Echo capability of ip address from domain name for development with DNSdist

A DNSdist configuration example to map any IP address to a hostname for development purpose. The following formats are supported:

10.0.0.1.local.dev will return A record as A 10.0.0.1
192-168-1-250.local.dev will return A record as A 192.168.1.250
app.10.8.0.1.local.dev will return A record as A 10.8.0.1
app-116-203-255-68.local.dev will return A record as A 116.203.255.68
customer1.app.10.0.0.1.local.dev will return A record as A 10.0.0.1
customer-app1-127-0-0-1.local.dev will return A record as A 127.0.0.1
0a000803.local.dev will return A record as A 10.0.8.3
app-c0a801fc.local.dev will return A record as 192.168.1.252
customer3-app-7f000101.local.dev will return A record as 127.0.1.1

Invalid IP will return CNAME record.

In the following example, the local.dev domain is used to map IP addresses otherwise all other DNS queries are forwarded to the default backend 1.1.1.1.

The full dnsdist.conf example:

The latest version of the configuration can be downloaded from github.

setLocal("0.0.0.0:53", {})
newServer({address = "1.1.1.1:53"})


-- Echo capability of ip address from domain name for development
local function onEchoIpAddress(dq)
        -- list of regexs to find ip in qname
        ipsregex = {}

        -- 10.0.0.1.local.dev maps to A 10.0.0.1
        -- 192-168-1-250.local.dev maps to A 192.168.1.250
        ipsregex.ip4  = "^(%d+[%.-]%d+[%.-]%d+[%.-]%d+)%."

        -- app.10.8.0.1.local.dev maps to A 10.8.0.1
        -- app-116-203-255-68.local.dev maps to A 116.203.255.68
        -- customer1.app.10.0.0.1.local.dev maps to A 10.0.0.1
        -- customer-app1-127-0-0-1.local.dev maps to A 127.0.0.1
        ipsregex.ip4name = "[^a-z0-9A-Z]%.?(%d+[%.-]%d+[%.-]%d+[%.-]%d+)%."

        -- 0a000803.local.dev maps to A 10.0.8.3
        ipsregex.ip4hex = "^([0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F])%."

        -- app-c0a801fc.local.dev maps to A 192.168.1.252
        -- customer3-app-7f000101.local.dev maps to 127.0.1.1
        ipsregex.ip4hexname = "[^a-z0-9A-Z]%.?([0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F])%."

        -- default ip to return on no matched
        local retip = "127.0.0.2"

        -- iter over each regex to find ip
        for k, pattern in pairs(ipsregex) do
           addr  = string.match(dq.qname:toString(), pattern)
           if addr then
             retip = string.gsub(addr, "-", ".")

             if k == "ip4hex" or k == "ip4hexname" then
                retip = tonumber(retip, 16)
             end

             break
           end
        end

        return DNSAction.Spoof, retip
end

-- rule to match local domain
addAction("local.dev.", LuaAction(onEchoIpAddress))

-- default rule
addAction( AllRule(), PoolAction("default"))

Use the dig command to test this configuration:

dig 10.0.0.1.local.dev

;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24739
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;10.0.0.1.local.dev.            IN      A

;; ANSWER SECTION:
10.0.0.1.local.dev.     60      IN      A       10.0.0.1

;; Query time: 0 msec
;; SERVER: 127.0.0.1#5553(127.0.0.1) (TCP)
;; WHEN: Sat Aug 12 21:16:14 CEST 2023
;; MSG SIZE  rcvd: 63

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Echo capability of ip address from domain name for development with DNSdist