network_helpers.c

// SPDX-License-Identifier: GPL-2.0-only
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <arpa/inet.h>

#include <sys/epoll.h>

#include <linux/err.h>
#include <linux/in.h>
#include <linux/in6.h>

#include "bpf_util.h"
#include "network_helpers.h"

#define clean_errno() (errno == 0 ? "None" : strerror(errno))
#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
	__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)

struct ipv4_packet pkt_v4 = {
	.eth.h_proto = __bpf_constant_htons(ETH_P_IP),
	.iph.ihl = 5,
	.iph.protocol = IPPROTO_TCP,
	.iph.tot_len = __bpf_constant_htons(MAGIC_BYTES),
	.tcp.urg_ptr = 123,
	.tcp.doff = 5,
};

struct ipv6_packet pkt_v6 = {
	.eth.h_proto = __bpf_constant_htons(ETH_P_IPV6),
	.iph.nexthdr = IPPROTO_TCP,
	.iph.payload_len = __bpf_constant_htons(MAGIC_BYTES),
	.tcp.urg_ptr = 123,
	.tcp.doff = 5,
};

int start_server_with_port(int family, int type, __u16 port)
{
	struct sockaddr_storage addr = {};
	socklen_t len;
	int fd;

	if (family == AF_INET) {
		struct sockaddr_in *sin = (void *)&addr;

		sin->sin_family = AF_INET;
		sin->sin_port = htons(port);
		len = sizeof(*sin);
	} else {
		struct sockaddr_in6 *sin6 = (void *)&addr;

		sin6->sin6_family = AF_INET6;
		sin6->sin6_port = htons(port);
		len = sizeof(*sin6);
	}

	fd = socket(family, type | SOCK_NONBLOCK, 0);
	if (fd < 0) {
		log_err("Failed to create server socket");
		return -1;
	}

	if (bind(fd, (const struct sockaddr *)&addr, len) < 0) {
		log_err("Failed to bind socket");
		close(fd);
		return -1;
	}

	if (type == SOCK_STREAM) {
		if (listen(fd, 1) < 0) {
			log_err("Failed to listed on socket");
			close(fd);
			return -1;
		}
	}

	return fd;
}

int start_server(int family, int type)
{
	return start_server_with_port(family, type, 0);
}

static const struct timeval timeo_sec = { .tv_sec = 3 };
static const size_t timeo_optlen = sizeof(timeo_sec);

int connect_to_fd(int family, int type, int server_fd)
{
	int fd, save_errno;

	fd = socket(family, type, 0);
	if (fd < 0) {
		log_err("Failed to create client socket");
		return -1;
	}

	if (connect_fd_to_fd(fd, server_fd) < 0 && errno != EINPROGRESS) {
		save_errno = errno;
		close(fd);
		errno = save_errno;
		return -1;
	}

	return fd;
}

int connect_fd_to_fd(int client_fd, int server_fd)
{
	struct sockaddr_storage addr;
	socklen_t len = sizeof(addr);
	int save_errno;

	if (setsockopt(client_fd, SOL_SOCKET, SO_RCVTIMEO, &timeo_sec,
		       timeo_optlen)) {
		log_err("Failed to set SO_RCVTIMEO");
		return -1;
	}

	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
		log_err("Failed to get server addr");
		return -1;
	}

	if (connect(client_fd, (const struct sockaddr *)&addr, len) < 0) {
		if (errno != EINPROGRESS) {
			save_errno = errno;
			log_err("Failed to connect to server");
			errno = save_errno;
		}
		return -1;
	}

	return 0;
}

int connect_wait(int fd)
{
	struct epoll_event ev = {}, events[2];
	int timeout_ms = 1000;
	int efd, nfd;

	efd = epoll_create1(EPOLL_CLOEXEC);
	if (efd < 0) {
		log_err("Failed to open epoll fd");
		return -1;
	}

	ev.events = EPOLLRDHUP | EPOLLOUT;
	ev.data.fd = fd;

	if (epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ev) < 0) {
		log_err("Failed to register fd=%d on epoll fd=%d", fd, efd);
		close(efd);
		return -1;
	}

	nfd = epoll_wait(efd, events, ARRAY_SIZE(events), timeout_ms);
	if (nfd < 0)
		log_err("Failed to wait for I/O event on epoll fd=%d", efd);

	close(efd);
	return nfd;
}