Re: [PATCH net] selftests: forwarding: vxlan_bridge_1d: Fix vxlan ecn decapsulate value

On Fri, Mar 19, 2021 at 10:33:14PM +0800, Hangbin Liu wrote:

The ECN bit defines ECT(1) = 1, ECT(0) = 2. So inner 0x02 + outer 0x01
should be inner ECT(0) + outer ECT(1). Based on the description of
__INET_ECN_decapsulate, the final decapsulate value should be
ECT(1). So fix the test expect value to 0x01.

Before the fix:
TEST: VXLAN: ECN decap: 01/02->0x02                                 [FAIL]
        Expected to capture 10 packets, got 0.

After the fix:
TEST: VXLAN: ECN decap: 01/02->0x01                                 [ OK ]

Fixes: a0b61f3d8ebf ("selftests: forwarding: vxlan_bridge_1d: Add an ECN decap test")
Signed-off-by: Hangbin Liu <redacted>

Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040")

The commit you cited is from 2018 whereas this one is from 2020. The
test stopped working after the latter. The reason I didn't see it is
because this commit only changed one caller of __INET_ECN_decapsulate().
Another caller is mlxsw which uses the function to understand how to
program the hardware to perform decapsulation. See commit 28e450333d4d
("inet: Refactor INET_ECN_decapsulate()").

After your patch I get:

TEST: VXLAN: ECN decap: 01/02->0x01                                 [FAIL]
        Expected to capture 10 packets, got 0.

Fixed by:

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_ipip.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_ipip.c
index b8b08a6a1d10..61eb34e20fde 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_ipip.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_ipip.c

@@ -341,7 +341,12 @@ static int mlxsw_sp_ipip_ecn_decap_init_one(struct mlxsw_sp *mlxsw_sp,
        u8 new_inner_ecn;
 
        trap_en = __INET_ECN_decapsulate(outer_ecn, inner_ecn, &set_ce);
-       new_inner_ecn = set_ce ? INET_ECN_CE : inner_ecn;
+       if (set_ce)
+               new_inner_ecn = INET_ECN_CE;
+       else if (outer_ecn == INET_ECN_ECT_1)
+               new_inner_ecn = INET_ECN_ECT_1;
+       else
+               new_inner_ecn = inner_ecn;
 
        mlxsw_reg_tidem_pack(tidem_pl, outer_ecn, inner_ecn, new_inner_ecn,
                             trap_en, trap_en ? MLXSW_TRAP_ID_DECAP_ECN0 : 0);

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c
index e5ec595593f4..74f2c4ce7063 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c

@@ -913,7 +913,12 @@ static int __mlxsw_sp_nve_ecn_decap_init(struct mlxsw_sp *mlxsw_sp,
        u8 new_inner_ecn;
 
        trap_en = !!__INET_ECN_decapsulate(outer_ecn, inner_ecn, &set_ce);
-       new_inner_ecn = set_ce ? INET_ECN_CE : inner_ecn;
+       if (set_ce)
+               new_inner_ecn = INET_ECN_CE;
+       else if (outer_ecn == INET_ECN_ECT_1)
+               new_inner_ecn = INET_ECN_ECT_1;
+       else
+               new_inner_ecn = inner_ecn;
 
        mlxsw_reg_tndem_pack(tndem_pl, outer_ecn, inner_ecn, new_inner_ecn,
                             trap_en, trap_en ? MLXSW_TRAP_ID_DECAP_ECN0 : 0);

I will prepare a patch