/*
 * Copy me if you can.
 * by 20h
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <poll.h>
#include <ctype.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <libgen.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <linux/types.h>
#include <linux/netlink.h>

#include "arg.h"
#include "log.h"

pid_t
spawn_handler(int fd, char **argv)
{
	pid_t pid = fork();

	if (pid < 0)
		edie("fork");

	if (pid == 0) {
		dup2(fd, 0);
		execv(argv[0], argv);
		edie("execl");
	}
	return pid;
}

void
sighandler(int sig)
{
	switch(sig) {
	case SIGHUP:
	case SIGINT:
	case SIGQUIT:
	case SIGABRT:
	case SIGTERM:
		exit(0);
		break;
	default:
		break;
	}
}

void
initsignals(void)
{
	signal(SIGHUP, sighandler);
	signal(SIGINT, sighandler);
	signal(SIGQUIT, sighandler);
	signal(SIGABRT, sighandler);
	signal(SIGTERM, sighandler);

	signal(SIGCHLD, SIG_IGN);
	signal(SIGPIPE, SIG_IGN);
}

int
init_netlink_socket(void)
{
	struct sockaddr_nl nls;
	int fd, slen;

	memset(&nls, 0, sizeof(nls));
	nls.nl_family = AF_NETLINK;
	nls.nl_pid = getpid();
	nls.nl_groups = -1;

	fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
	if (fd < 0)
		edie("socket");

	slen = 64*1024;
	if (setsockopt(fd, SOL_SOCKET, SO_RCVBUFFORCE, &slen,
				sizeof(slen)) < 0) {
		edie("setsockopt");
	}
	slen = 1;
	if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &slen,
				sizeof(slen)) < 0) {
		edie("setsockopt");
	}

	if (bind(fd, (void *)&nls, sizeof(nls)))
		edie("bind");

	fcntl(fd, F_SETFD, FD_CLOEXEC);
	return fd;
}

void
usage(void)
{
	die("usage: %s runpath [...]\n", argv0);
}

int
main(int argc, char *argv[])
{
	struct pollfd fds;

	ARGBEGIN {
	default:
		usage();
	} ARGEND;

	fds.events = POLLIN;
	fds.fd = init_netlink_socket();

	initsignals();

	while (poll(&fds, 1, -1) > -1) {
		if (fds.revents & POLLIN) {
			int status;
			pid_t childpid = spawn_handler(fds.fd, argv);
			waitpid(childpid, &status, 0);
		}
	}

	return 0;
}