feat: support dscp classes in socket iptos (#2594)

* refactor: Replace ToS with DSCP

IP TOS was superseded by DSCP in RFC 2474.

Co-authored-by: dgcampea <dgcampea@outlook.com>

cli/cli.cc

@@ -76,7 +76,13 @@ static auto constexpr Options = std::array<tr_option, 19>{
       { 'm', "portmap", "Enable portmapping via NAT-PMP or UPnP", "m", false, nullptr },
       { 'M', "no-portmap", "Disable portmapping", "M", false, nullptr },
       { 'p', "port", "Port for incoming peers (Default: " TR_DEFAULT_PEER_PORT_STR ")", "p", true, "<port>" },
-      { 't', "tos", "Peer socket TOS (0 to 255, default=" TR_DEFAULT_PEER_SOCKET_TOS_STR ")", "t", true, "<tos>" },
+      { 't',
+        "tos",
+        "Peer socket DSCP / ToS setting (number, or a DSCP string, e.g. 'af11' or 'cs0', default=" TR_DEFAULT_PEER_SOCKET_TOS_STR
+        ")",
+        "t",
+        true,
+        "<dscp-or-tos>" },
       { 'u', "uplimit", "Set max upload speed in " SPEED_K_STR, "u", true, "<speed>" },
       { 'U', "no-uplimit", "Don't limit the upload speed", "U", false, nullptr },
       { 'v', "verify", "Verify the specified torrent", "v", false, nullptr },
@@ -434,7 +440,7 @@ static int parseCommandLine(tr_variant* d, int argc, char const** argv)
             break;
 
         case 't':
-            tr_variantDictAddInt(d, TR_KEY_peer_socket_tos, atoi(my_optarg));
+            tr_variantDictAddStr(d, TR_KEY_peer_socket_tos, my_optarg);
             break;
 
         case 'u':

cli/transmission-cli.1

@@ -32,7 +32,7 @@
 .Op Fl h
 .Op Fl m | M
 .Op Fl p Ar port
-.Op Fl t Ar tos
+.Op Fl -tos Ar tos
 .Op Fl u Ar number | Fl U
 .Op Fl v
 .Op Fl w Ar directory
@@ -74,17 +74,43 @@ Enable portmapping via NAT-PMP or UPnP
 Disable portmapping
 .It Fl p -port Ar port
 Set the port to listen for incoming peers. (Default: 51413)
-.It Fl t -tos Ar tos
+.It Fl -tos Ar tos
-Set the peer socket TOS for local router-based traffic shaping.
+.nf
-Valid values are
+Use a ToS or DSCP name to set the peer socket service type for
+local router-based traffic shaping. Valid values are a decimal
+value 0-255, or any of these DSCP strings:
+.fi
 .Pp
+.Dq af11 ,
+.Dq af12 ,
+.Dq af13 ,
+.Dq af21 ,
+.Dq af22 ,
+.Dq af23 ,
+.Dq af31 ,
+.Dq af32 ,
+.Dq af33 ,
+.Dq af41 ,
+.Dq af42 ,
+.Dq af43 ,
+.Dq cs0 ,
+.Dq cs1 ,
+.Dq cs2 ,
+.Dq cs3 ,
+.Dq cs4 ,
+.Dq cs5 ,
+.Dq cs6 ,
+.Dq cs7 ,
+.Dq ef ,
+.Dq le
+
+These ToS keys are deprecated and will be removed in the future:
 .Dq default ,
 .Dq lowcost ,
-.Dq throughput ,
+.Dq lowdelay,
 .Dq reliability ,
-.Dq lowdelay ,
+.Dq throughput
 .Pp
-a decimal value 0-255 or a hexidecimal value 0x00-0xff)
 .It Fl u -uplimit Ar number
 Set the maximum upload speed in KB/s
 .It Fl U -no-uplimit

libtransmission/net.cc

@@ -1,4 +1,4 @@
-// This file Copyright © 2010 Transmission authors and contributors.
+// This file Copyright © 2010-2022 Transmission authors and contributors.
 // It may be used under the MIT (SPDX: MIT) license.
 // License text can be found in the licenses/ folder.
 
@@ -9,6 +9,7 @@
 #include <cstring>
 #include <ctime>
 #include <string_view>
+#include <utility> // std::pair
 
 #include <sys/types.h>
 
@@ -149,8 +150,70 @@ int tr_address_compare(tr_address const* a, tr_address const* b)
  * TCP sockets
  **********************************************************************/
 
+// RFCs 2474, 3246, 4594 & 8622
+// Service class names are defined in RFC 4594, RFC 5865, and RFC 8622.
+// Not all platforms have these IPTOS_ definitions, so hardcode them here
+static auto constexpr IpTosNames = std::array<std::pair<int, std::string_view>, 28>{ {
+    { 0x00, "cs0" }, // IPTOS_CLASS_CS0
+    { 0x04, "le" },
+    { 0x20, "cs1" }, // IPTOS_CLASS_CS1
+    { 0x28, "af11" }, // IPTOS_DSCP_AF11
+    { 0x30, "af12" }, // IPTOS_DSCP_AF12
+    { 0x38, "af13" }, // IPTOS_DSCP_AF13
+    { 0x40, "cs2" }, // IPTOS_CLASS_CS2
+    { 0x48, "af21" }, // IPTOS_DSCP_AF21
+    { 0x50, "af22" }, // IPTOS_DSCP_AF22
+    { 0x58, "af23" }, // IPTOS_DSCP_AF23
+    { 0x60, "cs3" }, // IPTOS_CLASS_CS3
+    { 0x68, "af31" }, // IPTOS_DSCP_AF31
+    { 0x70, "af32" }, // IPTOS_DSCP_AF32
+    { 0x78, "af33" }, // IPTOS_DSCP_AF33
+    { 0x80, "cs4" }, // IPTOS_CLASS_CS4
+    { 0x88, "af41" }, // IPTOS_DSCP_AF41
+    { 0x90, "af42" }, // IPTOS_DSCP_AF42
+    { 0x98, "af43" }, // IPTOS_DSCP_AF43
+    { 0xa0, "cs5" }, // IPTOS_CLASS_CS5
+    { 0xb8, "ef" }, // IPTOS_DSCP_EF
+    { 0xc0, "cs6" }, // IPTOS_CLASS_CS6
+    { 0xe0, "cs7" }, // IPTOS_CLASS_CS7
+
+    // <netinet/ip.h> lists these TOS names as deprecated,
+    // but keep them defined here for backward compatibility
+    { 0x00, "routine" }, // IPTOS_PREC_ROUTINE
+    { 0x02, "lowcost" }, // IPTOS_LOWCOST
+    { 0x02, "mincost" }, // IPTOS_MINCOST
+    { 0x04, "reliable" }, // IPTOS_RELIABILITY
+    { 0x08, "throughput" }, // IPTOS_THROUGHPUT
+    { 0x10, "lowdelay" }, // IPTOS_LOWDELAY
+} };
+
+std::string tr_netTosToName(int tos)
+{
+    auto const test = [tos](auto const& pair)
+    {
+        return pair.first == tos;
+    };
+    auto const it = std::find_if(std::begin(IpTosNames), std::end(IpTosNames), test);
+    return it == std::end(IpTosNames) ? std::to_string(tos) : std::string{ it->second };
+}
+
+std::optional<int> tr_netTosFromName(std::string_view name)
+{
+    auto const test = [&name](auto const& pair)
+    {
+        return pair.second == name;
+    };
+    auto const it = std::find_if(std::begin(IpTosNames), std::end(IpTosNames), test);
+    return it != std::end(IpTosNames) ? it->first : tr_parseNum<int>(name);
+}
+
 void tr_netSetTOS([[maybe_unused]] tr_socket_t s, [[maybe_unused]] int tos, tr_address_type type)
 {
+    if (s == TR_BAD_SOCKET)
+    {
+        return;
+    }
+
     if (type == TR_AF_INET)
     {
 #if defined(IP_TOS) && !defined(_WIN32)

libtransmission/net.h

@@ -9,6 +9,8 @@
 #endif
 
 #include <cstddef> // size_t
+#include <optional>
+#include <string>
 #include <string_view>
 
 #ifdef _WIN32
@@ -104,23 +106,12 @@ constexpr bool tr_address_is_valid(tr_address const* a)
  * Sockets
  **********************************************************************/
 
-/* https://en.wikipedia.org/wiki/Differentiated_services#Class_Selector */
-enum
-{
-    TR_IPTOS_LOWCOST = 0x38, /* AF13: low prio, high drop */
-    TR_IPTOS_LOWDELAY = 0x70, /* AF32: high prio, mid drop */
-    TR_IPTOS_THRUPUT = 0x20, /* CS1: low prio, undef drop */
-    TR_IPTOS_RELIABLE = 0x28 /* AF11: low prio, low drop */
-};
-
 struct tr_session;
 
 tr_socket_t tr_netBindTCP(tr_address const* addr, tr_port port, bool suppressMsgs);
 
 tr_socket_t tr_netAccept(tr_session* session, tr_socket_t bound, tr_address* setme_addr, tr_port* setme_port);
 
-void tr_netSetTOS(tr_socket_t s, int tos, tr_address_type type);
-
 void tr_netSetCongestionControl(tr_socket_t s, char const* algorithm);
 
 void tr_netClose(tr_session* session, tr_socket_t s);
@@ -129,6 +120,17 @@ void tr_netCloseSocket(tr_socket_t fd);
 
 bool tr_net_hasIPv6(tr_port);
 
+/// TOS / DSCP
+
+// get a string of one of <netinet/ip.h>'s IPTOS_ values, e.g. "cs0"
+std::string tr_netTosToName(int tos);
+
+// get the number that corresponds to the specified IPTOS_ name, e.g. "cs0" returns 0x00
+std::optional<int> tr_netTosFromName(std::string_view name);
+
+// set the IPTOS_ value for the specified socket
+void tr_netSetTOS(tr_socket_t sock, int tos, tr_address_type type);
+
 /**
  * @brief get a human-representable string representing the network error.
  * @param err an errno on Unix/Linux and an WSAError on win32)

libtransmission/peer-io.cc

@@ -624,7 +624,7 @@ static tr_peerIo* tr_peerIoNew(
 
     if (socket.type == TR_PEER_SOCKET_TYPE_TCP)
     {
-        tr_netSetTOS(socket.handle.tcp, session->peerSocketTos(), addr->type);
+        session->setSocketTOS(socket.handle.tcp, addr->type);
         maybeSetCongestionAlgorithm(socket.handle.tcp, session->peerCongestionAlgorithm());
     }
 
@@ -979,7 +979,7 @@ int tr_peerIoReconnect(tr_peerIo* io)
     io->event_write = event_new(session->event_base, io->socket.handle.tcp, EV_WRITE, event_write_cb, io);
 
     event_enable(io, pendingEvents);
-    tr_netSetTOS(io->socket.handle.tcp, session->peerSocketTos(), io->addr.type);
+    io->session->setSocketTOS(io->socket.handle.tcp, io->addr.type);
     maybeSetCongestionAlgorithm(io->socket.handle.tcp, session->peerCongestionAlgorithm());
 
     return 0;

libtransmission/session.cc

@@ -250,62 +250,6 @@ tr_address const* tr_sessionGetPublicAddress(tr_session const* session, int tr_a
 ****
 ***/
 
-static int parseTos(std::string_view tos_in)
-{
-    auto tos = tr_strlower(tr_strvStrip(tos_in));
-
-    if (tos == ""sv || tos == "default"sv)
-    {
-        return 0;
-    }
-
-    if (tos == "lowcost"sv || tos == "mincost"sv)
-    {
-        return TR_IPTOS_LOWCOST;
-    }
-
-    if (tos == "throughput"sv)
-    {
-        return TR_IPTOS_THRUPUT;
-    }
-
-    if (tos == "reliability"sv)
-    {
-        return TR_IPTOS_RELIABLE;
-    }
-
-    if (tos == "lowdelay"sv)
-    {
-        return TR_IPTOS_LOWDELAY;
-    }
-
-    return std::stoi(tos);
-}
-
-static std::string format_tos(int value)
-{
-    switch (value)
-    {
-    case 0:
-        return "default";
-
-    case TR_IPTOS_LOWCOST:
-        return "lowcost";
-
-    case TR_IPTOS_THRUPUT:
-        return "throughput";
-
-    case TR_IPTOS_RELIABLE:
-        return "reliability";
-
-    case TR_IPTOS_LOWDELAY:
-        return "lowdelay";
-
-    default:
-        return std::to_string(value);
-    }
-}
-
 #ifdef TR_LIGHTWEIGHT
 #define TR_DEFAULT_ENCRYPTION TR_CLEAR_PREFERRED
 #else
@@ -416,7 +360,7 @@ void tr_sessionGetSettings(tr_session const* s, tr_variant* d)
     tr_variantDictAddBool(d, TR_KEY_peer_port_random_on_start, s->isPortRandom);
     tr_variantDictAddInt(d, TR_KEY_peer_port_random_low, s->randomPortLow);
     tr_variantDictAddInt(d, TR_KEY_peer_port_random_high, s->randomPortHigh);
-    tr_variantDictAddStr(d, TR_KEY_peer_socket_tos, format_tos(s->peerSocketTos()));
+    tr_variantDictAddStr(d, TR_KEY_peer_socket_tos, tr_netTosToName(s->peer_socket_tos_));
     tr_variantDictAddStr(d, TR_KEY_peer_congestion_algorithm, s->peerCongestionAlgorithm());
     tr_variantDictAddBool(d, TR_KEY_pex_enabled, s->isPexEnabled);
     tr_variantDictAddBool(d, TR_KEY_port_forwarding_enabled, tr_sessionIsPortForwardingEnabled(s));
@@ -827,9 +771,16 @@ static void sessionSetImpl(void* vdata)
         tr_sessionSetEncryption(session, tr_encryption_mode(i));
     }
 
-    if (tr_variantDictFindStrView(settings, TR_KEY_peer_socket_tos, &sv))
+    if (tr_variantDictFindInt(settings, TR_KEY_peer_socket_tos, &i))
     {
-        session->setPeerSocketTos(parseTos(sv));
+        session->peer_socket_tos_ = i;
+    }
+    else if (tr_variantDictFindStrView(settings, TR_KEY_peer_socket_tos, &sv))
+    {
+        if (auto ip_tos = tr_netTosFromName(sv); ip_tos)
+        {
+            session->peer_socket_tos_ = *ip_tos;
+        }
     }
 
     sv = ""sv;

libtransmission/session.h

@@ -231,14 +231,9 @@ public:
         peer_congestion_algorithm_ = algorithm;
     }
 
-    int peerSocketTos() const
+    void setSocketTOS(tr_socket_t sock, tr_address_type type)
     {
-        return peer_socket_tos_;
+        tr_netSetTOS(sock, peer_socket_tos_, type);
-    }
-
-    void setPeerSocketTos(int tos)
-    {
-        peer_socket_tos_ = tos;
     }
 
 public:
@@ -358,6 +353,11 @@ public:
 
     std::unique_ptr<tr_rpc_server> rpc_server_;
 
+    // One of <netinet/ip.h>'s IPTOS_ values.
+    // See tr_netTos*() in libtransmission/net.h for more info
+    // Only session.cc should use this.
+    int peer_socket_tos_ = *tr_netTosFromName(TR_DEFAULT_PEER_SOCKET_TOS_STR);
+
 private:
     static std::recursive_mutex session_mutex_;
 
@@ -367,8 +367,6 @@ private:
     std::string incomplete_dir_;
     std::string peer_congestion_algorithm_;
 
-    int peer_socket_tos_ = 0;
-
     std::array<bool, TR_SCRIPT_N_TYPES> scripts_enabled_;
     bool blocklist_enabled_ = false;
     bool incomplete_dir_enabled_ = false;

libtransmission/tr-udp.cc

@@ -107,22 +107,8 @@ void tr_udpSetSocketBuffers(tr_session* session)
 
 void tr_udpSetSocketTOS(tr_session* session)
 {
-    auto const tos = session->peerSocketTos();
+    session->setSocketTOS(session->udp_socket, TR_AF_INET);
-
+    session->setSocketTOS(session->udp6_socket, TR_AF_INET6);
-    if (tos != 0)
-    {
-        return;
-    }
-
-    if (session->udp_socket != TR_BAD_SOCKET)
-    {
-        tr_netSetTOS(session->udp_socket, tos, TR_AF_INET);
-    }
-
-    if (session->udp6_socket != TR_BAD_SOCKET)
-    {
-        tr_netSetTOS(session->udp6_socket, tos, TR_AF_INET6);
-    }
 }
 
 /* BEP-32 has a rather nice explanation of why we need to bind to one

libtransmission/transmission.h

@@ -126,7 +126,7 @@ char const* tr_getDefaultDownloadDir(void);
 #define TR_DEFAULT_RPC_PORT 9091
 #define TR_DEFAULT_RPC_URL_STR "/transmission/"
 #define TR_DEFAULT_PEER_PORT_STR "51413"
-#define TR_DEFAULT_PEER_SOCKET_TOS_STR "default"
+#define TR_DEFAULT_PEER_SOCKET_TOS_STR "le"
 #define TR_DEFAULT_PEER_LIMIT_GLOBAL_STR "200"
 #define TR_DEFAULT_PEER_LIMIT_TORRENT_STR "50"
 #define TR_DEFAULT_PEER_LIMIT_TORRENT 50

qt/Prefs.cc

@@ -129,7 +129,7 @@ std::array<Prefs::PrefItem, Prefs::PREFS_COUNT> const Prefs::Items{
     { QUEUE_STALLED_MINUTES, TR_KEY_queue_stalled_minutes, QVariant::Int },
     { SCRIPT_TORRENT_DONE_ENABLED, TR_KEY_script_torrent_done_enabled, QVariant::Bool },
     { SCRIPT_TORRENT_DONE_FILENAME, TR_KEY_script_torrent_done_filename, QVariant::String },
-    { SOCKET_TOS, TR_KEY_peer_socket_tos, QVariant::Int },
+    { SOCKET_TOS, TR_KEY_peer_socket_tos, QVariant::String },
     { START, TR_KEY_start_added_torrents, QVariant::Bool },
     { TRASH_ORIGINAL, TR_KEY_trash_original_torrent_files, QVariant::Bool },
     { PEX_ENABLED, TR_KEY_pex_enabled, QVariant::Bool },