[PATCH net] net/sched: cls_u32: fix cls_u32 on filter replace

[PATCH net] net/sched: cls_u32: fix cls_u32 on filter replace

[Ivan Vecera]

The following sequence is currently broken:

 # tc qdisc add dev foo ingress
 # tc filter replace dev foo protocol all ingress \
   u32 match u8 0 0 action mirred egress mirror dev bar1
 # tc filter replace dev foo protocol all ingress \
   handle 800::800 pref 49152 \
   u32 match u8 0 0 action mirred egress mirror dev bar2
 Error: cls_u32: Key node flags do not match passed flags.
 We have an error talking to the kernel, -1

The error comes from u32_change() when comparing new and
existing flags. The existing ones always contains one of
TCA_CLS_FLAGS_{,NOT}_IN_HW flag depending on offloading state.
These flags cannot be passed from userspace so the condition
(n->flags != flags) in u32_change() always fails.

Fix the condition so the flags TCA_CLS_FLAGS_NOT_IN_HW and
TCA_CLS_FLAGS_IN_HW are not taken into account.

Fixes: 24d3dc6d27ea ("net/sched: cls_u32: Reflect HW offload status")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
 net/sched/cls_u32.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 6311a548046b..c75e68e839c7 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -955,7 +955,8 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 			return -EINVAL;
 		}
 
-		if (n->flags != flags) {
+		if ((n->flags ^ flags) &
+		    ~(TCA_CLS_FLAGS_IN_HW | TCA_CLS_FLAGS_NOT_IN_HW)) {
 			NL_SET_ERR_MSG_MOD(extack, "Key node flags do not match passed flags");
 			return -EINVAL;
 		}
-- 
2.13.6

Re: [PATCH net] net/sched: cls_u32: fix cls_u32 on filter replace

[David Miller]

From: Ivan Vecera <ivecera@redhat.com>
Date: Thu,  8 Feb 2018 16:10:39 +0100

> The following sequence is currently broken:
> 
>  # tc qdisc add dev foo ingress
>  # tc filter replace dev foo protocol all ingress \
>    u32 match u8 0 0 action mirred egress mirror dev bar1
>  # tc filter replace dev foo protocol all ingress \
>    handle 800::800 pref 49152 \
>    u32 match u8 0 0 action mirred egress mirror dev bar2
>  Error: cls_u32: Key node flags do not match passed flags.
>  We have an error talking to the kernel, -1
> 
> The error comes from u32_change() when comparing new and
> existing flags. The existing ones always contains one of
> TCA_CLS_FLAGS_{,NOT}_IN_HW flag depending on offloading state.
> These flags cannot be passed from userspace so the condition
> (n->flags != flags) in u32_change() always fails.
> 
> Fix the condition so the flags TCA_CLS_FLAGS_NOT_IN_HW and
> TCA_CLS_FLAGS_IN_HW are not taken into account.
> 
> Fixes: 24d3dc6d27ea ("net/sched: cls_u32: Reflect HW offload status")
> Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Ugh, private kernel flags are always troublesome for this reason.

Applied and queued up for -stable.