From d467ff7abd1aa30dca064883071bdd74d238567e Mon Sep 17 00:00:00 2001

From: "Daniel P. Berrange" <berrange@redhat.com>

Date: Wed, 20 Dec 2017 17:56:55 +0100

Subject: [PATCH 15/42] io: simplify websocket ping reply handling

RH-Author: Daniel P. Berrange <berrange@redhat.com>

Message-id: <20171220175702.29663-14-berrange@redhat.com>

Patchwork-id: 78465

O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH v2 13/20] io: simplify websocket ping reply handling

Bugzilla: 1518649

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

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>

(cherry picked from commit 57b0cdf152b7266e68bfa3e84635d4bdb64ef2cd)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 include/io/channel-websock.h |  2 +-

 io/channel-websock.c         | 28 +++++++++++++++-------------

 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/include/io/channel-websock.h b/include/io/channel-websock.h

index ff32d86..3762707 100644

--- a/include/io/channel-websock.h

+++ b/include/io/channel-websock.h

@@ -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;

diff --git a/io/channel-websock.c b/io/channel-websock.c

index 04bcc05..6083f74 100644

--- a/io/channel-websock.c

+++ 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 pong queued, in which case we drop the new pong */

+        if (ioc->pong_remain == 0) {

+            qio_channel_websock_encode_buffer(

+                ioc, &ioc->encoutput, QIO_CHANNEL_WEBSOCK_OPCODE_PONG,

+                &ioc->encinput);

+            ioc->pong_remain = ioc->encoutput.offset;

+        }

     }   /* pong frames are ignored */

     if (payload_len) {

@@ -888,7 +891,6 @@ static void qio_channel_websock_finalize(Object *obj)

     buffer_free(&ioc->encoutput);

     buffer_free(&ioc->rawinput);

     buffer_free(&ioc->rawoutput);

-    buffer_free(&ioc->ping_reply);

     object_unref(OBJECT(ioc->master));

     if (ioc->io_tag) {

         g_source_remove(ioc->io_tag);

@@ -946,12 +948,7 @@ static ssize_t qio_channel_websock_write_wire(QIOChannelWebsock *ioc,

     ssize_t ret;

     ssize_t done = 0;

-    /* ping replies take priority over binary data */

-    if (!ioc->ping_reply.offset) {

-        qio_channel_websock_encode(ioc);

-    } else if (!ioc->encoutput.offset) {

-        buffer_move_empty(&ioc->encoutput, &ioc->ping_reply);

-    }

+    qio_channel_websock_encode(ioc);

     while (ioc->encoutput.offset > 0) {

         ret = qio_channel_write(ioc->master,

@@ -968,6 +965,11 @@ static ssize_t qio_channel_websock_write_wire(QIOChannelWebsock *ioc,

         }

         buffer_advance(&ioc->encoutput, ret);

         done += ret;

+        if (ioc->pong_remain < ret) {

+            ioc->pong_remain = 0;

+        } else {

+            ioc->pong_remain -= ret;

+        }

     }

     return done;

 }

@@ -1026,7 +1028,7 @@ static void qio_channel_websock_set_watch(QIOChannelWebsock *ioc)

         return;

     }

-    if (ioc->encoutput.offset || ioc->ping_reply.offset) {

+    if (ioc->encoutput.offset) {

         cond |= G_IO_OUT;

     }

     if (ioc->encinput.offset < QIO_CHANNEL_WEBSOCK_MAX_BUFFER &&

-- 

1.8.3.1