NAME

hostRecvRaNHD - Verifying net-hop determination

TARGET

Host only

INITIALIZATION

Clear the Prefix List that was learned by RAs.
Clear the Default Router List.
Set its state to REACHABLE.
The Router Lifetime of a RA is ether 0 or 600.
A RA includes or excludes a prefix option.

  TN                 NUT
  ----------------------


  State: No neighbor cache entry (for TN)


  ==== unsolicited RA ===>
       src=TN's link-local
       dst=all-node
       M=0, O=0
       RouterLifetime=0 or 600
       ReachableTime=0
       RetransTimer=0
       w/ SLLA
       w/o Prefix option or Prefix Option:
           L=1, A=1
           ValidLifetime=2592000
           PreferredLifetime=604800
           Prefix=3ffe:501:ffff:100::/64


  State: STALE (for TN)


  <=== Ns for DAD (if any) ====
       src=unspecified
       dst=solicited-node[NUT's global, prefix=3ffe:501:ffff:100::/64]
       target=NUT's global


  Wait (3 sec)


  ==== solicited NA ===>
        src=TN's link-local
        dst=NUT's link-local
        R=1, S=1, O=1
        target=TN's link-local
        TLLA=TN's LLA


  State: REACHABLE (for TN)

TEST PROCEDURE

hostRecvRaNHD verifies next-hop determination for an unicast address:

A case where a given address should be off-link
A cast where a given address should be on-link

Off-link

  TN               NUT
  ----------------------


  State: REACHABLE (for TN)


  ==== echo-request ===>
       src=off-link global, but LLA is TN's one
       dst=NUT's global


  <=== Judgment #2: echo-reply ====
       src=NUT's global
       dst=off-link global, but LLA is TN's one

On-link

  TN               NUT
  ----------------------


  State: REACHABLE (for TN)


  ==== echo-request ===>
       src=off-link global, but LLA is TN's one
       dst=NUT's global


  <=== Judgment #3: multicast NS ====
        src=NUT's link-local or global
        dst=solicited-node[off-link global]
        target=off-link global
        w/ SLLA

JUDGMENT

1. Next-hop determination

  =========+========+==========================================
  RA received       | NUT
  by NUT            |
  ---------+--------+-----------------+-------------+---------
  Prefix   |Router  | The Prefix List | The Default | Next Hop
  Option   |Lifetime|                 | Router List |
  =========+========+=================+=============+==========
  none     | 0      | empty           | empty       | on-link
  ---------+--------+-----------------+-------------+----------
  none     | 600    | empty           | NOT empty   | off-link
  ---------+--------+-----------------+-------------+----------
  exist    | 0      | NOT empty       | empty       | on-link
  =========+========+=================+=============+==========



  2. NUT throws an echo-reply to the default router (i.e. TN)
     because the given address should be off-link.



  3. NUT sends multicast NSs for the given address
     because it should be on-link.

TERMINATION

  Send RA with RouterLifetime=0 to clear the Default Router List.

  Clear the Prefix List and the Default Router List by remote commands. XXX

NOTE

  1. RFC2461 describes that a host assumes the destination is on-link
     if the Default Router List is empty. However, it also describes
     that multihomed related issues are not concerned.
     It is also one of the issues that a host assumes an address is
     on-link if the Default Router List is empty. This test judges
     NUT "WARN" instead of "FAIL" in such case.

  2. The echo request that NUT captures has an off-link source address
     and a link-local source address. It is reasonable for NUT not to
     throw the echo-reply to the default router because its source
     address is a link-local. This test judges NUT "WARN" instead of "FAIL"
     in such case.

  3. The test invokes the following command:
     - Clear the Prefix List
     - Clear the Default Router List

REFERENCE

RFC2461

5.2.  Conceptual Sending Algorithm

   Next-hop determination for a given unicast destination operates as
   follows.  The sender performs a longest prefix match against the
   Prefix List to determine whether the packet's destination is on- or
   off-link.  If the destination is on-link, the next-hop address is the
   same as the packet's destination address.  Otherwise, the sender
   selects a router from the Default Router List.  (following the rules
   described in Section 6.3.6).  If the Default Router List is empty,
   the sender assumes that the destination is on-link.