Hello, My fix intended that Haskell code behaves the same in various environments. That is, one socket catches both IPv4 and IPv6. And the fix works even in both IPv4-only env and IPv6-only env. Johan's observation is correct. Network.listenOn is alreay fixed but Network.Socket.listen, which Warp relies on, is not fixed yet. I will try to fix it. When the next version of the network library will be released, the problem will disappear, I hope. --Kazu

Hi Michael,

Kazu recently fixed this (in the stable branch on GitHub) in Network.listenOn but perhaps the more basic Network.Socket.listen should also be changed. Lets discuss what's the right thing to do in this thread.

On Wed, Sep 21, 2011 at 1:38 PM, Michael Snoyman wrote:

...

Hi,

One of the recurring issues that comes up in Warp is binding to IPv4 versus IPv6 hosts. Our current code is available at [1]. It was updated to look like that in this commit [2] in order to support both IPv4 and IPv6 hosts by default. However, now it seems than on Debian and FreeBSD, it *only* responds to IPv6 by default[3][4]. I'm frankly stumped at this point on how to have our cake and eat it too.

Does anyone have an idea of the correct incantation to get Warp to do the Right Thing(tm) here? And if not, is there any advice on sensible default behavior? I'm considering allowing a few special host values:

* "*" (default, what we have now): Make this bind to IPv4 * "ipv4": Again, bind to IPv4. Guaranteed not to change in the future * "ipv6": Bind to IPv6.

Michael

[1] https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/ Warp.hs#L119 [2] https://github.com/snoyberg/warp/commit/ 02c1396c86e3fceb48cbe7df58cb631c804e24d4 [3] https://github.com/snoyberg/warp/issues/9 [4] http://stackoverflow.com/questions/7486257/ yesod-devel-server-only-listening-on-ipv6

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Hi,

We should consider how we fix this. Right now N.S.listen just wraps the underlying system call. Is that the right place to set socket options? Perhaps we should set them when creating the socket instead?

Yes, of course. If I remember correctly, this option works only between socket() and listen(). I need to check that this option is effective to all sockets or only to listing sockets. Anyway, I will try this in the next week. I used to be an expert of IPv6 but I forget many things recently... I should remember. --Kazu

I've released a new version of network, 2.3.0.6, that contains the fix. On Wed, Sep 28, 2011 at 1:34 AM, Kazu Yamamoto wrote:

Hello,

Sorry for the delay but I made a patch and sent a pull request:

https://github.com/haskell/network/pull/18

After consideration, I realized that Johan's opinion is better. Please read the comment of this request above.

When the next network package will be released, this problem will disappear, I hope. We don't have to change Warp at all.

--Kazu

...

Hi,

...

We should consider how we fix this. Right now N.S.listen just wraps the underlying system call. Is that the right place to set socket options? Perhaps we should set them when creating the socket instead?

Yes, of course.

If I remember correctly, this option works only between socket() and listen(). I need to check that this option is effective to all sockets or only to listing sockets. Anyway, I will try this in the next week.

I used to be an expert of IPv6 but I forget many things recently... I should remember.

--Kazu

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