ospfd: check the LS-Ack's recentness instead of only comparing the #seq
ISSUE:
RTA(DR)-----(BackupDR)RTB
RTA advertises a new LSA to RTB, and then flushes the LSA (with setting
the age of the LSA to MaxAge) within 1 second. Then the LSA is deleted
from RTA, while it still exists on RTB with non-MaxAge and can not be
flushed any more.
FIX:
The reason can be explained in below:
a) RTA -- new LSA, #seq=1 --> RTB (RTB will send the delayed Ack in 1s)
b) RTA -- MaxAge LSA, #seq=1 --> RTB (RTB discards it for the MIN_LS_ARRIVAL)
c) RTA <-- Ack for the new LSA, #seq=1 -- RTB (RTA accepts it)
In the step c), ospf_ls_ack() compares the #seq of the entry in the LS-Ack
with that of local MaxAge LSA. The #seq of the two entries are same. So
the Ack is accepted and the LSA is removed from the retransmit-list (while
it should not).
In RFC2328, section 13.7. Receiving link state acknowledgments:
o If the acknowledgment is for the same instance that is <==
contained on the list, remove the item from the list and
examine the next acknowledgment. Otherwise:
where "same instance" does not mean the same #seq. We must call
ospf_lsa_more_recent() to check whether the two instances are same.
Signed-off-by: Feng Lu <lu.feng@6wind.com>
Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
1 file changed