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