Naut/src/discovery/tracker_client.c

/* tracker_client.c — HTTP/UDP tracker announce client.
 *
 * The wire codec (query building, bencode/UDP packet encode+decode) comes from
 * the sibling `torrent-tracker` library; this file owns only the socket glue and
 * the conversion between Naut's announce types and torrent-tracker's. */
#include "naut/tracker.h"
#include "naut/log.h"

#include "tracker.h"  /* torrent-tracker public ABI */

#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/time.h>

#define TRACKER_RESPONSE_MAX (16u << 20)

void naut_tracker_response_free(naut_tracker_response *r) {
    if (!r) return;
    free(r->peers);
    free(r->failure);
    r->peers = NULL;
    r->failure = NULL;
    r->num_peers = 0;
}

/* naut_announce_req -> torrent-tracker request (compact IPv4 announce). */
static void to_tracker_request(const naut_announce_req *req,
                               tracker_announce_request *out) {
    memset(out, 0, sizeof *out);
    memcpy(out->info_hash, req->info_hash, 20);
    memcpy(out->peer_id, req->peer_id, 20);
    out->port = req->port;
    out->uploaded = req->uploaded;
    out->downloaded = req->downloaded;
    out->left = req->left;
    out->numwant = req->numwant;
    out->key = req->key;
    out->has_key = 1;
    out->compact = 1;
    out->event = (tracker_event)req->event;   /* codes match BEP-15 */
}

/* Copy torrent-tracker IPv4 peers into a freshly malloc'd naut_peer_addr array. */
static naut_err collect_peers(const tracker_peer *peers, size_t count,
                              const tracker_announce_response *resp,
                              naut_tracker_response *out) {
    out->interval = (int32_t)resp->interval;
    out->min_interval = (int32_t)resp->min_interval;
    out->seeders = (int32_t)resp->complete;
    out->leechers = (int32_t)resp->incomplete;
    out->peers = NULL;
    out->num_peers = 0;
    if (count == 0) return NAUT_OK;
    naut_peer_addr *v = malloc(count * sizeof *v);
    if (!v) return NAUT_ERR_NOMEM;
    size_t n = 0;
    for (size_t i = 0; i < count; i++) {
        if (peers[i].family != TRACKER_ADDR_IPV4) continue;  /* IPv4 only */
        memcpy(v[n].ip, peers[i].addr, 4);
        v[n].port = peers[i].port;
        n++;
    }
    out->peers = v;
    out->num_peers = n;
    return NAUT_OK;
}

size_t naut_tracker_http_url(const char *base, const naut_announce_req *req,
                             char *out, size_t outsz) {
    tracker_announce_request treq;
    to_tracker_request(req, &treq);
    char query[2048];
    size_t qlen = 0;
    if (tracker_http_write_announce_query(&treq, query, sizeof query, &qlen) !=
        TRACKER_OK)
        return 0;
    const char sep = strchr(base, '?') ? '&' : '?';
    int n = snprintf(out, outsz, "%s%c%.*s", base, sep, (int)qlen, query);
    if (n < 0 || (size_t)n >= outsz) return 0;
    return (size_t)n;
}

/* --- HTTP --------------------------------------------------------------- */

static int dial(const char *host, const char *port, int socktype) {
    struct addrinfo hints, *res = NULL, *ai;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;        /* IPv4 (compact peers are v4) */
    hints.ai_socktype = socktype;
    if (getaddrinfo(host, port, &hints, &res) != 0) return -1;
    int fd = -1;
    for (ai = res; ai; ai = ai->ai_next) {
        fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
        if (fd < 0) continue;
        struct timeval tv = { .tv_sec = 10, .tv_usec = 0 };
        setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof tv);
        if (connect(fd, ai->ai_addr, ai->ai_addrlen) == 0) break;
        close(fd); fd = -1;
    }
    freeaddrinfo(res);
    return fd;
}

/* split "http://host[:port]/path" */
static bool parse_http_url(const char *url, char *host, size_t hostsz,
                           char *port, size_t portsz, const char **path) {
    if (strncmp(url, "http://", 7) != 0) return false;
    const char *h = url + 7;
    const char *slash = strchr(h, '/');
    const char *hostend = slash ? slash : h + strlen(h);
    const char *colon = memchr(h, ':', (size_t)(hostend - h));
    size_t hlen = colon ? (size_t)(colon - h) : (size_t)(hostend - h);
    if (hlen >= hostsz) return false;
    memcpy(host, h, hlen); host[hlen] = 0;
    if (colon) {
        size_t plen = (size_t)(hostend - colon - 1);
        if (plen >= portsz) return false;
        memcpy(port, colon + 1, plen); port[plen] = 0;
    } else { snprintf(port, portsz, "80"); }
    *path = slash ? slash : "/";
    return true;
}

static bool write_all(int fd, const void *data, size_t len) {
    const uint8_t *p = data;
    while (len) {
        ssize_t n = write(fd, p, len);
        if (n < 0) {
            if (errno == EINTR) continue;
            return false;
        }
        p += (size_t)n;
        len -= (size_t)n;
    }
    return true;
}

naut_err naut_tracker_announce_http(const char *url, naut_tracker_response *out) {
    char host[256], port[16]; const char *path;
    if (!parse_http_url(url, host, sizeof host, port, sizeof port, &path))
        return NAUT_ERR_INVAL;
    int fd = dial(host, port, SOCK_STREAM);
    if (fd < 0) { NAUT_WARN("tracker connect %s:%s failed", host, port); return NAUT_ERR_IO; }

    char req[4096];
    int rn = snprintf(req, sizeof req,
        "GET %s HTTP/1.0\r\nHost: %s\r\nUser-Agent: Naut/0.1\r\nAccept: */*\r\n\r\n",
        path, host);
    if (rn < 0 || (size_t)rn >= sizeof req ||
        !write_all(fd, req, (size_t)rn)) {
        close(fd);
        return NAUT_ERR_IO;
    }

    /* read whole response (server closes on HTTP/1.0) */
    size_t cap = 1 << 16, len = 0;
    uint8_t *buf = malloc(cap);
    if (!buf) { close(fd); return NAUT_ERR_NOMEM; }
    naut_err read_error = NAUT_OK;
    for (;;) {
        if (len == cap) {
            if (cap == TRACKER_RESPONSE_MAX) { read_error = NAUT_ERR_FULL; break; }
            size_t next_cap = NAUT_MIN(cap * 2, (size_t)TRACKER_RESPONSE_MAX);
            uint8_t *next = realloc(buf, next_cap);
            if (!next) { read_error = NAUT_ERR_NOMEM; break; }
            buf = next;
            cap = next_cap;
        }
        ssize_t r = read(fd, buf + len, cap - len);
        if (r < 0) {
            if (errno == EINTR) continue;
            read_error = NAUT_ERR_IO;
            break;
        }
        if (r == 0) break;
        len += (size_t)r;
    }
    close(fd);
    if (read_error != NAUT_OK) { free(buf); return read_error; }

    /* find body after CRLFCRLF */
    uint8_t *body = NULL; size_t blen = 0;
    for (size_t i = 0; i + 3 < len; i++)
        if (buf[i]=='\r'&&buf[i+1]=='\n'&&buf[i+2]=='\r'&&buf[i+3]=='\n') {
            body = buf + i + 4; blen = len - (i + 4); break;
        }
    bool ok = len >= 12 && memcmp(buf, "HTTP/", 5) == 0 && buf[9] == '2';
    if (!ok || !body) { free(buf); return NAUT_ERR_PROTO; }

    tracker_peer peers[TRACKER_MAX_PEERS];
    tracker_announce_response resp;
    memset(&resp, 0, sizeof resp);
    naut_err e = NAUT_ERR_PROTO;
    if (tracker_http_parse_announce_response(body, blen, peers,
                                             TRACKER_MAX_PEERS, &resp) ==
        TRACKER_OK)
        e = collect_peers(resp.peers, resp.peer_count, &resp, out);
    free(buf);
    return e;
}

/* --- UDP (BEP-15) ------------------------------------------------------- */

naut_err naut_tracker_announce_udp(const char *host, uint16_t port,
                                   const naut_announce_req *req,
                                   naut_tracker_response *out) {
    char portstr[16]; snprintf(portstr, sizeof portstr, "%u", port);
    int fd = dial(host, portstr, SOCK_DGRAM);
    if (fd < 0) return NAUT_ERR_IO;

    srand((unsigned)time(NULL) ^ (unsigned)getpid());
    uint32_t txid = (uint32_t)rand();

    uint8_t pkt[128], resp[2048];
    size_t written = 0;
    if (tracker_udp_write_connect_request(txid, pkt, sizeof pkt, &written) !=
            TRACKER_OK ||
        !write_all(fd, pkt, written)) {
        close(fd); return NAUT_ERR_IO;
    }
    ssize_t r = read(fd, resp, sizeof resp);
    uint64_t cid = 0;
    if (r < 0 ||
        tracker_udp_parse_connect_response(resp, (size_t)r, txid, &cid) !=
            TRACKER_OK) {
        close(fd); return NAUT_ERR_IO;
    }

    txid++;
    tracker_announce_request treq;
    to_tracker_request(req, &treq);
    if (tracker_udp_write_announce_request(cid, txid, &treq, pkt, sizeof pkt,
                                           &written) != TRACKER_OK ||
        !write_all(fd, pkt, written)) {
        close(fd); return NAUT_ERR_IO;
    }
    r = read(fd, resp, sizeof resp);
    naut_err e = NAUT_ERR_IO;
    if (r >= 0) {
        tracker_peer peers[TRACKER_MAX_PEERS];
        tracker_announce_response tresp;
        memset(&tresp, 0, sizeof tresp);
        e = NAUT_ERR_PROTO;
        if (tracker_udp_parse_announce_response(resp, (size_t)r, txid,
                                                TRACKER_ADDR_IPV4, peers,
                                                TRACKER_MAX_PEERS, &tresp) ==
            TRACKER_OK)
            e = collect_peers(tresp.peers, tresp.peer_count, &tresp, out);
    }
    close(fd);
    return e;
}