/*      $OpenBSD: rip6cksum.c,v 1.1.1.1 2019/05/09 15:54:31 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 <errno.h>
#include <err.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <netinet/in.h>

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

void __dead usage(void);

void __dead
usage(void)
{
        fprintf(stderr, "rip6cksum [-ehw] [-c ckoff] [-r recvsz] [-s sendsz] "
            "[-- scapy ...]\n"
            "    -c ckoff   set checksum offset within rip header\n"
            "    -e         expect error when setting ckoff\n"
            "    -h         help, show usage\n"
            "    -r recvsz  expected payload size from socket\n"
            "    -s sendsz  send payload of given size to socket\n"
            "    -w         wait for packet on socket, timeout 10 seconds\n"
            "    scapy ...  run scapy program after socket setup\n"
        );
        exit(1);
}

const struct in6_addr loop6 = IN6ADDR_LOOPBACK_INIT;
int
main(int argc, char *argv[])
{
        int s, ch, eflag, cflag, rflag, sflag, wflag;
        int ckoff;
        size_t recvsz, sendsz;
        const char *errstr;
        struct sockaddr_in6 sin6;

        if (setvbuf(stdout, NULL, _IOLBF, 0) != 0)
                err(1, "setvbuf stdout line buffered");

        eflag = cflag = rflag = sflag = wflag = 0;
        while ((ch = getopt(argc, argv, "c:ehr:s:w")) != -1) {
                switch (ch) {
                case 'c':
                        ckoff = strtonum(optarg, INT_MIN, INT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "ckoff is %s: %s", errstr, optarg);
                        cflag = 1;
                        break;
                case 'e':
                        eflag = 1;
                        break;
                case 'r':
                        recvsz = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "recvsz is %s: %s", errstr, optarg);
                        rflag = 1;
                        break;
                case 's':
                        sendsz = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "sendsz is %s: %s", errstr, optarg);
                        sflag = 1;
                        break;
                case 'w':
                        wflag = 1;
                        break;
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        printf("socket inet6 raw 255\n");
        s = socket(AF_INET6, SOCK_RAW, 255);
        if (s == -1)
                err(1, "socket raw");
        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_family = AF_INET6;
        sin6.sin6_addr = loop6;
        printf("bind ::1\n");
        if (bind(s, (struct sockaddr *)&sin6, sizeof(sin6)) == -1)
                err(1, "bind ::1");
        printf("connect ::1\n");
        if (connect(s, (struct sockaddr *)&sin6, sizeof(sin6)) == -1)
                err(1, "connect ::1");

        if (cflag) {
                printf("setsockopt ipv6 checksum %d\n", ckoff);
                if (setsockopt(s, IPPROTO_IPV6, IPV6_CHECKSUM, &ckoff,
                     sizeof(ckoff)) == -1) {
                        if (!eflag)
                                err(1, "setsockopt ckoff");
                        printf("setsockopt failed as expected: %s\n",
                            strerror(errno));
                } else {
                        if (eflag)
                                errx(1, "setsockopt succeeded unexpectedly");
                }
        }

        if (argc) {
                pid_t pid;

                printf("fork child process\n");
                pid = fork();
                if (pid == -1)
                        err(1, "fork");
                if (pid == 0) {
                        /* child */
                        printf("execute %s\n", argv[0]);
                        execvp(argv[0], argv);
                        err(1, "execvp %s", argv[0]);
                }
                printf("child pid %d\n", pid);
        }

        if (wflag) {
                int n;
                ssize_t r;
                size_t rsz;
                fd_set fds;
                struct timeval to;
                char buf[1<<16];

                FD_ZERO(&fds);
                FD_SET(s, &fds);
                to.tv_sec = 10;
                to.tv_usec = 0;
                printf("select socket read\n");
                n = select(s + 1, &fds, NULL, NULL, &to);
                switch (n) {
                case -1:
                        err(1, "select");
                case 0:
                        errx(1, "timeout");
                default:
                        printf("selected %d\n", n);
                }
                printf("recv packet\n");
                r = recv(s, buf, sizeof(buf), 0);
                if (r < 0)
                        err(1, "recv");
                rsz = r;
                printf("received payload size %zd\n", rsz);
                if (rflag) {
                        if (rsz != recvsz)
                                errx(1, "wrong payload size, expected %zu",                                         recvsz);
                }
        }

        if (sflag) {
                size_t i;
                char *buf;

                buf = malloc(sendsz);
                if (buf == NULL)
                        err(1, "malloc sendsz");
                for (i = 0; i < sendsz; i++)
                        buf[i] = i & 0xff;
                printf("send payload of size %zu\n", sendsz);
                if (send(s, buf, sendsz, 0) == -1)
                        err(1, "send");
                free(buf);
        }

        if (argc) {
                int status;

                printf("wait for child\n");
                if (wait(&status) == -1)
                        err(1, "wait");
                if (status != 0)
                        errx(1, "child program %s status %d", argv[0], status);
                printf("child program %s status %d\n", argv[0], status);
        }

        return 0;
}