finagle-http2: Handle upgrade events properly in APCH

Problem / Solution

The AdapterProxyChannelHandler is relying on a Netty but that was fixed
sometime between version 4.1.35 and 4.1.37. We're not upgrading to 4.1.37
but we should fix the behavior anyway.

JIRA Issues: CSL-8436

Differential Revision: https://phabricator.twitter.biz/D336428

CHANGELOG.rst

@@ -15,6 +15,13 @@ Breaking API Changes
   of `GenSerialClientDispatcher` and `SerialClientDispatcher` have been removed.
   ``PHAB_ID=D342883``
 
+Runtime Behavior Changes
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+* finagle-core: Failed reads on Linux due to a remote peer disconnecting should now be properly
+  seen as `c.t.f.ChannelClosedException` instead of a `c.t.f.UnknownChannelException`.
+  ``PHAB_ID=D336428``
+
 19.7.0
 ------
 

finagle-core/src/main/scala/com/twitter/finagle/IOExceptionStrings.scala

@@ -8,6 +8,7 @@ private[finagle] object IOExceptionStrings {
     "Broken pipe", // Found on linux
     "An existing connection was forcibly closed by the remote host", // Found on windows
     "syscall:read(..) failed: Connection reset by peer", // Found on linux w/ native epoll
+    "readAddress(..) failed: Connection reset by peer", // Found on linux w/ native epoll
     "writeAddress(..) failed: Connection reset by peer" // Found on linux w/ native epoll
   )
 

finagle-http2/src/main/scala/com/twitter/finagle/http2/transport/AdapterProxyChannelHandler.scala

@@ -2,10 +2,11 @@ package com.twitter.finagle.http2.transport
 
 import com.twitter.finagle.FailureFlags
 import com.twitter.finagle.http2.transport.StreamMessage._
-import com.twitter.finagle.stats.{StatsReceiver, NullStatsReceiver}
-import com.twitter.logging.{Logger, Level, HasLogLevel}
+import com.twitter.finagle.stats.{NullStatsReceiver, StatsReceiver}
+import com.twitter.logging.{HasLogLevel, Level, Logger}
 import io.netty.channel._
 import io.netty.channel.embedded.EmbeddedChannel
+import io.netty.handler.codec.http.HttpClientUpgradeHandler.UpgradeEvent
 import io.netty.handler.codec.http.{HttpObject, LastHttpContent}
 import io.netty.util.ReferenceCountUtil
 import io.netty.util.concurrent.PromiseCombiner
@@ -153,6 +154,7 @@ private[http2] final class AdapterProxyChannelHandler(
     case Ping => ctx.fireChannelRead(Ping)
     case exn: StreamException => ctx.fireChannelRead(exn)
     case upgrade: Http2UpgradingTransport.UpgradeResult => ctx.fireChannelRead(upgrade)
+    case upgrade: UpgradeEvent => ctx.fireChannelRead(upgrade)
     case _ =>
       val wrongType = new IllegalArgumentException(
         s"Expected a StreamMessage or UpgradeEvent, got ${msg.getClass.getName} instead."