X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/a510028bb96130264bc711a0dfeaf6959ddde43c..2e0aae4f59a1481b82dd5ce16f579d4ec9b2c09b:/doc/config.but

diff --git a/doc/config.but b/doc/config.but
index 98427584..6d812482 100644
--- a/doc/config.but
+++ b/doc/config.but
@@ -3208,6 +3208,29 @@ send an over-sized packet.  If this bug is enabled when talking to a
 correct server, the session will work correctly, but download
 performance will be less than it could be.
 
+\S{config-ssh-bug-winadj} \q{Chokes on PuTTY's SSH-2 \cq{winadj} requests}
+
+\cfg{winhelp-topic}{ssh.bugs.winadj}
+
+PuTTY sometimes sends a special request to SSH servers in the middle
+of channel data, with the name \cw{winadj@putty.projects.tartarus.org}
+(see \k{sshnames-channel}). The purpose of this request is to measure
+the round-trip time to the server, which PuTTY uses to tune its flow
+control. The server does not actually have to \e{understand} the
+message; it is expected to send back a \cw{SSH_MSG_CHANNEL_FAILURE}
+message indicating that it didn't understand it. (All PuTTY needs for
+its timing calculations is \e{some} kind of response.)
+
+It has been known for some SSH servers to get confused by this message
+in one way or another \dash because it has a long name, or because
+they can't cope with unrecognised request names even to the extent of
+sending back the correct failure response, or because they handle it
+sensibly but fill up the server's log file with pointless spam, or
+whatever. PuTTY therefore supports this bug-compatibility flag: if it
+believes the server has this bug, it will never send its
+\cq{winadj@putty.projects.tartarus.org} request, and will make do
+without its timing data.
+
 \H{config-serial} The Serial panel
 
 The \i{Serial} panel allows you to configure options that only apply