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Revert "chardev/char-socket: Fix TLS io channels sending too much data to the backend" 

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 462945cd22

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
(cherry picked from commit e8ee827ffd)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Daniel P. Berrangé 2024-03-18 13:03:19 +00:00 committed by Michael Tokarev
parent 509525dc67
commit de742b16b3
1 changed files with 3 additions and 3 deletions
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6
chardev/char-socket.c
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@ -492,9 +492,9 @@ static gboolean tcp_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque)
s->max_size <= 0) {
return TRUE;
}
len = tcp_chr_read_poll(opaque);
if (len > sizeof(buf)) {
len = sizeof(buf);
len = sizeof(buf);
if (len > s->max_size) {
len = s->max_size;
}
size = tcp_chr_recv(chr, (void *)buf, len);
if (size == 0 || (size == -1 && errno != EAGAIN)) {