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Re: Problem with line which is longer than 256 characters

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  • Rolf E. Sonneveld
    ... thanks for your answer. I did a tcpdump for the session but when analysing it, I could not find a clear cause. At the end of the day, it appeared to have
    Message 1 of 4 , Feb 16, 2013
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      On 02/11/2013 11:36 PM, Wietse Venema wrote:
      > Rolf E. Sonneveld:
      >> In general, Postfix is running fine and this Postfix instance is also
      >> running fine. However, there is one SMTP client (of which we are not in
      >> control), that sends messages with long lines to this server running
      >> Postfix. There is a problem with the communication between this client
      >> and the server: whenever the clients sends a message which includes one
      >> long line (377 characters, excluding the CRLF), the client seems to
      >> 'hang' after character # 256 of this long line is transmitted. Then,
      >> after some time the connection times out.
      > A tcpdump recording will reveal if the client stops sending or if
      > the server stops reading (it's revealed by TCP receive window size).
      > Once this is known the search can be focused. It could be somethinh
      > as stupid as poorly-implemented anti-virus software.
      >
      > http://www.postfix.org/DEBUG_README.html#sniffer

      thanks for your answer. I did a tcpdump for the session but when
      analysing it, I could not find a clear cause. At the end of the day, it
      appeared to have been a cli/tty related limitation (of Solaris?). See
      for a discussion
      https://forums.oracle.com/forums/thread.jspa?messageID=8292168). When
      sending the same data using a perl script it worked without a problem.

      /rolf
    • Wietse Venema
      ... Based on the bits on the wire it is 100% clear whether the client stops sending or whether the receiver stops receiving. Just look at the TCP window.
      Message 2 of 4 , Feb 16, 2013
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        Rolf E. Sonneveld:
        > On 02/11/2013 11:36 PM, Wietse Venema wrote:
        > > Rolf E. Sonneveld:
        > >> In general, Postfix is running fine and this Postfix instance is also
        > >> running fine. However, there is one SMTP client (of which we are not in
        > >> control), that sends messages with long lines to this server running
        > >> Postfix. There is a problem with the communication between this client
        > >> and the server: whenever the clients sends a message which includes one
        > >> long line (377 characters, excluding the CRLF), the client seems to
        > >> 'hang' after character # 256 of this long line is transmitted. Then,
        > >> after some time the connection times out.
        > > A tcpdump recording will reveal if the client stops sending or if
        > > the server stops reading (it's revealed by TCP receive window size).
        > > Once this is known the search can be focused. It could be somethinh
        > > as stupid as poorly-implemented anti-virus software.
        > >
        > > http://www.postfix.org/DEBUG_README.html#sniffer
        >
        > thanks for your answer. I did a tcpdump for the session but when
        > analysing it, I could not find a clear cause.

        Based on the bits on the wire it is 100% clear whether the client
        stops sending or whether the receiver stops receiving. Just look
        at the TCP window.

        Wietse

        > At the end of the day, it
        > appeared to have been a cli/tty related limitation (of Solaris?). See
        > for a discussion
        > https://forums.oracle.com/forums/thread.jspa?messageID=8292168). When
        > sending the same data using a perl script it worked without a problem.
        >
        > /rolf
        >
        >
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