blob: 428fd6d623f056627898e5e9ba6e484f0cf95710 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* Example only. Do not run in production.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
struct entry {
uint8_t pubkey[32];
uint32_t ip;
uint16_t port;
};
enum { MAX_ENTRIES = 65536, PORT = 49918 };
static struct entry entries[MAX_ENTRIES];
static unsigned int next_entry;
/* XX: this should use a hash table */
static struct entry *find_entry(uint8_t key[32])
{
int i;
for (i = 0; i < MAX_ENTRIES; ++i) {
if (!memcmp(entries[i].pubkey, key, 32))
return &entries[i];
}
return NULL;
}
/* XX: this is obviously vulnerable to DoS */
static struct entry *find_or_insert_entry(uint8_t key[32])
{
struct entry *entry = find_entry(key);
if (!entry) {
entry = &entries[next_entry++ % MAX_ENTRIES];
memcpy(entry->pubkey, key, 32);
}
return entry;
}
int main(int argc, char *argv[])
{
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_addr = { .s_addr = htonl(INADDR_ANY) },
.sin_port = htons(PORT)
};
struct {
uint8_t my_pubkey[32];
uint8_t their_pubkey[32];
} __attribute__((packed)) packet;
struct {
uint32_t ip;
uint16_t port;
} __attribute__((packed)) reply;
struct entry *entry;
socklen_t len;
ssize_t retlen;
int optval;
int sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
perror("socket");
return errno;
}
optval = 1;
if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
perror("setsockopt");
return errno;
}
if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("bind");
return errno;
}
for (;;) {
len = sizeof(addr);
if (recvfrom(sock, &packet, sizeof(packet), 0, (struct sockaddr *)&addr, &len) != sizeof(packet)) {
perror("recvfrom");
continue;
}
entry = find_or_insert_entry(packet.my_pubkey);
entry->ip = addr.sin_addr.s_addr;
entry->port = addr.sin_port;
entry = find_entry(packet.their_pubkey);
if (entry) {
reply.ip = entry->ip;
reply.port = entry->port;
if (sendto(sock, &reply, sizeof(reply), 0, (struct sockaddr *)&addr, len) < 0) {
perror("sendto");
continue;
}
} else {
if (sendto(sock, NULL, 0, 0, (struct sockaddr *)&addr, len) < 0) {
perror("sendto");
continue;
}
}
}
close(sock);
return 0;
}