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io/channel-websock: handle continuous reads without any data 

According to the current implementation of websocket protocol in QEMU,
qio_channel_websock_handshake_io tries to read handshake from the
channel to start communication over socket. But this approach
doesn't cover scenario when socket was closed while handshaking.
Therefore, if G_IO_IN is caught and qio_channel_read returns zero,
error has to be set and connection has to be done.

Such behaviour causes 100% CPU load in main QEMU loop, because main loop
poll continues to receive and handle G_IO_IN events from websocket.

Step to reproduce 100% CPU load:
1) start qemu with the simplest configuration
$ qemu -vnc [::1]:1,websocket=7500
2) open any vnc listener (which doesn't follow websocket
protocol)
$ vncviewer :7500
3) kill listener
4) qemu main thread eats 100% CPU

Signed-off-by: Edgar Kaziakhmedov <edgar.kaziakhmedov@virtuozzo.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Edgar Kaziakhmedov 2018-01-10 18:39:24 +03:00 committed by Daniel P. Berrangé
parent 28bb0a59f8
commit a46ded1de5
1 changed files with 5 additions and 2 deletions
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7
io/channel-websock.c
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@ -499,9 +499,12 @@ static int qio_channel_websock_handshake_read(QIOChannelWebsock *ioc,
error_setg(errp,
"End of headers not found in first 4096 bytes");
return 1;
} else {
return 0;
} else if (ret == 0) {
error_setg(errp,
"End of headers not found before connection closed");
return -1;
}
return 0;
}
*handshake_end = '\0';