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start to add NAT-PMP port mapping

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Change-Id: Id8061ab8e907a9473f0931deebd6cabcd32deffc
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2024-07-29 09:55:04 -07:00
parent 40814eafb4
commit ae484da02e
1 changed files with 53 additions and 4 deletions
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57
natlab/natlabd/natlabd.go
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@ -44,8 +44,9 @@ import (
)
var (
listen = flag.String("listen", "/tmp/qemu.sock", "path to listen on")
hard = flag.Bool("hard", false, "use hard NAT")
listen = flag.String("listen", "/tmp/qemu.sock", "path to listen on")
hard = flag.Bool("hard", false, "use hard NAT")
portmap = flag.Bool("portmap", false, "enable portmapping")
)
const nicID = 1
@ -84,6 +85,7 @@ func main() {
s.nodes[node1.mac] = node1
net1.InitNAT(*hard)
net1.portmap = *portmap
net2 := &network{
s: s,
mac: MAC{0x52, 0x54, 0x00, 0x01, 0x01, 0x2},
@ -437,6 +439,7 @@ type network struct {
s *Server
mac MAC
doesNAT bool
portmap bool
wanIP netip.Addr
lanIP netip.Prefix // with host bits set (e.g. 192.168.2.1/24)
nodesByIP map[netip.Addr]*node
@ -679,11 +682,18 @@ func (n *network) HandleEthernetPacket(ep EthernetPacket) {
// LAN IP here and wrapped in an ethernet layer and delivered
// to the network.
func (n *network) HandleUDPPacket(p UDPPacket) {
src := p.Src
dst := n.doNATIn(p.Src, p.Dst)
if !dst.IsValid() {
return
}
p.Dst = dst
n.WriteUDPPacketNoNAT(p)
}
// WriteUDPPacketNoNAT writes a UDP packet to the network, without
// doing any NAT translation.
func (n *network) WriteUDPPacketNoNAT(p UDPPacket) {
src, dst := p.Src, p.Dst
node, ok := n.nodesByIP[dst.Addr()]
if !ok {
log.Printf("no node for dest IP %v in UDP packet %v=>%v", dst.Addr(), p.Src, p.Dst)
@ -732,7 +742,7 @@ func (n *network) HandleEthernetIPv4PacketForRouter(ep EthernetPacket) {
}
srcIP, _ := netip.AddrFromSlice(v4.SrcIP)
dstIP, _ := netip.AddrFromSlice(v4.DstIP)
toForward := dstIP != n.lanIP.Addr()
toForward := dstIP != n.lanIP.Addr() && dstIP != netip.IPv4Unspecified()
udp, isUDP := packet.Layer(layers.LayerTypeUDP).(*layers.UDP)
if isDHCPRequest(packet) {
@ -762,6 +772,15 @@ func (n *network) HandleEthernetIPv4PacketForRouter(ep EthernetPacket) {
return
}
if !toForward && isNATPMP(packet) {
n.handleNATPMPRequest(UDPPacket{
Src: netip.AddrPortFrom(srcIP, uint16(udp.SrcPort)),
Dst: netip.AddrPortFrom(dstIP, uint16(udp.DstPort)),
Payload: udp.Payload,
})
return
}
if toForward && isUDP {
src := netip.AddrPortFrom(srcIP, uint16(udp.SrcPort))
dst := netip.AddrPortFrom(dstIP, uint16(udp.DstPort))
@ -960,6 +979,11 @@ func isDNSRequest(pkt gopacket.Packet) bool {
return ok && dns.QR == false && len(dns.Questions) > 0
}
func isNATPMP(pkt gopacket.Packet) bool {
udp, ok := pkt.Layer(layers.LayerTypeUDP).(*layers.UDP)
return ok && udp.DstPort == 5351 && len(udp.Payload) > 0 && udp.Payload[0] == 0 // version 0, not 2 for PCP
}
func makeSTUNReply(req UDPPacket) (res UDPPacket, ok bool) {
txid, err := stun.ParseBindingRequest(req.Payload)
if err != nil {
@ -1128,6 +1152,31 @@ func (n *network) createARPResponse(pkt gopacket.Packet) ([]byte, error) {
return buffer.Bytes(), nil
}
func (n *network) handleNATPMPRequest(req UDPPacket) {
if string(req.Payload) == "\x00\x00" {
// https://www.rfc-editor.org/rfc/rfc6886#section-3.2
res := make([]byte, 0, 12)
res = append(res,
0, // version 0 (NAT-PMP)
128, // response to op 0 (128+0)
0, 0, // result code success
)
res = binary.BigEndian.AppendUint32(res, uint32(time.Now().Unix()))
wan4 := n.wanIP.As4()
res = append(res, wan4[:]...)
n.WriteUDPPacketNoNAT(UDPPacket{
Src: req.Dst,
Dst: req.Src,
Payload: res,
})
return
}
log.Printf("TODO: handle NAT-PMP packet % 02x", req.Payload)
// TODO: handle NAT-PMP packet 00 01 00 00 ed 40 00 00 00 00 1c 20
}
type NetworkID string
type Node struct {