matchrelay

Name

matchrelay - match IP addresses and selectively relay them to specific upstream

Description

Module aims to provide a way to segregate traffic based on source IP of a query similar to how routers perform source based routing instead of destination domains which coredns is normally doing.

This module has a dependency on the forward module and support multi proxies and resource optimizations as with the forward module.

to build, pull coredns code

git clone https://github.com/coredns/coredns.git

add this line into plugin.cfg

...
etcd:etcd
loop:loop
matchrelay:github.com/kelchy/matchrelay
forward:forward
grpc:grpc
...

take note of the order as ordinality of the plugins matter for coredns

since cache is above matchrelay, cache may serve responses without hitting matchrelay this may cause unexpected behaviours, avoid using cache with matchrelay if the order of plugins is made this way

you may need to set git to use ssh

git config --global url."git@github.com:".insteadOf "https://github.com/"

and set to private

export GOPRIVATE=github.com/kelchy/matchrelay

then use "make" to build

make

or

go get github.com/kelchy/matchrelay
go generate
go build

Syntax

matchrelay {
    net <source ip>
    match ./list.txt
    reload 10s
    relay <destination server>
}

"net" is a declaration of a network host/subnet "match" will look for a file containing list of declarations and "reload" will automatically reload the list if md5 of the file changes "relay" will round robin destinations for the matched requests

Examples

Start a server on the default port and load the matchrelay

example.org {
    matchrelay {
        net 10.1.2.3/32
        relay 8.8.8.8:53 1.1.1.1:53
    }
}

or by importing a file instead of using the internal match and reload mechanism. note that if you use reload module, the whole Corefile will be loaded in each reload. if the number of zones or list is high, this may cause huge spikes in CPU which may bring down performance. For very dynamic environments, use the match and reload mechanism

example.org {
    matchrelay {
        import ./list.txt
        relay 8.8.8.8:53 1.1.1.1:53
    }
}

Author

Kelvin Chua kelvin@circles.asia