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net/portmapper: move pcp code to separate file

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This moves all the PCP code to a separate file in preparation for portmapping with PCP.

Signed-off-by: julianknodt <julianknodt@gmail.com>
This commit is contained in:
julianknodt 2021-08-03 15:28:13 -07:00 committed by Brad Fitzpatrick
parent eee6b85b9b
commit 5c98b1b8d0
2 changed files with 94 additions and 73 deletions
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94
net/portmapper/pcp.go Normal file
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@ -0,0 +1,94 @@
// 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.
package portmapper
import (
"crypto/rand"
"encoding/binary"
"inet.af/netaddr"
)
// References:
//
// https://www.rfc-editor.org/rfc/pdfrfc/rfc6887.txt.pdf
// https://tools.ietf.org/html/rfc6887
// PCP constants
const (
pcpVersion = 2
pcpPort = 5351
pcpMapLifetimeSec = 7200 // TODO does the RFC recommend anything? This is taken from PMP.
pcpCodeOK = 0
pcpCodeNotAuthorized = 2
pcpOpReply = 0x80 // OR'd into request's op code on response
pcpOpAnnounce = 0
pcpOpMap = 1
pcpUDPMapping = 17 // portmap UDP
pcpTCPMapping = 6 // portmap TCP
)
// pcpMapRequest generates a PCP packet with a MAP opcode.
func pcpMapRequest(myIP netaddr.IP, mapToLocalPort int, delete bool) []byte {
const udpProtoNumber = 17
lifetimeSeconds := uint32(1)
if delete {
lifetimeSeconds = 0
}
const opMap = 1
// 24 byte header + 36 byte map opcode
pkt := make([]byte, (32+32+128)/8+(96+8+24+16+16+128)/8)
// The header (https://tools.ietf.org/html/rfc6887#section-7.1)
pkt[0] = 2 // version
pkt[1] = opMap
binary.BigEndian.PutUint32(pkt[4:8], lifetimeSeconds)
myIP16 := myIP.As16()
copy(pkt[8:], myIP16[:])
// The map opcode body (https://tools.ietf.org/html/rfc6887#section-11.1)
mapOp := pkt[24:]
rand.Read(mapOp[:12]) // 96 bit mappping nonce
mapOp[12] = udpProtoNumber
binary.BigEndian.PutUint16(mapOp[16:], uint16(mapToLocalPort))
v4unspec := netaddr.MustParseIP("0.0.0.0")
v4unspec16 := v4unspec.As16()
copy(mapOp[20:], v4unspec16[:])
return pkt
}
// pcpAnnounceRequest generates a PCP packet with an ANNOUNCE opcode.
func pcpAnnounceRequest(myIP netaddr.IP) []byte {
// See https://tools.ietf.org/html/rfc6887#section-7.1
pkt := make([]byte, 24)
pkt[0] = pcpVersion // version
pkt[1] = pcpOpAnnounce
myIP16 := myIP.As16()
copy(pkt[8:], myIP16[:])
return pkt
}
type pcpResponse struct {
OpCode uint8
ResultCode uint8
Lifetime uint32
Epoch uint32
}
func parsePCPResponse(b []byte) (res pcpResponse, ok bool) {
if len(b) < 24 || b[0] != pcpVersion {
return
}
res.OpCode = b[1]
res.ResultCode = b[3]
res.Lifetime = binary.BigEndian.Uint32(b[4:])
res.Epoch = binary.BigEndian.Uint32(b[8:])
return res, true
}

73
net/portmapper/portmapper.go
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@ -8,7 +8,6 @@
import (
"context"
"crypto/rand"
"encoding/binary"
"errors"
"fmt"
@ -36,7 +35,6 @@
// References:
//
// NAT-PMP: https://tools.ietf.org/html/rfc6886
// PCP: https://tools.ietf.org/html/rfc6887
// portMapServiceTimeout is the time we wait for port mapping
// services (UPnP, NAT-PMP, PCP) to respond before we give up and
@ -669,77 +667,6 @@ func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) {
}
}
const (
pcpVersion = 2
pcpPort = 5351
pcpCodeOK = 0
pcpCodeNotAuthorized = 2
pcpOpReply = 0x80 // OR'd into request's op code on response
pcpOpAnnounce = 0
pcpOpMap = 1
)
// pcpAnnounceRequest generates a PCP packet with an ANNOUNCE opcode.
func pcpAnnounceRequest(myIP netaddr.IP) []byte {
// See https://tools.ietf.org/html/rfc6887#section-7.1
pkt := make([]byte, 24)
pkt[0] = pcpVersion // version
pkt[1] = pcpOpAnnounce
myIP16 := myIP.As16()
copy(pkt[8:], myIP16[:])
return pkt
}
// pcpMapRequest generates a PCP packet with a MAP opcode.
func pcpMapRequest(myIP netaddr.IP, mapToLocalPort int, delete bool) []byte {
const udpProtoNumber = 17
lifetimeSeconds := uint32(1)
if delete {
lifetimeSeconds = 0
}
const opMap = 1
// 24 byte header + 36 byte map opcode
pkt := make([]byte, (32+32+128)/8+(96+8+24+16+16+128)/8)
// The header (https://tools.ietf.org/html/rfc6887#section-7.1)
pkt[0] = 2 // version
pkt[1] = opMap
binary.BigEndian.PutUint32(pkt[4:8], lifetimeSeconds)
myIP16 := myIP.As16()
copy(pkt[8:], myIP16[:])
// The map opcode body (https://tools.ietf.org/html/rfc6887#section-11.1)
mapOp := pkt[24:]
rand.Read(mapOp[:12]) // 96 bit mappping nonce
mapOp[12] = udpProtoNumber
binary.BigEndian.PutUint16(mapOp[16:], uint16(mapToLocalPort))
v4unspec := netaddr.MustParseIP("0.0.0.0")
v4unspec16 := v4unspec.As16()
copy(mapOp[20:], v4unspec16[:])
return pkt
}
type pcpResponse struct {
OpCode uint8
ResultCode uint8
Lifetime uint32
Epoch uint32
}
func parsePCPResponse(b []byte) (res pcpResponse, ok bool) {
if len(b) < 24 || b[0] != pcpVersion {
return
}
res.OpCode = b[1]
res.ResultCode = b[3]
res.Lifetime = binary.BigEndian.Uint32(b[4:])
res.Epoch = binary.BigEndian.Uint32(b[8:])
return res, true
}
var pmpReqExternalAddrPacket = []byte{0, 0} // version 0, opcode 0 = "Public address request"
const (