Bug 41876 - Mono 4.4 loses ability to send web requests to IP addresses
Summary: Mono 4.4 loses ability to send web requests to IP addresses
Status: RESOLVED DUPLICATE of bug 41782
Alias: None
Product: Class Libraries
Classification: Mono
Component: System ()
Version: 4.5.X
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2016-06-16 02:22 UTC by Jim Borden
Modified: 2016-06-16 19:18 UTC (History)
4 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Jim Borden 2016-06-16 02:22:10 UTC
Possibly related to #41782 and affects 4.4, but not (release on homebrew).  When I try to get a response from a server using its IP address (unless it is localhost, which seems to take a special code path), GetHostByAddr_internal appears to hang.  Eventually the request will simply time out without ever getting sent over the wire.  Here is a small repro case that works on but fails on 4.4:

> var request = WebRequest.CreateHttp(""); //www.google.com
> request.Timeout = 10000;
> request.Method = "HEAD";
> try
> {
>     var response = (HttpWebResponse)request.GetResponse();
>     Console.WriteLine($"Got response {response.StatusCode}");
> }
> catch (Exception e)
> {
>     Console.WriteLine("ERROR {0}", e);
> }

> Console.ReadKey(true);

Output on
Got response OK

Output on 4.4:
ERROR System.Net.WebException: The request timed out
  at System.Net.HttpWebRequest.EndGetResponse (IAsyncResult asyncResult) [0x00046] in /private/tmp/source-mono-4.4.0-c7-baseline/bockbuild-mono-4.4.0-c7-baseline/profiles/mono-mac-xamarin/build-root/mono-x86/mcs/class/System/System.Net/HttpWebRequest.cs:1001 
  at System.Net.HttpWebRequest.GetResponse () [0x0000e] in /private/tmp/source-mono-4.4.0-c7-baseline/bockbuild-mono-4.4.0-c7-baseline/profiles/mono-mac-xamarin/build-root/mono-x86/mcs/class/System/System.Net/HttpWebRequest.cs:1019 
  at WTFWebRequest.MainClass.Main (System.String[] args) [0x00024] in /Users/borrrden/Projects/WTFWebRequest/Program.cs:35 

Pausing in the debugger shows 4.4 stuck on this line:
> bool ret = GetHostByAddr_internal(address, out h_name, out h_aliases, out h_addrlist);

Two other threads are on the same line in WaitHandle.WaitOne():
> return (WaitOne_internal(safe_wait_handle.DangerousGetHandle (), millisecondsTimeout, exitContext));

One comes from blocking on GetResponse, and the other comes from a timer somewhere.
Comment 1 Jim Borden 2016-06-16 02:38:57 UTC
I changed the affected version because I just compiled and tried 4.5.1:

Mono JIT compiler version 4.5.1 (mono-4.5.1-branch/8a2fd1e Thu Jun 16 11:21:48 JST 2016)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           normal
	SIGSEGV:       altstack
	Notification:  kqueue
	Architecture:  x86
	Disabled:      none
	Misc:          softdebug 
	LLVM:          supported, not enabled.
	GC:            sgen

With the same result
Comment 2 Marek Safar 2016-06-16 19:18:43 UTC

*** This bug has been marked as a duplicate of bug 41782 ***