Your message dated Sat, 4 Nov 2023 00:35:17 +0100
with message-id <[email protected]>
and subject line Re: Bug#141466: ppp: pty + ssh hangs
has caused the Debian Bug report #141466,
regarding ppp: pty + ssh hangs
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
141466: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=141466
Debian Bug Tracking System
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--- Begin Message ---
Package: ppp
Version: 2.4.1.uus-4
Severity: normal
This hang has been there since day one. It happens when the ssh spawned
through the pty mechanism does a tcsetattr(..., TCADRAIN, ...). Now
pseudo-terminals only keep configuration on the slave. So most ioctls
act on it even when applied to the master. This means that TCADRAIN
will block when there is data from the slave to the master, not the other
way around. This kernel behaviour is intentional.
You may argue that ssh should not be sending TCADRAIN in this case.
However, ssh is designed to run on only real ttys, that is, it does
not like master pseudo-terminals. In most other situations where
pseudo-terminals are used, the program allocating the pair dealt direclty
with the master and passed the slave to its children.
So perhaps pppd should also do this, that is, use the master instead of
the slave and give the slave to ssh.
I have a patch which does just this. I'll send it if you agree with
this approach.
-- System Information
Debian Release: 3.0
Kernel Version: Linux gondolin 2.4.18-686-smp #1 SMP Fri Mar 1 00:33:20 EST
2002 i686 unknown
Versions of the packages ppp depends on:
ii libc6 2.2.5-3 GNU C Library: Shared libraries and Timezone
ii libpam-modules 0.72-35 Pluggable Authentication Modules for PAM
ii libpam0g 0.72-35 Pluggable Authentication Modules library
ii libpcap0 0.6.2-2 System interface for user-level packet captu
ii makedev 2.3.1-58 Creates device files in /dev.
ii netbase 4.07 Basic TCP/IP networking system
ii procps 2.0.7-8 The /proc file system utilities.
ii sysvinit 2.84-2 System-V like init.
--- End Message ---
--- Begin Message ---
On Apr 06, [email protected] wrote:
> So perhaps pppd should also do this, that is, use the master instead of
> the slave and give the slave to ssh.
I am unable to assess if this change is appropriate.
If you still believe this to be a relevant issue then please submit your
patch upstream (https://github.com/ppp-project/ppp/pulls).
--
ciao,
Marco
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