Re: [PATCH 2/3 for 9.0] Revert "chardev/char-socket: Fix TLS io channels sending too much data to the backend"

[Thomas Huth <thuth@redhat.com>]

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>