netdev - [PATCH net-next 1/2] mlxsw: spectrum: Use a stable ECMP/LAG seed

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Date:   Sun, 21 Apr 2019 07:18:34 +0000
From:   Ido Schimmel <idosch@...lanox.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>, mlxsw <mlxsw@...lanox.com>,
        "dsahern@...il.com" <dsahern@...il.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net-next 1/2] mlxsw: spectrum: Use a stable ECMP/LAG seed

In order to get a consistent behavior of traffic flows across reboots /
module unload, we need to use the same ECMP/LAG seed.

Calculate the seed by hashing the base MAC of the device. This results
in a seed that is both unique (to avoid polarization) and consistent.

Signed-off-by: Ido Schimmel <idosch@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum.c        | 4 ++--
 drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
index fc325f1213fb..a1c2b117a2b3 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
@@ -21,7 +21,7 @@
 #include <linux/dcbnl.h>
 #include <linux/inetdevice.h>
 #include <linux/netlink.h>
-#include <linux/random.h>
+#include <linux/jhash.h>
 #include <net/switchdev.h>
 #include <net/pkt_cls.h>
 #include <net/tc_act/tc_mirred.h>
@@ -4227,7 +4227,7 @@ static int mlxsw_sp_lag_init(struct mlxsw_sp *mlxsw_sp)
 	u32 seed;
 	int err;
 
-	get_random_bytes(&seed, sizeof(seed));
+	seed = jhash(mlxsw_sp->base_mac, sizeof(mlxsw_sp->base_mac), 0);
 	mlxsw_reg_slcr_pack(slcr_pl, MLXSW_REG_SLCR_LAG_HASH_SMAC |
 				     MLXSW_REG_SLCR_LAG_HASH_DMAC |
 				     MLXSW_REG_SLCR_LAG_HASH_ETHERTYPE |
diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 64498c9f55ab..6c73400b1508 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -13,9 +13,9 @@
 #include <linux/socket.h>
 #include <linux/route.h>
 #include <linux/gcd.h>
-#include <linux/random.h>
 #include <linux/if_macvlan.h>
 #include <linux/refcount.h>
+#include <linux/jhash.h>
 #include <net/netevent.h>
 #include <net/neighbour.h>
 #include <net/arp.h>
@@ -7831,7 +7831,7 @@ static int mlxsw_sp_mp_hash_init(struct mlxsw_sp *mlxsw_sp)
 	char recr2_pl[MLXSW_REG_RECR2_LEN];
 	u32 seed;
 
-	get_random_bytes(&seed, sizeof(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(recr2_pl);
 	mlxsw_sp_mp6_hash_init(recr2_pl);
-- 
2.20.1