openssh bugs - Oct 2018 - [Bug 2918] New: ssh ConnectTimeout is obeyed only on 1st ConnectionAttempt

https://bugzilla.mindrot.org/show_bug.cgi?id=2918

            Bug ID: 2918
           Summary: ssh ConnectTimeout is obeyed only on 1st
                    ConnectionAttempt
           Product: Portable OpenSSH
           Version: 7.6p1
          Hardware: amd64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: vide at fastmail.com

Setting the SSH option ConnectTimeout=N only works on the first
ConnectionAttempts. So, if you set ConnectionAttempts=2 for example, it
will time out after N second on the first attempt and wait the full,
default TCP timeout on the second attempt.

Example of the error:

$ time ssh -vvvv -o ConnectTimeout=2 -o ConnectionAttempts=2 -o
StrictHostKeyChecking=false -o UserKnownHostsFile=/dev/null 1.2.3.4
OpenSSH_7.6p1 Ubuntu-4, OpenSSL 1.0.2n 7 Dec 2017
debug1: Reading configuration data /home/vide/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "1.2.3.4" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 1.2.3.4 [1.2.3.4] port 22.
debug2: fd 3 setting O_NONBLOCK
debug1: connect to address 1.2.3.4 port 22: Connection timed out
debug1: Trying again...
debug1: Connecting to 1.2.3.4 [1.2.3.4] port 22.
debug1: connect to address 1.2.3.4 port 22: Connection timed out
ssh: connect to host 1.2.3.4 port 22: Connection timed out

real 2m13,670s
user 0m0,012s
sys 0m0,018s

This seems a regression from OpenSSH 7.5 where it works as expected.
OpenSSH 7.8 seems affected as well
The first timeout happens after 2 seconds, the second after ~2 minutes

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Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dtucker at dtucker.net

--- Comment #1 from Darren Tucker <dtucker at dtucker.net> ---
Comparing sshconnect.c between the two versions, I think I see what
happened: 7.6 added waitrfd(), which writes the remaining timeout back
to timeoutp.  After the 1st timeout, this does not get reset on the 2nd
and subsequent connection attempts, and a timeout of 0 means "no
timeout".

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--- Comment #2 from Darren Tucker <dtucker at dtucker.net> ---
Created attachment 3233
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3233&action=edit
Save initial timeout and reused for 2nd and subsequent connection
attempts

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Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |2915


Referenced Bugs:

https://bugzilla.mindrot.org/show_bug.cgi?id=2915
[Bug 2915] Tracking bug for 8.0 release
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Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org
   Attachment #3233|                            |ok?(djm at mindrot.org)
              Flags|                            |

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--- Comment #3 from Darren Tucker <dtucker at dtucker.net> ---
Test case with patch:
$ time ssh/obj/ssh -vvv -o ConnectTimeout=2 -o ConnectionAttempts=2 -o
StrictHostKeyChecking=false -o UserKnownHostsFile=/dev/null 1.2.3.4
[...]
debug2: ssh_connect_direct
debug1: Connecting to 1.2.3.4 [1.2.3.4] port 22.
debug2: fd 3 setting O_NONBLOCK
debug1: connect to address 1.2.3.4 port 22: Operation timed out
debug1: Trying again...
debug1: Connecting to 1.2.3.4 [1.2.3.4] port 22.
debug2: fd 3 setting O_NONBLOCK
debug1: connect to address 1.2.3.4 port 22: Operation timed out
ssh: connect to host 1.2.3.4 port 22: Operation timed out

real    0m5.077s
user    0m0.010s
sys     0m0.030s

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Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #4 from Darren Tucker <dtucker at dtucker.net> ---
Patch has been applied and will be in the 8.0 release.  Thanks for the
report and especially specifying exactly the versions where it changed.

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
Move resolved bugs -> CLOSED after 8.0 release

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jik at kamens.us

--- Comment #6 from Damien Miller <djm at mindrot.org> ---
*** Bug 3066 has been marked as a duplicate of this bug. ***

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #3233|ok?(djm at mindrot.org)        |
              Flags|                            |

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