/*      $OpenBSD: mc6recv.c,v 1.2 2021/07/06 11:50:34 bluhm Exp $       */
/*
 * Copyright (c) 2019 Alexander Bluhm <bluhm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

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

#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>

#include <err.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

void __dead usage(void);
void sigexit(int);

void __dead
usage(void)
{
        fprintf(stderr,
"mc6recv [-f file] [-g group] [-i ifname] [-n timeout] [-p port] [-r timeout]\n"
"    [mc6send ...]\n"
"    -f file         print message to log file, default stdout\n"
"    -g group        multicast group, default 224.0.0.123\n"
"    -i ifname       multicast interface name\n"
"    -n timeout      expect not to receive any message until timeout\n"
"    -p port         destination port number, default 12345\n"
"    -r timeout      receive timeout in seconds\n"
"    mc6send ...      after setting up receive, fork and exec send command\n");
        exit(2);
}

int
main(int argc, char *argv[])
{
        struct sockaddr_in6 sin6;
        struct ipv6_mreq mreq6;
        FILE *log;
        const char *errstr, *file, *group, *ifname;
        char msg[256];
        ssize_t n;
        int ch, s, norecv, port, status;
        unsigned int timeout;
        pid_t pid;

        log = stdout;
        file = NULL;
        group = "ff04::123";
        ifname = "lo0";
        norecv = 0;
        port = 12345;
        timeout = 0;
        while ((ch = getopt(argc, argv, "f:g:i:n:p:r:")) != -1) {
                switch (ch) {
                case 'f':
                        file = optarg;
                        break;
                case 'g':
                        group = optarg;
                        break;
                case 'i':
                        ifname = optarg;
                        break;
                case 'n':
                        norecv = 1;
                        timeout = strtonum(optarg, 1, INT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "no timeout is %s: %s", errstr, optarg);
                        break;
                case 'p':
                        port = strtonum(optarg, 1, 0xffff, &errstr);
                        if (errstr != NULL)
                                errx(1, "port is %s: %s", errstr, optarg);
                        break;
                case 'r':
                        timeout = strtonum(optarg, 1, INT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "timeout is %s: %s", errstr, optarg);
                        break;
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (file != NULL) {
                log = fopen(file, "w");
                if (log == NULL)
                        err(1, "fopen %s", file);
        }

        s = socket(AF_INET6, SOCK_DGRAM, 0);
        if (s == -1)
                err(1, "socket");
        if (inet_pton(AF_INET6, group, &mreq6.ipv6mr_multiaddr) == -1)
                err(1, "inet_pton %s", group);
        mreq6.ipv6mr_interface = if_nametoindex(ifname);
        if (mreq6.ipv6mr_interface == 0)
                err(1, "if_nametoindex %s", ifname);
        if (setsockopt(s, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq6,
            sizeof(mreq6)) == -1)
                err(1, "setsockopt IPV6_JOIN_GROUP %s %s", group, ifname);

        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_len = sizeof(sin6);
        sin6.sin6_family = AF_INET6;
        sin6.sin6_port = htons(port);
        if (inet_pton(AF_INET6, group, &sin6.sin6_addr) == -1)
                err(1, "inet_pton %s", group);
        if (IN6_IS_ADDR_LINKLOCAL(&sin6.sin6_addr) ||
            IN6_IS_ADDR_MC_LINKLOCAL(&sin6.sin6_addr) ||
            IN6_IS_ADDR_MC_INTFACELOCAL(&sin6.sin6_addr)) {
                sin6.sin6_scope_id = mreq6.ipv6mr_interface;
        }
        if (bind(s, (struct sockaddr *)&sin6, sizeof(sin6)) == -1)
                err(1, "bind [%s]:%d", group, port);

        if (argc) {
                pid = fork();
                switch (pid) {
                case -1:
                        err(1, "fork");
                case 0:
                        execvp(argv[0], argv);
                        err(1, "exec %s", argv[0]);
                }
        }
        if (timeout) {
                if (norecv) {
                        if (signal(SIGALRM, sigexit) == SIG_ERR)
                                err(1, "signal SIGALRM");
                }
                alarm(timeout);
        }
        n = recv(s, msg, sizeof(msg) - 1, 0);
        if (n == -1)
                err(1, "recv");
        msg[n] = '\0';
        fprintf(log, "<<< %s\n", msg);
        fflush(log);

        if (norecv)
                errx(1, "received %s", msg);

        if (argc) {
                if (waitpid(pid, &status, 0) == -1)
                        err(1, "waitpid %d", pid);
                if (status)
                        errx(1, "%s %d", argv[0], status);
        }

        return 0;
}

void
sigexit(int sig)
{
        _exit(0);
}