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Re: [PATCH 2/3 for 9.0] Revert "chardev/char-socket: Fix TLS io channels


From: Thomas Huth
Subject: Re: [PATCH 2/3 for 9.0] Revert "chardev/char-socket: Fix TLS io channels sending too much data to the backend"
Date: Tue, 19 Mar 2024 09:09:13 +0100
User-agent: Mozilla Thunderbird

On 18/03/2024 19.23, Daniel P. Berrangé wrote:
This commit results in unexpected termination of the TLS connection.
When 'fd_can_read' returns 0, the code goes on to pass a zero length
buffer to qio_channel_read. The TLS impl calls into gnutls_recv()
with this zero length buffer, at which point GNUTLS returns an error
GNUTLS_E_INVALID_REQUEST. This is treated as fatal by QEMU's TLS code
resulting in the connection being torn down by the chardev.

Simply skipping the qio_channel_read when the buffer length is zero
is also not satisfactory, as it results in a high CPU burn busy loop
massively slowing QEMU's functionality.

The proper solution is to avoid tcp_chr_read being called at all
unless the frontend is able to accept more data. This will be done
in a followup commit.

This reverts commit 1907f4d149c3589ade641423c6a33fd7598fa4d3.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
  chardev/char-socket.c | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: Thomas Huth <thuth@redhat.com>




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