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 <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, ...) ({						\
			int __save = errno;				\
			fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
				__FILE__, __LINE__, clean_errno(),	\
				##__VA_ARGS__);				\
			errno = __save;					\
})

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,
};

static int settimeo(int fd, int timeout_ms)
{
	struct timeval timeout = { .tv_sec = 3 };

	if (timeout_ms > 0) {
		timeout.tv_sec = timeout_ms / 1000;
		timeout.tv_usec = (timeout_ms % 1000) * 1000;
	}

	if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeout,
		       sizeof(timeout))) {
		log_err("Failed to set SO_RCVTIMEO");
		return -1;
	}

	if (setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeout,
		       sizeof(timeout))) {
		log_err("Failed to set SO_SNDTIMEO");
		return -1;
	}

	return 0;
}

#define save_errno_close(fd) ({ int __save = errno; close(fd); errno = __save; })

int start_server(int family, int type, const char *addr_str, __u16 port,
		 int timeout_ms)
{
	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);
		if (addr_str &&
		    inet_pton(AF_INET, addr_str, &sin->sin_addr) != 1) {
			log_err("inet_pton(AF_INET, %s)", addr_str);
			return -1;
		}
		len = sizeof(*sin);
	} else {
		struct sockaddr_in6 *sin6 = (void *)&addr;

		sin6->sin6_family = AF_INET6;
		sin6->sin6_port = htons(port);
		if (addr_str &&
		    inet_pton(AF_INET6, addr_str, &sin6->sin6_addr) != 1) {
			log_err("inet_pton(AF_INET6, %s)", addr_str);
			return -1;
		}
		len = sizeof(*sin6);
	}

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

	if (settimeo(fd, timeout_ms))
		goto error_close;

	if (bind(fd, (const struct sockaddr *)&addr, len) < 0) {
		log_err("Failed to bind socket");
		goto error_close;
	}

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

	return fd;

error_close:
	save_errno_close(fd);
	return -1;
}

static int connect_fd_to_addr(int fd,
			      const struct sockaddr_storage *addr,
			      socklen_t addrlen)
{
	if (connect(fd, (const struct sockaddr *)addr, addrlen)) {
		log_err("Failed to connect to server");
		return -1;
	}

	return 0;
}

int connect_to_fd(int server_fd, int timeout_ms)
{
	struct sockaddr_storage addr;
	struct sockaddr_in *addr_in;
	socklen_t addrlen, optlen;
	int fd, type;

	optlen = sizeof(type);
	if (getsockopt(server_fd, SOL_SOCKET, SO_TYPE, &type, &optlen)) {
		log_err("getsockopt(SOL_TYPE)");
		return -1;
	}

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

	addr_in = (struct sockaddr_in *)&addr;
	fd = socket(addr_in->sin_family, type, 0);
	if (fd < 0) {
		log_err("Failed to create client socket");
		return -1;
	}

	if (settimeo(fd, timeout_ms))
		goto error_close;

	if (connect_fd_to_addr(fd, &addr, addrlen))
		goto error_close;

	return fd;

error_close:
	save_errno_close(fd);
	return -1;
}

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

	if (settimeo(client_fd, timeout_ms))
		return -1;

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

	if (connect_fd_to_addr(client_fd, &addr, len))
		return -1;

	return 0;
}