kernel: cake: backport upstream tweaks & fixes

From upstream:
b8392808eb3f sch_cake: add RFC 8622 LE PHB support to CAKE diffserv handling
3f608f0c4136 sch_cake: fix a few style nits
8c95eca0bb8c sch_cake: don't call diffserv parsing code when it is not needed
9208d2863ac6 sch_cake: don't try to reallocate or unshare skb unconditionally

From netdev not yet accepted:
sch_cake: fix IP protocol handling in the presence of VLAN tags

The VLAN tag handling is actually wider than just cake so upstream are
working out how to fix it generically.  We fix it here just for cake.

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>

1 files changed, 57 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/399-5.9-sch_cake-add-RFC-8622-LE-PHB-support-to-CAKE-diffser.patch b/target/linux/generic/backport-5.4/399-5.9-sch_cake-add-RFC-8622-LE-PHB-support-to-CAKE-diffser.patch
new file mode 100644
index 0000000000..e171b4cec7
--- /dev/null
+++ b/target/linux/generic/backport-5.4/399-5.9-sch_cake-add-RFC-8622-LE-PHB-support-to-CAKE-diffser.patch
@@ -0,0 +1,57 @@
+From b8392808eb3fc28e523e28cb258c81ca246deb9b Mon Sep 17 00:00:00 2001
+From: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
+Date: Thu, 25 Jun 2020 22:18:00 +0200
+Subject: [PATCH] sch_cake: add RFC 8622 LE PHB support to CAKE diffserv
+ handling
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Change tin mapping on diffserv3, 4 & 8 for LE PHB support, in essence
+making LE a member of the Bulk tin.
+
+Bulk has the least priority and minimum of 1/16th total bandwidth in the
+face of higher priority traffic.
+
+NB: Diffserv 3 & 4 swap tin 0 & 1 priorities from the default order as
+found in diffserv8, in case anyone is wondering why it looks a bit odd.
+
+Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
+[ reword commit message slightly ]
+Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/sched/sch_cake.c | 8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+--- a/net/sched/sch_cake.c
++++ b/net/sched/sch_cake.c
+@@ -312,8 +312,8 @@ static const u8 precedence[] = {
+ };
+ 
+ static const u8 diffserv8[] = {
+-	2, 5, 1, 2, 4, 2, 2, 2,
+-	0, 2, 1, 2, 1, 2, 1, 2,
++	2, 0, 1, 2, 4, 2, 2, 2,
++	1, 2, 1, 2, 1, 2, 1, 2,
+ 	5, 2, 4, 2, 4, 2, 4, 2,
+ 	3, 2, 3, 2, 3, 2, 3, 2,
+ 	6, 2, 3, 2, 3, 2, 3, 2,
+@@ -323,7 +323,7 @@ static const u8 diffserv8[] = {
+ };
+ 
+ static const u8 diffserv4[] = {
+-	0, 2, 0, 0, 2, 0, 0, 0,
++	0, 1, 0, 0, 2, 0, 0, 0,
+ 	1, 0, 0, 0, 0, 0, 0, 0,
+ 	2, 0, 2, 0, 2, 0, 2, 0,
+ 	2, 0, 2, 0, 2, 0, 2, 0,
+@@ -334,7 +334,7 @@ static const u8 diffserv4[] = {
+ };
+ 
+ static const u8 diffserv3[] = {
+-	0, 0, 0, 0, 2, 0, 0, 0,
++	0, 1, 0, 0, 2, 0, 0, 0,
+ 	1, 0, 0, 0, 0, 0, 0, 0,
+ 	0, 0, 0, 0, 0, 0, 0, 0,
+ 	0, 0, 0, 0, 0, 0, 0, 0,