#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdbool.h>

#define PIPE_RD 0
#define PIPE_WR 1

int
main(int argc, char **argv) {
	int sfd;
	struct sockaddr_in addr;
	socklen_t addrsz = sizeof(addr);
	int pfd[2];
	int r;
	int cfd;
	int zfd;
	size_t total = 0;

	if (argc != 3) {
		fprintf(stderr, "Usage: %s <addr> <port>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	sfd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
	if (sfd < 0) {
		perror("socket");
		exit(EXIT_FAILURE);
	}

	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(atoi(argv[2]));
	addr.sin_addr.s_addr = inet_addr(argv[1]);

	int enable = 1;
	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable)) < 0) {
		perror("setsockopt");
		exit(EXIT_FAILURE);
	}

	r = bind(sfd, (struct sockaddr *)&addr, sizeof(addr));
	if (r < 0) {
		perror("bind");
		exit(EXIT_FAILURE);
	}

	r = listen(sfd, 100);
	if (r < 0) {
		perror("listen");
		exit(EXIT_FAILURE);
	}

	cfd = accept4(sfd, (struct sockaddr *)&addr, &addrsz, SOCK_CLOEXEC);
	if (cfd < 0) {
		perror("accept");
		exit(EXIT_FAILURE);
	}

	zfd = open("/dev/null", O_WRONLY | O_CLOEXEC);
	if (zfd < 0) {
		perror("open");
		exit(EXIT_FAILURE);
	}

	if (pipe2(pfd, O_CLOEXEC) < 0) {
		perror("pipe2");
		exit(EXIT_FAILURE);
	}

	while (true) {
		ssize_t r, w;

		r = splice(cfd, NULL, pfd[PIPE_WR], NULL, 64 * 1024, SPLICE_F_MOVE);
		if (r < 0)
			perror("splice");
		//fprintf(stderr, "Read %zi bytes from socket\n", r);
		if (r == 0)
			break;
		w = splice(pfd[PIPE_RD], NULL, zfd, NULL, r, SPLICE_F_MOVE);
		if (w < 0)
			perror("splice");
		if (w != r) {
			fprintf(stderr, "Losing bytes\n");
			exit(EXIT_FAILURE);
		}
		//fprintf(stderr, "Wrote %zi bytes to /dev/null\n", r);

		total += w;
	}

	printf("Server: received %zu bytes\n", total);
}