Initial Commit

.github/workflows/release.yml

@@ -0,0 +1,26 @@
+on:
+  push:
+    tags:
+      - v*.*.*
+
+env:
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  GO111MODULE: "on"
+
+name: release
+jobs:
+  release:
+    name: release
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout Repo
+      uses: actions/checkout@v2
+    - name: Setup Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.17.x
+    - name: Run GoReleaser
+      uses: goreleaser/goreleaser-action@v2
+      with:
+        args: release --rm-dist
+        version: latest

.gitignore

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+
+dist/

.goreleaser.yaml

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+before:
+  hooks:
+    # You may remove this if you don't use go modules.
+    - go mod tidy
+    # you may remove this if you don't need go generate
+    - go generate ./...
+builds:
+  - env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - windows
+      - darwin
+    main: cmd/sparse_dns/main.go
+archives:
+  - replacements:
+      darwin: Darwin
+      linux: Linux
+      windows: Windows
+      386: i386
+      amd64: x86_64
+    format: binary
+checksum:
+  name_template: 'checksums.txt'
+snapshot:
+  name_template: "{{ incpatch .Version }}-next"
+changelog:
+  sort: asc
+  filters:
+    exclude:
+      - '^docs:'
+      - '^test:'

README.md

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+sparse-dns
+===
+
+A simple DNS forwarder that forwards DNS queries to various upstreams. If an upstream returns NXDomain, the next upstream is tried.
+
+Usage
+---
+
+```
+Usage of ./sparse_dns:
+  -debug
+        Debug mode
+  -listen string
+        Address to listen to (TCP and UDP) (default ":53")
+  -maxclients uint
+        Maximum number of simultaneous clients (default 1000)
+  -maxrtt float
+        Maximum mean RTT for upstream queries before marking a server as dead (default 0.25)
+  -upstream string
+        Comma-delimited list of upstream servers (default "8.8.8.8:53,8.8.4.4:53")
+```

cmd/sparse_dns/main.go

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+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+const (
+	// MaxUDPBufferSize UDP buffer size
+	MaxUDPBufferSize = 16 * 1024 * 1024
+)
+
+// QueuedResponse Response to an asynchronous query
+type QueuedResponse struct {
+	resolved *dns.Msg
+	rtt      time.Duration
+	err      error
+}
+
+// QueuedRequest Asynchronous DNS request
+type QueuedRequest struct {
+	ts           time.Time
+	req          *dns.Msg
+	responseChan chan QueuedResponse
+}
+
+var (
+	address            = flag.String("listen", ":53", "Address to listen to (TCP and UDP)")
+	upstreamServersStr = flag.String("upstream", "8.8.8.8:53,8.8.4.4:53", "Comma-delimited list of upstream servers")
+	upstreamServers    []string
+	maxClients         = flag.Uint("maxclients", 1000, "Maximum number of simultaneous clients")
+	maxRTT             = flag.Float64("maxrtt", 0.25, "Maximum mean RTT for upstream queries before marking a server as dead")
+	debug              = flag.Bool("debug", false, "Debug mode")
+	resolverRing       chan QueuedRequest
+	globalTimeout      = 1 * time.Second
+	udpClient          dns.Client
+	tcpClient          dns.Client
+)
+
+func main() {
+	flag.Parse()
+
+	upstreamServers = strings.Split(*upstreamServersStr, ",") // parseUpstreamServers(*upstreamServersStr)
+	resolverRing = make(chan QueuedRequest, *maxClients)
+	udpClient = dns.Client{Net: "udp", DialTimeout: globalTimeout, ReadTimeout: globalTimeout, WriteTimeout: globalTimeout, SingleInflight: true}
+	tcpClient = dns.Client{Net: "tcp", DialTimeout: globalTimeout, ReadTimeout: globalTimeout, WriteTimeout: globalTimeout, SingleInflight: true}
+
+	for i := uint(0); i < *maxClients; i++ {
+		go func() {
+			resolverThread()
+		}()
+	}
+
+	dns.HandleFunc(".", route)
+	defer dns.HandleRemove(".")
+
+	// UDP Server
+	udpServer := &dns.Server{Addr: *address, Net: "udp"}
+	defer udpServer.Shutdown()
+	udpAddr, err := net.ResolveUDPAddr(udpServer.Net, udpServer.Addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	udpPacketConn, err := net.ListenUDP(udpServer.Net, udpAddr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	udpServer.PacketConn = udpPacketConn
+	udpPacketConn.SetReadBuffer(MaxUDPBufferSize)
+	udpPacketConn.SetWriteBuffer(MaxUDPBufferSize)
+
+	// TCP Server
+	tcpServer := &dns.Server{Addr: *address, Net: "tcp"}
+	defer tcpServer.Shutdown()
+	tcpAddr, err := net.ResolveTCPAddr(tcpServer.Net, tcpServer.Addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	tcpListener, err := net.ListenTCP(tcpServer.Net, tcpAddr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	tcpServer.Listener = tcpListener
+
+	// Start Servers
+	go func() {
+		log.Fatal(udpServer.ActivateAndServe())
+	}()
+	go func() {
+		log.Fatal(tcpServer.ActivateAndServe())
+	}()
+	fmt.Println("Ready")
+
+	select {}
+}
+
+func getMaxPayloadSize(req *dns.Msg) uint16 {
+	opt := req.IsEdns0()
+	if opt == nil {
+		return dns.MinMsgSize
+	}
+	maxPayloadSize := opt.UDPSize()
+	if maxPayloadSize < dns.MinMsgSize {
+		maxPayloadSize = dns.MinMsgSize
+	}
+	return maxPayloadSize
+}
+
+func pickUpstream(req *dns.Msg) (*string, error) {
+	res := upstreamServers[0]
+	return &res, nil
+}
+
+func syncResolve(req *dns.Msg) (*dns.Msg, time.Duration, error) {
+	var resolved *dns.Msg
+	var rtt time.Duration
+	var err error
+
+	for _, addr := range upstreamServers {
+		if *debug {
+			log.Printf("Querying %v for %v\n", addr, req.Question[0].Name)
+		}
+
+		resolved, rtt, err = udpClient.Exchange(req, addr)
+		if err != nil || (resolved != nil && resolved.Truncated) {
+			resolved, rtt, err = tcpClient.Exchange(req, addr)
+		}
+		if (dns.RcodeToString[resolved.Rcode] != "NOERROR") {
+			continue
+		}
+		if err == nil {
+			break
+		}
+	}
+
+	if err != nil {
+		return nil, 0, err
+	}
+
+	return resolved, rtt, nil
+}
+
+func resolverThread() {
+	for {
+		queuedRequest := <-resolverRing
+		if time.Since(queuedRequest.ts).Seconds() > *maxRTT {
+			response := QueuedResponse{resolved: nil, rtt: 0, err: errors.New("Request too old")}
+			queuedRequest.responseChan <- response
+			close(queuedRequest.responseChan)
+			continue
+		}
+		resolved, rtt, err := syncResolve(queuedRequest.req)
+		response := QueuedResponse{resolved: resolved, rtt: rtt, err: err}
+		queuedRequest.responseChan <- response
+		close(queuedRequest.responseChan)
+	}
+}
+
+func resolveViaResolverThreads(req *dns.Msg) (*dns.Msg, time.Duration, error) {
+	responseChan := make(chan QueuedResponse)
+	queuedRequest := QueuedRequest{ts: time.Now(), req: req, responseChan: responseChan}
+	for queued := false; queued == false; {
+		select {
+		case resolverRing <- queuedRequest:
+			queued = true
+		default:
+			old := <-resolverRing
+			evictedResponse := QueuedResponse{resolved: nil, rtt: 0, err: errors.New("Evicted")}
+			old.responseChan <- evictedResponse
+		}
+	}
+	response := <-responseChan
+	if response.err != nil {
+		return nil, response.rtt, response.err
+	}
+	return response.resolved, response.rtt, nil
+}
+
+func resolve(req *dns.Msg) (*dns.Msg, error) {
+	extra2 := []dns.RR{}
+	for _, extra := range req.Extra {
+		if extra.Header().Rrtype != dns.TypeOPT {
+			extra2 = append(extra2, extra)
+		}
+	}
+
+	dnssec := false
+	for _, extra := range req.Extra {
+		if extra.Header().Rrtype == dns.TypeOPT {
+			dnssec = extra.(*dns.OPT).Do()
+		}
+	}
+
+	req.Extra = extra2
+	req.SetEdns0(dns.DefaultMsgSize, dnssec)
+	resolved, _, err := resolveViaResolverThreads(req)
+	if err != nil {
+		return nil, err
+	}
+	resolved.Compress = true
+	return resolved, nil
+}
+
+func sendTruncated(w dns.ResponseWriter, msgHdr dns.MsgHdr) {
+	emptyResp := new(dns.Msg)
+	emptyResp.MsgHdr = msgHdr
+	emptyResp.Response = true
+	if _, isTCP := w.RemoteAddr().(*net.TCPAddr); isTCP {
+		dns.HandleFailed(w, emptyResp)
+		return
+	}
+	emptyResp.Truncated = true
+	w.WriteMsg(emptyResp)
+}
+
+func route(w dns.ResponseWriter, req *dns.Msg) {
+	maxPayloadSize := getMaxPayloadSize(req)
+
+	resp, err := resolve(req)
+	if err != nil {
+		w.Close()
+		return
+	}
+
+	packed, _ := resp.Pack()
+	packedLen := len(packed)
+	if uint16(packedLen) > maxPayloadSize {
+		sendTruncated(w, resp.MsgHdr)
+	} else {
+		w.WriteMsg(resp)
+	}
+}

go.mod

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+module github.com/matchlighter/sparse-dns
+
+go 1.17
+
+require github.com/miekg/dns v1.1.46
+
+require (
+	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
+)

go.sum

@@ -0,0 +1,35 @@
+github.com/miekg/dns v1.1.46 h1:uzwpxRtSVxtcIZmz/4Uz6/Rn7G11DvsaslXoy5LxQio=
+github.com/miekg/dns v1.1.46/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 h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
+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=