Add scrape-only UDP tracker
This commit is contained in:
parent
a7ea02282f
commit
c6c9166172
2
Makefile
2
Makefile
@ -1,7 +1,7 @@
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PROG= bt
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NOMAN= noman
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SRCS= bt.c bcode.c
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SRCS= bt.c bcode.c tracker.c util.c
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WARNINGS= Yes
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36
bt.h
36
bt.h
@ -18,6 +18,14 @@
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#include <stdint.h>
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/*
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* CONSTANTS
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*/
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#define BTIH_LEN 20
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/*
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* STRUCTS
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*/
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@ -25,6 +33,18 @@
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struct bcode;
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struct bttc_ctx;
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struct btt_scrape_stats {
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uint32_t seeders;
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uint32_t completed;
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uint32_t leechers;
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};
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struct btih {
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uint8_t hash[BTIH_LEN];
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} __packed;
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/*
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* PROTOTYPES
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@ -36,3 +56,19 @@ struct bcode;
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struct bcode *bcode_parse(const uint8_t *, size_t);
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void bcode_free(struct bcode *);
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void bcode_print(FILE *, const struct bcode *);
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/* Tracker client */
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struct bttc_ctx *bttc_ctx_new(const char *);
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void bttc_ctx_free(struct bttc_ctx *);
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const char *bttc_get_tracker(const struct bttc_ctx *);
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int bttc_announce(struct bttc_ctx *, const uint8_t *,
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const char **);
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int bttc_scrape(struct bttc_ctx *, struct btt_scrape_stats *,
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const struct btih *, size_t, const char **);
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/* Utilities */
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int btih_parse(struct btih *, const char *);
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346
tracker.c
Normal file
346
tracker.c
Normal file
@ -0,0 +1,346 @@
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/*
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* Copyright (c) 2025 Lucas Gabriel Vuotto <lucas@lgv5.net>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <endian.h>
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#include <errno.h>
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#include <inttypes.h>
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#include <netdb.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "bt.h"
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#ifndef nitems
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#define nitems(_a) (sizeof((_a)) / sizeof((_a)[0]))
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#endif
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#define BTTC_UDP_ANNOUNCE_MAGIC UINT64_C(0x41727101980)
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#define BTT_UDP_ACTION_CONNECT 0
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#define BTT_UDP_ACTION_ANNOUNCE 1
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#define BTT_UDP_ACTION_SCRAPE 2
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struct bttc_ctx {
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const char *url;
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char *host;
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char *port;
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int socktype;
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int sock;
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uint64_t cid;
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};
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struct udpc_req_head {
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uint64_t connection_id;
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uint32_t action;
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uint32_t transaction_id;
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} __packed;
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struct udpc_res_head {
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uint32_t action;
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uint32_t transaction_id;
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} __packed;
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struct udpc_connect_req {
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uint64_t protocol_id;
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uint32_t action;
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uint32_t transaction_id;
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} __packed;
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struct udpc_connect_res {
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uint32_t action;
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uint32_t transaction_id;
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uint64_t connection_id;
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} __packed;
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struct udpc_scrape_res {
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uint32_t *seeders;
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uint32_t *completed;
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uint32_t *leechers;
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};
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static int tracker_dial(const char *, const char *, int, const char **);
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static int url_parse(const char *, char **, char **);
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static int udpc_action_connect(int, uint64_t *);
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static int udpc_action_scrape(int, uint64_t, struct btt_scrape_stats *,
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const struct btih *, size_t);
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static int
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tracker_dial(const char *host, const char *port, int socktype,
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const char **cause)
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{
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struct addrinfo hints, *res, *res0;
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int error, save_errno, s;
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*cause = NULL;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = socktype;
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error = getaddrinfo(host, port, &hints, &res0);
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if (error) {
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*cause = gai_strerror(error);
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return -1;
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}
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s = -1;
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for (res = res0; res != NULL; res = res->ai_next) {
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s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
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if (s == -1) {
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*cause = "socket";
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continue;
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}
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if (connect(s, res->ai_addr, res->ai_addrlen) == -1) {
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*cause = "connect";
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save_errno = errno;
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close(s);
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errno = save_errno;
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s = -1;
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continue;
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}
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break;
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}
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return s;
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}
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static int
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url_parse(const char *tracker, char **host, char **port)
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{
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const char *colon, *end;
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size_t hostlen, portlen;
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colon = strchr(tracker, ':');
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if (colon == NULL || colon == tracker)
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return 0;
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hostlen = colon - tracker + 1;
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colon++;
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end = strchr(colon, '/');
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if (end == NULL)
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end = strchr(colon, '\0');
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if (end == colon)
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return 0;
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portlen = end - colon + 1;
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*host = malloc(hostlen);
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*port = malloc(portlen);
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if (*host == NULL || *port == NULL) {
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free(*host);
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free(*port);
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*host = *port = NULL;
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return 0;
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}
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(void)strlcpy(*host, tracker, hostlen);
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(void)strlcpy(*port, colon, portlen);
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/* XXX handle extensions. */
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return 1;
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}
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static int
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udpc_action_connect(int s, uint64_t *cid)
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{
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char buf[512];
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struct udpc_connect_req req;
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struct udpc_connect_res res;
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uint32_t tid;
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tid = arc4random();
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req.protocol_id = htobe64(BTTC_UDP_ANNOUNCE_MAGIC);
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req.action = htobe32(BTT_UDP_ACTION_CONNECT);
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req.transaction_id = htobe32(tid);
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if (send(s, &req, sizeof(req), 0) != sizeof(req))
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return 0;
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if (recv(s, buf, sizeof(buf), 0) < (ssize_t)sizeof(res))
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return 0;
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memcpy(&res, buf, sizeof(res));
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if (be32toh(res.action) != BTT_UDP_ACTION_CONNECT ||
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be32toh(res.transaction_id) != tid)
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return 0;
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*cid = be64toh(res.connection_id);
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return 1;
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}
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static int
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udpc_action_scrape(int s, uint64_t cid, struct btt_scrape_stats *stats,
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const struct btih *btih, size_t btihlen)
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{
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struct iovec reqiov[2], resiov[2];
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uint32_t *rawstats;
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uint8_t *rawbtih;
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struct msghdr reqmsg, resmsg;
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struct udpc_req_head reqhead;
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struct udpc_res_head reshead;
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size_t i;
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ssize_t n;
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uint32_t tid;
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if (btihlen == 0)
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return 0;
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rawbtih = reallocarray(NULL, btihlen, BTIH_LEN * sizeof(uint8_t));
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if (rawbtih == NULL)
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return 0;
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tid = arc4random();
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reqhead.connection_id = htobe64(cid);
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reqhead.action = htobe32(BTT_UDP_ACTION_SCRAPE);
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reqhead.transaction_id = htobe32(tid);
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reqiov[0].iov_base = &reqhead;
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reqiov[0].iov_len = sizeof(reqhead);
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for (i = 0; i < btihlen; i++)
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memcpy(&rawbtih[i * BTIH_LEN], btih[i].hash,
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BTIH_LEN * sizeof(uint8_t));
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reqiov[1].iov_base = rawbtih;
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reqiov[1].iov_len = btihlen * BTIH_LEN * sizeof(uint8_t);
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memset(&reqmsg, 0, sizeof(reqmsg));
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reqmsg.msg_iov = reqiov;
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reqmsg.msg_iovlen = nitems(reqiov);
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n = sendmsg(s, &reqmsg, 0);
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free(rawbtih);
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if (n == -1)
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return 0;
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rawstats = reallocarray(NULL, btihlen, 3 * sizeof(uint32_t));
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if (rawstats == NULL)
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return 0;
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resiov[0].iov_base = &reshead;
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resiov[0].iov_len = sizeof(reshead);
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resiov[1].iov_base = rawstats;
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resiov[1].iov_len = btihlen * 3 * sizeof(uint32_t);
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memset(&resmsg, 0, sizeof(resmsg));
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resmsg.msg_iov = resiov;
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resmsg.msg_iovlen = nitems(resiov);
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n = recvmsg(s, &resmsg, 0);
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if (n == -1) {
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free(rawstats);
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return 0;
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}
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if (be32toh(reshead.action) != BTT_UDP_ACTION_SCRAPE ||
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be32toh(reshead.transaction_id) != tid) {
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free(rawstats);
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return 0;
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}
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for (i = 0; i < btihlen; i++) {
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stats[i].seeders = be32toh(rawstats[3 * i]);
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stats[i].completed = be32toh(rawstats[3 * i + 1]);
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stats[i].leechers = be32toh(rawstats[3 * i + 2]);
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}
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free(rawstats);
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return 1;
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}
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struct bttc_ctx *
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bttc_ctx_new(const char *tracker)
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{
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struct bttc_ctx *ctx;
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if (tracker == NULL)
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return NULL;
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ctx = calloc(1, sizeof(*ctx));
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if (ctx == NULL)
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return NULL;
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if (strncmp(tracker, "udp://", 6) == 0) {
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if (!url_parse(tracker + 6, &ctx->host, &ctx->port))
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return 0;
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ctx->socktype = SOCK_DGRAM;
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} else {
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free(ctx);
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return NULL;
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}
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ctx->url = tracker;
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ctx->sock = -1;
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return ctx;
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}
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void
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bttc_ctx_free(struct bttc_ctx *ctx)
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{
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if (ctx == NULL)
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return;
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if (ctx->sock != -1)
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(void)close(ctx->sock);
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free(ctx->host);
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free(ctx->port);
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free(ctx);
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}
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const char *
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bttc_get_tracker(const struct bttc_ctx *ctx)
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{
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return ctx->url;
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}
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int
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bttc_scrape(struct bttc_ctx *ctx, struct btt_scrape_stats *stats,
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const struct btih *btih, size_t btihlen, const char **cause)
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{
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*cause = NULL;
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if (ctx->sock == -1) {
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ctx->sock = tracker_dial(ctx->host, ctx->port, ctx->socktype,
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cause);
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if (ctx->sock == -1)
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return 0;
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}
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if (!udpc_action_connect(ctx->sock, &ctx->cid)) {
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*cause = "failed connection handshake";
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return 0;
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}
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if (!udpc_action_scrape(ctx->sock, ctx->cid, stats, btih, btihlen)) {
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*cause = "failed scrape";
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return 0;
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}
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return 1;
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}
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51
util.c
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51
util.c
Normal file
@ -0,0 +1,51 @@
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/*
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* Copyright (c) 2025 Lucas Gabriel Vuotto <lucas@lgv5.net>
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*
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* Permission to use, copy, modify, and distribute this software for any
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||||
* purpose with or without fee is hereby granted, provided that the above
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||||
* copyright notice and this permission notice appear in all copies.
|
||||
*
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||||
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
|
||||
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
|
||||
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
|
||||
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
|
||||
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
|
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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||||
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <ctype.h>
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#include <string.h>
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#include "bt.h"
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static inline unsigned int xdigittonum(char c);
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static inline unsigned int
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xdigittonum(char c)
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{
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return c >= 'a' ? c - 'a' + 10 : c >= 'A' ? c - 'A' + 10 : c - '0';
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}
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int
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btih_parse(struct btih *btih, const char *s)
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{
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const unsigned char *us = s;
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struct btih h;
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size_t i;
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if (strlen(s) != 2 * BTIH_LEN)
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return 0;
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for (i = 0; i < BTIH_LEN; i++) {
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if (!isxdigit(us[2 * i]) || !isxdigit(us[2 * i + 1]))
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return 0;
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h.hash[i] = (xdigittonum(s[2 * i]) << 4) |
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xdigittonum(s[2 * i + 1]);
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}
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memcpy(btih, &h, sizeof(h));
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return 1;
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}
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