[ovs-dev] [PATCH ovn] ovn-sbctl: Sort "dump-flows" output by actions if all else fails.

[Han Zhou]

On Fri, Mar 5, 2021 at 2:54 PM Ben Pfaff <blp at ovn.org> wrote:
>
> The Logical_Flow table can have rows that differ only in actions.  Such
> rows would have identical matches and priorities and be in the same
> datapath.  At first glance, any these rows would be a bug, since they'd
> match the same packets and there'd be no way to choose between them.
>
> In practice, though, actions can have prerequisites.  If two different
> flows have mutually exclusive prerequisites, the otherwise identical
> flows are actually valid.
>
> This comes up in practice in DNS response flows.  There are two of
> them, in the same table and pipeline and with the same match expression
> "udp.dst == 53 && reg0[4]", but one of them includes the action
> "ip4.src <-> ip4.dst;" and the other "ip6.src <-> ip6.dst;".  Because
> the first has an IPv4 prerequisite and the latter an IPv6 prerequisite,
> their matches don't really overlap.
>
> Anyway, regardless of whether they're valid, it's still good to sort
> consistently, so that's all a digression.
>
> Signed-off-by: Ben Pfaff <blp at ovn.org>
> ---
>  utilities/ovn-sbctl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/utilities/ovn-sbctl.c b/utilities/ovn-sbctl.c
> index c38e8ec3bdbd..94e33d2bdfe6 100644
> --- a/utilities/ovn-sbctl.c
> +++ b/utilities/ovn-sbctl.c
> @@ -754,13 +754,14 @@ sbctl_lflow_cmp(const void *a_, const void *b_)
>
>      int a_pipeline = pipeline_encode(a->pipeline);
>      int b_pipeline = pipeline_encode(b->pipeline);
> -    return (a_pipeline > b_pipeline ? 1
> +    cmp = (a_pipeline > b_pipeline ? 1
>              : a_pipeline < b_pipeline ? -1
>              : a->table_id > b->table_id ? 1
>              : a->table_id < b->table_id ? -1
>              : a->priority > b->priority ? -1
>              : a->priority < b->priority ? 1
>              : strcmp(a->match, b->match));
> +    return cmp ? cmp : strcmp(a->actions, b->actions);
>  }
>
>  static char *
> --
> 2.29.2
>
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Acked-by: Han Zhou <hzhou at ovn.org>