On Fri, Jun 30, 2023 at 11:47:04AM +0200, Simon Horman wrote:
> On Thu, Jun 29, 2023 at 04:30:05PM -0400, Eric Garver wrote:
> > This adds an explicit drop action. This is used by OVS to drop packets
> > for which it cannot determine what to do. An explicit action in the
> > kernel allows passing the reason _why_ the packet is being dropped. We
> > can then use perf tracing to match on the drop reason.
> >
> > e.g. trace all OVS dropped skbs
> >
> > # perf trace -e skb:kfree_skb --filter="reason >= 0x30000"
> > [..]
> > 106.023 ping/2465 skb:kfree_skb(skbaddr: 0xffffa0e8765f2000, \
> > location:0xffffffffc0d9b462, protocol: 2048, reason: 196610)
> >
> > reason: 196610 --> 0x30002 (OVS_XLATE_RECURSION_TOO_DEEP)
> >
> > Signed-off-by: Eric Garver <e...@garver.life>
>
> ...
>
> > --- a/net/openvswitch/actions.c
> > +++ b/net/openvswitch/actions.c
> > @@ -32,6 +32,7 @@
> > #include "vport.h"
> > #include "flow_netlink.h"
> > #include "openvswitch_trace.h"
> > +#include "drop.h"
> >
> > struct deferred_action {
> > struct sk_buff *skb;
> > @@ -1477,6 +1478,18 @@ static int do_execute_actions(struct datapath *dp,
> > struct sk_buff *skb,
> > return dec_ttl_exception_handler(dp, skb,
> > key, a);
> > break;
> > +
> > + case OVS_ACTION_ATTR_DROP:
> > + u32 reason = nla_get_u32(a);
> > +
> > + reason |= SKB_DROP_REASON_SUBSYS_OPENVSWITCH <<
> > + SKB_DROP_REASON_SUBSYS_SHIFT;
> > +
> > + if (reason == OVS_XLATE_OK)
> > + break;
> > +
> > + kfree_skb_reason(skb, reason);
> > + return 0;
> > }
>
> Hi Eric,
>
> thanks for your patches. This is an interesting new feature.
>
> unfortunately clang-16 doesn't seem to like this very much.
> I think that it is due to the declaration of reason not
> being enclosed in a block - { }.
>
> net/openvswitch/actions.c:1483:4: error: expected expression
> u32 reason = nla_get_u32(a);
> ^
> net/openvswitch/actions.c:1485:4: error: use of undeclared identifier
> 'reason'
> reason |= SKB_DROP_REASON_SUBSYS_OPENVSWITCH <<
> ^
> net/openvswitch/actions.c:1488:8: error: use of undeclared identifier
> 'reason'
> if (reason == OVS_XLATE_OK)
> ^
> net/openvswitch/actions.c:1491:26: error: use of undeclared identifier
> 'reason'
> kfree_skb_reason(skb, reason);
> ^
> 4 errors generated.
>
>
> net-next is currently closed.
> So please provide a v2 once it reposts, after 10th July.
oof. My bad. I'll fix the clang issue and post v2 in a couple weeks.
Thanks.
Eric.
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