#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <sys/wait.h>

#include <err.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define TEST_FILENAME   "/tmp/passdesc"

static int      test_buflen;
static void     *test_buf;

static void
test_send_desc(int s, int fd)
{
        struct msghdr msg;
        struct iovec iov;
        union {
                struct cmsghdr cm;
                uint8_t data[CMSG_SPACE(sizeof(int))];
        } ctrl;
        struct cmsghdr *cm;
        int n;

        iov.iov_base = test_buf;
        iov.iov_len = test_buflen;

        memset(&msg, 0, sizeof(msg));
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        msg.msg_control = ctrl.data;
        msg.msg_controllen = sizeof(ctrl.data);

        memset(&ctrl, 0, sizeof(ctrl));
        cm = CMSG_FIRSTHDR(&msg);
        cm->cmsg_len = CMSG_LEN(sizeof(int));
        cm->cmsg_level = SOL_SOCKET;
        cm->cmsg_type = SCM_RIGHTS;
        *((int *)CMSG_DATA(cm)) = fd;

        n = sendmsg(s, &msg, 0);
        if (n < 0)
                err(1, "sendmsg failed");
        else if (n != test_buflen)
                errx(1, "sendmsg sent %d", n);
        close(fd);
}

static void
test_recv_desc(int s)
{
        struct msghdr msg;
        struct iovec iov;
        union {
                struct cmsghdr cm;
                uint8_t data[CMSG_SPACE(sizeof(int))];
        } ctrl;
        struct cmsghdr *cm;
        int n, fd;
        char data[16];

        iov.iov_base = test_buf;
        iov.iov_len = test_buflen;

        memset(&msg, 0, sizeof(msg));
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        msg.msg_control = ctrl.data;
        msg.msg_controllen = sizeof(ctrl.data);

        n = recvmsg(s, &msg, MSG_WAITALL);
        if (n < 0)
                err(1, "recvmsg failed");
        else if (n != test_buflen)
                errx(1, "recvmsg received %d", n);

        cm = CMSG_FIRSTHDR(&msg);
        if (cm == NULL)
                errx(1, "no cmsg");
        if (cm->cmsg_len != CMSG_LEN(sizeof(int)))
                errx(1, "cmsg len mismatch");
        if (cm->cmsg_level != SOL_SOCKET)
                errx(1, "cmsg level mismatch");
        if (cm->cmsg_type != SCM_RIGHTS)
                errx(1, "cmsg type mismatch");

        fd = *((int *)CMSG_DATA(cm));

        n = read(fd, data, sizeof(data) - 1);
        if (n < 0)
                err(1, "read failed");
        data[n] = '\0';

        fprintf(stderr, "fd content: %s\n", data);
}

static void
usage(const char *cmd)
{
        fprintf(stderr, "%s [-d] [-s] [-p payload_len]\n", cmd);
        exit(1);
}

int
main(int argc, char *argv[])
{
        int s[2], fd, status, n, discard, skipfd;
        int opt;
        off_t ofs;

        discard = 0;
        skipfd = 0;
        while ((opt = getopt(argc, argv, "dp:s")) != -1) {
                switch (opt) {
                case 'd':
                        discard = 1;
                        break;

                case 'p':
                        test_buflen = strtoul(optarg, NULL, 10);
                        break;

                case 's':
                        skipfd = 1;
                        break;

                default:
                        usage(argv[0]);
                }
        }

        if (test_buflen <= 0)
                test_buflen = sizeof(int);
        test_buf = malloc(test_buflen);
        if (test_buf == NULL)
                err(1, "malloc %d failed", test_buflen);

        if (socketpair(AF_LOCAL, SOCK_STREAM, 0, s) < 0)
                err(1, "socketpair(LOCAL, STREAM) failed");

        if (fork() == 0) {
                close(s[0]);
                if (!discard && !skipfd) {
                        test_recv_desc(s[1]);
                } else if (skipfd) {
                        int buf;

                        fprintf(stderr, "skipfd\n");
                        n = read(s[1], &buf, sizeof(buf));
                        if (n < 0)
                                err(1, "read failed");
                } else {
                        fprintf(stderr, "discard msg\n");
                        sleep(5);
                }
                exit(0);
        }
        close(s[1]);

        fd = open(TEST_FILENAME, O_RDWR | O_TRUNC | O_CREAT,
            S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
        if (fd < 0)
                err(1, "open " TEST_FILENAME " failed");

        n = write(fd, TEST_FILENAME, strlen(TEST_FILENAME));
        if (n < 0)
                err(1, "write failed");
        else if (n != strlen(TEST_FILENAME))
                errx(1, "write %d", n);

        ofs = lseek(fd, 0, SEEK_SET);
        if (ofs < 0)
                err(1, "lseek failed");
        else if (ofs != 0)
                errx(1, "lseek offset %jd", (intmax_t)ofs);

        test_send_desc(s[0], fd);

        wait(&status);
        exit(0);
}