[Bug 708493] Re: Can't login anymore: Read from socket failed: Connection reset by peer

[Steve Brown]

Howdy,

I know that in my case, this was definitely an MTU problem, and it
exhibits exactly the behavior stated above.

to test this, call
ping -M do -s 1500 <host>
If it goes through, this is probably not your issue.  If it does not, try lowering the -s value until it does go through.  If the value that you find is lower than the MTU on your interface, this is likely the problem.

The solution would be to change your MTU size on the interface.  You can check this with
ifconfig
and set it with
sudo ifconfig <interface> mtu 1000

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https://bugs.launchpad.net/bugs/708493

Title:
  Can't login anymore: Read from socket failed: Connection reset by peer

Status in “openssh” package in Ubuntu:
  Confirmed
Status in “openssh” package in Debian:
  New

Bug description:
  After todays update to
  1:5.7p1-1ubuntu1
  I cannot login to SOME (!) of my servers. Example of a server failing:

  ~$ ssh -v root at mail
  OpenSSH_5.7p1 Debian-1ubuntu1, OpenSSL 0.9.8o 01 Jun 2010
  debug1: Reading configuration data /home/hildeb/.ssh/config
  debug1: Reading configuration data /etc/ssh/ssh_config
  debug1: Applying options for *
  debug1: Connecting to mail [141.42.202.200] port 22.
  debug1: Connection established.
  debug1: identity file /home/hildeb/.ssh/id_rsa type -1
  debug1: identity file /home/hildeb/.ssh/id_rsa-cert type -1
  debug1: identity file /home/hildeb/.ssh/id_dsa type 2
  debug1: Checking blacklist file /usr/share/ssh/blacklist.DSA-1024
  debug1: Checking blacklist file /etc/ssh/blacklist.DSA-1024
  debug1: identity file /home/hildeb/.ssh/id_dsa-cert type -1
  debug1: identity file /home/hildeb/.ssh/id_ecdsa type -1
  debug1: identity file /home/hildeb/.ssh/id_ecdsa-cert type -1
  debug1: Remote protocol version 1.99, remote software version OpenSSH_5.5p1 Debian-6
  debug1: match: OpenSSH_5.5p1 Debian-6 pat OpenSSH*
  debug1: Enabling compatibility mode for protocol 2.0
  debug1: Local version string SSH-2.0-OpenSSH_5.7p1 Debian-1ubuntu1
  debug1: SSH2_MSG_KEXINIT sent
  debug1: SSH2_MSG_KEXINIT received
  debug1: kex: server->client aes128-ctr hmac-md5 none
  debug1: kex: client->server aes128-ctr hmac-md5 none
  debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
  debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
  Read from socket failed: Connection reset by peer

  There is NOTHING in daemon.log, auth.log or syslog on the server I'm
  trying to connect to.

  Example of a server NOT failing:

  $ ssh -v root at netsight
  OpenSSH_5.7p1 Debian-1ubuntu1, OpenSSL 0.9.8o 01 Jun 2010
  debug1: Reading configuration data /home/hildeb/.ssh/config
  debug1: Reading configuration data /etc/ssh/ssh_config
  debug1: Applying options for *
  debug1: Connecting to netsight [10.47.2.222] port 22.
  debug1: Connection established.
  debug1: identity file /home/hildeb/.ssh/id_rsa type -1
  debug1: identity file /home/hildeb/.ssh/id_rsa-cert type -1
  debug1: identity file /home/hildeb/.ssh/id_dsa type 2
  debug1: Checking blacklist file /usr/share/ssh/blacklist.DSA-1024
  debug1: Checking blacklist file /etc/ssh/blacklist.DSA-1024
  debug1: identity file /home/hildeb/.ssh/id_dsa-cert type -1
  debug1: identity file /home/hildeb/.ssh/id_ecdsa type -1
  debug1: identity file /home/hildeb/.ssh/id_ecdsa-cert type -1
  debug1: Remote protocol version 2.0, remote software version OpenSSH_5.5p1 Debian-6
  debug1: match: OpenSSH_5.5p1 Debian-6 pat OpenSSH*
  debug1: Enabling compatibility mode for protocol 2.0
  debug1: Local version string SSH-2.0-OpenSSH_5.7p1 Debian-1ubuntu1
  debug1: SSH2_MSG_KEXINIT sent
  debug1: SSH2_MSG_KEXINIT received
  debug1: kex: server->client aes128-ctr hmac-md5 none
  debug1: kex: client->server aes128-ctr hmac-md5 none
  debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
  debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
  debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
  debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
  debug1: Server host key: RSA 18:ce:76:c7:7c:f4:98:94:28:8f:62:4a:31:e8:5b:c9
  debug1: Host 'netsight' is known and matches the RSA host key.
  debug1: Found key in /home/hildeb/.ssh/known_hosts:56
  debug1: ssh_rsa_verify: signature correct
  debug1: SSH2_MSG_NEWKEYS sent
  debug1: expecting SSH2_MSG_NEWKEYS
  debug1: SSH2_MSG_NEWKEYS received
  debug1: Roaming not allowed by server
  debug1: SSH2_MSG_SERVICE_REQUEST sent
  debug1: SSH2_MSG_SERVICE_ACCEPT received
  debug1: Authentications that can continue: publickey,keyboard-interactive
  debug1: Next authentication method: publickey
  debug1: Offering DSA public key: /home/hildeb/.ssh/id_dsa
  debug1: Server accepts key: pkalg ssh-dss blen 433
  debug1: Authentication succeeded (publickey).
  Authenticated to netsight ([10.47.2.222]:22).
  debug1: channel 0: new [client-session]
  debug1: Requesting no-more-sessions at openssh.com
  debug1: Entering interactive session.
  debug1: Sending environment.
  debug1: Sending env LC_MESSAGES = en_US.utf8
  debug1: Sending env LANG = de_DE.UTF-8

  ProblemType: Bug
  DistroRelease: Ubuntu 11.04
  Package: openssh-client 1:5.7p1-1ubuntu1
  ProcVersionSignature: Ubuntu 2.6.37-12.26-generic 2.6.37
  Uname: Linux 2.6.37-12-generic x86_64
  Architecture: amd64
  Date: Thu Jan 27 09:13:15 2011
  ProcEnviron:
   LANGUAGE=en_US:en
   LANG=de_DE.UTF-8
   LC_MESSAGES=en_US.utf8
   SHELL=/bin/bash
  RelatedPackageVersions:
   ssh-askpass N/A
   libpam-ssh N/A
   keychain N/A
   ssh-askpass-gnome 1:5.7p1-1ubuntu1
  SSHClientVersion: OpenSSH_5.7p1 Debian-1ubuntu1, OpenSSL 0.9.8o 01 Jun 2010
  SourcePackage: openssh

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