Check UE IP Address using SD flag instead of Source Interface

[louisroyer]

UPF/internal/app/up-handler.go

Lines 546 to 582 in 68acd6a

	func checkUEIPAddress(ueipaddress *ie.UEIPAddressFields, sourceInterface uint8, pdu []byte) (res bool, err error) {
	var srcpdu net.IP
	var dstpdu net.IP
	ueIpAddressIE := ie.NewUEIPAddress(ueipaddress.Flags, ueipaddress.IPv4Address.String(), ueipaddress.IPv6Address.String(), ueipaddress.IPv6PrefixDelegationBits, ueipaddress.IPv6PrefixLength)
	if waterutil.IsIPv4(pdu) {
	p := gopacket.NewPacket(pdu, layers.LayerTypeIPv4, gopacket.Default).NetworkLayer().(*layers.IPv4)
	srcpdu = p.SrcIP
	dstpdu = p.DstIP
	} else if waterutil.IsIPv6(pdu) {
	p := gopacket.NewPacket(pdu, layers.LayerTypeIPv6, gopacket.Default).NetworkLayer().(*layers.IPv6)
	srcpdu = p.SrcIP
	dstpdu = p.DstIP
	} else {
	return false, fmt.Errorf("PDU is not IPv4 or IPv6")
	}
	if ueipaddress == nil {
	return false, fmt.Errorf("Invalid UE IP Address")
	}
	if sourceInterface == ie.SrcInterfaceAccess {
	// check ip src field
	if ueIpAddressIE.HasIPv4() && ueipaddress.IPv4Address.Equal(srcpdu) {
	return true, nil
	}
	if ueIpAddressIE.HasIPv6() && ueipaddress.IPv6Address.Equal(srcpdu) {
	return true, nil
	}
	} else {
	// check ip dst field
	if ueIpAddressIE.HasIPv4() && ueipaddress.IPv4Address.Equal(dstpdu) {
	return true, nil
	}
	if ueIpAddressIE.HasIPv6() && ueipaddress.IPv6Address.Equal(dstpdu) {
	return true, nil
	}
	}
	return false, nil
	}

Bit 3 – S/D: This bit is only applicable to the UE IP Address IE in the PDI IE. It shall be set to "0" and ignored by the receiver in IEs other than PDI IE. In the PDI IE, if this bit is set to "0", this indicates a Source IP address; if this bit is set to "1", this indicates a Destination IP address.
(TS 29.244 V17.4.0, section 8.2.62 "UE IP Address", p. 279)

Must be tested against:

• NextMN/cp-lite
• free5GC SMF with feat: add UE IP Address IE on downlink PDRs free5gc/smf#146
  • in classical scenario
  • with handover scenario

[louisroyer]

Note: this bug is not critical because, the "source interface" logic is working in practice, but this is not conform to 3GPP spec.