Re: [PATCH v2 net-next 1/4] net: bridge: add fdb flag to extent locked port feature

Nikolay Aleksandrov
2022-03-17T09:47:30Z

On 17/03/2022 11:38, Hans Schultz wrote:
> Add an intermediate state for clients behind a locked port to allow for
> possible opening of the port for said clients. This feature corresponds
> to the Mac-Auth and MAC Authentication Bypass (MAB) named features. The
> latter defined by Cisco.
> Only the kernel can set this FDB entry flag, while userspace can read
> the flag and remove it by deleting the FDB entry.
>
> Signed-off-by: Hans Schultz <schultz.hans+netdev@gmail.com>
> ---
> include/uapi/linux/neighbour.h | 1 +
> net/bridge/br_fdb.c | 6 ++++++
> net/bridge/br_input.c | 10 +++++++++-
> net/bridge/br_private.h | 3 ++-
> 4 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/neighbour.h b/include/uapi/linux/neighbour.h
> index db05fb55055e..a2df3b9b2f68 100644
> --- a/include/uapi/linux/neighbour.h
> +++ b/include/uapi/linux/neighbour.h
> @@ -51,6 +51,7 @@ enum {
> #define NTF_ROUTER (1 << 7)
> /* Extended flags under NDA_FLAGS_EXT: */
> #define NTF_EXT_MANAGED (1 << 0)
> +#define NTF_EXT_LOCKED (1 << 1)
>
> /*
> * Neighbor Cache Entry States.
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 6ccda68bd473..57ec559a85a7 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -105,6 +105,7 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
> struct nda_cacheinfo ci;
> struct nlmsghdr *nlh;
> struct ndmsg *ndm;
> + u8 ext_flags = 0;

Let's not limit ourselves to 8 bits only for new flags, we'll need to extend them
very soon. The neigh code defines the attribute as u32 which seems more appropriate.

>
> nlh = nlmsg_put(skb, portid, seq, type, sizeof(*ndm), flags);
> if (nlh == NULL)
> @@ -125,11 +126,16 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
> ndm->ndm_flags |= NTF_EXT_LEARNED;
> if (test_bit(BR_FDB_STICKY, &fdb->flags))
> ndm->ndm_flags |= NTF_STICKY;
> + if (test_bit(BR_FDB_ENTRY_LOCKED, &fdb->flags))
> + ext_flags |= NTF_EXT_LOCKED;
>
> if (nla_put(skb, NDA_LLADDR, ETH_ALEN, &fdb->key.addr))
> goto nla_put_failure;
> if (nla_put_u32(skb, NDA_MASTER, br->dev->ifindex))
> goto nla_put_failure;
> + if (nla_put_u8(skb, NDA_FLAGS_EXT, ext_flags))
> + goto nla_put_failure;
> +

You have to account for the new attribute size in fdb_nlmsg_size().

> ci.ndm_used = jiffies_to_clock_t(now - fdb->used);
> ci.ndm_confirmed = 0;
> ci.ndm_updated = jiffies_to_clock_t(now - fdb->updated);
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index e0c13fcc50ed..5ef25a496806 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -94,8 +94,16 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
> br_fdb_find_rcu(br, eth_hdr(skb)->h_source, vid);
>
> if (!fdb_src || READ_ONCE(fdb_src->dst) != p ||
> - test_bit(BR_FDB_LOCAL, &fdb_src->flags))
> + test_bit(BR_FDB_LOCAL, &fdb_src->flags) ||
> + test_bit(BR_FDB_ENTRY_LOCKED, &fdb_src->flags)) {
> + if (!fdb_src) {
> + unsigned long flags = 0;
> +
> + set_bit(BR_FDB_ENTRY_LOCKED, &flags);

__set_bit()

> + br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, flags);
> + }
> goto drop;
> + }
> }
>
> nbp_switchdev_frame_mark(p, skb);
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 48bc61ebc211..f5a0b68c4857 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -248,7 +248,8 @@ enum {
> BR_FDB_ADDED_BY_EXT_LEARN,
> BR_FDB_OFFLOADED,
> BR_FDB_NOTIFY,
> - BR_FDB_NOTIFY_INACTIVE
> + BR_FDB_NOTIFY_INACTIVE,
> + BR_FDB_ENTRY_LOCKED,
> };
>
> struct net_bridge_fdb_key {