refactor: remove miekg/dns dep (#72)

* fix: remove dns dependency that is used only for one util

* test: add unit tests for isFqdn and fqdn functions

improve function documentation to explain escaped dot handling

---------

Co-authored-by: Marcin Rataj <lidel@lidel.org>

Author: v1rtl

go.mod

@@ -1,9 +1,6 @@
 module github.com/multiformats/go-multiaddr-dns
 
-require (
-	github.com/miekg/dns v1.1.41
-	github.com/multiformats/go-multiaddr v0.13.0
-)
+require github.com/multiformats/go-multiaddr v0.13.0
 
 require (
 	github.com/ipfs/go-cid v0.0.7 // indirect
@@ -18,7 +15,6 @@ require (
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
 	golang.org/x/crypto v0.18.0 // indirect
 	golang.org/x/exp v0.0.0-20230725012225-302865e7556b // indirect
-	golang.org/x/net v0.10.0 // indirect
 	golang.org/x/sys v0.16.0 // indirect
 	lukechampine.com/blake3 v1.2.1 // indirect
 )

go.sum

@@ -4,8 +4,6 @@ github.com/ipfs/go-cid v0.0.7 h1:ysQJVJA3fNDF1qigJbsSQOdjhVLsOEoPdh0+R97k3jY=
 github.com/ipfs/go-cid v0.0.7/go.mod h1:6Ux9z5e+HpkQdckYoX1PG/6xqKspzlEIR5SDmgqgC/I=
 github.com/klauspost/cpuid/v2 v2.2.6 h1:ndNyv040zDGIDh8thGkXYjnFtiN02M1PVVF+JE/48xc=
 github.com/klauspost/cpuid/v2 v2.2.6/go.mod h1:Lcz8mBdAVJIBVzewtcLocK12l3Y+JytZYpaMropDUws=
-github.com/miekg/dns v1.1.41 h1:WMszZWJG0XmzbK9FEmzH2TVcqYzFesusSIB41b8KHxY=
-github.com/miekg/dns v1.1.41/go.mod h1:p6aan82bvRIyn+zDIv9xYNUpwa73JcSh9BKwknJysuI=
 github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1/go.mod h1:pD8RvIylQ358TN4wwqatJ8rNavkEINozVn9DtGI3dfQ=
 github.com/minio/sha256-simd v0.1.1-0.20190913151208-6de447530771/go.mod h1:B5e1o+1/KgNmWrSQK08Y6Z1Vb5pwIktudl0J58iy0KM=
 github.com/minio/sha256-simd v1.0.1 h1:6kaan5IFmwTNynnKKpDHe6FWHohJOHhCPchzK49dzMM=
@@ -44,22 +42,12 @@ golang.org/x/crypto v0.18.0/go.mod h1:R0j02AL6hcrfOiy9T4ZYp/rcWeMxM3L6QYxlOuEG1m
 golang.org/x/exp v0.0.0-20230725012225-302865e7556b h1:tK7yjGqVRzYdXsBcfD2MLhFAhHfDgGLm2rY1ub7FA9k=
 golang.org/x/exp v0.0.0-20230725012225-302865e7556b/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
-golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
-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 v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
 golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-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/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/yaml.v3 v3.0.0 h1:hjy8E9ON/egN1tAYqKb61G10WtihqetD4sz2H+8nIeA=
 gopkg.in/yaml.v3 v3.0.0/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 lukechampine.com/blake3 v1.2.1 h1:YuqqRuaqsGV71BV/nm9xlI0MKUv4QC54jQnBChWbGnI=

resolve.go

@@ -5,10 +5,38 @@ import (
 	"net"
 	"strings"
 
-	"github.com/miekg/dns"
 	ma "github.com/multiformats/go-multiaddr"
 )
 
+// isFqdn checks if s is a fully qualified domain name.
+// A domain is fully qualified if it ends with an unescaped dot.
+// Escaped dots (preceded by an odd number of backslashes) do not count
+// as terminators.
+func isFqdn(s string) bool {
+	if s == "" || s[len(s)-1] != '.' {
+		return false
+	}
+	s = s[:len(s)-1]
+	if s == "" || s[len(s)-1] != '\\' {
+		return true
+	}
+	// Check if the dot is escaped by counting backslashes
+	i := strings.LastIndexFunc(s, func(r rune) bool {
+		return r != '\\'
+	})
+	return (len(s)-i)%2 != 0
+}
+
+// fqdn returns the fully qualified domain name of s by appending a trailing
+// dot if one is not already present. If s is already fully qualified, it is
+// returned unchanged.
+func fqdn(s string) string {
+	if isFqdn(s) {
+		return s
+	}
+	return s + "."
+}
+
 var (
 	dnsaddrProtocol = ma.ProtocolWithCode(ma.P_DNSADDR)
 	dns4Protocol    = ma.ProtocolWithCode(ma.P_DNS4)
@@ -75,14 +103,14 @@ func WithDomainResolver(domain string, rslv BasicResolver) Option {
 		if r.custom == nil {
 			r.custom = make(map[string]BasicResolver)
 		}
-		fqdn := dns.Fqdn(domain)
+		fqdn := fqdn(domain)
 		r.custom[fqdn] = rslv
 		return nil
 	}
 }
 
 func (r *Resolver) getResolver(domain string) BasicResolver {
-	fqdn := dns.Fqdn(domain)
+	fqdn := fqdn(domain)
 
 	// we match left-to-right, with more specific resolvers superseding generic ones.
 	// So for a domain a.b.c, we will try a.b,c, b.c, c, and fallback to the default if

resolve_test.go

@@ -387,3 +387,43 @@ func TestLimitResolver(t *testing.T) {
 		t.Fatalf("expected %d, got %d", maxResolvedAddrs, len(addrs))
 	}
 }
+
+func TestIsFqdn(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected bool
+	}{
+		{"", false},
+		{".", true},
+		{"example.com", false},
+		{"example.com.", true},
+		{"example\\.com.", true},      // escaped dot in middle, real dot at end
+		{"example.com\\.", false},     // trailing dot is escaped
+		{"example.com\\\\.", true},    // escaped backslash before real dot
+		{"example.com\\\\\\.", false}, // escaped backslash + escaped dot
+	}
+	for _, tc := range tests {
+		if got := isFqdn(tc.input); got != tc.expected {
+			t.Errorf("isFqdn(%q) = %v, want %v", tc.input, got, tc.expected)
+		}
+	}
+}
+
+func TestFqdn(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"", "."},
+		{".", "."},
+		{"example.com", "example.com."},
+		{"example.com.", "example.com."},
+		{"example.com\\.", "example.com\\.."},    // escaped dot, needs real dot added
+		{"example.com\\\\.", "example.com\\\\."}, // already fqdn
+	}
+	for _, tc := range tests {
+		if got := fqdn(tc.input); got != tc.expected {
+			t.Errorf("fqdn(%q) = %q, want %q", tc.input, got, tc.expected)
+		}
+	}
+}