[Interest] It is happening again.

Thiago Macieira thiago.macieira at intel.com
Wed Sep 23 22:00:10 CEST 2015

On Tuesday 22 September 2015 16:09:57 Bill Crocker wrote:
> 2 - During these periods, the invalid SYN cookies number on the server
> steadily  rises:
>      >netstat -ts | grep SYN
>          302658 invalid SYN cookies received    <-------
>      >netstat -ts | grep SYN
>          302745 invalid SYN cookies received    <-------

Hi Bill

What are invalid SYN cookies here? Can you capture the traffic on the server 
with tcpdump?

What class are you using here? QTcpSocket, QSslSocket or QNetworkReply?

For a regular QTcpSocket, RemoteHostClosedError only happens on 
QNativeSocketEngine::read if the native read() call returned 0 (that is, EOF). 
But that should only happen after the connection established successfully and 
that doesn't match what you're seeing. Can you also capture the strace on the 
client? I'm only interested in connect() and read() calls (strace -f -e 
connect,read,close should do it).

Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center

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