refactor: rename `mcast_socket_` to `mcast_sockets_`

Signed-off-by: Dzmitry Neviadomski <nevack.d@gmail.com>

CONTRIBUTING.md

@@ -41,7 +41,7 @@ On macOS, Transmission is usually built with Xcode. Everywhere else, it's CMake
 - Prefer `enum class` over `enum`
 - Prefer new-style headers, e.g. `<cstring>` over `<string.h>`
 - Fix any warnings in new code before merging
-- Run `./code-style.sh` on your code to ensure the whole codebase has consistent indentation.
+- Run `./code_style.sh` on your code to ensure the whole codebase has consistent indentation.
 
 Note that Transmission existed in C for over a decade and those idioms don't change overnight. "Follow the C++ core guidelines" can be difficult when working with older code, and the maintainers will understand that when reviewing your PRs. :smiley:
 

libtransmission/net.cc

@@ -16,8 +16,12 @@
 #include <utility> // std::pair
 
 #ifdef _WIN32
+#include <winsock2.h> // must come before iphlpapi.h
+#include <iphlpapi.h>
 #include <ws2tcpip.h>
 #else
+#include <ifaddrs.h>
+#include <net/if.h>
 #include <netinet/tcp.h> /* TCP_CONGESTION */
 #endif
 
@@ -556,6 +560,92 @@ std::pair<tr_address, std::byte const*> tr_address::from_compact_ipv6(std::byte
     return { address, compact };
 }
 
+std::optional<unsigned> tr_address::to_interface_index() const noexcept
+{
+    if (!is_valid())
+    {
+        tr_logAddDebug("Invalid target address to find interface index");
+        return {};
+    }
+
+    tr_logAddDebug(fmt::format("Find interface index for {}", display_name()));
+
+#ifdef _WIN32
+    auto p_addresses = std::unique_ptr<void, void (*)(void*)>{ nullptr, operator delete };
+    for (auto p_addesses_size = ULONG{ 15000 } /* 15KB */;;)
+    {
+        p_addresses.reset(operator new(p_addesses_size, std::nothrow));
+        if (!p_addresses)
+        {
+            tr_logAddDebug("Could not allocate memory for interface list");
+            return {};
+        }
+
+        if (auto ret = GetAdaptersAddresses(
+                AF_UNSPEC,
+                GAA_FLAG_SKIP_FRIENDLY_NAME,
+                nullptr,
+                reinterpret_cast<PIP_ADAPTER_ADDRESSES>(p_addresses.get()),
+                &p_addesses_size);
+            ret != ERROR_BUFFER_OVERFLOW)
+        {
+            if (ret != ERROR_SUCCESS)
+            {
+                tr_logAddDebug(fmt::format("Failed to retrieve interface list: {} ({})", ret, tr_win32_format_message(ret)));
+                return {};
+            }
+            break;
+        }
+    }
+
+    for (auto const* cur = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(p_addresses.get()); cur != nullptr; cur = cur->Next)
+    {
+        if (cur->OperStatus != IfOperStatusUp)
+        {
+            continue;
+        }
+
+        for (auto const* sa_p = cur->FirstUnicastAddress; sa_p != nullptr; sa_p = sa_p->Next)
+        {
+            if (auto if_addr = tr_socket_address::from_sockaddr(sa_p->Address.lpSockaddr);
+                if_addr && if_addr->address() == *this)
+            {
+                auto const ret = type == TR_AF_INET ? cur->IfIndex : cur->Ipv6IfIndex;
+                tr_logAddDebug(fmt::format("Found interface index for {}: {}", display_name(), ret));
+                return ret;
+            }
+        }
+    }
+#else
+    struct ifaddrs* ifa = nullptr;
+    if (getifaddrs(&ifa) != 0)
+    {
+        auto err = errno;
+        tr_logAddDebug(fmt::format("Failed to retrieve interface list: {} ({})", err, tr_strerror(err)));
+        return {};
+    }
+    auto const ifa_uniq = std::unique_ptr<ifaddrs, void (*)(struct ifaddrs*)>{ ifa, freeifaddrs };
+
+    for (; ifa != nullptr; ifa = ifa->ifa_next)
+    {
+        if (ifa->ifa_addr == nullptr || (ifa->ifa_flags & IFF_UP) == 0U)
+        {
+            continue;
+        }
+
+        if (auto if_addr = tr_socket_address::from_sockaddr(ifa->ifa_addr); if_addr && if_addr->address() == *this)
+        {
+            auto const ret = if_nametoindex(ifa->ifa_name);
+            tr_logAddDebug(fmt::format("Found interface index for {}: {}", display_name(), ret));
+            return ret;
+        }
+    }
+#endif
+
+    tr_logAddDebug(fmt::format("Could not find interface index for {}", display_name()));
+    return {};
+}
+
 int tr_address::compare(tr_address const& that) const noexcept // <=>
 {
     // IPv6 addresses are always "greater than" IPv4
@@ -718,6 +808,19 @@ bool tr_socket_address::is_valid_for_peers(tr_peer_from from) const noexcept
         !is_martian_addr(address_, from);
 }
 
+std::optional<tr_socket_address> tr_socket_address::from_string(std::string_view sockaddr_sv)
+{
+    auto ss = sockaddr_storage{};
+    auto sslen = int{ sizeof(ss) };
+    if (evutil_parse_sockaddr_port(tr_strbuf<char, TR_ADDRSTRLEN>{ sockaddr_sv }, reinterpret_cast<sockaddr*>(&ss), &sslen) !=
+        0)
+    {
+        return {};
+    }
+
+    return from_sockaddr(reinterpret_cast<struct sockaddr const*>(&ss));
+}
+
 std::optional<tr_socket_address> tr_socket_address::from_sockaddr(struct sockaddr const* from)
 {
     if (from == nullptr)

libtransmission/net.h

@@ -161,11 +161,11 @@ struct tr_address
     [[nodiscard]] static std::pair<tr_address, std::byte const*> from_compact_ipv4(std::byte const* compact) noexcept;
     [[nodiscard]] static std::pair<tr_address, std::byte const*> from_compact_ipv6(std::byte const* compact) noexcept;
 
-    // write the text form of the address, e.g. inet_ntop()
+    // --- write the text form of the address, e.g. inet_ntop()
     std::string_view display_name(char* out, size_t outlen) const;
     [[nodiscard]] std::string display_name() const;
 
-    ///
+    // ---
 
     [[nodiscard]] constexpr auto is_ipv4() const noexcept
     {
@@ -177,7 +177,7 @@ struct tr_address
         return type == TR_AF_INET6;
     }
 
-    /// bt protocol compact form
+    // --- bt protocol compact form
 
     // compact addr only -- used e.g. as `yourip` value in extension protocol handshake
 
@@ -208,7 +208,11 @@ struct tr_address
         }
     }
 
-    // comparisons
+    // ---
+
+    [[nodiscard]] std::optional<unsigned> to_interface_index() const noexcept;
+
+    // --- comparisons
 
     [[nodiscard]] int compare(tr_address const& that) const noexcept;
 
@@ -232,7 +236,7 @@ struct tr_address
         return this->compare(that) > 0;
     }
 
-    //
+    // ---
 
     [[nodiscard]] bool is_global_unicast_address() const noexcept;
 
@@ -374,6 +378,7 @@ struct tr_socket_address
 
     // --- sockaddr helpers
 
+    [[nodiscard]] static std::optional<tr_socket_address> from_string(std::string_view sockaddr_sv);
     [[nodiscard]] static std::optional<tr_socket_address> from_sockaddr(sockaddr const*);
     [[nodiscard]] static std::pair<sockaddr_storage, socklen_t> to_sockaddr(tr_address const& addr, tr_port port) noexcept;
 
@@ -404,7 +409,7 @@ struct tr_socket_address
 };
 
 template<>
-class std::hash<tr_socket_address>
+struct std::hash<tr_socket_address>
 {
 public:
     std::size_t operator()(tr_socket_address const& socket_address) const noexcept

libtransmission/tr-lpd.cc

@@ -14,13 +14,14 @@
 #include <optional>
 #include <string>
 #include <string_view>
+#include <type_traits>
 #include <vector>
 
 #ifdef _WIN32
 #include <ws2tcpip.h>
 #else
-#include <sys/socket.h> /* socket(), bind() */
 #include <netinet/in.h> /* sockaddr_in */
+#include <sys/socket.h> /* socket(), bind() */
 #endif
 
 #include <event2/event.h>
@@ -47,6 +48,8 @@ using namespace std::literals;
 namespace
 {
 
+using ipp_t = std::underlying_type_t<tr_address_type>;
+
 // opaque value, allowing the sending client to filter out its
 // own announces if it receives them via multicast loopback
 auto makeCookie()
@@ -62,8 +65,8 @@ auto makeCookie()
     return std::string{ std::data(buf), std::size(buf) };
 }
 
-constexpr char const* const McastGroup = "239.192.152.143"; /**<LPD multicast group */
-auto constexpr McastPort = tr_port::from_host(6771); /**<LPD source and destination UPD port */
+auto constexpr McastSockAddr = std::array{ "239.192.152.143:6771"sv, "[ff15::efc0:988f]:6771"sv };
+static_assert(std::size(McastSockAddr) == NUM_TR_AF_INET_TYPES);
 
 /*
  * A LSD announce is formatted as follows:
@@ -84,14 +87,23 @@ auto constexpr McastPort = tr_port::from_host(6771); /**<LPD source and destinat
  * multiple infohashes the packet length should not exceed 1400
  * bytes to avoid MTU/fragmentation problems.
  */
-auto makeAnnounceMsg(std::string_view cookie, tr_port port, std::vector<std::string_view> const& info_hash_strings)
+std::string makeAnnounceMsg(
+    tr_address_type ip_protocol,
+    std::string_view cookie,
+    tr_port port,
+    std::vector<std::string_view> const& info_hash_strings)
 {
+    TR_ASSERT(tr_address::is_valid(ip_protocol));
+    if (!tr_address::is_valid(ip_protocol))
+    {
+        return {};
+    }
+
     auto ret = fmt::format(
         "BT-SEARCH * HTTP/1.1\r\n"
-        "Host: {:s}:{:d}\r\n"
+        "Host: {:s}\r\n"
         "Port: {:d}\r\n",
-        McastGroup,
-        McastPort.host(),
+        McastSockAddr[ip_protocol],
         port.host());
 
     for (auto const& info_hash : info_hash_strings)
@@ -230,11 +242,17 @@ public:
 
     ~tr_lpd_impl() override
     {
-        event_.reset();
-
-        if (mcast_socket_ != TR_BAD_SOCKET)
+        for (auto& event : events_)
         {
-            tr_net_close_socket(mcast_socket_);
+            event.reset();
+        }
+
+        for (auto const sock : mcast_sockets_)
+        {
+            if (sock != TR_BAD_SOCKET)
+            {
+                tr_net_close_socket(sock);
+            }
         }
 
         tr_logAddTrace("Done uninitialising Local Peer Discovery");
@@ -243,19 +261,34 @@ public:
 private:
     bool init(struct event_base* event_base)
     {
-        if (initImpl(event_base))
+        ipp_t n_success = NUM_TR_AF_INET_TYPES;
+        if (!initImpl<TR_AF_INET>(event_base))
         {
-            return true;
+            auto const err = sockerrno;
+            tr_net_close_socket(mcast_sockets_[TR_AF_INET]);
+            mcast_sockets_[TR_AF_INET] = TR_BAD_SOCKET;
+            tr_logAddWarn(fmt::format(
+                _("Couldn't initialize {ip_protocol} LPD: {error} ({error_code})"),
+                fmt::arg("ip_protocol", tr_ip_protocol_to_sv(TR_AF_INET)),
+                fmt::arg("error", tr_strerror(err)),
+                fmt::arg("error_code", err)));
+            --n_success;
         }
 
-        auto const err = sockerrno;
-        tr_net_close_socket(mcast_socket_);
-        mcast_socket_ = TR_BAD_SOCKET;
-        tr_logAddWarn(fmt::format(
-            _("Couldn't initialize LPD: {error} ({error_code})"),
-            fmt::arg("error", tr_strerror(err)),
-            fmt::arg("error_code", err)));
-        return false;
+        if (!initImpl<TR_AF_INET6>(event_base))
+        {
+            auto const err = sockerrno;
+            tr_net_close_socket(mcast_sockets_[TR_AF_INET6]);
+            mcast_sockets_[TR_AF_INET6] = TR_BAD_SOCKET;
+            tr_logAddWarn(fmt::format(
+                _("Couldn't initialize {ip_protocol} LPD: {error} ({error_code})"),
+                fmt::arg("ip_protocol", tr_ip_protocol_to_sv(TR_AF_INET6)),
+                fmt::arg("error", tr_strerror(err)),
+                fmt::arg("error_code", err)));
+            --n_success;
+        }
+
+        return n_success != 0U;
     }
 
     /**
@@ -263,76 +296,80 @@ private:
      *
      * For the most part, this means setting up an appropriately configured multicast socket
      * and event-based message handling.
-     *
-     * @remark Since the LPD service does not use another protocol family yet, this code is
-     * IPv4 only for the time being.
      */
+    template<tr_address_type ip_protocol>
     bool initImpl(struct event_base* event_base)
     {
         auto const opt_on = 1;
+        auto& sock = mcast_sockets_[ip_protocol];
 
         static_assert(AnnounceScope > 0);
+        static_assert(tr_address::is_valid(ip_protocol));
 
-        tr_logAddDebug("Initialising Local Peer Discovery");
+        tr_logAddDebug(fmt::format("Initialising {} Local Peer Discovery", tr_ip_protocol_to_sv(ip_protocol)));
 
-        /* setup datagram socket */
+        // setup datagram socket
+        sock = socket(tr_ip_protocol_to_af(ip_protocol), SOCK_DGRAM, 0);
+
+        if (sock == TR_BAD_SOCKET)
         {
-            mcast_socket_ = socket(PF_INET, SOCK_DGRAM, 0);
+            return false;
+        }
 
-            if (mcast_socket_ == TR_BAD_SOCKET)
-            {
-                return false;
-            }
+        if (evutil_make_socket_nonblocking(sock) == -1)
+        {
+            return false;
+        }
 
-            if (evutil_make_socket_nonblocking(mcast_socket_) == -1)
-            {
-                return false;
-            }
-
-            if (setsockopt(mcast_socket_, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) ==
-                -1)
-            {
-                return false;
-            }
+        if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) == -1)
+        {
+            return false;
+        }
 
 #if HAVE_SO_REUSEPORT
-            if (setsockopt(mcast_socket_, SOL_SOCKET, SO_REUSEPORT, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) ==
+        if (setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) == -1)
+        {
+            return false;
+        }
+#endif
+
+        if constexpr (ip_protocol == TR_AF_INET6)
+        {
+            // must be done before binding on Linux
+            if (evutil_make_listen_socket_ipv6only(sock) == -1)
+            {
+                return false;
+            }
+        }
+
+        auto const mcast_sockaddr = tr_socket_address::from_string(McastSockAddr[ip_protocol]);
+        TR_ASSERT(mcast_sockaddr);
+        auto const [mcast_ss, mcast_sslen] = mcast_sockaddr->to_sockaddr();
+
+        auto const [bind_ss, bind_sslen] = tr_socket_address::to_sockaddr(tr_address::any(ip_protocol), mcast_sockaddr->port());
+        if (bind(sock, reinterpret_cast<sockaddr const*>(&bind_ss), bind_sslen) == -1)
+        {
+            return false;
+        }
+
+        if constexpr (ip_protocol == TR_AF_INET)
+        {
+            std::memcpy(&mcast_addr_, &mcast_ss, mcast_sslen);
+
+            // we want to join that LPD multicast group
+            struct ip_mreq mcast_req = {};
+            mcast_req.imr_multiaddr = mcast_addr_.sin_addr;
+            mcast_req.imr_interface = mediator_.bind_address(ip_protocol).addr.addr4;
+
+            if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, reinterpret_cast<char const*>(&mcast_req), sizeof(mcast_req)) ==
                 -1)
             {
                 return false;
             }
-#endif
-
-            auto const [bind_ss, bind_sslen] = tr_socket_address::to_sockaddr(mediator_.bind_address(TR_AF_INET), McastPort);
-
-            if (bind(mcast_socket_, reinterpret_cast<sockaddr const*>(&bind_ss), bind_sslen) == -1)
-            {
-                return false;
-            }
-
-            auto const mcast_addr = tr_address::from_string(McastGroup);
-            TR_ASSERT(mcast_addr);
-            auto const [mcast_ss, mcast_sslen] = tr_socket_address::to_sockaddr(*mcast_addr, McastPort);
-            std::memcpy(&mcast_addr_, &mcast_ss, mcast_sslen);
-
-            /* we want to join that LPD multicast group */
-            ip_mreq mcast_req = {};
-            mcast_req.imr_multiaddr = mcast_addr_.sin_addr;
-            mcast_req.imr_interface = reinterpret_cast<sockaddr_in const*>(&bind_ss)->sin_addr;
 
+            // configure outbound multicast TTL
             if (setsockopt(
-                    mcast_socket_,
-                    IPPROTO_IP,
-                    IP_ADD_MEMBERSHIP,
-                    reinterpret_cast<char const*>(&mcast_req),
-                    sizeof(mcast_req)) == -1)
-            {
-                return false;
-            }
-
-            /* configure outbound multicast TTL */
-            if (setsockopt(
-                    mcast_socket_,
+                    sock,
                     IPPROTO_IP,
                     IP_MULTICAST_TTL,
                     reinterpret_cast<char const*>(&AnnounceScope),
@@ -340,12 +377,71 @@ private:
             {
                 return false;
             }
+
+            if (setsockopt(
+                    sock,
+                    IPPROTO_IP,
+                    IP_MULTICAST_IF,
+                    reinterpret_cast<char const*>(&mcast_req.imr_interface),
+                    sizeof(mcast_req.imr_interface)) == -1)
+            {
+                return false;
+            }
+
+            // needed to announce to BT clients on the same interface
+            if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_LOOP, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) == -1)
+            {
+                return false;
+            }
+        }
+        else // TR_AF_INET6
+        {
+            std::memcpy(&mcast6_addr_, &mcast_ss, mcast_sslen);
+
+            // we want to join that LPD multicast group
+            struct ipv6_mreq mcast_req = {};
+            mcast_req.ipv6mr_multiaddr = mcast6_addr_.sin6_addr;
+            mcast_req.ipv6mr_interface = mediator_.bind_address(ip_protocol).to_interface_index().value_or(0);
+
+            if (setsockopt(sock, IPPROTO_IPV6, IPV6_JOIN_GROUP, reinterpret_cast<char const*>(&mcast_req), sizeof(mcast_req)) ==
+                -1)
+            {
+                return false;
+            }
+
+            // configure outbound multicast TTL
+            if (setsockopt(
+                    sock,
+                    IPPROTO_IPV6,
+                    IPV6_MULTICAST_HOPS,
+                    reinterpret_cast<char const*>(&AnnounceScope),
+                    sizeof(AnnounceScope)) == -1)
+            {
+                return false;
+            }
+
+            if (setsockopt(
+                    sock,
+                    IPPROTO_IPV6,
+                    IPV6_MULTICAST_IF,
+                    reinterpret_cast<char const*>(&mcast_req.ipv6mr_interface),
+                    sizeof(mcast_req.ipv6mr_interface)) == -1)
+            {
+                return false;
+            }
+
+            // needed to announce to BT clients on the same interface
+            if (setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, reinterpret_cast<char const*>(&opt_on), sizeof(opt_on)) ==
+                -1)
+            {
+                return false;
+            }
         }
 
-        event_.reset(event_new(event_base, mcast_socket_, EV_READ | EV_PERSIST, event_callback, this));
-        event_add(event_.get(), nullptr);
+        events_[ip_protocol].reset(event_new(event_base, sock, EV_READ | EV_PERSIST, event_callback<ip_protocol>, this));
+        event_add(events_[ip_protocol].get(), nullptr);
 
-        tr_logAddDebug("Local Peer Discovery initialised");
+        tr_logAddDebug(fmt::format("{} Local Peer Discovery initialised", tr_ip_protocol_to_sv(ip_protocol)));
 
         return true;
     }
@@ -354,27 +450,34 @@ private:
     * @brief Processing of timeout notifications and incoming data on the socket
     * @note maximum rate of read events is limited according to @a lpd_maxAnnounceCap
     * @see DoS */
+    template<tr_address_type ip_protocol>
     static void event_callback(evutil_socket_t /*s*/, short type, void* vself)
     {
         if ((type & EV_READ) != 0)
         {
-            static_cast<tr_lpd_impl*>(vself)->onCanRead();
+            static_cast<tr_lpd_impl*>(vself)->onCanRead(ip_protocol);
         }
     }
 
-    void onCanRead()
+    void onCanRead(tr_address_type ip_protocol)
     {
+        TR_ASSERT(tr_address::is_valid(ip_protocol));
+        if (!tr_address::is_valid(ip_protocol))
+        {
+            return;
+        }
+
         if (!mediator_.allowsLPD())
         {
             return;
         }
 
         // process announcement from foreign peer
-        struct sockaddr_in foreign_addr = {};
+        struct sockaddr_storage foreign_addr = {};
         auto addr_len = socklen_t{ sizeof(foreign_addr) };
         auto foreign_msg = std::array<char, MaxDatagramLength>{};
         auto const res = recvfrom(
-            mcast_socket_,
+            mcast_sockets_[ip_protocol],
             std::data(foreign_msg),
             MaxDatagramLength,
             0,
@@ -386,6 +489,7 @@ private:
         {
             return;
         }
+        TR_ASSERT(tr_af_to_ip_protocol(foreign_addr.ss_family) == ip_protocol);
 
         // If it doesn't look like a BEP14 message, discard it
         auto const msg = std::string_view{ std::data(foreign_msg), static_cast<size_t>(res) };
@@ -410,10 +514,14 @@ private:
             return;
         }
 
-        auto [peer_addr, compact] = tr_address::from_compact_ipv4(reinterpret_cast<std::byte*>(&foreign_addr.sin_addr));
+        auto peer_sockaddr = tr_socket_address::from_sockaddr(reinterpret_cast<sockaddr*>(&foreign_addr));
+        if (!peer_sockaddr)
+        {
+            return;
+        }
         for (auto const& hash_string : parsed->info_hash_strings)
         {
-            if (!mediator_.onPeerFound(hash_string, peer_addr, parsed->port))
+            if (!mediator_.onPeerFound(hash_string, peer_sockaddr->address(), parsed->port))
             {
                 tr_logAddDebug(fmt::format("Cannot serve torrent #{:s}", hash_string));
             }
@@ -462,19 +570,30 @@ private:
         std::sort(std::begin(torrents), std::end(torrents), TorrentComparator);
 
         // cram in as many as will fit in a message
-        auto const baseline_size = std::size(makeAnnounceMsg(cookie_, mediator_.port(), {}));
-        auto const size_with_one = std::size(makeAnnounceMsg(cookie_, mediator_.port(), { torrents.front().info_hash_str }));
-        auto const size_per_hash = size_with_one - baseline_size;
+        auto baseline_size = size_t{};
+        for (ipp_t ipp = 0; ipp < NUM_TR_AF_INET_TYPES; ++ipp)
+        {
+            baseline_size = std::max(
+                baseline_size,
+                std::size(makeAnnounceMsg(static_cast<tr_address_type>(ipp), cookie_, mediator_.port(), {})));
+        }
+        auto const size_per_hash = std::size(torrents.front().info_hash_str);
         auto const max_torrents_per_announce = (MaxDatagramLength - baseline_size) / size_per_hash;
+        auto const torrents_this_announce = std::min(std::size(torrents), max_torrents_per_announce);
         auto info_hash_strings = std::vector<std::string_view>{};
-        info_hash_strings.resize(std::min(std::size(torrents), max_torrents_per_announce));
+        info_hash_strings.reserve(torrents_this_announce);
         std::transform(
             std::begin(torrents),
-            std::begin(torrents) + std::size(info_hash_strings),
-            std::begin(info_hash_strings),
+            std::begin(torrents) + torrents_this_announce,
+            std::back_inserter(info_hash_strings),
             [](auto const& tor) { return tor.info_hash_str; });
 
-        if (!sendAnnounce(info_hash_strings))
+        auto success = false;
+        for (ipp_t ipp = 0; ipp < NUM_TR_AF_INET_TYPES; ++ipp)
+        {
+            success |= sendAnnounce(static_cast<tr_address_type>(ipp), info_hash_strings);
+        }
+        if (!success)
         {
             return;
         }
@@ -508,28 +627,40 @@ private:
      * matter). A listening client on the same network might react by adding us to his
      * peer pool for torrent t.
      */
-    bool sendAnnounce(std::vector<std::string_view> const& info_hash_strings)
+    bool sendAnnounce(tr_address_type ip_protocol, std::vector<std::string_view> const& info_hash_strings)
     {
-        auto const announce = makeAnnounceMsg(cookie_, mediator_.port(), info_hash_strings);
+        TR_ASSERT(tr_address::is_valid(ip_protocol));
+        if (!tr_address::is_valid(ip_protocol))
+        {
+            return false;
+        }
+
+        if (mcast_sockets_[ip_protocol] == TR_BAD_SOCKET)
+        {
+            return true;
+        }
+
+        auto const announce = makeAnnounceMsg(ip_protocol, cookie_, mediator_.port(), info_hash_strings);
         TR_ASSERT(std::size(announce) <= MaxDatagramLength);
         auto const res = sendto(
-            mcast_socket_,
+            mcast_sockets_[ip_protocol],
             std::data(announce),
             std::size(announce),
             0,
-            reinterpret_cast<sockaddr const*>(&mcast_addr_),
-            sizeof(mcast_addr_));
-        auto const sent = res == static_cast<int>(std::size(announce));
-        return sent;
+            ip_protocol == TR_AF_INET ? reinterpret_cast<sockaddr const*>(&mcast_addr_) :
+                                        reinterpret_cast<sockaddr const*>(&mcast6_addr_),
+            ip_protocol == TR_AF_INET ? sizeof(mcast_addr_) : sizeof(mcast6_addr_));
+        return res == static_cast<int>(std::size(announce));
     }
 
     std::string const cookie_ = makeCookie();
     Mediator& mediator_;
-    tr_socket_t mcast_socket_ = TR_BAD_SOCKET; /**multicast socket */
-    libtransmission::evhelpers::event_unique_ptr event_;
+    std::array<tr_socket_t, NUM_TR_AF_INET_TYPES> mcast_sockets_ = { TR_BAD_SOCKET, TR_BAD_SOCKET }; /**multicast sockets */
+    std::array<libtransmission::evhelpers::event_unique_ptr, NUM_TR_AF_INET_TYPES> events_;
 
     static auto constexpr MaxDatagramLength = size_t{ 1400 };
     sockaddr_in mcast_addr_ = {}; /**<initialized from the above constants in init() */
+    sockaddr_in6 mcast6_addr_ = {}; /**<initialized from the above constants in init() */
 
     // BEP14: "To avoid causing multicast storms on large networks a
     // client should send no more than 1 announce per minute."

tests/libtransmission/lpd-test.cc

@@ -41,9 +41,11 @@ public:
     {
     }
 
-    [[nodiscard]] tr_address bind_address(tr_address_type /* type */) const override
+    [[nodiscard]] tr_address bind_address(tr_address_type type) const override
     {
-        return {};
+        auto ret = tr_address{};
+        ret.type = type;
+        return ret;
     }
 
     [[nodiscard]] tr_port port() const override

utils/transmission-remote.1

@@ -150,7 +150,7 @@ Get a file list for the current torrent(s)
 .It Fl g Fl -get Ar all | file-index | files
 Mark file(s) for download.
 .Ar all
-marks all all of the torrent's files for downloading,
+marks all of the torrent's files for downloading,
 .Ar file-index
 adds a single file to the download list, and
 .Ar files