New RIP MD5 interface option to avoid sequence check

[Olivier Benghozi]

Hello,

I'm currently using RIP/Ripng with md5 auth with some Cisco/Juniper and Quagga gears.
I'm looking to switch from quagga to Bird(2).
I would have a feature request about the RIP MD5 sequence number check (RFC rule, implemented by BIRD, is: accept only increasing sequence numbers, or accept lower only if restarting at 0).
In our current usecase, end-to-end interfaces are not contiguous, and it happens that some various cases (like powercuts at one end) can lead to a situation when one dead RIP speaker comes back to life before full end to end connectivity is restored BUT before route expiration at the other side: therefore the received seqnumber starts at something higher than 0 but lower than the previous known one, so the routing will just fail.
Quagga doesn't check seqnumbers at all, Cisco gears don't seem to, and Juniper gears have a hidden option to disable this check (no-check-sequence).
So we would have use/need for a config option (probably at the interface level), to avoid the received crypto sequence number check (therefore md5 is just a way to avoid transmitting the clear password on the wire).

Apart for the new option definition, the actual check is in master/proto/rip/packets.c, I guess that the check in current line 391 would have to include an additional «&& new_option_isnt_defined» to avoid yelling about a sequence number too low...
line 391:   if ((rcv_csn < n->csn) && (rcv_csn || n->uc))

What about such an additional feature ?


Thank you,
Olivier


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