netdev - [PATCH net-next 3/4] mlxsw: spectrum_router: Apply user-defined multipath hash seed

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Date: Wed, 29 May 2024 13:18:43 +0200
From: Petr Machata <petrm@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <netdev@...r.kernel.org>
CC: Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>, "David
 Ahern" <dsahern@...nel.org>
Subject: [PATCH net-next 3/4] mlxsw: spectrum_router: Apply user-defined multipath hash seed

When Spectrum machines compute hash for the purposes of ECMP routing, they
use a seed specified through RECR_v2 (Router ECMP Configuration Register).
Up until now mlxsw computed the seed by hashing the machine's base MAC.
Now that we can optionally have a user-provided seed, use that if possible.

Signed-off-by: Petr Machata <petrm@...dia.com>
Reviewed-by: Ido Schimmel <idosch@...dia.com>
---
 .../net/ethernet/mellanox/mlxsw/spectrum_router.c  | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 40ba314fbc72..e5b669f0822d 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -11449,13 +11449,23 @@ static int mlxsw_sp_mp_hash_parsing_depth_adjust(struct mlxsw_sp *mlxsw_sp,
 static int mlxsw_sp_mp_hash_init(struct mlxsw_sp *mlxsw_sp)
 {
 	bool old_inc_parsing_depth, new_inc_parsing_depth;
+	struct sysctl_fib_multipath_hash_seed *mphs;
 	struct mlxsw_sp_mp_hash_config config = {};
+	struct net *net = mlxsw_sp_net(mlxsw_sp);
 	char recr2_pl[MLXSW_REG_RECR2_LEN];
 	unsigned long bit;
-	u32 seed;
+	u32 seed = 0;
 	int err;
 
-	seed = jhash(mlxsw_sp->base_mac, sizeof(mlxsw_sp->base_mac), 0);
+	rcu_read_lock();
+	mphs = rcu_dereference(net->ipv4.sysctl_fib_multipath_hash_seed);
+	if (mphs)
+		seed = mphs->user_seed;
+	rcu_read_unlock();
+
+	if (!seed)
+		seed = jhash(mlxsw_sp->base_mac, sizeof(mlxsw_sp->base_mac), 0);
+
 	mlxsw_reg_recr2_pack(recr2_pl, seed);
 	mlxsw_sp_mp4_hash_init(mlxsw_sp, &config);
 	mlxsw_sp_mp6_hash_init(mlxsw_sp, &config);
-- 
2.45.0