PuTTY bug telnet-option-loop

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summary: PuTTY violates RFC-854 option-loop prevention
class: bug: This is clearly an actual problem we want fixed.
difficulty: fun: Just needs tuits, and not many of them.
priority: medium: This should be fixed one day.
present-in: 0.57
fixed-in: 2005-03-17 780ca6231173169ac1f3d47c451565a4b50adad2 (0.58)

RFC 854 includes the following rule to prevent option-negotiation loops:

      b. If a party receives what appears to be a request to enter some
      mode it is already in, the request should not be acknowledged.
      This non-response is essential to prevent endless loops in the
      negotiation.  It is required that a response be sent to requests
      for a change of mode -- even if the mode is not changed.

PuTTY gets this wrong for options that it doesn't support.
Audit trail for this bug.

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(last revision of this bug record was at 2016-12-27 11:40:22 +0000)