reuseport_rst_test_fork.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <arpa/inet.h>

int
bind_sock()
{
	int fd = socket(AF_INET, SOCK_STREAM, 0);
	if (fd < 0) {
		perror("socket");
		exit(1);
	}

	int val = 1;
	/* SO_REUSEPORT implies SO_REUSEADDR */
	if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val)) < 0) {
		perror("setsockopt");
		exit(1);
	}

	struct sockaddr_in addr;
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_port = htons(12345);
	memset(&addr.sin_zero, 0, sizeof(addr.sin_zero));
	
	if (bind(fd, (void*)&addr, sizeof(addr)) < 0) {
		perror("bind");
		exit(1);
	}

	if (listen(fd, 128) < 0) {
		perror("listen");
		exit(1);
	}

	return fd;
}

int
main() {
	char buf[] = "ACCEPTED\r\n";

	int fd = bind_sock();
	if (fork()) {
		close(fd);
		fd = bind_sock();
		while (1) {
			int cfd = accept(fd, NULL, NULL);
			send(cfd, buf, strlen(buf), MSG_NOSIGNAL);
			close(cfd);
		}
	} else {
		printf("telnet to 127.0.0.1:12345 and press enter:");
		getchar();
	}
}