netdev - [RFC PATCH net-next 5/5] bridge: verify "HW only" flags can't be set without HW support

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Date:   Fri,  9 Mar 2018 19:03:08 -0800
From:   Igor Mitsyanko <igor.mitsyanko.os@...ntenna.com>
To:     bridge@...ts.linux-foundation.org, netdev@...r.kernel.org
Cc:     sergey.matyukevich.os@...ntenna.com, smaksimenko@...ntenna.com,
        ashevchenko@...ntenna.com, dlebed@...ntenna.com, jiri@...nulli.us,
        ivecera@...hat.com, igor.mitsyanko.os@...ntenna.com
Subject: [RFC PATCH net-next 5/5] bridge: verify "HW only" flags can't be set without HW support

Setting bridge flag BR_FLOOD_OFFLOAD only makes sense if underlying
port hardware advertises support for it. Make sure kernel checks that
condition before allowing to update the flag value.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@...ntenna.com>
---
 net/bridge/br_private.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index a6d2f2b..6d2f8b1 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -50,6 +50,9 @@ enum {
 /* Path to usermode spanning tree program */
 #define BR_STP_PROG	"/sbin/bridge-stp"
 
+/* Flags that can only be set if HW supports it */
+#define BR_PORT_FLAGS_HW_ONLY	BR_FLOOD_OFFLOAD
+
 typedef struct bridge_id bridge_id;
 typedef struct mac_addr mac_addr;
 typedef __u16 port_id;
@@ -1150,7 +1153,7 @@ static inline int br_switchdev_set_port_flag(struct net_bridge_port *p,
 					     unsigned long flags,
 					     unsigned long mask)
 {
-	return 0;
+	return mask & BR_PORT_FLAGS_HW_ONLY ? -EOPNOTSUPP : 0;
 }
 
 static inline void
-- 
2.9.5