getPeerName: invalid argument (Transport endpoint is not connected)

[hvr]

I'm using code like the following, which causes problems with haproxys default keepalive check which consists in sending a PROXY header and closing the connection right ahead:

(s,sa) <- accept sock
(inst,outst) <- socketToStreams s
localPInfo <- socketToProxyInfo s

The problem is that by the time getPeerName is called, the connection is already closed, so the system calls fails.

However, if I there was a function which allowed me to pass in the sa I already got from the accept, i.e.

socketToProxyInfo :: N.Socket -> IO ProxyInfo
socketToProxyInfo s = socketToProxyInfoWithPeerName s =<< N.getPeerName s

socketToProxyInfoWithPeerName :: N.Socket -> N.SockAddr -> IO ProxyInfo
socketToProxyInfoWithPeerName s sa = do
    da <- N.getSocketName s
    let (N.MkSocket _ _ !sty _ _) = s
    return $! makeProxyInfo sa da (addrFamily sa) sty

I can write the code like below and avoid calling getPeerName (and thus avoid the failure):

(s,sa) <- accept sock
(inst,outst) <- socketToStreams s
localPInfo <- socketToProxyInfoWithPeerName s sa

[gregorycollins]

Hey Herbert, what is the status on this? Do you think you know what the right fix is?

[hvr]

I'd say this this an API design question.

I don't see a way around changing the API to be able to use the sa information returned by (s,sa) <- accept sock instead of (redundantly) calling getPeerName again on the s which may have been closed by then already.

[gregorycollins]

It's not released on hackage yet, so we can go ahead and change it. Do you want to have a stab at fixing it? Otherwise I'll add it to my queue :)

[gregorycollins]

OK, I'm about to fix this, but I'll have to ask you to test it. I'm worried the call to getSocketName is going to cause the same issue.