[PATCH 6.6 041/158] net: sparx5: flower: fix fragment flags handling

Greg Kroah-Hartman
2024-04-23T21:43:05Z

From: Asbjørn Sloth Tønnesen <ast@fiberby.net>

[ Upstream commit 68aba00483c7c4102429bcdfdece7289a8ab5c8e ]

I noticed that only 3 out of the 4 input bits were used,
mt.key->flags & FLOW_DIS_IS_FRAGMENT was never checked.

In order to avoid a complicated maze, I converted it to
use a 16 byte mapping table.

As shown in the table below the old heuristics doesn't
always do the right thing, ie. when FLOW_DIS_IS_FRAGMENT=1/1
then it used to only match follow-up fragment packets.

Here are all the combinations, and their resulting new/old
VCAP key/mask filter:

/- FLOW_DIS_IS_FRAGMENT (key/mask)
| /- FLOW_DIS_FIRST_FRAG (key/mask)
| | /-- new VCAP fragment (key/mask)
v v v v- old VCAP fragment (key/mask)

0/0 0/0 -/- -/- impossible (due to entry cond. on mask)
0/0 0/1 -/- 0/3 !! invalid (can't match non-fragment + follow-up frag)
0/0 1/0 -/- -/- impossible (key > mask)
0/0 1/1 1/3 1/3 first fragment

0/1 0/0 0/3 3/3 !! not fragmented
0/1 0/1 0/3 3/3 !! not fragmented (+ not first fragment)
0/1 1/0 -/- -/- impossible (key > mask)
0/1 1/1 -/- 1/3 !! invalid (non-fragment and first frag)

1/0 0/0 -/- -/- impossible (key > mask)
1/0 0/1 -/- -/- impossible (key > mask)
1/0 1/0 -/- -/- impossible (key > mask)
1/0 1/1 -/- -/- impossible (key > mask)

1/1 0/0 1/1 3/3 !! some fragment
1/1 0/1 3/3 3/3 follow-up fragment
1/1 1/0 -/- -/- impossible (key > mask)
1/1 1/1 1/3 1/3 first fragment

In the datasheet the VCAP fragment values are documented as:
0 = no fragment
1 = initial fragment
2 = suspicious fragment
3 = valid follow-up fragment

Result: 3 combinations match the old behavior,
3 combinations have been corrected,
2 combinations are now invalid, and fail,
8 combinations are impossible.

It should now be aligned with how FLOW_DIS_IS_FRAGMENT
and FLOW_DIS_FIRST_FRAG is set in __skb_flow_dissect() in
net/core/flow_dissector.c

Since the VCAP fragment values are not a bitfield, we have
to ignore the suspicious fragment value, eg. when matching
on any kind of fragment with FLOW_DIS_IS_FRAGMENT=1/1.

Only compile tested, and logic tested in userspace, as I
unfortunately don't have access to this switch chip (yet).

Fixes: d6c2964db3fe ("net: microchip: sparx5: Adding more tc flower keys for the IS2 VCAP")
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Tested-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20240411111321.114095-1-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../microchip/sparx5/sparx5_tc_flower.c | 61 ++++++++++++-------
1 file changed, 40 insertions(+), 21 deletions(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c b/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
index 523e0c470894f..55f255a3c9db6 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
@@ -36,6 +36,27 @@ struct sparx5_tc_flower_template {
u16 l3_proto; /* protocol specified in the template */
};

+/* SparX-5 VCAP fragment types:
+ * 0 = no fragment, 1 = initial fragment,
+ * 2 = suspicious fragment, 3 = valid follow-up fragment
+ */
+enum { /* key / mask */
+ FRAG_NOT = 0x03, /* 0 / 3 */
+ FRAG_SOME = 0x11, /* 1 / 1 */
+ FRAG_FIRST = 0x13, /* 1 / 3 */
+ FRAG_LATER = 0x33, /* 3 / 3 */
+ FRAG_INVAL = 0xff, /* invalid */
+};
+
+/* Flower fragment flag to VCAP fragment type mapping */
+static const u8 sparx5_vcap_frag_map[4][4] = { /* is_frag */
+ { FRAG_INVAL, FRAG_INVAL, FRAG_INVAL, FRAG_FIRST }, /* 0/0 */
+ { FRAG_NOT, FRAG_NOT, FRAG_INVAL, FRAG_INVAL }, /* 0/1 */
+ { FRAG_INVAL, FRAG_INVAL, FRAG_INVAL, FRAG_INVAL }, /* 1/0 */
+ { FRAG_SOME, FRAG_LATER, FRAG_INVAL, FRAG_FIRST } /* 1/1 */
+ /* 0/0 0/1 1/0 1/1 <-- first_frag */
+};
+
static int
sparx5_tc_flower_es0_tpid(struct vcap_tc_flower_parse_usage *st)
{
@@ -145,29 +166,27 @@ sparx5_tc_flower_handler_control_usage(struct vcap_tc_flower_parse_usage *st)
flow_rule_match_control(st->frule, &mt);

if (mt.mask->flags) {
- if (mt.mask->flags & FLOW_DIS_FIRST_FRAG) {
- if (mt.key->flags & FLOW_DIS_FIRST_FRAG) {
- value = 1; /* initial fragment */
- mask = 0x3;
- } else {
- if (mt.mask->flags & FLOW_DIS_IS_FRAGMENT) {
- value = 3; /* follow up fragment */
- mask = 0x3;
- } else {
- value = 0; /* no fragment */
- mask = 0x3;
- }
- }
- } else {
- if (mt.mask->flags & FLOW_DIS_IS_FRAGMENT) {
- value = 3; /* follow up fragment */
- mask = 0x3;
- } else {
- value = 0; /* no fragment */
- mask = 0x3;
- }
+ u8 is_frag_key = !!(mt.key->flags & FLOW_DIS_IS_FRAGMENT);
+ u8 is_frag_mask = !!(mt.mask->flags & FLOW_DIS_IS_FRAGMENT);
+ u8 is_frag_idx = (is_frag_key << 1) | is_frag_mask;
+
+ u8 first_frag_key = !!(mt.key->flags & FLOW_DIS_FIRST_FRAG);
+ u8 first_frag_mask = !!(mt.mask->flags & FLOW_DIS_FIRST_FRAG);
+ u8 first_frag_idx = (first_frag_key << 1) | first_frag_mask;
+
+ /* Lookup verdict based on the 2 + 2 input bits */
+ u8 vdt = sparx5_vcap_frag_map[is_frag_idx][first_frag_idx];
+
+ if (vdt == FRAG_INVAL) {
+ NL_SET_ERR_MSG_MOD(st->fco->common.extack,
+ "Match on invalid fragment flag combination");
+ return -EINVAL;
}

+ /* Extract VCAP fragment key and mask from verdict */
+ value = (vdt >> 4) & 0x3;
+ mask = vdt & 0x3;
+
err = vcap_rule_add_key_u32(st->vrule,
VCAP_KF_L3_FRAGMENT_TYPE,
value, mask);
--
2.43.0