It appears that in commit 7efd79c0e689 ("bnxt_en: Add drop action
support for ntuple"), bnxt gained support for ntuple filters for packet
drops.

However, support for this does not seem to work in recent kernels or
against net-next:

  % sudo ethtool -U eth0 flow-type udp4 src-ip 1.1.1.1 action -1
    rmgr: Cannot insert RX class rule: Operation not supported
    Cannot insert classification rule

The issue is that the existing code uses ethtool_get_flow_spec_ring_vf,
which will return a non-zero value if the ring_cookie is set to
RX_CLS_FLOW_DISC, which then causes bnxt_add_ntuple_cls_rule to return
-EOPNOTSUPP because it thinks the user is trying to set an ntuple filter
for a vf.

Fix this by first checking that the ring_cookie is not RX_CLS_FLOW_DISC.

After this patch, ntuple filters for drops can be added:

  % sudo ethtool -U eth0 flow-type udp4 src-ip 1.1.1.1 action -1
  Added rule with ID 0

  % ethtool -n eth0
  44 RX rings available
  Total 1 rules

  Filter: 0
      Rule Type: UDP over IPv4
      Src IP addr: 1.1.1.1 mask: 0.0.0.0
      Dest IP addr: 0.0.0.0 mask: 255.255.255.255
      TOS: 0x0 mask: 0xff
      Src port: 0 mask: 0xffff
      Dest port: 0 mask: 0xffff
      Action: Drop

Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Joe Damato <joe@dama.to>
---
v3:
 - Removed unused vf variable as suggested by Michael Chan
 - Added Michael Chan's Reviewed-by

v2: https://lore.kernel.org/netdev/20260130002323.2561266-1-joe@dama.to/
  - Extract the FLOW_MAC_EXT and FLOW_EXT check so it happens unconditionally. 
  - Eliminate the local variable ring, which was used in only one place and
    call ethtool_get_flow_spec_ring instead.

v1: https://lore.kernel.org/netdev/20260128222718.1679581-1-joe@dama.to/
 drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index 6b15fedbb16f..53a83b6680c4 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -1346,16 +1346,17 @@ static int bnxt_add_ntuple_cls_rule(struct bnxt *bp,
 	struct bnxt_l2_filter *l2_fltr;
 	struct bnxt_flow_masks *fmasks;
 	struct flow_keys *fkeys;
-	u32 idx, ring;
+	u32 idx;
 	int rc;
-	u8 vf;
 
 	if (!bp->vnic_info)
 		return -EAGAIN;
 
-	vf = ethtool_get_flow_spec_ring_vf(fs->ring_cookie);
-	ring = ethtool_get_flow_spec_ring(fs->ring_cookie);
-	if ((fs->flow_type & (FLOW_MAC_EXT | FLOW_EXT)) || vf)
+	if (fs->flow_type & (FLOW_MAC_EXT | FLOW_EXT))
+		return -EOPNOTSUPP;
+
+	if (fs->ring_cookie != RX_CLS_FLOW_DISC &&
+	    ethtool_get_flow_spec_ring_vf(fs->ring_cookie))
 		return -EOPNOTSUPP;
 
 	if (flow_type == IP_USER_FLOW) {
@@ -1481,7 +1482,7 @@ static int bnxt_add_ntuple_cls_rule(struct bnxt *bp,
 	if (fs->ring_cookie == RX_CLS_FLOW_DISC)
 		new_fltr->base.flags |= BNXT_ACT_DROP;
 	else
-		new_fltr->base.rxq = ring;
+		new_fltr->base.rxq = ethtool_get_flow_spec_ring(fs->ring_cookie);
 	__set_bit(BNXT_FLTR_VALID, &new_fltr->base.state);
 	rc = bnxt_insert_ntp_filter(bp, new_fltr, idx);
 	if (!rc) {

base-commit: 6ad42b24413630199cb9f35d073f71768788f8dc
-- 
2.47.3