net/portmapper: make PCP/PMP result codes stringers

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

net/portmapper/pcp.go

@@ -19,6 +19,10 @@ import (
 // https://www.rfc-editor.org/rfc/pdfrfc/rfc6887.txt.pdf
 // https://tools.ietf.org/html/rfc6887
 
+//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file pcpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pcpResultCode -trimprefix=pcpCode
+
+type pcpResultCode uint8
+
 // PCP constants
 const (
 	pcpVersion     = 2
@@ -26,14 +30,14 @@ const (
 
 	pcpMapLifetimeSec = 7200 // TODO does the RFC recommend anything? This is taken from PMP.
 
-	pcpCodeOK            = 0
+	pcpCodeOK            pcpResultCode = 0
-	pcpCodeNotAuthorized = 2
+	pcpCodeNotAuthorized pcpResultCode = 2
 	// From RFC 6887:
 	// ADDRESS_MISMATCH: The source IP address of the request packet does
 	// not match the contents of the PCP Client's IP Address field, due
 	// to an unexpected NAT on the path between the PCP client and the
 	// PCP-controlled NAT or firewall.
-	pcpCodeAddressMismatch = 12
+	pcpCodeAddressMismatch pcpResultCode = 12
 
 	pcpOpReply    = 0x80 // OR'd into request's op code on response
 	pcpOpAnnounce = 0
@@ -146,7 +150,7 @@ func pcpAnnounceRequest(myIP netaddr.IP) []byte {
 
 type pcpResponse struct {
 	OpCode     uint8
-	ResultCode uint8
+	ResultCode pcpResultCode
 	Lifetime   uint32
 	Epoch      uint32
 }
@@ -156,7 +160,7 @@ func parsePCPResponse(b []byte) (res pcpResponse, ok bool) {
 		return
 	}
 	res.OpCode = b[1]
-	res.ResultCode = b[3]
+	res.ResultCode = pcpResultCode(b[3])
 	res.Lifetime = binary.BigEndian.Uint32(b[4:])
 	res.Epoch = binary.BigEndian.Uint32(b[8:])
 	return res, true

net/portmapper/pcpresultcode_string.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by "stringer -type=pcpResultCode -trimprefix=pcpCode"; DO NOT EDIT.
+
+package portmapper
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[pcpCodeOK-0]
+	_ = x[pcpCodeNotAuthorized-2]
+	_ = x[pcpCodeAddressMismatch-12]
+}
+
+const (
+	_pcpResultCode_name_0 = "OK"
+	_pcpResultCode_name_1 = "NotAuthorized"
+	_pcpResultCode_name_2 = "AddressMismatch"
+)
+
+func (i pcpResultCode) String() string {
+	switch {
+	case i == 0:
+		return _pcpResultCode_name_0
+	case i == 2:
+		return _pcpResultCode_name_1
+	case i == 12:
+		return _pcpResultCode_name_2
+	default:
+		return "pcpResultCode(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+}

net/portmapper/pmpresultcode_string.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by "stringer -type=pmpResultCode -trimprefix=pmpCode"; DO NOT EDIT.
+
+package portmapper
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[pmpCodeOK-0]
+	_ = x[pmpCodeUnsupportedVersion-1]
+	_ = x[pmpCodeNotAuthorized-2]
+	_ = x[pmpCodeNetworkFailure-3]
+	_ = x[pmpCodeOutOfResources-4]
+	_ = x[pmpCodeUnsupportedOpcode-5]
+}
+
+const _pmpResultCode_name = "OKUnsupportedVersionNotAuthorizedNetworkFailureOutOfResourcesUnsupportedOpcode"
+
+var _pmpResultCode_index = [...]uint8{0, 2, 20, 33, 47, 61, 78}
+
+func (i pmpResultCode) String() string {
+	if i >= pmpResultCode(len(_pmpResultCode_index)-1) {
+		return "pmpResultCode(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _pmpResultCode_name[_pmpResultCode_index[i]:_pmpResultCode_index[i+1]]
+}

net/portmapper/portmapper.go

@@ -564,6 +564,8 @@ func (c *Client) createOrGetMapping(ctx context.Context) (external netaddr.IPPor
 	}
 }
 
+//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file pmpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pmpResultCode -trimprefix=pmpCode
+
 type pmpResultCode uint16
 
 // NAT-PMP constants.