[PATCH 2/2] net/ixgbe: fix unexpected VLAN Rx in promisc mode on VF

[Olivier Matz <olivier.matz@6wind.com>]

When the promiscuous mode is enabled on a VF, the IXGBE_VMOLR_VPE
bit (VLAN Promiscuous Enable) is set. This means that the VF will
receive packets whose VLAN is not the same as the VLAN of the VF.

For instance, in this situation:

┌────────┐    ┌────────┐    ┌────────┐
│        │    │        │    │        │
│        │    │        │    │        │
│     VF0├────┤VF1  VF2├────┤VF3     │
│        │    │        │    │        │
└────────┘    └────────┘    └────────┘
   VM1           VM2           VM3

vf 0:  vlan 1000
vf 1:  vlan 1000
vf 2:  vlan 1001
vf 3:  vlan 1001

If we tcpdump on VF3, we see all the packets, even those transmitted
on vlan 1000.

This behavior prevents to bridge VF1 and VF2 in VM2, because it will
create a loop: packets transmitted on VF1 will be received by VF2 and
vice-versa, and bridged again through the software bridge.

This patch remove the activation of VLAN Promiscuous when a VF enables
the promiscuous mode. However, the IXGBE_VMOLR_UPE bit (Unicast
Promiscuous) is kept, so that a VF receives all packets that has the
same VLAN, whatever the destination MAC address.

A similar patch was accepted in Linux kernel (see link).

Fixes: 0355c379b71f ("net/ixgbe: support VF promiscuous by PF driver")
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7bb0fb7c63df

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 drivers/net/ixgbe/ixgbe_pf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ixgbe/ixgbe_pf.c b/drivers/net/ixgbe/ixgbe_pf.c
index c5ef940533..0a0f639e39 100644
--- a/drivers/net/ixgbe/ixgbe_pf.c
+++ b/drivers/net/ixgbe/ixgbe_pf.c
@@ -771,9 +771,9 @@ ixgbe_set_vf_mc_promisc(struct rte_eth_dev *dev, uint32_t vf, uint32_t *msgbuf)
 			return -1;
 		}
 
-		disable = 0;
+		disable = IXGBE_VMOLR_VPE;
 		enable = IXGBE_VMOLR_BAM | IXGBE_VMOLR_ROMPE |
-			 IXGBE_VMOLR_MPE | IXGBE_VMOLR_UPE | IXGBE_VMOLR_VPE;
+			 IXGBE_VMOLR_MPE | IXGBE_VMOLR_UPE;
 		break;
 	default:
 		return -1;
-- 
2.30.2