fix: misc net.cc and blocklist.cc fixes (#6717)

* fix: `tr_address` should be invalid by default

* fix: allow loopback address for LPD and incoming connections

* fix: `parseCidrline()` should set address type

* code review: keep `memcmp`

libtransmission/announcer-http.cc

@@ -339,7 +339,7 @@ void tr_announcerParseHttpAnnounceResponse(tr_announce_response& response, std::
         {
             BasicHandler::EndDict(context);
 
-            if (pex_.is_valid_for_peers())
+            if (pex_.is_valid())
             {
                 response_.pex.push_back(pex_);
                 pex_ = {};

libtransmission/blocklist.cc

@@ -204,10 +204,12 @@ std::optional<address_range_t> parseCidrLine(std::string_view line)
         return {};
     }
 
-    auto const mask = uint32_t{ 0xFFFFFFFF } << (32 - *pflen);
-    auto const ip_u = htonl(addrpair.first.addr.addr4.s_addr);
-    addrpair.first.addr.addr4.s_addr = ntohl(ip_u & mask);
-    addrpair.second.addr.addr4.s_addr = ntohl(ip_u | (~mask));
+    auto const mask = ~(~uint32_t{ 0 } >> *pflen);
+    auto const ip_u = ntohl(addrpair.first.addr.addr4.s_addr);
+    auto tmp = htonl(ip_u & mask);
+    std::tie(addrpair.first, std::ignore) = tr_address::from_compact_ipv4(reinterpret_cast<std::byte*>(&tmp));
+    tmp = htonl(ip_u | (~mask));
+    std::tie(addrpair.second, std::ignore) = tr_address::from_compact_ipv4(reinterpret_cast<std::byte*>(&tmp));
     return addrpair;
 }
 

libtransmission/net.cc

@@ -231,7 +231,7 @@ tr_peer_socket tr_netOpenPeerSocket(tr_session* session, tr_socket_address const
     TR_ASSERT(addr.is_valid());
     TR_ASSERT(!tr_peer_socket::limit_reached(session));
 
-    if (tr_peer_socket::limit_reached(session) || !session->allowsTCP() || !socket_address.is_valid_for_peers())
+    if (tr_peer_socket::limit_reached(session) || !session->allowsTCP() || !socket_address.is_valid())
     {
         return {};
     }
@@ -446,23 +446,29 @@ namespace is_valid_for_peers_helpers
 
 /* isMartianAddr was written by Juliusz Chroboczek,
    and is covered under the same license as third-party/dht/dht.c. */
-[[nodiscard]] auto is_martian_addr(tr_address const& addr)
+[[nodiscard]] auto is_martian_addr(tr_address const& addr, tr_peer_from from)
 {
     static auto constexpr Zeroes = std::array<unsigned char, 16>{};
+    auto const loopback_allowed = from == TR_PEER_FROM_INCOMING || from == TR_PEER_FROM_LPD || from == TR_PEER_FROM_RESUME;
 
     switch (addr.type)
     {
     case TR_AF_INET:
         {
             auto const* const address = reinterpret_cast<unsigned char const*>(&addr.addr.addr4);
-            return address[0] == 0 || address[0] == 127 || (address[0] & 0xE0) == 0xE0;
+            return address[0] == 0 || // 0.x.x.x
+                (!loopback_allowed && address[0] == 127) || // 127.x.x.x
+                (address[0] & 0xE0) == 0xE0; // multicast address
         }
 
     case TR_AF_INET6:
         {
             auto const* const address = reinterpret_cast<unsigned char const*>(&addr.addr.addr6);
-            return address[0] == 0xFF ||
-                (memcmp(address, std::data(Zeroes), 15) == 0 && (address[15] == 0 || address[15] == 1));
+            return address[0] == 0xFF || // multicast address
+                (std::memcmp(address, std::data(Zeroes), 15) == 0 &&
+                 (address[15] == 0 || // ::
+                  (!loopback_allowed && address[15] == 1)) // ::1
+                );
         }
 
     default:
@@ -703,12 +709,12 @@ std::string tr_socket_address::display_name(tr_address const& address, tr_port p
     return fmt::format("[{:s}]:{:d}", address.display_name(), port.host());
 }
 
-bool tr_socket_address::is_valid_for_peers() const noexcept
+bool tr_socket_address::is_valid_for_peers(tr_peer_from from) const noexcept
 {
     using namespace is_valid_for_peers_helpers;
 
     return is_valid() && !std::empty(port_) && !is_ipv6_link_local_address(address_) && !is_ipv4_mapped_address(address_) &&
-        !is_martian_addr(address_);
+        !is_martian_addr(address_, from);
 }
 
 std::optional<tr_socket_address> tr_socket_address::from_sockaddr(struct sockaddr const* from)

libtransmission/net.h

@@ -60,6 +60,8 @@ using tr_socket_t = int;
 #define sockerrno errno
 #endif
 
+#include "libtransmission/transmission.h" // tr_peer_from
+
 #include "libtransmission/tr-assert.h"
 #include "libtransmission/utils.h" // for tr_compare_3way()
 
@@ -234,7 +236,7 @@ struct tr_address
 
     [[nodiscard]] bool is_global_unicast_address() const noexcept;
 
-    tr_address_type type;
+    tr_address_type type = NUM_TR_AF_INET_TYPES;
     union
     {
         struct in6_addr addr6;
@@ -306,7 +308,7 @@ struct tr_socket_address
         return address_.is_valid();
     }
 
-    [[nodiscard]] bool is_valid_for_peers() const noexcept;
+    [[nodiscard]] bool is_valid_for_peers(tr_peer_from from) const noexcept;
 
     [[nodiscard]] int compare(tr_socket_address const& that) const noexcept
     {

libtransmission/peer-io.cc

@@ -129,11 +129,6 @@ std::shared_ptr<tr_peerIo> tr_peerIo::new_outgoing(
     TR_ASSERT(socket_address.is_valid());
     TR_ASSERT(utp || session->allowsTCP());
 
-    if (!socket_address.is_valid_for_peers())
-    {
-        return {};
-    }
-
     auto peer_io = tr_peerIo::create(session, parent, &info_hash, false, is_seed);
     auto const func = small::max_size_map<preferred_key_t, std::function<bool()>, TR_NUM_PREFERRED_TRANSPORT>{
         { TR_PREFER_UTP,

libtransmission/peer-mgr.cc

@@ -1439,7 +1439,7 @@ size_t tr_peerMgrAddPex(tr_torrent* tor, tr_peer_from from, tr_pex const* pex, s
     for (tr_pex const* const end = pex + n_pex; pex != end; ++pex)
     {
         if (tr_isPex(pex) && /* safeguard against corrupt data */
-            !s->manager->blocklists_.contains(pex->socket_address.address()) && pex->is_valid_for_peers() &&
+            !s->manager->blocklists_.contains(pex->socket_address.address()) && pex->is_valid_for_peers(from) &&
             from != TR_PEER_FROM_INCOMING && (from != TR_PEER_FROM_PEX || (pex->flags & ADDED_F_CONNECTABLE) != 0))
         {
             // we store this peer since it is supposedly connectable (socket address should be the peer's listening address)

libtransmission/peer-mgr.h

@@ -517,9 +517,14 @@ struct tr_pex
         return compare(that) < 0;
     }
 
-    [[nodiscard]] bool is_valid_for_peers() const noexcept
+    [[nodiscard]] bool is_valid() const noexcept
     {
-        return socket_address.is_valid_for_peers();
+        return socket_address.is_valid();
+    }
+
+    [[nodiscard]] bool is_valid_for_peers(tr_peer_from from) const noexcept
+    {
+        return socket_address.is_valid_for_peers(from);
     }
 
     tr_socket_address socket_address;