recvNaRFlag - Verifying that a IsRouter flag is modified by a NA
Host only
recvNaRFlag .seq [-tooloption ...] -p recvNaRFlag.def
TN NUT ----------------------
State: NONCE (for TN)
==== unsolicited RA ===> src=TN's link-local dst=all-node M=0, O=0 RouterLifetime=600 ReachableTime=0 RetransTimer=0 Prefix Option: L=1, A=1 ValidLifetime=2592000 PreferredLifetime=604800 Prefix=3ffe:501:ffff:100::/64
<=== Ns for DAD ==== src=unspecified dst=solicited-node[NUT's global] target=NUT's global
State: INCOMPLETE (for TN)
<=== multicast NS ==== src=NUT's link-local dst=solicited-node[TN's link-local] target=TN's link-local w/ SLLA timeout=RETRANS_TIMER * MAX_MULTICAST_SOLICIT
==== 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)
TN NUT ----------------------
State: NONCE (for TN)
==== unsolicited RA ===> src=TN's link-local dst=all-node M=0, O=0 RouterLifetime=600 ReachableTime=0 RetransTimer=0 Prefix Option: L=1, A=1 ValidLifetime=2592000 PreferredLifetime=604800 Prefix=3ffe:501:ffff:100::/64
<=== Ns for DAD ==== src=unspecified dst=solicited-node[NUT's global] target=NUT's global
State: INCOMPLETE (for TN)
<=== multicast NS ==== src=NUT's link-local dst=solicited-node[TN's link-local] target=TN's link-local w/ SLLA timeout=RETRANS_TIMER * MAX_MULTICAST_SOLICIT
==== solicited NA ===> src=TN's link-local dst=NUT's link-local R=1, S=1, O=1 target=TN's link-local TLLA=a bogus LLA
State: REACHABLE (for TN)
recvNaRFlag verifies that a IsRouter flag is modified by a NA. in REACHABLE state when receiving an NA.
TN NUT ----------------------
State: REACHABLE (for TN)
==== NA ===> src=TN's link-local dst=the NUT's link-local or all-node R=0, S=0/1, O=0/1 Target=TN's link-local w/ or w/o TLL
==== 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
JUDGMENT
1. Modification of the IsRouter flag depend upon both its neighbor cache state and a NS.
=========+================================+================= Current |NA received by NUT |IsRouter flag State +---------------+-+--+-+---------+-------+--------- |Destination |r| s|o|TLLA |Current|New =========+===============+=+==+=+=========+=======+========= REACHABLE Unicast 0 0 0 none 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 0 1 none 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 1 0 none 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 1 1 none 1 0 +===============+=+==+=+=========+=======+========= Unicast 0 0 0 same 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 0 1 same 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 1 0 same 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 1 1 same 1 0 +===============+=+==+=+=========+=======+========= Unicast 0 0 0 different 1 unchanged +---------------+-+--+-+---------+-------+--------- Unicast 0 0 1 different 1 0 +---------------+-+--+-+---------+-------+--------- Unicast 0 1 0 different 1 unchanged +---------------+-+--+-+---------+-------+--------- Unicast 0 1 1 different 1 0 +===============+=+==+=+=========+=======+========= *Multicast 0 0 0 *none 1 unchanged *invalid? +---------------+-+--+-+---------+-------+--------- *Multicast 0 0 1 *none 1 unchanged *invalid? +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 0 *none 1 unchanged *invalid +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 1 *none 1 unchanged invalid +===============+=+==+=+=========+=======+========= Multicast 0 0 0 same 1 0 +---------------+-+--+-+---------+-------+--------- Multicast 0 0 1 same 1 0 +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 0 same 1 unchanged *invalid +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 1 same 1 unchanged *invalid +===============+=+==+=+=========+=======+========= Multicast 0 0 0 different 1 unchanged +---------------+-+--+-+---------+-------+--------- Multicast 0 0 1 different 1 0 +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 0 different 1 unchanged *invalid +---------------+-+--+-+---------+-------+--------- *Multicast 0 *1 1 different 1 unchanged *invalid =========+===============+=+==+=+=========+=======+========= 2. If a IsRouter flag is modified by rule, NUT will NOT throw an echo-reply to the default router (i.e. TN).
TERMINATION
Send RA with RouterLifetime=0 to clear the Default Router List.
NOTE
1. The test does not invoke any remote command.
2. An implementation may update Rflag of an NCE when receiving an multicast NA w/o TLL. The NA is not invalid as a receiver side, whereas it is invalid as a sender side (please see the following). In such case, this test judges "WARN" that never means the implementation is wrong. The test intends to inform such behavior.
Sender side:
4.4. Neighbor Advertisement Message Format
Possible options:
Target link-layer address The link-layer address for the target, i.e., the sender of the advertisement. This option MUST be included on link layers that have addresses when responding to multicast solicitations. When responding to a unicast Neighbor Solicitation this option SHOULD be included.
Receiver side:
7.1.2. Validation of Neighbor Advertisements
A node MUST silently discard any received Neighbor Advertisement messages that do not satisfy all of the following validity checks:
- The IP Hop Limit field has a value of 255, i.e., the packet could not possibly have been forwarded by a router.
- If the message includes an IP Authentication Header, the message authenticates correctly.
- ICMP Checksum is valid.
- ICMP Code is 0.
- ICMP length (derived from the IP length) is 24 or more octets.
- Target Address is not a multicast address.
- If the IP Destination Address is a multicast address the Solicited flag is zero.
- All included options have a length that is greater than zero.
REFERENCE
RFC2461
7.2.5. Receipt of Neighbor Advertisements
When a valid Neighbor Advertisement is received (either solicited or unsolicited), the Neighbor Cache is searched for the target's entry. If no entry exists, the advertisement SHOULD be silently discarded. There is no need to create an entry if none exists, since the recipient has apparently not initiated any communication with the target.
Once the appropriate Neighbor Cache entry has been located, the specific actions taken depend on the state of the Neighbor Cache entry, the flags in the advertisement and the actual link-layer address supplied.
IF(State == INCOMPLETE) { If the target's Neighbor Cache entry is in the INCOMPLETE state when the advertisement is received, one of two things happens. If the link layer has addresses and no Target Link-Layer address option is included, the receiving node should silently discard the received advertisement. Otherwise, the receiving node performs the following steps:
- It records the link-layer address in the Neighbor Cache entry.
- If the advertisement's Solicited flag is set, the state of the entry is set to REACHABLE, otherwise it is set to STALE.
- It sets the IsRouter flag in the cache entry based on the Router flag in the received advertisement.
- It sends any packets queued for the neighbor awaiting address resolution.
Note that the Override flag is ignored if the entry is in the INCOMPLETE state. } ELSIF(State != INCOMPLETE) { If the target's Neighbor Cache entry is in any state other than INCOMPLETE when the advertisement is received, processing becomes quite a bit more complex.
IF(Override==0 && TLLA!=LLA) { If the Override flag is clear and the supplied link-layer address differs from that in the cache, then one of two actions takes place:
IF(REACHABLE) { if the state of the entry is REACHABLE, set it to STALE, but do not update the entry in any other way; } ELSE { otherwise, the received advertisement should be ignored and must not update the cache. } } ELSIF(Override==1 || (Override==0 && TLLA==LLA) || TLLA==NULL) { If the Override flag is set, both the Override flag is clear and the supplied link-layer address is the same as that in the cache, or no Target Link-layer address option was supplied, the received advertisement must update the Neighbor Cache entry as follows:
- The link-layer address in the Target Link-Layer Address option must be inserted in the cache (if one is supplied and is different than the already recorded address).
- If the Solicited flag is set, the state of the entry must be set to REACHABLE. If the Solicited flag is zero and the link-layer address was updated with a different address the state must be set to STALE. Otherwise, the entry's state remains unchanged.
An advertisement's Solicited flag should only be set if the advertisement is a response to a Neighbor Solicitation. Because Neighbor Unreachability Detection Solicitations are sent to the cached link-layer address, receipt of a solicited advertisement indicates that the forward path is working. Receipt of an unsolicited advertisement, however, suggests that a neighbor has urgent information to announce (e.g., a changed link-layer address). If the urgent information indicates a change from what a node is currently using, the node should verify the reachability of the (new) path when it sends the next packet. There is no need to update the state for unsolicited advertisements that do not change the contents of the cache.
- The IsRouter flag in the cache entry must be set based on the Router flag in the received advertisement. In those cases where the IsRouter flag changes from TRUE to FALSE as a result of this update, the node must remove that router from the Default Router List and update the Destination Cache entries for all destinations using that neighbor as a router as specified in Section 7.3.3. This is needed to detect when a node that is used as a router stops forwarding packets due to being configured as a host. } }
SEE ALSO
perldoc V6evalTool perldoc V6evalRemote