Add SVCB dohpath key

parse_test.go

@@ -1652,6 +1652,8 @@ func TestParseSVCB(t *testing.T) {
 		`example.com.   SVCB   16 foo.example.org. alpn=h2,h3-19 mandatory=ipv4hint,alpn ipv4hint=192.0.2.1`: `example.com.	3600	IN	SVCB	16 foo.example.org. alpn="h2,h3-19" mandatory="ipv4hint,alpn" ipv4hint="192.0.2.1"`,
 		`example.com.   SVCB   16 foo.example.org. alpn="f\\\\oo\\,bar,h2"`: `example.com.	3600	IN	SVCB	16 foo.example.org. alpn="f\\\\oo\\,bar,h2"`,
 		`example.com.   SVCB   16 foo.example.org. alpn=f\\\092oo\092,bar,h2`: `example.com.	3600	IN	SVCB	16 foo.example.org. alpn="f\\\092oo\092,bar,h2"`,
+		// From draft-ietf-add-ddr-06
+		`_dns.example.net. SVCB 1 example.net. alpn=h2 dohpath=/dns-query{?dns}`: `_dns.example.net.	3600	IN	SVCB	1 example.net. alpn="h2" dohpath="/dns-query{?dns}"`,
 	}
 	for s, o := range svcbs {
 		rr, err := NewRR(s)

svcb.go

@@ -22,6 +22,7 @@ const (
 	SVCB_IPV4HINT
 	SVCB_ECHCONFIG
 	SVCB_IPV6HINT
+	SVCB_DOHPATH // draft-ietf-add-svcb-dns-02 Section 9
 
 	svcb_RESERVED SVCBKey = 65535
 )
@@ -34,6 +35,7 @@ var svcbKeyToStringMap = map[SVCBKey]string{
 	SVCB_IPV4HINT:        "ipv4hint",
 	SVCB_ECHCONFIG:       "ech",
 	SVCB_IPV6HINT:        "ipv6hint",
+	SVCB_DOHPATH:         "dohpath",
 }
 
 var svcbStringToKeyMap = reverseSVCBKeyMap(svcbKeyToStringMap)
@@ -196,6 +198,8 @@ func makeSVCBKeyValue(key SVCBKey) SVCBKeyValue {
 		return new(SVCBECHConfig)
 	case SVCB_IPV6HINT:
 		return new(SVCBIPv6Hint)
+	case SVCB_DOHPATH:
+		return new(SVCBDoHPath)
 	case svcb_RESERVED:
 		return nil
 	default:
@@ -669,6 +673,62 @@ func (s *SVCBIPv6Hint) copy() SVCBKeyValue {
 	}
 }
 
+// SVCBDoHPath pair is used to indicate the URI template that the
+// clients may use to construct a DNS over HTTPS URI.
+//
+// See RFC xxxx (https://datatracker.ietf.org/doc/html/draft-ietf-add-svcb-dns-02)
+// and RFC yyyy (https://datatracker.ietf.org/doc/html/draft-ietf-add-ddr-06).
+//
+// Basic use pattern for using the dohpath option together with an alpn
+// option:
+//
+//	s := new(dns.SVCB)
+//	s.Hdr = dns.RR_Header{Name: ".", Rrtype: dns.TypeSVCB, Class: dns.ClassINET}
+//	e := new(dns.SVCBAlpn)
+//	e.Alpn = []string{"h2", "h3"}
+//	p := new(dns.SVCBDoHPath)
+//	p.Template = "/dns-query{?dns}"
+//	s.Value = append(s.Value, e, p)
+//
+// The parsing currently only validates the length of Template.
+// It doesn't validate that Template is a valid RFC 6570 URI template.
+type SVCBDoHPath struct {
+	Template string
+}
+
+func (*SVCBDoHPath) Key() SVCBKey { return SVCB_DOHPATH }
+func (s *SVCBDoHPath) len() int   { return len(s.Template) }
+
+func (s *SVCBDoHPath) pack() ([]byte, error) {
+	if len(s.Template) > 65535 {
+		return nil, errors.New("dns: svcbdohpath: template too long")
+	}
+	return []byte(s.Template), nil
+}
+
+func (s *SVCBDoHPath) unpack(b []byte) error {
+	s.Template = string(b)
+	return nil
+}
+
+func (s *SVCBDoHPath) String() string {
+	return s.Template
+}
+
+func (s *SVCBDoHPath) parse(b string) error {
+	if len(b) > 65535 {
+		return errors.New("dns: svcbdohpath: template too long")
+	}
+	s.Template = b
+	return nil
+}
+
+func (s *SVCBDoHPath) copy() SVCBKeyValue {
+	return &SVCBDoHPath{
+		Template: s.Template,
+	}
+}
+
 // SVCBLocal pair is intended for experimental/private use. The key is recommended
 // to be in the range [SVCB_PRIVATE_LOWER, SVCB_PRIVATE_UPPER].
 // Basic use pattern for creating a keyNNNNN option:

svcb_test.go

@@ -18,6 +18,7 @@ func TestSVCB(t *testing.T) {
 		{`no-default-alpn`, ``},
 		{`ipv6hint`, `1::4:4:4:4,1::3:3:3:3`},
 		{`ech`, `YUdWc2JHOD0=`},
+		{`dohpath`, `/dns-query{?dns}`},
 		{`key65000`, `4\ 3`},
 		{`key65001`, `\"\ `},
 		{`key65002`, ``},