[PATCH net v2 1/2] net: ethtool: Don't check if RSS context exists in case of context 0

[Gal Pressman <gal@nvidia.com>]

Context 0 (default context) always exists, there is no need to check
whether it exists or not when adding a flow steering rule.

The existing check fails when creating a flow steering rule for context
0 as it is not stored in the rss_ctx xarray.

For example:
$ ethtool --config-ntuple eth2 flow-type tcp4 dst-ip 194.237.147.23 dst-port 19983 context 0 loc 618
rmgr: Cannot insert RX class rule: Invalid argument
Cannot insert classification rule

An example usecase for this could be:
- A high-priority rule (loc 0) directing specific port traffic to
  context 0.
- A low-priority rule (loc 1) directing all other TCP traffic to context
  1.

Fixes: de7f7582dff2 ("net: ethtool: prevent flow steering to RSS contexts which don't exist")
Cc: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
---
 net/ethtool/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 39ec920f5de7..71c828d0bf31 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1083,7 +1083,8 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
 		    ethtool_get_flow_spec_ring(info.fs.ring_cookie))
 			return -EINVAL;
 
-		if (!xa_load(&dev->ethtool->rss_ctx, info.rss_context))
+		if (info.rss_context &&
+		    !xa_load(&dev->ethtool->rss_ctx, info.rss_context))
 			return -EINVAL;
 	}
 
-- 
2.40.1