Re: [PATCH net v5 0/6] Fix listing (IPv4, IPv6) and flushing (IPv6) of cached route exceptions

On 6/18/19 7:20 AM, Stefano Brivio wrote:

For IPv6 cached routes, the commands 'ip -6 route list cache' and
'ip -6 route flush cache' don't work at all after route exceptions have
been moved to a separate hash table in commit 2b760fcf5cfb ("ipv6: hook
up exception table to store dst cache").

For IPv4 cached routes, the command 'ip route list cache' has also
stopped working in kernel 3.5 after commit 4895c771c7f0 ("ipv4: Add FIB
nexthop exceptions.") introduced storage for route exceptions as a
separate entity.

Fix this by allowing userspace to clearly request cached routes with
the RTM_F_CLONED flag used as a filter (in conjuction with strict
checking) and by retrieving and dumping cached routes if requested.

If strict checking is not requested (iproute2 < 5.0.0), we don't have a
way to consistently filter results on other selectors (e.g. on tables),
so skip filtering entirely and dump both regular routes and exceptions.

I'm submitting this for net as these changes fix rather relevant
breakages. However, the scope might be a bit broad, and said breakages
have been introduced 7 and 2 years ago, respectively, for IPv4 and IPv6.
Let me know if I should rebase this on net-next instead.

For IPv4, cache flushing uses a completely different mechanism, so it
wasn't affected. Listing of exception routes (modified routes pre-3.5) was
tested against these versions of kernel and iproute2:

Changing the dump code has been notoriously tricky to get right in one
go, no matter how much testing you have done. Given that I think this
should go to net-next first and once it proves ok there we can look at a
backport to stable trees.