From e6a1d3ffbc62224d200c2b914fcc4c3c0bc4bde3 Mon Sep 17 00:00:00 2001
From: Kimura Youichi <kim.upsilon@bucyou.net>
Date: Tue, 11 Aug 2015 17:23:24 +0900
Subject: [PATCH] =?utf8?q?pbs.twimg.com=E3=81=B8=E3=81=AE=E6=8E=A5?=
 =?utf8?q?=E7=B6=9A=E3=81=ABIPv4=E3=82=92=E5=BC=B7=E5=88=B6=E3=81=99?=
 =?utf8?q?=E3=82=8B=E3=82=B3=E3=83=BC=E3=83=89=E3=81=8C=E6=84=8F=E5=9B=B3?=
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 =?utf8?q?=E3=81=8B=E3=81=A3=E3=81=9F=E3=81=93=E3=81=A8=E3=81=AB=E5=AF=BE?=
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---
 OpenTween/Connection/Networking.cs | 53 +++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 18 deletions(-)

diff --git a/OpenTween/Connection/Networking.cs b/OpenTween/Connection/Networking.cs
index 86a1461c..334a58e4 100644
--- a/OpenTween/Connection/Networking.cs
+++ b/OpenTween/Connection/Networking.cs
@@ -70,24 +70,10 @@ namespace OpenTween.Connection
                 if (forceIPv4 == value)
                     return;
 
-                if (value)
-                {
-                    BindIPEndPoint forceIPv4Delegate = (_, __, ___) => new IPEndPoint(IPAddress.Any, 0);
-
-                    ServicePointManager.FindServicePoint("http://pbs.twimg.com/", proxy)
-                        .BindIPEndPointDelegate = forceIPv4Delegate;
-                    ServicePointManager.FindServicePoint("https://pbs.twimg.com/", proxy)
-                        .BindIPEndPointDelegate = forceIPv4Delegate;
-                }
-                else
-                {
-                    ServicePointManager.FindServicePoint("http://pbs.twimg.com/", proxy)
-                        .BindIPEndPointDelegate = null;
-                    ServicePointManager.FindServicePoint("https://pbs.twimg.com/", proxy)
-                        .BindIPEndPointDelegate = null;
-                }
-
                 forceIPv4 = value;
+
+                // Network.Http を再作成させる
+                OnWebProxyChanged(EventArgs.Empty);
             }
         }
 
@@ -167,7 +153,12 @@ namespace OpenTween.Connection
                 handler.UseProxy = false;
             }
 
-            var client = new HttpClient(handler);
+            HttpClient client;
+            if (ForceIPv4)
+                client = new HttpClient(new ForceIPv4Handler(handler));
+            else
+                client = new HttpClient(handler);
+
             client.Timeout = Networking.DefaultTimeout;
             client.DefaultRequestHeaders.Add("User-Agent", Networking.GetUserAgentString());
 
@@ -201,6 +192,32 @@ namespace OpenTween.Connection
             if (WebProxyChanged != null)
                 WebProxyChanged(null, e);
         }
+
+        private class ForceIPv4Handler : DelegatingHandler
+        {
+            private readonly IPAddress ipv4Address;
+
+            public ForceIPv4Handler(HttpMessageHandler innerHandler)
+                : base(innerHandler)
+            {
+                foreach (var address in Dns.GetHostAddresses("pbs.twimg.com"))
+                    if (address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
+                        this.ipv4Address = address;
+            }
+
+            protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+            {
+                var requestUri = request.RequestUri;
+                if (requestUri.Host == "pbs.twimg.com")
+                {
+                    var rewriteUriStr = requestUri.GetLeftPart(UriPartial.Scheme) + this.ipv4Address + requestUri.PathAndQuery;
+                    request.RequestUri = new Uri(rewriteUriStr);
+                    request.Headers.Host = "pbs.twimg.com";
+                }
+
+                return base.SendAsync(request, cancellationToken);
+            }
+        }
     }
 
     public enum ProxyType
-- 
2.11.0