path: root/vsockserver-socketbinder.c

// SPDX-License-Identifier: GPL-2.0-or-later
// SPDX-FileCopyrightText: 2020-2021 Alyssa Ross <hi@alyssa.is>

#define _GNU_SOURCE

#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
#include <sys/socket.h>
#include <sysexits.h>
#include <unistd.h>

#include <linux/vm_sockets.h>

#include "log.h"
#include "num.h"
#include "vsock.h"

static const int LISTEN_BACKLOG = 40;

noreturn static void ex_usage(void)
{
	if (verbosity)
		fprintf(stderr, "Usage: %s cid port prog...\n",
		        program_invocation_short_name);
	exit(EX_USAGE);
}

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

	// A skeleton of an option parser to reject any options that
	// are given, so we can add options in the future without
	// worrying about breaking backwards compatibility because
	// they were previously interpreted as a first argument.
	while ((opt = getopt(argc, argv, "+")) != -1) {
		switch (opt) {
		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();

	// Parse the `cid' argument.
	if (!strcmp(argv[optind], "-1"))
		cid = VMADDR_CID_ANY;
	else if (getu32(argv[optind], 0, UINT32_MAX, &cid))
		ex_usage();
	optind++;

	// Parse the `port' argument.
	if (!strcmp(argv[optind], "-1"))
		port = VMADDR_PORT_ANY;
	else if (getu32(argv[optind], 0, UINT32_MAX, &port))
		ex_usage();
	optind++;

	// Set up the socket.
	fd = socket(AF_VSOCK, SOCK_STREAM, 0);
	if (fd == -1)
		diee(EX_OSERR, "socket");
	if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1)
		diee(EX_OSERR, "fcntl");
	if (vsock_bind(fd, cid, port) == -1)
		diee(EX_OSERR, "bind");
	if (listen(fd, LISTEN_BACKLOG) == -1)
		diee(EX_OSERR, "listen");

	// Place the socket at stdout.
	if (dup2(fd, STDIN_FILENO) == -1)
		diee(EX_OSERR, "dup2");
	if (fd != STDIN_FILENO)
		close(fd);

	// Finally, exec into `prog'.
	execvp(argv[optind], &argv[optind]);
	diee(EX_OSERR, "execvp");
}