116 lines
2.4 KiB
C
116 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0
|
|
*
|
|
* Copyright (C) 2015-2018 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;
|
|
}
|