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Re: [Xen-devel] [RFC PATCH] allow connecting to xenconsole from remote h

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC PATCH] allow connecting to xenconsole from remote hosts
From: Muli Ben-Yehuda <muli@xxxxxxxxxx>
Date: Wed, 6 Sep 2006 20:22:40 +0300
Cc: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Orran Y Krieger <okrieg@xxxxxxxxxx>
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On Wed, Sep 06, 2006 at 04:52:38PM +0100, Keir Fraser wrote:

> Possibly, yes, but this patch seems to do a fair bit more than just add
> minimal socket support. What's all the message queue stuff about? Can't you
> treat the console I/O as character streams?

A message is just a bunch of characters we've read at once. Messages
are read from one stream and written to another. After being read and
before being written, they're held on queues. The messages and queues
serve two purposes:

- they give us a place to hold characters we read from one stream
  (console pty or socket) until the other becomes writable. With
  stdout/stdin everything is always readable and writable - with a
  socket this isn't necessarily true.

- 'noecho' mode, where we discard stuff that we read back from a given
  fd after we've just written it there ourselves. Without this you get
  every console command echo'd back to you from the pty
  immediately. For what it's worth this happens without the socket
  support as well, except there we put stdout into raw mode so that
  the terminal does the 'echo cancelation'. I didn't find a way to
  have the pty not echo everything back at me and I didn't want to
  rely on the remote tty being in 'raw' mode, so I implemented it


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