When does Squid reset upstream connections?

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When does Squid reset upstream connections?

Kaiwang Chen
Hello,

After a few pairs of HTTP Get and Response, actually for different
clients to retrieve data, over the same persistent upstream
connection, Squid(3.1.11) may send one RST+ACK, following by a few
RST's with the same sequence number as RST+ACK.  In some other cases,
Squid gracefully closes the upstream connection by initiating a
FIN+ACK packet. I guess Squid has some management procedure to
distinguish these cases... then what are the approaches?


Thanks,
Kaiwang
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Re: When does Squid reset upstream connections?

Amos Jeffries
Administrator
 On Thu, 25 Aug 2011 01:58:53 +0800, Kaiwang Chen wrote:
> Hello,
>
> After a few pairs of HTTP Get and Response, actually for different
> clients to retrieve data, over the same persistent upstream
> connection, Squid(3.1.11) may send one RST+ACK, following by a few
> RST's with the same sequence number as RST+ACK.  In some other cases,
> Squid gracefully closes the upstream connection by initiating a
> FIN+ACK packet. I guess Squid has some management procedure to
> distinguish these cases... then what are the approaches?

 RST or FIN as per the TCP specifications. Basically RST in errors.

 When a client disconnects and the server connection cannot be re-used.
 When client disconnects and object is not cacheable. When excess data is
 pushed into the link by the server. When the server replies with invalid
 response.

 Amos
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Re: When does Squid reset upstream connections?

jbhasin83
Hello,

I have a squid set up in transparent proxy. Squid sends a TCP RESET message
to the uperstream server but does not put an outgoing TCP outgoing mark.
Squid puts an outgoing TCP mark on every other packet going upstream.
Is this a bug ?

Thanks,
Jatin Bhasin



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Re: When does Squid reset upstream connections?

Amos Jeffries
Administrator
On 27/04/18 00:20, jbhasin83 wrote:
> Hello,
>
> I have a squid set up in transparent proxy. Squid sends a TCP RESET message
> to the uperstream server but does not put an outgoing TCP outgoing mark.
> Squid puts an outgoing TCP mark on every other packet going upstream.
> Is this a bug ?

Maybe, *if* the RESET was sent by Squid. The TCP network stack itself
can also generate them if data arrives on a socket/port which was
previously closed by Squid with a FIN, FIN+ACK, or earlier RST packet.

Amos
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