I am confused about DNS caching. I am writing a small forward proxy server and want to use OS DNS cache on a Linux system.
If I understand correctly, then there is DNS caching at the browser level. Then there is DNS caching at OS level (Windows has it. I am not sure if Linux distros have it by default).
So, how does a browser/proxy_server use OS DNS caching? I am trying to find if I can rely on Linux for DNS caching instead of doing it on my own inside my proxy.
Thanks
This question is related to
linux
networking
operating-system
dns
You have here available an example of DNS Caching in Debian using dnsmasq.
Configuration summary:
# Ensure you add this line
DNSMASQ_OPTS="-r /etc/resolv.dnsmasq"
# Your preferred servers
nameserver 1.1.1.1
nameserver 8.8.8.8
nameserver 2001:4860:4860::8888
nameserver 127.0.0.1
Then just restart dnsmasq.
Benchmark test using DNS 1.1.1.1:
for i in {1..100}; do time dig slashdot.org @1.1.1.1; done 2>&1 | grep ^real | sed -e s/.*m// | awk '{sum += $1} END {print sum / NR}'
Benchmark test using you local cached DNS:
for i in {1..100}; do time dig slashdot.org; done 2>&1 | grep ^real | sed -e s/.*m// | awk '{sum += $1} END {print sum / NR}'
Here are two other software packages which can be used for DNS caching on Linux:
After configuring the software for DNS forwarding and caching, you then set the system's DNS resolver to 127.0.0.1 in /etc/resolv.conf.
If your system is using NetworkManager you can either try using the dns=dnsmasq
option in /etc/NetworkManager/NetworkManager.conf
or you can change your connection settings to Automatic (Address Only) and then use a script in the /etc/NetworkManager/dispatcher.d
directory to get the DHCP nameserver, set it as the DNS forwarding server in your DNS cache software and then trigger a configuration reload.
Firefox contains a dns cache. To disable the DNS cache:
When disabled, Firefox will use the DNS cache provided by the OS.
Source: Stackoverflow.com