Bug#546854: openssh-server: has unspecified limit for number of sessions tunnelled through controlmaster
Package: openssh-server
Version: 1:5.1p1-7
Severity: normal
Hi,
I can only reach most of my systems through a dual-homed host which I
access via proxycommand ssh dhhost socket %h %p. When I use
controlmaster, there seems to be a rather low session limit of around
ten sessions which can be tunneled through.
When this limit is reached, the server logs "error: no more sessions"
and the client holding the controlmaster spews "open failed:
administratively prohibited: open failed" to its console.
In some cases, closing one of the sessions does not immediately free
up a "slot", but new connections become possible after waiting a few
minutes.
Googling for the error message suggests that there is a macro
MAX_SESSIONS which can be increased, but the current sources only
contain this string inside debian/changelog when it was documented
that this macro was increased to 64 somewhen in 2007. So I suspect
that this is now dynamically allocated, eliminating the macro from the
sources.
However, the limit remains and is a rather severe limitation
especially when a security update needs to be rolled out (I do this in
parallel and frequently hit this limit).
Greetings
Marc
-- System Information:
Debian Release: squeeze/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.30.5-nc8000 (PREEMPT)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Versions of packages openssh-server depends on:
ii adduser 3.110 add and remove users and groups
ii debconf [debconf-2.0] 1.5.27 Debian configuration management sy
ii dpkg 1.15.3.1 Debian package management system
ii libc6 2.9-25 GNU C Library: Shared libraries
ii libcomerr2 1.41.8-2 common error description library
ii libgssapi-krb5-2 1.7dfsg~beta3-1 MIT Kerberos runtime libraries - k
ii libk5crypto3 1.7dfsg~beta3-1 MIT Kerberos runtime libraries - C
ii libkrb5-3 1.7dfsg~beta3-1 MIT Kerberos runtime libraries
ii libpam-modules 1.0.1-10 Pluggable Authentication Modules f
ii libpam-runtime 1.0.1-10 Runtime support for the PAM librar
ii libpam0g 1.0.1-10 Pluggable Authentication Modules l
ii libselinux1 2.0.85-1 SELinux shared libraries
ii libssl0.9.8 0.9.8k-4 SSL shared libraries
ii libwrap0 7.6.q-18 Wietse Venema's TCP wrappers libra
ii lsb-base 3.2-23 Linux Standard Base 3.2 init scrip
ii openssh-blacklist 0.4.1 list of default blacklisted OpenSS
ii openssh-client 1:5.1p1-7 secure shell client, an rlogin/rsh
ii procps 1:3.2.8-1 /proc file system utilities
ii zlib1g 1:1.2.3.3.dfsg-15 compression library - runtime
Versions of packages openssh-server recommends:
ii openssh-blacklist-extra 0.4.1 list of non-default blacklisted Op
ii xauth 1:1.0.3-2 X authentication utility
Versions of packages openssh-server suggests:
ii molly-guard 0.4.4-2 protects machines from accidental
pn rssh <none> (no description available)
ii ssh-askpass 1:1.2.4.1-7 under X, asks user for a passphras
pn ufw <none> (no description available)
-- debconf information excluded
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