ipv4: add net bool fib_offload_disabled

If something goes wrong with IPv4 FIB offload, mark entire net offload
disabled.  This is brute force policy to basically shut down IPv4 FIB offload
permanently if there is a problem offloading any route to an external device.
We can refine the policy in the future, to handle failures on a per-device or
per-route basis, but for now, this policy is per-net.

What we're trying to avoid is an inconsistent split between the kernel's FIB
and the offload device's FIB.  We don't want the device to fwd a pkt
inconsitent with what the kernel would do.  An example of a split is if device
has 10.0.0.0/16 and kernel has 10.0.0.0/16 and 10.0.0.0/24, the device wouldn't
see the longest prefix 10.0.0.0/24 and potentially forward pkts incorrectly.

Limited capacity or limited capability are two ways a route may fail to install
to the offload device.  We'll not differentiate between failures at this time,
and treat any failure as fatal and mark the net as fib_offload_disabled.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index db1db158a00e..1085e12f940f 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -47,6 +47,7 @@ struct netns_ipv4 {
         int                     fib_num_tclassid_users;
 #endif
         struct hlist_head       *fib_table_hash;
+        bool                    fib_offload_disabled;
         struct sock             *fibnl;
 
         struct sock  * __percpu *icmp_sk;