| Message ID | 20230529114835.372140-2-idosch@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7b4858df3bf7a8d43ed6b58f411543a040c56f10 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Add layer 2 miss indication and filtering | expand |
On 29/05/2023 14:48, Ido Schimmel wrote: > 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> > --- > > Notes: > v2: > * Use tc skb extension instead of adding a bit to the skb. > * Do not mark broadcast packets as they never perform a lookup and > therefore never incur a miss. > > include/linux/skbuff.h | 1 + > net/bridge/br_device.c | 1 + > net/bridge/br_forward.c | 3 +++ > net/bridge/br_input.c | 1 + > net/bridge/br_private.h | 27 +++++++++++++++++++++++++++ > 5 files changed, 33 insertions(+) > Nice approach. Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
On Mon, 29 May 2023 14:48:28 +0300 Ido Schimmel wrote: > 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. Acked-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 5951904413ab..e2f48ddb2f7c 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -330,6 +330,7 @@ struct tc_skb_ext { u8 post_ct_snat:1; u8 post_ct_dnat:1; u8 act_miss:1; /* Set if act_miss_cookie is used */ + u8 l2_miss:1; /* Set by bridge upon FDB or MDB miss */ }; #endif 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); diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c index 84d6dd5e5b1a..6116eba1bd89 100644 --- a/net/bridge/br_forward.c +++ b/net/bridge/br_forward.c @@ -203,6 +203,8 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb, struct net_bridge_port *prev = NULL; struct net_bridge_port *p; + br_tc_skb_miss_set(skb, pkt_type != BR_PKT_BROADCAST); + list_for_each_entry_rcu(p, &br->port_list, list) { /* Do not flood unicast traffic to ports that turn it off, nor * other traffic if flood off, except for traffic we originate @@ -295,6 +297,7 @@ void br_multicast_flood(struct net_bridge_mdb_entry *mdst, allow_mode_include = false; } else { p = NULL; + br_tc_skb_miss_set(skb, true); } while (p || rp) { diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index fc17b9fd93e6..c34a0b0901b0 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -334,6 +334,7 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb) return RX_HANDLER_CONSUMED; memset(skb->cb, 0, sizeof(struct br_input_skb_cb)); + br_tc_skb_miss_set(skb, false); p = br_port_get_rcu(skb->dev); if (p->flags & BR_VLAN_TUNNEL) diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 2119729ded2b..a63b32c1638e 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -15,6 +15,7 @@ #include <linux/u64_stats_sync.h> #include <net/route.h> #include <net/ip6_fib.h> +#include <net/pkt_cls.h> #include <linux/if_vlan.h> #include <linux/rhashtable.h> #include <linux/refcount.h> @@ -754,6 +755,32 @@ void br_boolopt_multi_get(const struct net_bridge *br, struct br_boolopt_multi *bm); void br_opt_toggle(struct net_bridge *br, enum net_bridge_opts opt, bool on); +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT) +static inline void br_tc_skb_miss_set(struct sk_buff *skb, bool miss) +{ + struct tc_skb_ext *ext; + + if (!tc_skb_ext_tc_enabled()) + return; + + ext = skb_ext_find(skb, TC_SKB_EXT); + if (ext) { + ext->l2_miss = miss; + return; + } + if (!miss) + return; + ext = tc_skb_ext_alloc(skb); + if (!ext) + return; + ext->l2_miss = true; +} +#else +static inline void br_tc_skb_miss_set(struct sk_buff *skb, bool miss) +{ +} +#endif + /* br_device.c */ void br_dev_setup(struct net_device *dev); void br_dev_delete(struct net_device *dev, struct list_head *list);
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> --- Notes: v2: * Use tc skb extension instead of adding a bit to the skb. * Do not mark broadcast packets as they never perform a lookup and therefore never incur a miss. include/linux/skbuff.h | 1 + net/bridge/br_device.c | 1 + net/bridge/br_forward.c | 3 +++ net/bridge/br_input.c | 1 + net/bridge/br_private.h | 27 +++++++++++++++++++++++++++ 5 files changed, 33 insertions(+)