From f1829618e0ad2d5ff974b5d6f295b897e301cda6 Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Wed, 30 Sep 2026 10:14:11 +0300 Subject: [PATCH] net: bridge: fdb: avoid VLAN lookups in unicast forwarding Pass the complete fdb destination to br_forward(). The tagged value is decoded once into br_fwd_dst on entry so all subsequent forwarding checks use the decoded port and VLAN. A cached port-VLAN is then used to avoid two VLAN hash lookups in the standard unicast forwarding path. A backup-port redirect also uses a raw destination because the cached VLAN belongs to the original port. [1] 64 byte vlan packets, 4k randomized fdb hits with 4k fdbs, 5 million packets passed 5 times for every case VIDs Ports Mpps Gbps CPU1 cycles/input before after gain before after before after reduction 64 8/2 2.375486 2.635811 11.0% 1.216 1.350 1724.6 1553.7 9.9% 64 8/4 2.376731 2.636459 10.9% 1.217 1.350 1714.8 1554.7 9.3% 64 8/8 2.376621 2.635783 10.9% 1.217 1.350 1722.6 1553.2 9.8% 64 32/2 2.375876 2.637897 11.0% 1.216 1.351 1726.7 1552.3 10.1% 64 32/16 2.376442 2.636426 10.9% 1.217 1.350 1721.3 1554.2 9.7% 64 32/32 2.376763 2.636268 10.9% 1.217 1.350 1726.8 1553.5 10.0% 64 64/2 2.375678 2.638707 11.1% 1.216 1.351 1725.0 1552.1 10.0% 64 64/32 2.376681 2.637359 11.0% 1.217 1.350 1725.1 1555.9 9.8% 64 64/64 2.376787 2.638396 11.0% 1.217 1.351 1722.8 1550.9 10.0% 1024 8/2 2.263768 2.498881 10.4% 1.159 1.279 1808.5 1637.1 9.5% 1024 8/4 2.264519 2.499075 10.4% 1.159 1.280 1807.6 1638.8 9.3% 1024 8/8 2.263551 2.499231 10.4% 1.159 1.280 1812.0 1640.2 9.5% 1024 32/2 2.263841 2.499120 10.4% 1.159 1.280 1806.8 1639.6 9.3% 1024 32/16 2.263990 2.499562 10.4% 1.159 1.280 1806.1 1639.2 9.2% 1024 32/32 2.263719 2.498905 10.4% 1.159 1.279 1807.7 1639.3 9.3% 1024 64/2 2.263635 2.501889 10.5% 1.159 1.281 1809.4 1635.6 9.6% 1024 64/32 2.264467 2.500359 10.4% 1.159 1.280 1806.5 1633.0 9.6% 1024 64/64 2.240494 2.470246 10.3% 1.147 1.265 1810.0 1637.1 9.6% Reviewed-by: Ido Schimmel Signed-off-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260930071411.2786201-13-razor@blackwall.org Signed-off-by: Jakub Kicinski --- net/bridge/br_device.c | 2 +- net/bridge/br_forward.c | 24 +++++++++++++----------- net/bridge/br_input.c | 2 +- net/bridge/br_mrp.c | 6 +++--- net/bridge/br_private.h | 2 +- net/bridge/netfilter/nft_reject_bridge.c | 8 ++++---- 6 files changed, 23 insertions(+), 21 deletions(-) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index 2423d69f2498..0a1ce9e59a4d 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -108,7 +108,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev) else br_flood(br, vlan, skb, BR_PKT_MULTICAST, false, true); } else if ((dst = br_fdb_find_rcu(br, dest, vid)) != NULL) { - br_forward(br_fdb_dst_port(dst), skb, false, true); + br_forward(br_fdb_dst_read(dst), skb, false, true); } else { br_flood(br, vlan, skb, BR_PKT_UNICAST, false, true); } diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c index b5eece1ff9e8..82645db32efb 100644 --- a/net/bridge/br_forward.c +++ b/net/bridge/br_forward.c @@ -17,7 +17,7 @@ #include "br_private.h" struct br_fwd_dst { - const struct net_bridge_port *port; + struct net_bridge_port *port; struct net_bridge_vlan *vlan; }; @@ -149,35 +149,37 @@ static int deliver_clone(const struct br_fwd_dst *fwd, /** * br_forward - forward a packet to a specific port - * @to: destination port + * @dst: bridge destination * @skb: packet being forwarded * @local_rcv: packet will be received locally after forwarding * @local_orig: packet is locally originated * * Should be called with rcu_read_lock. */ -void br_forward(const struct net_bridge_port *to, +void br_forward(struct net_bridge_dst dst, struct sk_buff *skb, bool local_rcv, bool local_orig) { struct br_fwd_dst fwd; - if (unlikely(!to)) + br_dst_decode(dst, &fwd.port, &fwd.vlan); + + if (unlikely(!fwd.port)) goto out; /* redirect to backup link if the destination port is down */ - if (rcu_access_pointer(to->backup_port) && - (!netif_carrier_ok(to->dev) || !netif_running(to->dev))) { + if (rcu_access_pointer(fwd.port->backup_port) && + (!netif_carrier_ok(fwd.port->dev) || + !netif_running(fwd.port->dev))) { struct net_bridge_port *backup_port; - backup_port = rcu_dereference(to->backup_port); + backup_port = rcu_dereference(fwd.port->backup_port); if (unlikely(!backup_port)) goto out; - BR_INPUT_SKB_CB(skb)->backup_nhid = READ_ONCE(to->backup_nhid); - to = backup_port; + BR_INPUT_SKB_CB(skb)->backup_nhid = READ_ONCE(fwd.port->backup_nhid); + fwd.port = backup_port; + fwd.vlan = NULL; } - fwd.port = to; - fwd.vlan = NULL; if (should_deliver(&fwd, skb)) { if (local_rcv) deliver_clone(&fwd, skb, local_orig); diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 44a217d65e7f..fc2e381c4fe0 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -225,7 +225,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb if (now != READ_ONCE(dst->used)) WRITE_ONCE(dst->used, now); - br_forward(br_fdb_dst_port(dst), skb, local_rcv, false); + br_forward(br_fdb_dst_read(dst), skb, local_rcv, false); } else { if (!mcast_hit) br_flood(br, vlan, skb, pkt_type, local_rcv, false); diff --git a/net/bridge/br_mrp.c b/net/bridge/br_mrp.c index dce6efa96c4c..c8cd5b4f3af8 100644 --- a/net/bridge/br_mrp.c +++ b/net/bridge/br_mrp.c @@ -1219,11 +1219,11 @@ static int br_mrp_rcv(struct net_bridge_port *p, forward: if (p_dst) - br_forward(p_dst, skb, true, false); + br_forward(br_port_to_dst(p_dst), skb, true, false); if (s_dst) - br_forward(s_dst, skb, true, false); + br_forward(br_port_to_dst(s_dst), skb, true, false); if (i_dst) - br_forward(i_dst, skb, true, false); + br_forward(br_port_to_dst(i_dst), skb, true, false); no_forward: return 1; diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index a1c5b1abc1ef..05921192ebda 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -1045,7 +1045,7 @@ enum br_pkt_type { BR_PKT_BROADCAST }; int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb); -void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, +void br_forward(struct net_bridge_dst dst, struct sk_buff *skb, bool local_rcv, bool local_orig); int br_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb); void br_flood(struct net_bridge *br, struct net_bridge_vlan *v, diff --git a/net/bridge/netfilter/nft_reject_bridge.c b/net/bridge/netfilter/nft_reject_bridge.c index cd2b04236a99..92b488793914 100644 --- a/net/bridge/netfilter/nft_reject_bridge.c +++ b/net/bridge/netfilter/nft_reject_bridge.c @@ -55,7 +55,7 @@ static void nft_reject_br_send_v4_tcp_reset(struct net *net, nft_reject_br_push_etherhdr(oldskb, nskb); - br_forward(br_port_get_rcu(dev), nskb, false, true); + br_forward(br_port_to_dst(br_port_get_rcu(dev)), nskb, false, true); } static void nft_reject_br_send_v4_unreach(struct net *net, @@ -71,7 +71,7 @@ static void nft_reject_br_send_v4_unreach(struct net *net, nft_reject_br_push_etherhdr(oldskb, nskb); - br_forward(br_port_get_rcu(dev), nskb, false, true); + br_forward(br_port_to_dst(br_port_get_rcu(dev)), nskb, false, true); } static void nft_reject_br_send_v6_tcp_reset(struct net *net, @@ -87,7 +87,7 @@ static void nft_reject_br_send_v6_tcp_reset(struct net *net, nft_reject_br_push_etherhdr(oldskb, nskb); - br_forward(br_port_get_rcu(dev), nskb, false, true); + br_forward(br_port_to_dst(br_port_get_rcu(dev)), nskb, false, true); } @@ -104,7 +104,7 @@ static void nft_reject_br_send_v6_unreach(struct net *net, nft_reject_br_push_etherhdr(oldskb, nskb); - br_forward(br_port_get_rcu(dev), nskb, false, true); + br_forward(br_port_to_dst(br_port_get_rcu(dev)), nskb, false, true); } static void nft_reject_bridge_eval(const struct nft_expr *expr,