On 29/10/15 15:49, Roopa Prabhu wrote:
From: Roopa Prabhu <ro...@cumulusnetworks.com>
Adds support for both RTNH_F_DEAD and RTNH_F_LINKDOWN flags.
This resembles ipv4 fib code. I also picked fib_rebalance from
ipv4. Enabled weights support for nexthop, just because the
infrastructure is already there.
Signed-off-by: Roopa Prabhu <ro...@cumulusnetworks.com>
---
I want to get this in before net-next closes as promised.
I have tested it for the dead/linkdown flags. The multipath selection
and hash calculation in the face of dead routes needs some more
work. I am short on cycles this week and thought of getting some
early feedback. Hence sending this out as RFC. I will continue with some
more testing. Robert, I am using your hash algo but it needs some more
work with dead routes. If you already have any thoughts on this, i will
take them. thanks!.
If you were to sort the array of nexthops (and by implication via
addresses) by their non-deadness keeping a count of the alive nexthops,
then there's no need to resort to an O(n) algorithm for selecting the
nexthop, and no need to store per-nh flags.
E.g. before eth0 link down:
+----------------------+
| rt_nhn = 3 |
| rt_nhn_alive = 3 |
+----------------------+
| nh 0: |
| dev = eth0, ... |
+----------------------+
| nh 1: |
| dev = eth1, ... |
+----------------------+
| nh 2: |
| dev = eth0, ... |
+----------------------+
| vias ... |
+----------------------+
after eth0 link down:
+----------------------+
| rt_nhn = 3 |
| rt_nhn_alive = 1 |
+----------------------+
| nh 0: |
| dev = eth1, ... |
+----------------------+
| nh 1: |
| dev = eth0, ... |
+----------------------+
| nh 2: |
| dev = eth0, ... |
+----------------------+
| vias ... |
+----------------------+
The mpls_select_multipath algorithm just then needs to be changed to use
rt_nhn_alive instead of rt_nhn and will work otherwise as-is.
On link down you'll need to alloc a new route for RCU-safety, but you
can presumably just do a kmemdup to reduce the amount of code you have
to write and sort the nexthops in the copy. Link up will be similar.
Then on the mpls_dump_route, if the index of the nexthop is >=
rt_nhn_alive then the path is link-down. If the nh_dev is NULL then
generate RTNH_F_DEAD|RTNH_F_LINKDOWN for the flags, otherwise just
RTNH_F_LINKDOWN.
This would use less memory and be faster for forwarding.
Thanks,
Rob
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