linux-kernel - [PATCH net-next v4 5/6] net: bridge: Add a configurable default FDB learning limit

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Message-Id: <20230919-fdb_limit-v4-5-39f0293807b8@avm.de>
Date:   Tue, 19 Sep 2023 10:12:52 +0200
From:   Johannes Nixdorf <jnixdorf-oss@....de>
To:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>, David Ahern <dsahern@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ido Schimmel <idosch@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>, Shuah Khan <shuah@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>
Cc:     bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Johannes Nixdorf <jnixdorf-oss@....de>
Subject: [PATCH net-next v4 5/6] net: bridge: Add a configurable default
 FDB learning limit

Add a Kconfig option to configure a default FDB learning limit system
wide, so a distributor building a special purpose kernel can limit all
created bridges by default.

The limit is only a soft default setting and overrideable on a per bridge
basis using netlink.

Signed-off-by: Johannes Nixdorf <jnixdorf-oss@....de>
---
 net/bridge/Kconfig     | 13 +++++++++++++
 net/bridge/br_device.c |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/net/bridge/Kconfig b/net/bridge/Kconfig
index 3c8ded7d3e84..c0d9c08088c4 100644
--- a/net/bridge/Kconfig
+++ b/net/bridge/Kconfig
@@ -84,3 +84,16 @@ config BRIDGE_CFM
 	  Say N to exclude this support and reduce the binary size.
 
 	  If unsure, say N.
+
+config BRIDGE_DEFAULT_FDB_MAX_LEARNED
+	int "Default FDB learning limit"
+	default 0
+	depends on BRIDGE
+	help
+	  Sets a default limit on the number of learned FDB entries on
+	  new bridges. This limit can be overwritten via netlink on a
+	  per bridge basis.
+
+	  The default of 0 disables the limit.
+
+	  If unsure, say 0.
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 9a5ea06236bd..3214391c15a0 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -531,6 +531,8 @@ void br_dev_setup(struct net_device *dev)
 	br->bridge_ageing_time = br->ageing_time = BR_DEFAULT_AGEING_TIME;
 	dev->max_mtu = ETH_MAX_MTU;
 
+	br->fdb_max_learned = CONFIG_BRIDGE_DEFAULT_FDB_MAX_LEARNED;
+
 	br_netfilter_rtable_init(br);
 	br_stp_timer_init(br);
 	br_multicast_init(br);

-- 
2.42.0