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.gitignore vendored Normal file
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# build output
local-ip.dev

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Dockerfile Normal file
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FROM golang:1.19-alpine AS build
WORKDIR /app
COPY . .
RUN go mod download
RUN CGO_ENABLED=0 go build -o /app/local-ip
FROM gcr.io/distroless/base-debian11
ENV PORT 53
WORKDIR /
COPY --from=build /app/local-ip /
EXPOSE $PORT
USER root
CMD ["/local-ip"]

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Apache License
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http://www.apache.org/licenses/
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fly.toml Normal file
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app = "local-ip"
kill_signal = "SIGINT"
kill_timeout = 5
processes = []
[env]
PORT = "53"
[experimental]
allowed_public_ports = []
auto_rollback = true
[[services]]
internal_port = 53
protocol = "udp"
[[services.ports]]
port = "53"

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module local-ip.dev
go 1.19
require (
github.com/miekg/dns v1.1.50 // indirect
golang.org/x/mod v0.4.2 // indirect
golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985 // indirect
golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c // indirect
golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2 // indirect
golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
)

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go.sum Normal file
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github.com/miekg/dns v1.1.50 h1:DQUfb9uc6smULcREF09Uc+/Gd46YWqJd5DbpPE9xkcA=
github.com/miekg/dns v1.1.50/go.mod h1:e3IlAVfNqAllflbibAZEWOXOQ+Ynzk/dDozDxY7XnME=
github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/mod v0.4.2 h1:Gz96sIWK3OalVv/I/qNygP42zyoKp3xptRVCWRFEBvo=
golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985 h1:4CSI6oo7cOjJKajidEljs9h+uP0rRZBPPPhcCbj5mw8=
golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I=
golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2 h1:BonxutuHCTL0rBDnZlKjpGIQFTjyUVTexFOdWkB6Fg0=
golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

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main.go Normal file
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package main
import (
"fmt"
"log"
"net"
"os"
"regexp"
"strconv"
"strings"
"github.com/miekg/dns"
)
const zone = "my.local-ip.dev."
func main() {
dns.HandleFunc(zone, handleDnsRequest)
port, err := strconv.Atoi(os.Getenv("PORT"))
if err != nil {
port = 9053
}
server := &dns.Server{
Addr: ":" + strconv.Itoa(port),
Net: "udp",
}
log.Printf("Starting at %d\n", port)
err = server.ListenAndServe()
defer server.Shutdown()
if err != nil {
log.Fatalf("Failed to start server: %s\n ", err.Error())
}
}
func handleDnsRequest(response dns.ResponseWriter, request *dns.Msg) {
go func() {
message := new(dns.Msg)
message.SetReply(request)
message.Compress = true
switch request.Opcode {
case dns.OpcodeQuery:
handleQuery(message)
default:
refuseMessage(message)
}
response.WriteMsg(message)
}()
}
func handleQuery(message *dns.Msg) {
for _, question := range message.Question {
switch question.Qtype {
case dns.TypeA:
ip := extractIp(question.Name)
log.Printf("%s => %s\n", question.Name, ip)
if ip == nil {
refuseMessage(message)
break
}
resource := new(dns.A)
resource.Hdr = dns.RR_Header{Ttl: 10, Name: question.Name, Rrtype: dns.TypeA, Class: dns.ClassINET}
resource.A = ip
message.Answer = append(message.Answer, resource)
}
}
}
func extractIp(fqdn string) net.IP {
var ip string
dashedIpRegex := regexp.MustCompile(fmt.Sprintf(`^(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4}).%s$`, zone))
matches := dashedIpRegex.FindStringSubmatch(fqdn)
if len(matches) < 2 {
return nil
}
ip = strings.ReplaceAll(matches[1], "-", ".")
return net.ParseIP(ip)
}
func refuseMessage(message *dns.Msg) {
message.MsgHdr.Rcode = dns.RcodeRefused
soa := new(dns.SOA)
soa.Hdr = dns.RR_Header{
Name: "my.local-ip.dev.",
Rrtype: dns.TypeSOA,
Class: dns.ClassINET,
Ttl: 10,
Rdlength: 0,
}
soa.Ns = "ns-1.local-ip.dev."
soa.Mbox = "admin.local-ip.dev."
soa.Serial = 2022102400
soa.Refresh = 10
soa.Retry = 10
soa.Expire = 10
soa.Minttl = 10
message.Ns = append(message.Ns, soa)
}