[Interest] It is happening again.

william.crocker at analog.com william.crocker at analog.com
Thu Sep 24 12:58:14 CEST 2015

On 09/23/2015 04:00 PM, Thiago Macieira wrote:
> 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?


Thanks for responding.
I have since restarted the server and all is well again.
I will have to wait for the failing behavior to happen
again and then apply tcpdump and strace.


> 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).

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