SSHSessionProcessProtocol.inConnectionLost() behavior breaks Git over Conch

New submission from bshi <None>:

The program gitconnbug.py (attached) wraps git-shell and and can be executed to start the sample server.  Run a command like

{{{
# The /abspath/to/git/repo should be readable by the server user
$ git clone ssh://user@localhost:2222/abspath/to/git/repo
(password "user")
}}}

To test the server.  I have encountered an issue that would cause a git client fail in an apparently non-deterministic manner.  On my workstation, I am able to reproduce the error at least once every 5 tries.  The behavior I see is attached at the end of this email.  As far as I can tell, the client fails due to a premature inConnectionLost() call in the SSHSessionProcessProtocol that sends an EOF.

As a workaround, when TraceProcessProtocol.inConnectionLost() is overriden to do nothing, this error goes away.


Successful case (server side logging, timestamp cut out):

{{{
[SSHChannel session (0) on SSHService ssh-connection
on SSHServerTransport,1,127.0.0.1] executing command
"git-upload-pack '/Users/bshi/sandbox/poop'"
[-] TPP.outReceived(...) 199 bytes
[-] TPP.outReceived(...) 146 bytes
[-] TPP.outReceived(...) 8 bytes
[-] TPP.outReceived(...) 33 bytes
[-] TPP.outReceived(...) 41 bytes
[-] TPP.outReceived(...) 77 bytes
[-] TPP.outReceived(...) 1228 bytes
[-] TPP.outReceived(...) 8192 bytes
[-] TPP.outReceived(...) 4567 bytes
[-] TPP.inConnectionLost()
[-] sending eof
[-] exitCode: 0
}}}

Successful case (client-side shell session):

{{{
$ GIT_TRACE=1 git clone ssh://user@localhost:2222/Users/bshi/sandbox/poop

trace: built-in: git 'clone' 'ssh://user@localhost:2222/Users/bshi/sandbox/poop'
Initialized empty Git repository in /tmp/poop/.git/
trace: run_command: 'ssh' '-p' '2222' 'user@localhost' 'git-upload-pack
       '\''/Users/bshi/sandbox/poop'\'''
user@localhost's password:
trace: run_command: 'index-pack' '--stdin' '-v' '--fix-thin'
             '--keep=fetch-pack 763 on Bo-Shis-MacBook-Pro.local'
trace: exec: 'git' 'index-pack' '--stdin' '-v' '--fix-thin'
             '--keep=fetch-pack 763 on Bo-Shis-MacBook-Pro.local'
trace: exec: 'git-index-pack' '--stdin' '-v' '--fix-thin'
             '--keep=fetch-pack 763 on Bo-Shis-MacBook-Pro.local'
trace: run_command: 'git-index-pack' '--stdin' '-v' '--fix-thin'
             '--keep=fetch-pack 763 on Bo-Shis-MacBook-Pro.local'
remote: Counting objects: 50, done.
remote: Compressing objects: 100% (35/35), done.
remote: Total 50 (delta 16), reused 43 (delta 14)
Receiving objects: 100% (50/50), 12.36 KiB, done.
Resolving deltas: 100% (16/16), done.
}}}

Failure case (server side):

{{{
   [SSHChannel session (0) on SSHService ssh-connection
   on SSHServerTransport,2,127.0.0.1] executing command
   "git-upload-pack '/Users/bshi/sandbox/poop'"
   [-] TPP.outReceived(...) 345 bytes
   [-] TPP.outReceived(...) 8 bytes
   [-] TPP.outReceived(...) 33 bytes
   [-] TPP.outReceived(...) 8192 bytes
   [-] TPP.inConnectionLost()
   [-] sending eof
   [-] TPP.outReceived(...) 5903 bytes
   [-] exitCode: 0
   [-] sending request exit-status
   [-] sending close 0
}}}

Failure case ("trace:" messages similar, cut out for readability):

{{{
   $ GIT_TRACE=1 git clone ssh://user@localhost:2222/Users/bshi/sandbox/poop
   user@localhost's password:
   ...
   ...
   remote: Counting objects: 50, done.
   fatal: The remote end hung up unexpectedly
   fatal: early EOF
   fatal: index-pack failed
}}}

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Type     : defect
Component: conch
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4350