Re: [PATCH net-next 1/5] skbuff: bridge: Add layer 2 miss indication
From: Nikolay Aleksandrov <razor@blackwall.org>
Date: 2023-05-18 16:09:00
Also in:
bridge
On 18/05/2023 14:33, Ido Schimmel wrote:
Allow the bridge driver to mark packets that did not match a layer 2
entry during forwarding by adding a 'l2_miss' bit to the skb.
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/MDB entry.
Subsequent patches will allow the flower classifier to match on this
bit. The motivating use case in non-DF (Designated Forwarder) filtering
where we would like to prevent decapsulated packets from being flooded
to a multi-homed host.
Do not allocate the bit if the kernel was not compiled with bridge
support and place it after the two bit fields in accordance with commit
4c60d04c2888 ("net: skbuff: push nf_trace down the bitfield"). The bit
does not increase the size of the structure as it is placed at an
existing hole. Layout with allmodconfig:
struct sk_buff {
[...]
__u8 csum_not_inet:1; /* 132: 3 1 */
__u8 l2_miss:1; /* 132: 4 1 */
/* XXX 3 bits hole, try to pack */
/* XXX 1 byte hole, try to pack */
__u16 tc_index; /* 134 2 */
u16 alloc_cpu; /* 136 2 */
[...]
} __attribute__((__aligned__(8)));
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
---
include/linux/skbuff.h | 4 ++++
net/bridge/br_device.c | 1 +
net/bridge/br_forward.c | 3 +++
net/bridge/br_input.c | 1 +
4 files changed, 9 insertions(+)[snip]
quoted hunk ↗ jump to hunk
while (p || rp) {diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index fc17b9fd93e6..d8ab5890cbe6 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)); + skb->l2_miss = 0; p = br_port_get_rcu(skb->dev); if (p->flags & BR_VLAN_TUNNEL)
Overall looks good, only this part is a bit worrisome and needs some additional investigation because now we'll unconditionally dirty a cache line for every packet that is forwarded. Could you please check the effect with perf? Thanks, Nik