On 10/10/2017 10:43 AM, Daniel P. Berrange wrote: > We must ensure we don't get flooded with ping replies if the outbound > channel is slow. Currently we do this by keeping the ping reply in a > separate temporary buffer and only writing it if the encoutput buffer > is completely empty. This is overly pessimistic, as it is reasonable > to add a ping reply to the encoutput buffer even if it has previous > data in it, as long as that previous data doesn't include a ping > reply. > > To track this better, put the ping reply directly into the encoutput > buffer, and then record the size of encoutput at this time in > ping_remain. As we write encoutput to the underlying channel, we > can decrement the ping_remain counter. Once it hits zero, we can > accept further ping replies for transmission. > > Signed-off-by: Daniel P. Berrange <[email protected]> > --- > include/io/channel-websock.h | 2 +- > io/channel-websock.c | 28 +++++++++++++++------------- > 2 files changed, 16 insertions(+), 14 deletions(-) >
> +++ b/io/channel-websock.c
> @@ -825,11 +825,14 @@ static int
> qio_channel_websock_decode_payload(QIOChannelWebsock *ioc,
> }
> return -1;
> } else if (ioc->opcode == QIO_CHANNEL_WEBSOCK_OPCODE_PING) {
> - /* ping frames produce an immediate reply */
> - buffer_reset(&ioc->ping_reply);
> - qio_channel_websock_encode_buffer(
> - ioc, &ioc->ping_reply, QIO_CHANNEL_WEBSOCK_OPCODE_PONG,
> - &ioc->encinput);
> + /* ping frames produce an immediate reply, as long as we've not still
> + * got a previous ping queued, in which case we drop the new pong */
Wouldn't that be a 'previous pong queued'?
> + if (ioc->ping_remain == 0) {
> + qio_channel_websock_encode_buffer(
> + ioc, &ioc->encoutput, QIO_CHANNEL_WEBSOCK_OPCODE_PONG,
> + &ioc->encinput);
> + ioc->ping_remain = ioc->encoutput.offset;
> + }
But if you change the comment, then naming the variable pong_remain may
make more sense.
But naming is a bikeshed issue, so either way,
Reviewed-by: Eric Blake <[email protected]>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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