NAME

        rfc2765_3.2_udp.seq - Verify IPv6 <-> IPv4 header 
        translation in accordance with RFC2765 [SIIT]

TARGET

        Router

SYNOPSIS

        rfc2765_3.2_udp.seq [-tooloption ...] 
        -p rfc2765_3.2_udp.def

INITIALIZATION

	Before this test starts, run initialize.seq.

TEST PROCEDURE

        This test verifies that NUT adjusts header checksum for UDP packets.
        
        Network Topology

        Link0
        --------------------------
            |               |
           TN              NUT
            |               |
        --------------------------
        Link1

        TN -- (Link0) -- NUT        NUT -- (Link1) -- TN
        
        ---------------------      ------------------------

        1.1.
                                   <===================
        IPv4 UDP packet
                IPv4 Header
                        src address : TN LINK1 IPv4 address
                        dst address : TN LINK0 IPv4 address
                        Don't Fragment = 1
                UDP packet
                        Checksum including IPv4 pseudo header
                        data = repeat(0xff,64)
        1.2.
        <<JUDGMENT>>
        <===================
        IPv6 UDP packet
                IPv6 Header
                        src address : TN LINK1 IPv4 embedded IPv6 address
                        dst address : TN LINK0 IPv4 embedded IPv6 address
                UDP packet
                        Checksum including IPv6 pseudo header
                        data = repeat(0xff,64)

        2.1.
                                   <===================
        IPv4 UDP packet
                IPv4 Header
                        src address : TN LINK1 IPv4 address
                        dst address : TN LINK0 IPv4 address
                        Don't Fragment = 1
                UDP packet
                        Checksum = 0xffff (zero checksum)
                        data = repeat(0xff,64)
        2.2.
        <<JUDGMENT>>
        <===================
        IPv6 UDP packet
                IPv6 Header
                        src address : TN LINK1 IPv4 embedded IPv6 address
                        dst address : TN LINK0 IPv4 embedded IPv6 address
                UDP packet
                        Checksum including IPv6 pseudo header
                        data = repeat(0xff,64)

        3.1.
                                   <===================
        IPv4 UDP packet
                IPv4 Header
                        src address : TN LINK1 IPv4 address
                        dst address : TN LINK0 IPv4 address
                        MF = 1
                UDP packet
                        Checksum including IPv4 pseudo header
                        data = repeat(0xff,64)
        3.2.
        <<JUDGMENT>>
        <===================
        IPv6 UDP packet
                IPv6 Header
                        src address : TN LINK1 IPv4 embedded IPv6 address
                        dst address : TN LINK0 IPv4 embedded IPv6 address
                Fragment Header
                        More fragments = 1
                UDP packet
                        Checksum including IPv6 pseudo header
                        data = repeat(0xff,64)

        4.1.
                                   <===================
        IPv4 UDP packet
                IPv4 Header
                        src address : TN LINK1 IPv4 address
                        dst address : TN LINK0 IPv4 address
                        MF = 1
                UDP packet
                        Checksum = 0xffff (zero checksum)
                        data = repeat(0xff,64)
        4.2.
        <<JUDGMENT>>
                Packet is silently dropped

JUDGMENT

        << PASS >>
                NUT adjusts header checksum for UDP packets with 
                checksum and recalculates it for UDP packets with
                zero checksum.
                Fragmented UDP packets with zero checksum are silently
                dropped.
                
        << FAIL >>      
                NUT send UDP packets with wrong checksum, or doesn't drop
                fragmented UDP with zero checksum.

NOTE

REFERENCE

RFC2765

3.2. Translating UDP over IPv4

   If a UDP packet has a zero UDP checksum then a valid checksum must be
   calculated in order to translate the packet.  A stateless translator
   can not do this for fragmented packets but [MILLER] indicates that
   fragmented UDP packets with a zero checksum appear to only be used
   for malicious purposes.  Thus this is not believed to be a noticeable
   limitation.

   When a translator receives the first fragment of a fragmented UDP
   IPv4 packet and the checksum field is zero the translator SHOULD drop
   the packet and generate a system management event specifying at least
   the IP addresses and port numbers in the packet.  When it receives
   fragments other than the first it SHOULD silently drop the packet,
   since there is no port information to log.

   When a translator receives an unfragmented UDP IPv4 packet and the
   checksum field is zero the translator MUST compute the missing UDP
   checksum as part of translating the packet.  Also, the translator
   SHOULD maintain a counter of how many UDP checksums are generated in
   this manner.