tree aa490b1c5c7e7aa51d7867980ec5dab352b77204
parent 30685b2a439b282b462e27ab0f8beb019719b7d9
author Fernando Gont <fgont@si6networks.com> 1587299097 -0300
committer David S. Miller <davem@davemloft.net> 1587670161 -0700

ipv6: Honor all IPv6 PIO Valid Lifetime values

RFC4862 5.5.3 e) prevents received Router Advertisements from reducing
the Valid Lifetime of configured addresses to less than two hours, thus
preventing hosts from reacting to the information provided by a router
that has positive knowledge that a prefix has become invalid.

This patch makes hosts honor all Valid Lifetime values, as per
draft-gont-6man-slaac-renum-06, Section 4.2. This is meant to help
mitigate the problem discussed in draft-ietf-v6ops-slaac-renum.

Note: Attacks aiming at disabling an advertised prefix via a Valid
Lifetime of 0 are not really more harmful than other attacks
that can be performed via forged RA messages, such as those
aiming at completely disabling a next-hop router via an RA that
advertises a Router Lifetime of 0, or performing a Denial of
Service (DoS) attack by advertising illegitimate prefixes via
forged PIOs.  In scenarios where RA-based attacks are of concern,
proper mitigations such as RA-Guard [RFC6105] [RFC7113] should
be implemented.

Signed-off-by: Fernando Gont <fgont@si6networks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>