/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2020 Netflix, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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/types.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/uio.h>

#include <netinet/in.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static char buf[1024*1024];
ssize_t readlen;
static volatile bool read_done = false;

static int
tcp_socketpair(int *sv)
{
        struct sockaddr_in sin = {
                .sin_len = sizeof(struct sockaddr_in),
                .sin_family = AF_INET,
                .sin_addr.s_addr = htonl(INADDR_LOOPBACK),
        };
        int flags;
        int ls;

        ls = socket(PF_INET, SOCK_STREAM, 0);
        if (ls < 0)
                err(1, "socket ls");

        if (setsockopt(ls, SOL_SOCKET, SO_REUSEADDR, &(socklen_t){1},
            sizeof(int)) < 0)
                err(1, "SO_REUSEADDR");

        if (bind(ls, (struct sockaddr *)&sin, sizeof(sin)) < 0)
                err(1, "bind ls");

        if (getsockname(ls, (struct sockaddr *)&sin,
            &(socklen_t){ sizeof(sin) }) < 0)
                err(1, "getsockname");

        if (listen(ls, 5) < 0)
                err(1, "listen ls");

        sv[0] = socket(PF_INET, SOCK_STREAM, 0);
        if (sv[0] < 0)
                err(1, "socket cs");

        flags = fcntl(sv[0], F_GETFL);
        flags |= O_NONBLOCK;
        if (fcntl(sv[0], F_SETFL, flags) == -1)
                err(1, "fcntl +O_NONBLOCK");

        if (connect(sv[0], (void *)&sin, sizeof(sin)) == -1 &&
            errno != EINPROGRESS)
                err(1, "connect cs");

        sv[1] = accept(ls, NULL, 0);
        if (sv[1] < 0)
                err(1, "accept ls");

        flags &= ~O_NONBLOCK;
        if (fcntl(sv[0], F_SETFL, flags) == -1)
                err(1, "fcntl -O_NONBLOCK");

        close(ls);

        return (0);
}

static void *
receiver(void *arg)
{
        int s = *(int *)arg;
        ssize_t rv;

        do {
                rv = read(s, buf, sizeof(buf));
                if (rv == -1)
                        err(2, "read receiver");
                if (rv == 0)
                        break;
                readlen -= rv;
        } while (readlen != 0);

        read_done = true;

        return NULL;
}

static void
usage(void)
{
        errx(1, "usage: %s [-u] <file> <start> <len> <flags>", getprogname());
}

int
main(int argc, char **argv)
{
        pthread_t pt;
        off_t start;
        int ch, fd, ss[2], flags, error;
        bool pf_unix = false;

        while ((ch = getopt(argc, argv, "u")) != -1)
                switch (ch) {
                case 'u':
                        pf_unix = true;
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc != 4)
                usage();

        start = strtoull(argv[1], NULL, 0);
        readlen = strtoull(argv[2], NULL, 0);
        flags = strtoul(argv[3], NULL, 0);

        fd = open(argv[0], O_RDONLY);
        if (fd < 0)
                err(1, "open");

        if (pf_unix) {
                if (socketpair(PF_LOCAL, SOCK_STREAM, 0, ss) != 0)
                        err(1, "socketpair");
        } else
                tcp_socketpair(ss);

        error = pthread_create(&pt, NULL, receiver, &ss[1]);
        if (error)
                errc(1, error, "pthread_create");

        if (sendfile(fd, ss[0], start, readlen, NULL, NULL, flags) < 0)
                err(3, "sendfile");

        while (!read_done)
                usleep(1000);

        exit(0);
}