp *sin = NULL;
        struct sockaddr_dl *sdl = NULL;
        struct sockaddr *sa;
        char *cp;
        unsigned int i;

        if (rtmsg(RTM_GET) < 0)
                return (1);

        if (rtm->rtm_addrs) {
                cp = ((char *)rtm + rtm->rtm_hdrlen);
                for (i = 1; i; i <<= 1) {
                        if (i & rtm->rtm_addrs) {
                                sa = (struct sockaddr *)cp;
                                switch (i) {
                                case RTA_DST:
                                        sin = (struct sockaddr_inarp *)sa;
                                        break;
                                case RTA_IFP:
                                        sdl = (struct sockaddr_dl *)sa;
                                        break;
                                default:
                                        break;
                                }
                                cp += ROUNDUP(sa->sa_len);
                        }
                }
        }

        if (sin == NULL || sdl == NULL)
                return (1);

        *sinp = sin;
        *sdlp = sdl;

        return (0);
}