net: sched: RED: Introduce an ECN nodrop mode
When the RED Qdisc is currently configured to enable ECN, the RED algorithm
is used to decide whether a certain SKB should be marked. If that SKB is
not ECN-capable, it is early-dropped.
It is also possible to keep all traffic in the queue, and just mark the
ECN-capable subset of it, as appropriate under the RED algorithm. Some
switches support this mode, and some installations make use of it.
To that end, add a new RED flag, TC_RED_NODROP. When the Qdisc is
configured with this flag, non-ECT traffic is enqueued instead of being
early-dropped.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/red.h b/include/net/red.h
index 6a2aaa6..fc45544 100644
--- a/include/net/red.h
+++ b/include/net/red.h
@@ -209,6 +209,11 @@ static inline int red_get_flags(unsigned char qopt_flags,
static inline int red_validate_flags(unsigned char flags,
struct netlink_ext_ack *extack)
{
+ if ((flags & TC_RED_NODROP) && !(flags & TC_RED_ECN)) {
+ NL_SET_ERR_MSG_MOD(extack, "nodrop mode is only meaningful with ECN");
+ return -EINVAL;
+ }
+
return 0;
}