Function makeUDP6PacketBuffer

wgengine/netstack/netstack_test.go:1415–1457

(src, dst netip.AddrPort)

}

func makeUDP6PacketBuffer(src, dst netip.AddrPort) *stack.PacketBuffer {
	if !src.Addr().Is6() || !dst.Addr().Is6() {
		panic("src and dst must be IPv6")
	}
	data := []byte("hello world\n")

	packetLen := header.IPv6MinimumSize + header.UDPMinimumSize
	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
		ReserveHeaderBytes: packetLen,
		Payload:            buffer.MakeWithData(data),
	})

	srcAddr := tcpip.AddrFrom16(src.Addr().As16())
	dstAddr := tcpip.AddrFrom16(dst.Addr().As16())

	// Add IP header
	ipHdr := header.IPv6(pkt.NetworkHeader().Push(header.IPv6MinimumSize))
	pkt.NetworkProtocolNumber = header.IPv6ProtocolNumber
	ipHdr.Encode(&header.IPv6Fields{
		SrcAddr:           srcAddr,
		DstAddr:           dstAddr,
		PayloadLength:     uint16(header.UDPMinimumSize + len(data)),
		TransportProtocol: header.UDPProtocolNumber,
		HopLimit:          64,
	})

	// Initialize the UDP header.
	udp := header.UDP(pkt.TransportHeader().Push(header.UDPMinimumSize))
	pkt.TransportProtocolNumber = header.UDPProtocolNumber

	length := uint16(pkt.Size())
	udp.Encode(&header.UDPFields{
		SrcPort: src.Port(),
		DstPort: dst.Port(),
		Length:  length,
	})

	// Calculate the UDP pseudo-header checksum.
	xsum := header.PseudoHeaderChecksum(header.UDPProtocolNumber, srcAddr, dstAddr, uint16(len(udp)))
	udp.SetChecksum(^udp.CalculateChecksum(xsum))

	return pkt
}

// TestIsSelfDst verifies that isSelfDst correctly identifies packets whose
// destination IP is a local Tailscale IP assigned to this node.