[PATCH 4.19 24/96] sch_cake: Simplify logic in cake_select_tin()

Greg Kroah-Hartman
2019-04-24T17:30:07Z

From: Toke Høiland-Jørgensen <toke@redhat.com>

[ Upstream commit 4976e3c683f328bc6f2edef555a4ffee6524486f ]

The logic in cake_select_tin() was getting a bit hairy, and it turns out we
can simplify it quite a bit. This also allows us to get rid of one of the
two diffserv parsing functions, which has the added benefit that
already-zeroed DSCP fields won't get re-written.

Suggested-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_cake.c | 44 ++++++++++++++++----------------------------
1 file changed, 16 insertions(+), 28 deletions(-)

--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1508,20 +1508,6 @@ static unsigned int cake_drop(struct Qdi
return idx + (tin << 16);
}

-static void cake_wash_diffserv(struct sk_buff *skb)
-{
- switch (skb->protocol) {
- case htons(ETH_P_IP):
- ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, 0);
- break;
- case htons(ETH_P_IPV6):
- ipv6_change_dsfield(ipv6_hdr(skb), INET_ECN_MASK, 0);
- break;
- default:
- break;
- }
-}
-
static u8 cake_handle_diffserv(struct sk_buff *skb, u16 wash)
{
int wlen = skb_network_offset(skb);
@@ -1564,25 +1550,27 @@ static struct cake_tin_data *cake_select
{
struct cake_sched_data *q = qdisc_priv(sch);
u32 tin;
+ u8 dscp;
+
+ /* Tin selection: Default to diffserv-based selection, allow overriding
+ * using firewall marks or skb->priority.
+ */
+ dscp = cake_handle_diffserv(skb,
+ q->rate_flags & CAKE_FLAG_WASH);
+
+ if (q->tin_mode == CAKE_DIFFSERV_BESTEFFORT)
+ tin = 0;

- if (TC_H_MAJ(skb->priority) == sch->handle &&
- TC_H_MIN(skb->priority) > 0 &&
- TC_H_MIN(skb->priority) <= q->tin_cnt) {
+ else if (TC_H_MAJ(skb->priority) == sch->handle &&
+ TC_H_MIN(skb->priority) > 0 &&
+ TC_H_MIN(skb->priority) <= q->tin_cnt)
tin = q->tin_order[TC_H_MIN(skb->priority) - 1];

- if (q->rate_flags & CAKE_FLAG_WASH)
- cake_wash_diffserv(skb);
- } else if (q->tin_mode != CAKE_DIFFSERV_BESTEFFORT) {
- /* extract the Diffserv Precedence field, if it exists */
- /* and clear DSCP bits if washing */
- tin = q->tin_index[cake_handle_diffserv(skb,
- q->rate_flags & CAKE_FLAG_WASH)];
+ else {
+ tin = q->tin_index[dscp];
+
if (unlikely(tin >= q->tin_cnt))
tin = 0;
- } else {
- tin = 0;
- if (q->rate_flags & CAKE_FLAG_WASH)
- cake_wash_diffserv(skb);
}

return &q->tins[tin];