// SPDX-License-Identifier: GPL-2.0-or-later
// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>

#define _GNU_SOURCE

#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>
#include <sys/socket.h>

#include <linux/vm_sockets.h>

#include "env.h"
#include "log.h"
#include "util.h"
#include "vsock.h"

static void ex_usage(void) __attribute__((noreturn));
static void ex_usage(void)
{
	if (verbosity)
		fprintf(stderr, "Usage: %s [ -q | -Q | -v ] cid port prog...\n",
			program_invocation_short_name);
	exit(EX_USAGE);
}

int main(int argc, char *argv[])
{
	int opt, fd;
	uint32_t rcid, rport;

	while ((opt = getopt(argc, argv, "+qQv")) != -1) {
		switch (opt) {
		case 'q':
			verbosity = nothing;
			break;
		case 'Q':
			verbosity = errors;
			break;
		case 'v':
			verbosity = all;
			break;
		default:
			ex_usage();
		}
	}

	// Check there are enough positional arguments (two for the
	// address and at least one to exec into).
	if (optind > argc - 3)
		ex_usage();

	if (getu32(argv[optind++], 0, UINT32_MAX, &rcid))
		ex_usage();
	if (getu32(argv[optind++], 0, UINT32_MAX, &rport))
		ex_usage();

	setenvf("VSOCKREMOTECID", 1, "%" PRIu32, rcid);
	setenvf("VSOCKREMOTEPORT", 1, "%" PRIu32, rport);

	ilog("connecting to %" PRIu32 ":%" PRIu32 "...", rcid, rport);

	// Linux will sometimes randomly time out connections, even on
	// the same host with no backlog, so retry a few times.
	{
		int i = 0;
		do fd = vsock_open(rcid, rport);
		while (i++ < 3 && fd == -1 && errno == ETIMEDOUT);
	}
	if (fd == -1)
		diee(EX_UNAVAILABLE,
		     "connect to %" PRIu32 ":%" PRIu32 " failed", rcid, rport);
	ilog("connected to %" PRIu32 ":%" PRIu32 "!", rcid, rport);

	// Set up the file descriptors to the well-known UCSPI numbers.
	if (dup2(fd, 6) == -1)
		diee(EX_OSERR, "dup2");
	if (dup2(fd, 7) == -1)
		diee(EX_OSERR, "dup2");
	if (fd != 6 && fd != 7)
		close(fd);

	execvp(argv[optind], &argv[optind]);
	diee(EX_OSERR, "exec");
}