[squid-users] R: Squid doesn't reload webpage like other clients do

[Troiano Alessio]

Thank you Alex.
Can't be an idea to "forward" the rst to the client? In this way the proxy will be totally transparent and the reload is demanded to the client (browser).

Alessio


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-----Messaggio originale-----
Da: Alex Rousskov [mailto:rousskov at measurement-factory.com]
Inviato: lunedì 30 ottobre 2017 17:22
A: Troiano Alessio <alessio.troiano at leonardocompany.com>; squid-users at lists.squid-cache.org
Oggetto: Re: [squid-users] Squid doesn't reload webpage like other clients do

On 10/30/2017 03:51 AM, Troiano Alessio wrote:

> I've squid 3.5.20 running on RHEL 7.4. I have a problem to access some
> websites, for example www.nato.int. This website apply an Anti-DDoS
> system that reset the first connection after the TCP 3-way handshake
> (SYN/SYN-ACK/ACK/RST-ACK). All subsequent TCP connections are
> accepted. The website administrator say's it is by design.


> When I browse the site with squid proxy the browser receive an "Empty
> Response" squid error page (HTTP error code 502 Bad Gateway) and
> doesn't do the automatic retry:

This is by design as well :-).

We can change Squid behavior to retry connection resets, but I am sure that some folks will not like the new behavior because in _their_ use cases a retry is wasteful and/or painful. IMHO, the new behavior should be controlled by a configuration directive, possibly an ACL-driven one.

Quality patches implementing the above feature should be welcomed IMO.
The tip of the relevant code is probably in ERR_ZERO_SIZE_OBJECT handling inside FwdState::fail(). There is a similar code that handles persistent connection races there already, but the zero-size reply code may need a new dedicated FwdState flag to prevent infinite retry loops when the origin server is broken (a much more typical use case than the weird attempt at DDoS mitigation that you have described above).

https://wiki.squid-cache.org/SquidFaq/AboutSquid#How_to_add_a_new_Squid_feature.2C_enhance.2C_of_fix_something.3F


HTH,

Alex.