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cae45a4 May 2, 2014
481 lines (409 sloc) 11.9 KB
/* 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_storage 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,
const unsigned char *info_hash,
const 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));
}
static unsigned char buf[4096];
int
main(int argc, char **argv)
{
int i, rc, fd;
int s = -1, s6 = -1, port;
int have_id = 0;
unsigned char myid[20];
time_t tosleep = 0;
char *id_file = "dht-example.id";
int opt;
int quiet = 0, ipv4 = 1, ipv6 = 1;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
struct sockaddr_storage from;
socklen_t fromlen;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
memset(&sin6, 0, sizeof(sin6));
sin6.sin6_family = AF_INET6;
while(1) {
opt = getopt(argc, argv, "q46b:i:");
if(opt < 0)
break;
switch(opt) {
case 'q': quiet = 1; break;
case '4': ipv6 = 0; break;
case '6': ipv4 = 0; break;
case 'b': {
char buf[16];
int rc;
rc = inet_pton(AF_INET, optarg, buf);
if(rc == 1) {
memcpy(&sin.sin_addr, buf, 4);
break;
}
rc = inet_pton(AF_INET6, optarg, buf);
if(rc == 1) {
memcpy(&sin6.sin6_addr, buf, 16);
break;
}
goto usage;
}
break;
case 'i':
id_file = optarg;
break;
default:
goto usage;
}
}
/* 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(id_file, O_RDONLY);
if(fd >= 0) {
rc = read(fd, myid, 20);
if(rc == 20)
have_id = 1;
close(fd);
}
fd = open("/dev/urandom", O_RDONLY);
if(fd < 0) {
perror("open(random)");
exit(1);
}
if(!have_id) {
int ofd;
rc = read(fd, myid, 20);
if(rc < 0) {
perror("read(random)");
exit(1);
}
have_id = 1;
close(fd);
ofd = open(id_file, O_WRONLY | O_CREAT | O_TRUNC, 0666);
if(ofd >= 0) {
rc = write(ofd, myid, 20);
if(rc < 20)
unlink(id_file);
close(ofd);
}
}
{
unsigned seed;
read(fd, &seed, sizeof(seed));
srandom(seed);
}
close(fd);
if(argc < 2)
goto usage;
i = optind;
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_socktype = SOCK_DGRAM;
if(!ipv6)
hints.ai_family = AF_INET;
else if(!ipv4)
hints.ai_family = AF_INET6;
else
hints.ai_family = 0;
rc = getaddrinfo(argv[i], argv[i + 1], &hints, &info);
if(rc != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rc));
exit(1);
}
i++;
if(i >= argc)
goto usage;
infop = info;
while(infop) {
memcpy(&bootstrap_nodes[num_bootstrap_nodes],
infop->ai_addr, infop->ai_addrlen);
infop = infop->ai_next;
num_bootstrap_nodes++;
}
freeaddrinfo(info);
i++;
}
/* If you set dht_debug to a stream, every action taken by the DHT will
be logged. */
if(!quiet)
dht_debug = stdout;
/* We need an IPv4 and an IPv6 socket, bound to a stable port. Rumour
has it that uTorrent works better when it is the same as your
Bittorrent port. */
if(ipv4) {
s = socket(PF_INET, SOCK_DGRAM, 0);
if(s < 0) {
perror("socket(IPv4)");
}
}
if(ipv6) {
s6 = socket(PF_INET6, SOCK_DGRAM, 0);
if(s6 < 0) {
perror("socket(IPv6)");
}
}
if(s < 0 && s6 < 0) {
fprintf(stderr, "Eek!");
exit(1);
}
if(s >= 0) {
sin.sin_port = htons(port);
rc = bind(s, (struct sockaddr*)&sin, sizeof(sin));
if(rc < 0) {
perror("bind(IPv4)");
exit(1);
}
}
if(s6 >= 0) {
int rc;
int val = 1;
rc = setsockopt(s6, IPPROTO_IPV6, IPV6_V6ONLY,
(char *)&val, sizeof(val));
if(rc < 0) {
perror("setsockopt(IPV6_V6ONLY)");
exit(1);
}
/* BEP-32 mandates that we should bind this socket to one of our
global IPv6 addresses. In this simple example, this only
happens if the user used the -b flag. */
sin6.sin6_port = htons(port);
rc = bind(s6, (struct sockaddr*)&sin6, sizeof(sin6));
if(rc < 0) {
perror("bind(IPv6)");
exit(1);
}
}
/* Init the dht. This sets the socket into non-blocking mode. */
rc = dht_init(s, s6, myid, (unsigned char*)"JC\0\0");
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((struct sockaddr*)&bootstrap_nodes[i],
sizeof(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);
if(s >= 0)
FD_SET(s, &readfds);
if(s6 >= 0)
FD_SET(s6, &readfds);
rc = select(s > s6 ? s + 1 : s6 + 1, &readfds, NULL, NULL, &tv);
if(rc < 0) {
if(errno != EINTR) {
perror("select");
sleep(1);
}
}
if(exiting)
break;
if(rc > 0) {
fromlen = sizeof(from);
if(s >= 0 && FD_ISSET(s, &readfds))
rc = recvfrom(s, buf, sizeof(buf) - 1, 0,
(struct sockaddr*)&from, &fromlen);
else if(s6 >= 0 && FD_ISSET(s6, &readfds))
rc = recvfrom(s6, buf, sizeof(buf) - 1, 0,
(struct sockaddr*)&from, &fromlen);
else
abort();
}
if(rc > 0) {
buf[rc] = '\0';
rc = dht_periodic(buf, rc, (struct sockaddr*)&from, fromlen,
&tosleep, callback, NULL);
} else {
rc = dht_periodic(NULL, 0, NULL, 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 second 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) {
if(s >= 0)
dht_search(hash, 0, AF_INET, callback, NULL);
if(s6 >= 0)
dht_search(hash, 0, AF_INET6, callback, NULL);
searching = 0;
}
/* For debugging, or idle curiosity. */
if(dumping) {
dht_dump_tables(stdout);
dumping = 0;
}
}
{
struct sockaddr_in sin[500];
struct sockaddr_in6 sin6[500];
int num = 500, num6 = 500;
int i;
i = dht_get_nodes(sin, &num, sin6, &num6);
printf("Found %d (%d + %d) good nodes.\n", i, num, num6);
}
dht_uninit();
return 0;
usage:
printf("Usage: dht-example [-q] [-4] [-6] [-i filename] [-b address]...\n"
" port [address port]...\n");
exit(1);
}
/* Functions called by the DHT. */
int
dht_blacklisted(const struct sockaddr *sa, int salen)
{
return 0;
}
/* 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
int
dht_random_bytes(void *buf, size_t size)
{
int fd, rc, save;
fd = open("/dev/urandom", O_RDONLY);
if(fd < 0)
return -1;
rc = read(fd, buf, size);
save = errno;
close(fd);
errno = save;
return rc;
}