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authorIdo Schimmel <idosch@nvidia.com>2023-05-29 14:48:28 +0300
committerJakub Kicinski <kuba@kernel.org>2023-05-30 23:37:00 -0700
commit7b4858df3bf7a8d43ed6b58f411543a040c56f10 (patch)
treeaa04c9d53cab262841ab34ef64ea1157f845b6c7 /net/bridge/br_device.c
parent2e246bca986598bdc9d7cae64cf0995257328a5d (diff)
skbuff: bridge: Add layer 2 miss indication
For EVPN non-DF (Designated Forwarder) filtering we need to be able to prevent decapsulated traffic from being flooded to a multi-homed host. Filtering of multicast and broadcast traffic can be achieved using the following flower filter: # tc filter add dev bond0 egress pref 1 proto all flower indev vxlan0 dst_mac 01:00:00:00:00:00/01:00:00:00:00:00 action drop Unlike broadcast and multicast traffic, it is not currently possible to filter unknown unicast traffic. The classification into unknown unicast is performed by the bridge driver, but is not visible to other layers such as tc. Solve this by adding a new 'l2_miss' bit to the tc skb extension. Clear the bit whenever a packet enters the bridge (received from a bridge port or transmitted via the bridge) and set it if the packet did not match an FDB or MDB entry. If there is no skb extension and the bit needs to be cleared, then do not allocate one as no extension is equivalent to the bit being cleared. The bit is not set for broadcast packets as they never perform a lookup and therefore never incur a miss. A bit that is set for every flooded packet would also work for the current use case, but it does not allow us to differentiate between registered and unregistered multicast traffic, which might be useful in the future. To keep the performance impact to a minimum, the marking of packets is guarded by the 'tc_skb_ext_tc' static key. When 'false', the skb is not touched and an skb extension is not allocated. Instead, only a 5 bytes nop is executed, as demonstrated below for the call site in br_handle_frame(). Before the patch: ``` memset(skb->cb, 0, sizeof(struct br_input_skb_cb)); c37b09: 49 c7 44 24 28 00 00 movq $0x0,0x28(%r12) c37b10: 00 00 p = br_port_get_rcu(skb->dev); c37b12: 49 8b 44 24 10 mov 0x10(%r12),%rax memset(skb->cb, 0, sizeof(struct br_input_skb_cb)); c37b17: 49 c7 44 24 30 00 00 movq $0x0,0x30(%r12) c37b1e: 00 00 c37b20: 49 c7 44 24 38 00 00 movq $0x0,0x38(%r12) c37b27: 00 00 ``` After the patch (when static key is disabled): ``` memset(skb->cb, 0, sizeof(struct br_input_skb_cb)); c37c29: 49 c7 44 24 28 00 00 movq $0x0,0x28(%r12) c37c30: 00 00 c37c32: 49 8d 44 24 28 lea 0x28(%r12),%rax c37c37: 48 c7 40 08 00 00 00 movq $0x0,0x8(%rax) c37c3e: 00 c37c3f: 48 c7 40 10 00 00 00 movq $0x0,0x10(%rax) c37c46: 00 #ifdef CONFIG_HAVE_JUMP_LABEL_HACK static __always_inline bool arch_static_branch(struct static_key *key, bool branch) { asm_volatile_goto("1:" c37c47: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) br_tc_skb_miss_set(skb, false); p = br_port_get_rcu(skb->dev); c37c4c: 49 8b 44 24 10 mov 0x10(%r12),%rax ``` Subsequent patches will extend the flower classifier to be able to match on the new 'l2_miss' bit and enable / disable the static key when filters that match on it are added / deleted. Signed-off-by: Ido Schimmel <idosch@nvidia.com> Acked-by: Nikolay Aleksandrov <razor@blackwall.org> Acked-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/bridge/br_device.c')
-rw-r--r--net/bridge/br_device.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 8eca8a5c80c6..9a5ea06236bd 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -39,6 +39,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
u16 vid = 0;
memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
+ br_tc_skb_miss_set(skb, false);
rcu_read_lock();
nf_ops = rcu_dereference(nf_br_ops);