emby: DLNA components fail to start/run

[dtzWill]

Issue description

After enabling the emby service on Nix 17.03, things seem to mostly work great (hooray!) but DLNA doesn't work. Investigating a bit this seems to be due to some problem while creating/configuring the necessary sockets.

Observed behavior is I'm unable to see DLNA devices on the network.

Relevant bit from server log:

2017-03-19 17:13:54.2491 Info App: Starting entry point Emby.Dlna.DlnaProfileEntryPoint
2017-03-19 17:13:54.2491 Info App: Entry point completed: Emby.Dlna.DlnaProfileEntryPoint. Duration: 2.6E-05 seconds
2017-03-19 17:13:54.2491 Info App: Starting entry point Emby.Dlna.Main.DlnaEntryPoint
2017-03-19 17:13:54.3161 Error Dlna: Error starting ssdp handlers
	*** Error Report ***
	Version: 3.2.4.0
	Command line: /nix/store/2x3kyck9gxcfnmxq1ippx9vn1br4gkqp-emby-3.2.4/bin/MediaBrowser.Server.Mono.exe -ffmpeg /nix/store/c9wwsf2sl3yggh15zqa1sxcgkvy831bq-ffmpeg-3.1.7-bin/bin/ffmpeg -ffprobe /nix/store/c9wwsf2sl3yggh15zqa1sxcgkvy831bq-ffmpeg-3.1.7-bin/bin/ffprobe
	Operating system: Unix 4.9.13.0
	64-Bit OS: True
	64-Bit Process: True
	Mono: 4.6.0 (Stable 4.6.0.182/3ed2bba Sat Mar 18 16:23:51 UTC 2017)
	Processor count: 8
	Program data path: /var/lib/emby/ProgramData-Server
	Application directory: /nix/store/2x3kyck9gxcfnmxq1ippx9vn1br4gkqp-emby-3.2.4/bin
	System.Net.Sockets.SocketException (0x80004005): Protocol option not supported
	  at System.Net.Sockets.Socket.SetSocketOption (System.Net.Sockets.SocketOptionLevel optionLevel, System.Net.Sockets.SocketOptionName optionName, System.Int32 optionValue) [0x0006d] in <ae4a5672e28e4473b7bfd6b7dc9718e2>:0 
	  at Emby.Common.Implementations.Net.SocketFactory.CreateUdpMulticastSocket (System.String ipAddress, System.Int32 multicastTimeToLive, System.Int32 localPort) [0x0006c] in <8e9ecee01d34431081e6e23647892497>:0 
	System.Net.Sockets.SocketException
	  at System.Net.Sockets.Socket.SetSocketOption (System.Net.Sockets.SocketOptionLevel optionLevel, System.Net.Sockets.SocketOptionName optionName, System.Int32 optionValue) [0x0006d] in <ae4a5672e28e4473b7bfd6b7dc9718e2>:0 
	  at Emby.Common.Implementations.Net.SocketFactory.CreateUdpMulticastSocket (System.String ipAddress, System.Int32 multicastTimeToLive, System.Int32 localPort) [0x0006c] in <8e9ecee01d34431081e6e23647892497>:0 
	
2017-03-19 17:13:54.3178 Error Dlna: Error registering endpoint
	*** Error Report ***
	Version: 3.2.4.0
	Command line: /nix/store/2x3kyck9gxcfnmxq1ippx9vn1br4gkqp-emby-3.2.4/bin/MediaBrowser.Server.Mono.exe -ffmpeg /nix/store/c9wwsf2sl3yggh15zqa1sxcgkvy831bq-ffmpeg-3.1.7-bin/bin/ffmpeg -ffprobe /nix/store/c9wwsf2sl3yggh15zqa1sxcgkvy831bq-ffmpeg-3.1.7-bin/bin/ffprobe
	Operating system: Unix 4.9.13.0
	64-Bit OS: True
	64-Bit Process: True
	Mono: 4.6.0 (Stable 4.6.0.182/3ed2bba Sat Mar 18 16:23:51 UTC 2017)
	Processor count: 8
	Program data path: /var/lib/emby/ProgramData-Server
	Application directory: /nix/store/2x3kyck9gxcfnmxq1ippx9vn1br4gkqp-emby-3.2.4/bin
	System.NullReferenceException: Object reference not set to an instance of an object
	  at Emby.Dlna.Main.DlnaEntryPoint+<RegisterServerEndpoints>d__36.MoveNext () [0x00044] in <51d32b087d0a4188b54ba80a5d0bd5df>:0 
	--- End of stack trace from previous location where exception was thrown ---
	  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult () [0x00000] in <4952428b354e47caa24a27798d61cd88>:0 
	  at Emby.Dlna.Main.DlnaEntryPoint+<StartDlnaServer>d__35.MoveNext () [0x0006f] in <51d32b087d0a4188b54ba80a5d0bd5df>:0 
	System.NullReferenceException
	  at Emby.Dlna.Main.DlnaEntryPoint+<RegisterServerEndpoints>d__36.MoveNext () [0x00044] in <51d32b087d0a4188b54ba80a5d0bd5df>:0 
	--- End of stack trace from previous location where exception was thrown ---
	  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in <4952428b354e47caa24a27798d61cd88>:0 
	  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult () [0x00000] in <4952428b354e47caa24a27798d61cd88>:0 
	  at Emby.Dlna.Main.DlnaEntryPoint+<StartDlnaServer>d__35.MoveNext () [0x0006f] in <51d32b087d0a4188b54ba80a5d0bd5df>:0 
	
2017-03-19 17:13:54.3178 Info App: Entry point completed: Emby.Dlna.Main.DlnaEntryPoint. Duration: 0.068887 seconds

I tried using different versions of Emby (including latest) and Mono, but no luck. In particular it seems Emby requires Mono 4.6.2 while we are using 4.6.0--but bumping our mono version didn't change this behavior, neither did using 4.4 or 4.2 (it failed to run with 4.2 if I remember correctly).

Steps to reproduce

• Enable emby service in configuration.nix
• Go to http://localhost:8096, complete setup wizard
• Browse to server dashboard/settings and inspect most recent server log
• (Alternatively, try to use DLNA functionality)

Technical details

• System: (NixOS: nixos-version, Ubuntu/Fedora: lsb_release -a, ...)
  17.03beta501.acb7958
• Nix version: (run nix-env --version)
  nix-env (Nix) 1.11.7
• Nixpkgs version: (run nix-instantiate --eval '<nixpkgs>' -A lib.nixpkgsVersion)
  "17.03beta501.acb7958"

[joachifm]

cc @fadenb

[fadenb]

@dtzWill can confirm that it is not working. IIRC this has always been the issue on NixOS.
I believe this is an issue in Emby on Linux and not NixOS specific but I will look into it (probably not this week)

[dtzWill]

Thanks for the confirmation and information. My investigation efforts suggested it was an Emby-on-Linux thing as well.

Here's the source from Emby around where the exception is thrown:

https://github.com/MediaBrowser/Emby/blob/6b52b8268148778bf6844f61d89bca37ccf547ef/Emby.Common.Implementations/Net/SocketFactory.cs#L157

I'm a mono noob so I'm not in a position to debug this properly but this might be an instance of:

https://bugzilla.xamarin.com/show_bug.cgi?id=36941

Which basically suggests that the way they set the MulticastTimeToLive socket option doesn't work on Linux (which AFAICT seems to be a mono bug but what do I know), and may be fixed with the suggested workaround (?).

EDIT: I've tracked down the problem a bit more, commented on the linked upstream bug.. let's see what they have to say :)

[dtzWill]

No response upstream yet, but I tried to reproduce the bug using a "known-good" copy of mono, so I tried it with a few versions of the ('mono' docker image)[https://hub.docker.com/_/mono/] and all of them worked where ours does not.

So maybe this is somehow a bug in how we build mono?

[dtzWill]

After a fair bit of debugging, I've got DLNA working now! 😀

The problem originates with our currently outdated copy of "/etc/protocols", see my comment on one of the PR's addressing this issue for an explanation of how this broke things: #24053 (comment)

Just fired up my ps4 and it had no trouble seeing my Emby server right away \o/.

What a doozy!

[dtzWill]

Closing, fixed when #24053 was merged. 👍