https://bugzilla.mindrot.org/show_bug.cgi?id=2420
Bug ID: 2420
Summary: Race condition regarding ControlPersist and
ControlMaster=auto
Product: Portable OpenSSH
Version: 6.6p1
Hardware: amd64
OS: Linux
Status: NEW
Severity: normal
Priority: P5
Component: ssh
Assignee: [email protected]
Reporter: [email protected]
There seems to be a race condition in ssh between looking for an
available control socket and actually using it. If in between those 2
steps the socket is removed by the original ssh client because
ControlPersist timed out, the socket will be gone by the time ssh tries
to use it and so ssh fails to connect.
How to reproduce:
* ssh -o ControlMaster=auto -o ControlPersist=$timeout -o
ControlPath=$controlpath $server
* exit
* sleep $timeout
* ssh -o ControlMaster=auto -o ControlPersist=$timeout -o
ControlPath=$controlpath $server
The second ssh client will occasionally (when the race condition hit)
say sth like
debug1: auto-mux: Trying existing master
debug1: Control socket
"/home/klein/.ansible/cp/ansible-ssh-alice-22-klein" does not exist
I am not a programmer, I did not read any code and I do not know the
ssh client code. But my assumptions seems proven to me by those logs.
My idea for a fix would be to look for a socket, if found, find the
original ssh process, talk to it, tell it to keep the socket open
because I want to use it and then use the socket. Not sure whether
that's doable and that's just to be taken as an administrator's, not a
programmer's idea.
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