Bug 29279 - Dns.GetHostEntry no longer returns hostname
Summary: Dns.GetHostEntry no longer returns hostname
Alias: None
Product: Class Libraries
Classification: Mono
Component: System (show other bugs)
Version: 4.0.0
Hardware: Macintosh Mac OS
: High normal
Target Milestone: Untriaged
Assignee: Bugzilla
: 56295 56299 (view as bug list)
Depends on:
Reported: 2015-04-21 16:26 UTC by matt
Modified: 2017-12-01 13:39 UTC (History)
12 users (show)

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


Description matt 2015-04-21 16:26:02 UTC
With mono 4.0 the reverse DNS broke. 
The following code always returns the IP address as string rather than the HostName.
Dns.GetHostEntry("my ip address").HostName

// IP for google.com
var google = Dns.GetHostEntry("");
Console.WriteLine("Hostname: " + google.HostName);
// outputs: "" instead of "google.com"

(This is with the mono 4.0 beta update. I didn't see the 4.0 version when filing this bug so hopefully someone can correct the ticket)
Comment 1 Cody Beyer (MSFT) 2015-05-15 20:36:24 UTC
Updating with test project

### Description

The following app demonstrates an issue within Mono 4, where the DNS.GetHostEntry method returns an incorrect result

### Test Case


### Steps to Reproduce

1. Open test case
2. Run with Mono

### Expected Results

A hostname should be returned

### Actual Results

The IP address is returned. 

### Working Version

Do the above with either mono 3.x or on Windows using CSC/.Net

### Versions

=== Xamarin Studio ===

Version 5.9.2 (build 0)
Installation UUID: 061f61cf-c366-4da7-b3c9-31033d0fc883
	Mono 4.0.1 ((detached/6d5afc1)
	GTK+ 2.24.23 (Raleigh theme)

	Package version: 400010034

=== Apple Developer Tools ===

Xcode 6.3.1 (7703)
Build 6D1002

=== Xamarin.iOS ===

Version: (Business Edition)
Hash: b39367d
Branch: master
Build date: 2015-05-14 08:50:11-0400

=== Xamarin.Android ===

Version: (Business Edition)
Android SDK: /Users/beyerc/Library/Developer/Xamarin/android-sdk-macosx
	Supported Android versions:
		2.3   (API level 10)
		4.0.3 (API level 15)
		4.4   (API level 19)
		5.0   (API level 21)
Java SDK: /usr
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)

=== Xamarin Android Player ===

Version: Unknown version
Location: /Applications/Xamarin Android Player.app

=== Xamarin.Mac ===

Version: (Business Edition)

=== Build Information ===

Release ID: 509020000
Git revision: f97f3598952edca4678fc9fdafffecb68ed24399
Build date: 2015-05-08 11:55:56-04
Xamarin addins: ab18ddff45f507ed74f36c2b65df9aee22e28a56

=== Operating System ===

Mac OS X 10.10.3
Darwin Codys-MBP.router 14.3.0 Darwin Kernel Version 14.3.0
    Mon Mar 23 11:59:05 PDT 2015
    root:xnu-2782.20.48~5/RELEASE_X86_64 x86_64
Comment 2 matt 2015-08-11 13:20:41 UTC
Is Xamarin bugzilla the most appropriate place for this ticket? Is there a higher likelihood of this getting fixed if reported elsewhere?
Comment 3 Konrad Mrożek 2015-09-18 09:11:38 UTC
It appears that the bug was introduced here:

Comment 4 Konrad Mrożek 2015-09-18 09:24:33 UTC
Ok. It is not the case :). Sorry :).
Comment 5 williamd 2016-01-12 14:34:21 UTC
Any idea when this will be fixed?
Comment 6 Brendan Zagaeski (Xamarin Team, assistant) 2017-06-05 18:52:53 UTC
*** Bug 56299 has been marked as a duplicate of this bug. ***
Comment 7 Brendan Zagaeski (Xamarin Team, assistant) 2017-06-05 18:53:37 UTC
*** Bug 56295 has been marked as a duplicate of this bug. ***
Comment 8 sam 2017-11-21 21:46:35 UTC
This is affecting me on Linux too. Currently standing in the way of an important ircd feature - reverse DNS lookups for blacklists (e.g. proxies). Version: mono

The same code works on Windows.

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