fixup: handle unhandled scrape/announce responses (#2701)

followup to the #2531 benc refactor

libtransmission/announcer-common.h

@@ -214,6 +214,10 @@ struct tr_announce_response
     /* key generated by and returned from an http tracker.
      * if this is provided, subsequent http announces must include this. */
     std::string tracker_id;
+
+    /* tracker extension that returns the client's public IP address.
+     * https://www.bittorrent.org/beps/bep_0024.html */
+    std::optional<tr_address> external_ip;
 };
 
 using tr_announce_response_func = void (*)(tr_announce_response const* response, void* userdata);

libtransmission/announcer-http.cc

@@ -253,6 +253,10 @@ void tr_announcerParseHttpAnnounceResponse(tr_announce_response& response, std::
             {
                 // unused
             }
+            else if (key == "external ip"sv && std::size(value) == 4)
+            {
+                response_.external_ip = tr_address::from_4byte_ipv4(value);
+            }
             else if (!tr_error_is_set(context.error))
             {
                 tr_error_set(context.error, EINVAL, tr_strvJoin("unexpected str: key["sv, key, "] value["sv, value, "]"sv));
@@ -402,6 +406,14 @@ void tr_announcerParseHttpScrapeResponse(tr_scrape_response& response, std::stri
             {
                 response_.rows[*row_].leechers = value;
             }
+            else if (row_ && key == "downloaders"sv)
+            {
+                response_.rows[*row_].downloaders = value;
+            }
+            else if (key == "min_request_interval"sv)
+            {
+                response_.min_request_interval = value;
+            }
             else if (!tr_error_is_set(context.error))
             {
                 auto const errmsg = tr_strvJoin("unexpected int: key["sv, key, "] value["sv, std::to_string(value), "]"sv);

libtransmission/announcer.cc

@@ -995,6 +995,11 @@ static void on_announce_done(tr_announce_response const* response, void* vdata)
         tier->isAnnouncing = false;
         tier->manualAnnounceAllowedAt = now + tier->announceMinIntervalSec;
 
+        if (response->external_ip)
+        {
+            data->session->setExternalIP(*response->external_ip);
+        }
+
         if (!response->did_connect)
         {
             on_announce_error(tier, _("Could not connect to tracker"), event);

libtransmission/net.cc

@@ -115,7 +115,7 @@ bool tr_address_from_string(tr_address* dst, std::string_view src)
 {
     // inet_pton() requires zero-terminated strings,
     // so make a zero-terminated copy here on the stack.
-    auto buf = std::array<char, 64>{};
+    auto buf = std::array<char, TR_ADDRSTRLEN>{};
     if (std::size(src) >= std::size(buf))
     {
         // shouldn't ever be that large; malformed address
@@ -127,6 +127,28 @@ bool tr_address_from_string(tr_address* dst, std::string_view src)
     return tr_address_from_string(dst, std::data(buf));
 }
 
+std::optional<tr_address> tr_address::from_string(std::string_view str)
+{
+    auto addr = tr_address{};
+
+    if (!tr_address_from_string(&addr, str))
+    {
+        return {};
+    }
+
+    return addr;
+}
+
+tr_address tr_address::from_4byte_ipv4(std::string_view in)
+{
+    TR_ASSERT(std::size(in) == 4);
+
+    auto addr = tr_address{};
+    addr.type = TR_AF_INET;
+    std::copy_n(std::begin(in), 4, reinterpret_cast<char*>(&addr.addr));
+    return addr;
+}
+
 /*
  * Compare two tr_address structures.
  * Returns:

libtransmission/net.h

@@ -68,14 +68,37 @@ enum tr_address_type
     NUM_TR_AF_INET_TYPES
 };
 
+struct tr_address;
+
+int tr_address_compare(tr_address const* a, tr_address const* b);
+
 struct tr_address
 {
+    static tr_address from_4byte_ipv4(std::string_view in);
+
+    static std::optional<tr_address> from_string(std::string_view str);
+
     tr_address_type type;
     union
     {
         struct in6_addr addr6;
         struct in_addr addr4;
     } addr;
+
+    bool operator==(tr_address const& that) const
+    {
+        return tr_address_compare(this, &that) == 0;
+    }
+
+    bool operator<(tr_address const& that) const
+    {
+        return tr_address_compare(this, &that) < 0;
+    }
+
+    bool operator>(tr_address const& that) const
+    {
+        return tr_address_compare(this, &that) > 0;
+    }
 };
 
 extern tr_address const tr_inaddr_any;
@@ -93,8 +116,6 @@ bool tr_address_from_string(tr_address* dst, std::string_view src);
 
 bool tr_address_from_sockaddr_storage(tr_address* setme, tr_port* port, struct sockaddr_storage const* src);
 
-int tr_address_compare(tr_address const* a, tr_address const* b);
-
 bool tr_address_is_valid_for_peers(tr_address const* addr, tr_port port);
 
 constexpr bool tr_address_is_valid(tr_address const* a)

libtransmission/session.h

@@ -239,6 +239,16 @@ public:
 
     bool useRpcWhitelist() const;
 
+    auto externalIP() const
+    {
+        return external_ip_;
+    }
+
+    void setExternalIP(tr_address external_ip)
+    {
+        external_ip_ = external_ip;
+    }
+
     // peer networking
 
     std::string const& peerCongestionAlgorithm() const
@@ -419,6 +429,7 @@ private:
     std::string default_trackers_str_;
     std::string incomplete_dir_;
     std::string peer_congestion_algorithm_;
+    std::optional<tr_address> external_ip_;
 
     std::array<bool, TR_SCRIPT_N_TYPES> scripts_enabled_;
     bool blocklist_enabled_ = false;

tests/libtransmission/announcer-test.cc

@@ -32,6 +32,7 @@ TEST_F(AnnouncerTest, parseHttpAnnounceResponseNoPeers)
             "8:interval" "i1803e"
             "12:min interval" "i1800e"
             "5:peers" "0:"
+            "11:external ip" "4:\x01\x02\x03\x04"
         "e"sv;
     // clang-format on
 
@@ -42,6 +43,7 @@ TEST_F(AnnouncerTest, parseHttpAnnounceResponseNoPeers)
     EXPECT_EQ(3, response.seeders);
     EXPECT_EQ(0, response.leechers);
     EXPECT_EQ(2, response.downloads);
+    EXPECT_EQ(*tr_address::from_string("1.2.3.4"), response.external_ip);
     EXPECT_EQ(0, std::size(response.pex));
     EXPECT_EQ(0, std::size(response.pex6));
     EXPECT_EQ(""sv, response.errmsg);