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transmission/third-party/dht/dht-example.c

329 lines
8.3 KiB
C

/* This example code was written by Juliusz Chroboczek.
You are free to cut'n'paste from it to your heart's content. */
/* For crypt */
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <sys/signal.h>
#include "dht.h"
#define MAX_BOOTSTRAP_NODES 20
static struct sockaddr_in bootstrap_nodes[MAX_BOOTSTRAP_NODES];
static int num_bootstrap_nodes = 0;
static volatile sig_atomic_t dumping = 0, searching = 0, exiting = 0;
static void
sigdump(int signo)
{
dumping = 1;
}
static void
sigtest(int signo)
{
searching = 1;
}
static void
sigexit(int signo)
{
exiting = 1;
}
static void
init_signals(void)
{
struct sigaction sa;
sigset_t ss;
sigemptyset(&ss);
sa.sa_handler = sigdump;
sa.sa_mask = ss;
sa.sa_flags = 0;
sigaction(SIGUSR1, &sa, NULL);
sigemptyset(&ss);
sa.sa_handler = sigtest;
sa.sa_mask = ss;
sa.sa_flags = 0;
sigaction(SIGUSR2, &sa, NULL);
sigemptyset(&ss);
sa.sa_handler = sigexit;
sa.sa_mask = ss;
sa.sa_flags = 0;
sigaction(SIGINT, &sa, NULL);
}
const unsigned char hash[20] = {
0x54, 0x57, 0x87, 0x89, 0xdf, 0xc4, 0x23, 0xee, 0xf6, 0x03,
0x1f, 0x81, 0x94, 0xa9, 0x3a, 0x16, 0x98, 0x8b, 0x72, 0x7b
};
/* The call-back function is called by the DHT whenever something
interesting happens. Right now, it only happens when we get a new value or
when a search completes, but this may be extended in future versions. */
static void
callback(void *closure,
int event,
unsigned char *info_hash,
void *data, size_t data_len)
{
if(event == DHT_EVENT_SEARCH_DONE)
printf("Search done.\n");
else if(event == DHT_EVENT_VALUES)
printf("Received %d values.\n", (int)(data_len / 6));
}
int
main(int argc, char **argv)
{
int i, rc, fd;
int s, port;
int have_id = 0;
unsigned char myid[20];
time_t tosleep = 0;
/* Ids need to be distributed evenly, so you cannot just use your
bittorrent id. Either generate it randomly, or take the SHA-1 of
something. */
fd = open("dht-example.id", O_RDONLY);
if(fd >= 0) {
rc = read(fd, myid, 20);
if(rc == 20)
have_id = 1;
close(fd);
}
if(!have_id) {
fd = open("/dev/urandom", O_RDONLY);
if(fd < 0) {
perror("open(random)");
exit(1);
}
rc = read(fd, myid, 20);
if(rc < 0) {
perror("read(random)");
exit(1);
}
have_id = 1;
close(fd);
fd = open("dht-example.id", O_WRONLY | O_CREAT | O_TRUNC, 0666);
if(fd >= 0) {
rc = write(fd, myid, 20);
if(rc < 20)
unlink("dht-example.id");
close(fd);
}
}
if(argc < 2)
goto usage;
i = 1;
if(argc < i + 1)
goto usage;
port = atoi(argv[i++]);
if(port <= 0 || port >= 0x10000)
goto usage;
while(i < argc) {
struct addrinfo hints, *info, *infop;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_DGRAM;
rc = getaddrinfo(argv[i], NULL, &hints, &info);
if(rc != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
exit(1);
}
i++;
infop = info;
while(infop) {
if(infop->ai_addr->sa_family == AF_INET) {
struct sockaddr_in sin;
memcpy(&sin, infop->ai_addr, infop->ai_addrlen);
sin.sin_port = htons(atoi(argv[i]));
bootstrap_nodes[num_bootstrap_nodes] = sin;
num_bootstrap_nodes++;
}
infop = infop->ai_next;
}
freeaddrinfo(info);
i++;
}
if(i < argc)
goto usage;
/* If you set dht_debug to a stream, every action taken by the DHT will
be logged. */
dht_debug = stdout;
/* We need an IPv4 socket, bound to a stable port. Rumour has it that
uTorrent works better when it is the same as your Bittorrent port. */
s = socket(PF_INET, SOCK_DGRAM, 0);
if(s < 0) {
perror("socket");
exit(1);
}
{
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(port);
rc = bind(s, (struct sockaddr*)&sin, sizeof(sin));
if(rc < 0) {
perror("bind");
exit(1);
}
}
/* Init the dht. This sets the socket into non-blocking mode. */
rc = dht_init(s, myid);
if(rc < 0) {
perror("dht_init");
exit(1);
}
init_signals();
/* For bootstrapping, we need an initial list of nodes. This could be
hard-wired, but can also be obtained from the nodes key of a torrent
file, or from the PORT bittorrent message.
Dht_ping_node is the brutal way of bootstrapping -- it actually
sends a message to the peer. If you're going to bootstrap from
a massive number of nodes (for example because you're restoring from
a dump) and you already know their ids, it's better to use
dht_insert_node. If the ids are incorrect, the DHT will recover. */
for(i = 0; i < num_bootstrap_nodes; i++) {
dht_ping_node(s, &bootstrap_nodes[i]);
usleep(random() % 100000);
}
while(1) {
struct timeval tv;
fd_set readfds;
tv.tv_sec = tosleep;
tv.tv_usec = random() % 1000000;
FD_ZERO(&readfds);
FD_SET(s, &readfds);
rc = select(s + 1, &readfds, NULL, NULL, &tv);
if(rc < 0) {
if(errno != EINTR) {
perror("select");
sleep(1);
}
}
if(exiting)
break;
rc = dht_periodic(s, rc > 0, &tosleep, callback, NULL);
if(rc < 0) {
if(errno == EINTR) {
continue;
} else {
perror("dht_periodic");
if(rc == EINVAL || rc == EFAULT)
abort();
tosleep = 1;
}
}
/* This is how you trigger a search for a torrent hash. If port
(the third argument) is non-zero, it also performs an announce.
Since peers expire announced data after 30 minutes, it's a good
idea to reannounce every 28 minutes or so. */
if(searching) {
dht_search(s, hash, 0, callback, NULL);
searching = 0;
}
/* For debugging, or idle curiosity. */
if(dumping) {
dht_dump_tables(stdout);
dumping = 0;
}
}
{
struct sockaddr_in sins[500];
int i;
i = dht_get_nodes(sins, 500);
printf("Found %d good nodes.\n", i);
}
dht_uninit(s, 1);
return 0;
usage:
fprintf(stderr, "Foo!\n");
exit(1);
}
/* We need to provide a reasonably strong cryptographic hashing function.
Here's how we'd do it if we had RSA's MD5 code. */
#if 0
void
dht_hash(void *hash_return, int hash_size,
const void *v1, int len1,
const void *v2, int len2,
const void *v3, int len3)
{
static MD5_CTX ctx;
MD5Init(&ctx);
MD5Update(&ctx, v1, len1);
MD5Update(&ctx, v2, len2);
MD5Update(&ctx, v3, len3);
MD5Final(&ctx);
if(hash_size > 16)
memset((char*)hash_return + 16, 0, hash_size - 16);
memcpy(hash_return, ctx.digest, hash_size > 16 ? 16 : hash_size);
}
#else
/* But for this example, we might as well use something weaker. */
void
dht_hash(void *hash_return, int hash_size,
const void *v1, int len1,
const void *v2, int len2,
const void *v3, int len3)
{
const char *c1 = v1, *c2 = v2, *c3 = v3;
char key[9]; /* crypt is limited to 8 characters */
int i;
memset(key, 0, 9);
#define CRYPT_HAPPY(c) ((c % 0x60) + 0x20)
for(i = 0; i < 2 && i < len1; i++)
key[i] = CRYPT_HAPPY(c1[i]);
for(i = 0; i < 4 && i < len1; i++)
key[2 + i] = CRYPT_HAPPY(c2[i]);
for(i = 0; i < 2 && i < len1; i++)
key[6 + i] = CRYPT_HAPPY(c3[i]);
strncpy(hash_return, crypt(key, "jc"), hash_size);
}
#endif