Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Sean Leather]

On Sat, Oct 10, 2009 at 15:13, Duncan Coutts wrote:

> From what Gregory and Anton have said, it sounds like the SockAddr6,
> HostAddress6 constructors should always be available, but that using
> them with the socket functions should fail at runtime on platforms with
> no IPv6 support, or when IPv6 support is turned off for some reason.
>
> That would probably make it rather easier to have portable programs that
> can optionally use IPv6. Having to use TH to test at compile time if a
> constructor is or is not exported from another package is more than a
> little unpleasant.
>

+1

Sean
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Duncan Coutts]

On Fri, 2009-10-09 at 12:22 -0700, Bryan O'Sullivan wrote:
> On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins
>  wrote:
>  
> There's been an open ticket for months; personally I think
> this is a job
> 
> for the C preprocessor, but nobody's written a patch yet.
> 
> Is there an open ticket against the network package? Can someone write
> a simple standalone repro for me that doesn't require happstack (i.e.
> only depends on network)? I have access to a Mac and Johan and I
> co-maintain the network package, so in principle this shouldn't be
> hard to fix, given enough details and pointers. 

>From what Gregory and Anton have said, it sounds like the SockAddr6,
HostAddress6 constructors should always be available, but that using
them with the socket functions should fail at runtime on platforms with
no IPv6 support, or when IPv6 support is turned off for some reason.

That would probably make it rather easier to have portable programs that
can optionally use IPv6. Having to use TH to test at compile time if a
constructor is or is not exported from another package is more than a
little unpleasant.

Duncan

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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Gregory Collins]

"Bryan O'Sullivan"  writes:

> On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins  
> wrote:
>  
>
> There's been an open ticket for months; personally I think this is
> a job for the C preprocessor, but nobody's written a patch yet.
>
> Is there an open ticket against the network package? Can someone write
> a simple standalone repro for me that doesn't require happstack
> (i.e. only depends on network)? I have access to a Mac and Johan and I
> co-maintain the network package, so in principle this shouldn't be
> hard to fix, given enough details and pointers.

No, against Happstack. The offending code:

--
-- find out at compile time if the SockAddr6 / HostAddress6
-- constructors are available

supportsIPv6 :: Bool
supportsIPv6 = $(let c = "Network.Socket.SockAddrInet6"; d = ''SockAddr in
 do TyConI (DataD _ _ _ cs _) <- reify d
if isJust (find (\(NormalC n _) -> show n == c) cs)
   then [| True |]
   else [| False |] )
   
...

-- | alternative implementation of accept to work around EAI_AGAIN errors
acceptLite :: S.Socket -> IO (Handle, S.HostName, S.PortNumber)
acceptLite sock = do
  (sock', addr) <- S.accept sock
  h <- S.socketToHandle sock' ReadWriteMode
  (N.PortNumber p) <- N.socketPort sock'
  
  let peer = $(if supportsIPv6
 then
 return $ CaseE (VarE (mkName "addr")) 
[Match 
 (ConP (mkName "S.SockAddrInet") 
  [WildP,VarP (mkName "ha")]) 
 (NormalB (AppE (VarE (mkName 
"showHostAddress")) 
   (VarE (mkName "ha" []
,Match (ConP (mkName "S.SockAddrInet6") 
[WildP,WildP,VarP (mkName "ha"),WildP])
 (NormalB (AppE (VarE (mkName 
"showHostAddress6")) (VarE (mkName "ha" []
,Match WildP (NormalB (AppE (VarE (mkName 
"error")) (LitE (StringL "Unsupported socket" []]
 -- the above mess is the equivalent of this: 
 {-[| case addr of
   (S.SockAddrInet _ ha)  -> showHostAddress ha
   (S.SockAddrInet6 _ _ ha _) -> showHostAddress6 ha
   _  -> error "Unsupported 
socket"
   |]-}
 else
 [| case addr of
  (S.SockAddrInet _ ha)  -> showHostAddress ha
  _  -> error "Unsupported 
socket"
 |])
 
  return (h, peer, p)
--

Frankly I think this approach is dubious at best.

G
-- 
Gregory Collins 
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Anton van Straaten]

Bryan O'Sullivan wrote:
On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins > wrote:
 


There's been an open ticket for months; personally I think this is a job
for the C preprocessor, but nobody's written a patch yet.


Is there an open ticket against the network package? Can someone write a 
simple standalone repro for me that doesn't require happstack (i.e. only 
depends on network)? I have access to a Mac and Johan and I co-maintain 
the network package, so in principle this shouldn't be hard to fix, 
given enough details and pointers.


I have the impression that the problem is at least partly with TH on the 
Mac, and there may not even be any relevant bug in the network package. 
  It's possible that the network package could provide some additional 
support to help Happstack solve this another way, though.


The main problem that Happstack faces here is to avoid referencing the
SockAddrInet6 constructor if it doesn't exist, i.e. if the network 
package was compiled without IPv6 support.


If Happstack had some reliable/portable way of accessing 
IPV6_SOCKET_SUPPORT, a C #define used by the network package, this could 
easily be done with the C preprocessor.  I don't think Cabal is up to 
that task, though.  Happstack would probably have to use its own 
configure script (it doesn't have one right now) to determine IPv6 
status for itself, and hope that it matches what the network package 
found when it was compiled.


The current solution in Happstack is to use TH to detect IPv6 support in 
the network package, by testing for the existence of the SockAddrInet6 
constructor, as follows (reformatted slightly for email):


-- find out at compile time if the SockAddr6 / HostAddress6 constructors
-- are available
supportsIPv6 :: Bool
supportsIPv6 = $(let c = "Network.Socket.SockAddrInet6"
 d = ''SockAddr in
 do TyConI (DataD _ _ _ cs _) <- reify d
if isJust (find (\(NormalC n _) -> show n == c) cs)
   then [| True |]
   else [| False |] )

If I had access to a Mac, the first thing I'd do is check what 
supportsIPv6 is getting set to, and whether it changes depending on the 
version of the network package being used.


However, some comments many months back seemed to indicate that 
supportsIPv6 might be getting set correctly, and that the problem was 
happening later.  In that case, it would be in 
Happstack/Server/HTTP/Socket.hs, which contains this test:


  let peer = $(if supportsIPv6

If supportsIPv6 is False, or somehow incorrectly treated as False, then 
the error message being reported could happen if the provided socket is 
actually IPv6.


Alternatively, if the True branch is taken, then a TH-encoded case 
expression is used to match the SockAddr value, without having to 
reference the SockAddrInet6 constructor directly in code.  But if this 
the part that executes, then for some mysterious reason, it is failing, 
only on the Mac, to match the appropriate constructor.  That sounds like 
a fascinating bug!  I hope someone with a Mac will track it down and let 
us know what was happening...


Anton
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Bryan O'Sullivan]

On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins wrote:


> There's been an open ticket for months; personally I think this is a job
> for the C preprocessor, but nobody's written a patch yet.


Is there an open ticket against the network package? Can someone write a
simple standalone repro for me that doesn't require happstack (i.e. only
depends on network)? I have access to a Mac and Johan and I co-maintain the
network package, so in principle this shouldn't be hard to fix, given enough
details and pointers.
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Anton van Straaten]

Gregory Collins wrote:

Sean Leather  writes:


On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote:

Sean Leather  writes:



Do you know if it's possible to permanently patch happstack-server?
I'm guessing the TH in the patch is used to support multiple versions
of the network package. Can we just change the minimum supported
version?


There's been an open ticket for months; personally I think this is a job
for the C preprocessor, but nobody's written a patch yet. I'm not sure
but I think IPv6 template Haskell stuff is there not to support old
versions of network, but to support platforms where IPv6 may not be
available.


I don't recall whether there was some objection to this suggestion 
previously, but assuming IPv6 support is available might work on more 
platforms.  Then special action would only need to be taken on platforms 
that lack IPv6.


Anton

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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Gregory Collins]

Sean Leather  writes:

> On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote:
>
> Sean Leather  writes:
>
> > We have run into an issue that it seems other people have already
> > found but has apparently not been resolved, yet. It manifests as with
> > the error "HTTP request failed with: Unsupported socket". The problem
> > is described in two places with different workarounds.
> >
> >   http://code.google.com/p/happstack/issues/detail?id=88
> >   http://groups.google.com/group/HAppS/msg/0c9a0d0fd7c6aff0
> >
> > One workaround is to rewrite part of the network package, and the
> > other is to downgrade the package. It could be the case that the
> > rewrite came from the older version, though I'm not sure.
> >
> > I'm curious if it is possible to fix this, either in Happstack or the
> > network package, once and for all. The workarounds are rather painful
> > when so many things depend on the network package.
>
> The following patch to happstack works for me:
>
> This worked for us as well. Thanks, Gregory.
>
> Do you know if it's possible to permanently patch happstack-server?
> I'm guessing the TH in the patch is used to support multiple versions
> of the network package. Can we just change the minimum supported
> version?

There's been an open ticket for months; personally I think this is a job
for the C preprocessor, but nobody's written a patch yet. I'm not sure
but I think IPv6 template Haskell stuff is there not to support old
versions of network, but to support platforms where IPv6 may not be
available.

G
-- 
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Sean Leather]

On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote:

> Sean Leather  writes:
>
> > We have run into an issue that it seems other people have already
> > found but has apparently not been resolved, yet. It manifests as with
> > the error "HTTP request failed with: Unsupported socket". The problem
> > is described in two places with different workarounds.
> >
> >   http://code.google.com/p/happstack/issues/detail?id=88
> >   http://groups.google.com/group/HAppS/msg/0c9a0d0fd7c6aff0
> >
> > One workaround is to rewrite part of the network package, and the
> > other is to downgrade the package. It could be the case that the
> > rewrite came from the older version, though I'm not sure.
> >
> > I'm curious if it is possible to fix this, either in Happstack or the
> > network package, once and for all. The workarounds are rather painful
> > when so many things depend on the network package.
>
> The following patch to happstack works for me:
>

This worked for us as well. Thanks, Gregory.

Do you know if it's possible to permanently patch happstack-server? I'm
guessing the TH in the patch is used to support multiple versions of the
network package. Can we just change the minimum supported version?

Sean
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Re: [Haskell-cafe] Happstack + network package issue on the Mac

[Gregory Collins]

Sean Leather  writes:

> We have run into an issue that it seems other people have already
> found but has apparently not been resolved, yet. It manifests as with
> the error "HTTP request failed with: Unsupported socket". The problem
> is described in two places with different workarounds.
>
>   http://code.google.com/p/happstack/issues/detail?id=88
>   http://groups.google.com/group/HAppS/msg/0c9a0d0fd7c6aff0
>
> One workaround is to rewrite part of the network package, and the
> other is to downgrade the package. It could be the case that the
> rewrite came from the older version, though I'm not sure.
>
> I'm curious if it is possible to fix this, either in Happstack or the
> network package, once and for all. The workarounds are rather painful
> when so many things depend on the network package.

The following patch to happstack works for me:

Mon May  4 10:35:54 EDT 2009  Gregory Collins 
  * Local fix: make networking work
  Ignore-this: f46cdf40b26ac1ca72e50b05c772c259
diff -rN -u old-happstack/happstack-server/src/Happstack/Server/HTTP/Socket.hs new-happstack/happstack-server/src/Happstack/Server/HTTP/Socket.hs
--- old-happstack/happstack-server/src/Happstack/Server/HTTP/Socket.hs	2009-10-08 10:34:22.0 -0400
+++ new-happstack/happstack-server/src/Happstack/Server/HTTP/Socket.hs	2009-10-08 10:34:22.0 -0400
@@ -24,29 +24,11 @@
   (sock', addr) <- S.accept sock
   h <- S.socketToHandle sock' ReadWriteMode
   (N.PortNumber p) <- N.socketPort sock'
-  
-  let peer = $(if supportsIPv6
- then
- return $ CaseE (VarE (mkName "addr")) 
-[Match 
- (ConP (mkName "S.SockAddrInet") 
-  [WildP,VarP (mkName "ha")]) 
- (NormalB (AppE (VarE (mkName "showHostAddress")) 
-   (VarE (mkName "ha" []
-,Match (ConP (mkName "S.SockAddrInet6") [WildP,WildP,VarP (mkName "ha"),WildP])
- (NormalB (AppE (VarE (mkName "showHostAddress6")) (VarE (mkName "ha" []
-,Match WildP (NormalB (AppE (VarE (mkName "error")) (LitE (StringL "Unsupported socket" []]
- -- the above mess is the equivalent of this: 
- {-[| case addr of
-   (S.SockAddrInet _ ha)  -> showHostAddress ha
-   (S.SockAddrInet6 _ _ ha _) -> showHostAddress6 ha
-   _  -> error "Unsupported socket"
-   |]-}
- else
- [| case addr of
-  (S.SockAddrInet _ ha)  -> showHostAddress ha
-  _  -> error "Unsupported socket"
- |])
- 
+
+  let peer = case addr of
+   (S.SockAddrInet _ ha)  -> showHostAddress ha
+   (S.SockAddrInet6 _ _ ha _) -> showHostAddress6 ha
+   _  -> error "Unsupported socket"
+
   return (h, peer, p)
 
diff -rN -u old-happstack/happstack-server/src/Happstack/Server/HTTP/SocketTH.hs new-happstack/happstack-server/src/Happstack/Server/HTTP/SocketTH.hs
--- old-happstack/happstack-server/src/Happstack/Server/HTTP/SocketTH.hs	2009-10-08 10:34:22.0 -0400
+++ new-happstack/happstack-server/src/Happstack/Server/HTTP/SocketTH.hs	2009-10-08 10:34:22.0 -0400
@@ -8,9 +8,4 @@
 
 -- find out at compile time if the SockAddr6 / HostAddress6 constructors are available
 supportsIPv6 :: Bool
-supportsIPv6 = $(let c = "Network.Socket.SockAddrInet6"; d = ''SockAddr in
- do TyConI (DataD _ _ _ cs _) <- reify d
-if isJust (find (\(NormalC n _) -> show n == c) cs)
-   then [| True |]
-   else [| False |] )
-   
+supportsIPv6 = True


G.
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[Haskell-cafe] Happstack + network package issue on the Mac

[Sean Leather]

We have run into an issue that it seems other people have already found but
has apparently not been resolved, yet. It manifests as with the error "HTTP
request failed with: Unsupported socket". The problem is described in two
places with different workarounds.

  http://code.google.com/p/happstack/issues/detail?id=88
  http://groups.google.com/group/HAppS/msg/0c9a0d0fd7c6aff0

One workaround is to rewrite part of the network package, and the other is
to downgrade the package. It could be the case that the rewrite came from
the older version, though I'm not sure.

I'm curious if it is possible to fix this, either in Happstack or the
network package, once and for all. The workarounds are rather painful when
so many things depend on the network package.

Thanks,
Sean
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