From 81c9653383c4ef07010c8efd1c5bd2d980804017 Mon Sep 17 00:00:00 2001
From: clyang <clyang@clyang.net>
Date: Wed, 2 Aug 2017 18:01:39 +0800
Subject: [PATCH] Improve ToS on IPv6 connections

---
 libtransmission/net.c     | 64 ++++++++++++++++++++++++++++++++++-----
 libtransmission/net.h     |  2 +-
 libtransmission/peer-io.c |  4 +--
 3 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/libtransmission/net.c b/libtransmission/net.c
index 588dc2b27..d96476808 100644
--- a/libtransmission/net.c
+++ b/libtransmission/net.c
@@ -153,22 +153,70 @@ int tr_address_compare(tr_address const* a, tr_address const* b)
  * TCP sockets
  **********************************************************************/
 
-void tr_netSetTOS(tr_socket_t s, int tos)
+void tr_netSetTOS(tr_socket_t s, int tos, tr_address_type type)
 {
+    if (type == TR_AF_INET)
+    {
 #if defined(IP_TOS) && !defined(_WIN32)
 
-    if (setsockopt(s, IPPROTO_IP, IP_TOS, (void const*)&tos, sizeof(tos)) == -1)
-    {
-        char err_buf[512];
-        tr_logAddNamedInfo("Net", "Can't set TOS '%d': %s", tos, tr_net_strerror(err_buf, sizeof(err_buf), sockerrno));
-    }
+        if (setsockopt(s, IPPROTO_IP, IP_TOS, (void const*)&tos, sizeof(tos)) == -1)
+        {
+            char err_buf[512];
+            tr_net_strerror(err_buf, sizeof(err_buf), sockerrno);
+            tr_logAddNamedInfo("Net", "Can't set TOS '%d': %s", tos, err_buf);
+        }
 
 #else
 
-    (void)s;
-    (void)tos;
+        (void)s;
+        (void)tos;
 
 #endif
+    }
+    else if (type == TR_AF_INET6)
+    {
+#if defined(IPV6_TCLASS) && !defined(_WIN32)
+
+        int dscp = 0;
+
+        switch (tos)
+        {
+        case 0x10:
+            dscp = 0x20; /* lowcost (CS1) */
+            break;
+
+        case 0x08:
+            dscp = 0x28; /* throughput (AF11) */
+            break;
+
+        case 0x04:
+            dscp = 0x04; /* reliability */
+            break;
+
+        case 0x02:
+            dscp = 0x30; /* low delay (AF12) */
+            break;
+        }
+
+        if (setsockopt(s, IPPROTO_IPV6, IPV6_TCLASS, (void const*)&dscp, sizeof(dscp)) == -1)
+        {
+            char err_buf[512];
+            tr_net_strerror(err_buf, sizeof(err_buf), sockerrno);
+            tr_logAddNamedInfo("Net", "Can't set IPv6 QoS '%d': %s", dscp, err_buf);
+        }
+
+#else
+
+        (void)s;
+        (void)tos;
+
+#endif
+    }
+    else
+    {
+        /* program should never reach here! */
+        tr_logAddNamedInfo("Net", "Something goes wrong while setting TOS/Traffic-Class");
+    }
 }
 
 void tr_netSetCongestionControl(tr_socket_t s, char const* algorithm)
diff --git a/libtransmission/net.h b/libtransmission/net.h
index 8973dc57a..82577a04e 100644
--- a/libtransmission/net.h
+++ b/libtransmission/net.h
@@ -128,7 +128,7 @@ tr_socket_t tr_netBindTCP(tr_address const* addr, tr_port port, bool suppressMsg
 
 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);
+void tr_netSetTOS(tr_socket_t s, int tos, tr_address_type type);
 
 void tr_netSetCongestionControl(tr_socket_t s, char const* algorithm);
 
diff --git a/libtransmission/peer-io.c b/libtransmission/peer-io.c
index 9fd955063..b84ed02de 100644
--- a/libtransmission/peer-io.c
+++ b/libtransmission/peer-io.c
@@ -637,7 +637,7 @@ static tr_peerIo* tr_peerIoNew(tr_session* session, tr_bandwidth* parent, tr_add
 
     if (socket.type == TR_PEER_SOCKET_TYPE_TCP)
     {
-        tr_netSetTOS(socket.handle.tcp, session->peerSocketTOS);
+        tr_netSetTOS(socket.handle.tcp, session->peerSocketTOS, addr->type);
         maybeSetCongestionAlgorithm(socket.handle.tcp, session->peer_congestion_algorithm);
     }
 
@@ -993,7 +993,7 @@ 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);
+    tr_netSetTOS(io->socket.handle.tcp, session->peerSocketTOS, io->addr.type);
     maybeSetCongestionAlgorithm(io->socket.handle.tcp, session->peer_congestion_algorithm);
 
     return 0;