DNS Querys and proxy (squid + dansguardian) responses – who’s reponsible for the query

dansguardiandomain-name-systemsquid

I'm having a trouble with squid (and dansguardian) in my network that slows web page browsing.

I'm focused now in the DNS queries – i think the DNS can share part of the blame. I've observing my machine with wireshark and the server with tcpdump.

I'm observing that, when i request a page, my machine tries to resolve the name and the squid server also does the same. Is this a normal behaviour ? Shouldn't my machine forward the request to the proxy and then the proxy server resolves the name and makes the request to that web page ?

My Firefox (if I make a mistake in the web page name) stays 30 seconds (i guess this has something to do with dns timeout) blocked (but really blocked) until the proxy server sends a default squid page of domain not found…or until the DNS resolves the query..

My question is only if my machine and my proxy server really have both to make the DNS query or it should only be the proxy server…

Thank you.

Best Answer

In general, yes, your local browser will try to resolve the hostname in DNS before sending the request to the proxy. With Firefox this is configurable using the network.proxy.socks_remote_dns setting. To modify this setting:

  • Enter about:config in the location bar.
  • Enter network.proxy.socks_remote_dns in the search field.
  • Double-click on the network.proxy.socks_remote_dns item to change it from false (the default) to true.

With this enabled, Firefox should pass requests to the proxy without performing DNS resolution locally.

NB: I don't know for certain if this applies only to socks proxies or not.

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