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net/portmapper: add hook for use with prev ip

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PCP handles external IPs by allowing the client to specify them in the packet, which is more
explicit than requiring 2 packets from PMP, so allow for future changes to add it in easily.

Signed-off-by: julianknodt <julianknodt@gmail.com>
This commit is contained in:
julianknodt
2021-08-05 12:33:13 -07:00
committed by Brad Fitzpatrick
parent 85304d7392
commit 98d36ee18d
2 changed files with 31 additions and 18 deletions
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17
net/portmapper/pcp.go
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@@ -59,14 +59,20 @@ func (p *pcpMapping) Release(ctx context.Context) {
return
}
defer uc.Close()
pkt := buildPCPRequestMappingPacket(p.internal.IP(), p.internal.Port(), p.external.Port(), 0)
pkt := buildPCPRequestMappingPacket(p.internal.IP(), p.internal.Port(), p.external.Port(), 0, p.external.IP())
uc.WriteTo(pkt, netaddr.IPPortFrom(p.gw, pcpPort).UDPAddr())
}
// buildPCPRequestMappingPacket generates a PCP packet with a MAP opcode.
// To create a packet which deletes a mapping, lifetimeSec should be set to 0.
// If prevPort is not known, it should be set to 0.
func buildPCPRequestMappingPacket(myIP netaddr.IP, localPort, prevPort uint16, lifetimeSec uint32) (pkt []byte) {
// If prevExternalIP is not known, it should be set to 0.0.0.0.
func buildPCPRequestMappingPacket(
myIP netaddr.IP,
localPort, prevPort uint16,
lifetimeSec uint32,
prevExternalIP netaddr.IP,
) (pkt []byte) {
// 24 byte common PCP header + 36 bytes of MAP-specific fields
pkt = make([]byte, 24+36)
pkt[0] = pcpVersion
@@ -84,11 +90,8 @@ func buildPCPRequestMappingPacket(myIP netaddr.IP, localPort, prevPort uint16, l
binary.BigEndian.PutUint16(mapOp[16:18], localPort)
binary.BigEndian.PutUint16(mapOp[18:20], prevPort)
// TODO: This can also be the previous external IP similar to how PMP caches the
// last external IP, not sure what the benefits of that are.
v4unspec := netaddr.MustParseIP("0.0.0.0")
v4unspec16 := v4unspec.As16()
copy(mapOp[20:], v4unspec16[:])
prevExternalIP16 := prevExternalIP.As16()
copy(mapOp[20:], prevExternalIP16[:])
return pkt
}