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io: simplify websocket ping reply handling

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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
pong_remain. As we write encoutput to the underlying channel, we
can decrement the pong_remain counter. Once it hits zero, we can
accept further ping replies for transmission.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2017-10-09 15:34:06 +01:00
parent a7b20a8efa
commit 57b0cdf152
2 changed files with 16 additions and 14 deletions
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2
include/io/channel-websock.h
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@ -60,8 +60,8 @@ struct QIOChannelWebsock {
Buffer encoutput;
Buffer rawinput;
Buffer rawoutput;
Buffer ping_reply;
size_t payload_remain;
size_t pong_remain;
QIOChannelWebsockMask mask;
guint io_tag;
Error *io_err;