commit 5d58353e997a49a06b5d06813f13b8f5554c9f8d Author: m5r Date: Thu Oct 27 23:19:23 2022 +0200 Initial commit diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..a1c0597 --- /dev/null +++ b/.gitignore @@ -0,0 +1,2 @@ +# build output +local-ip.dev diff --git a/Dockerfile b/Dockerfile new file mode 100644 index 0000000..a034c3a --- /dev/null +++ b/Dockerfile @@ -0,0 +1,20 @@ +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"] \ No newline at end of file diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..261eeb9 --- /dev/null +++ b/LICENSE @@ -0,0 +1,201 @@ + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. 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However, in accepting such obligations, You may act only + on Your own behalf and on Your sole responsibility, not on behalf + of any other Contributor, and only if You agree to indemnify, + defend, and hold each Contributor harmless for any liability + incurred by, or claims asserted against, such Contributor by reason + of your accepting any such warranty or additional liability. + + END OF TERMS AND CONDITIONS + + APPENDIX: How to apply the Apache License to your work. + + To apply the Apache License to your work, attach the following + boilerplate notice, with the fields enclosed by brackets "[]" + replaced with your own identifying information. (Don't include + the brackets!) The text should be enclosed in the appropriate + comment syntax for the file format. We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright [yyyy] [name of copyright owner] + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. diff --git a/fly.toml b/fly.toml new file mode 100644 index 0000000..e19c0ef --- /dev/null +++ b/fly.toml @@ -0,0 +1,18 @@ +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" diff --git a/go.mod b/go.mod new file mode 100644 index 0000000..b6babdf --- /dev/null +++ b/go.mod @@ -0,0 +1,12 @@ +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 +) diff --git a/go.sum b/go.sum new file mode 100644 index 0000000..c4d9417 --- /dev/null +++ b/go.sum @@ -0,0 +1,34 @@ +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= diff --git a/main.go b/main.go new file mode 100644 index 0000000..07800cc --- /dev/null +++ b/main.go @@ -0,0 +1,104 @@ +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) +}