Re: [PATCH RFC 1/7] net: bridge: extend the process of special frames

[Nikolay Aleksandrov]

On Fri, 2020-09-04 at 09:15 +0000, Henrik Bjoernlund wrote:
> This patch extends the processing of frames in the bridge. Currently MRP
> frames needs special processing and the current implementation doesn't
> allow a nice way to process different frame types. Therefore try to
> improve this by adding a list that contains frame types that need
> special processing. This list is iterated for each input frame and if
> there is a match based on frame type then these functions will be called
> and decide what to do with the frame. It can process the frame then the
> bridge doesn't need to do anything or don't process so then the bridge
> will do normal forwarding.
> 
> Signed-off-by: Henrik Bjoernlund  <henrik.bjoernlund@xxxxxxxxxxxxx>
> ---
>  net/bridge/br_device.c  |  1 +
>  net/bridge/br_input.c   | 31 ++++++++++++++++++++++++++++++-
>  net/bridge/br_mrp.c     | 19 +++++++++++++++----
>  net/bridge/br_private.h | 18 ++++++++++++------
>  4 files changed, 58 insertions(+), 11 deletions(-)
> 

Hi,
First I must say I do like this approach, thanks for generalizing it.
You can switch to a hlist so that there's just 1 pointer in the head.
I don't think you need list when you're walking only in one direction.
A few more minor comments below.

> diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
> index 9a2fb4aa1a10..a9232db03108 100644
> --- a/net/bridge/br_device.c
> +++ b/net/bridge/br_device.c
> @@ -473,6 +473,7 @@ void br_dev_setup(struct net_device *dev)
>  	spin_lock_init(&br->lock);
>  	INIT_LIST_HEAD(&br->port_list);
>  	INIT_HLIST_HEAD(&br->fdb_list);
> +	INIT_LIST_HEAD(&br->ftype_list);
>  #if IS_ENABLED(CONFIG_BRIDGE_MRP)
>  	INIT_LIST_HEAD(&br->mrp_list);
>  #endif
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index 59a318b9f646..0f475b21094c 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -254,6 +254,21 @@ static int nf_hook_bridge_pre(struct sk_buff *skb, struct sk_buff **pskb)
>  	return RX_HANDLER_CONSUMED;
>  }
>  
> +/* Return 0 if the frame was not processed otherwise 1
> + * note: already called with rcu_read_lock
> + */
> +static int br_process_frame_type(struct net_bridge_port *p,
> +				 struct sk_buff *skb)
> +{
> +	struct br_frame_type *tmp;
> +
> +	list_for_each_entry_rcu(tmp, &p->br->ftype_list, list) {
> +		if (unlikely(tmp->type == skb->protocol))
> +			return tmp->func(p, skb);
> +	}

Nit: you can drop the {}.

> +	return 0;
> +}
> +
>  /*
>   * Return NULL if skb is handled
>   * note: already called with rcu_read_lock
> @@ -343,7 +358,7 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
>  		}
>  	}
>  
> -	if (unlikely(br_mrp_process(p, skb)))
> +	if (unlikely(br_process_frame_type(p, skb)))
>  		return RX_HANDLER_PASS;
>  
>  forward:
> @@ -380,3 +395,17 @@ rx_handler_func_t *br_get_rx_handler(const struct net_device *dev)
>  
>  	return br_handle_frame;
>  }
> +
> +void br_add_frame(struct net_bridge *br, struct br_frame_type *ft)
> +{
> +	list_add_rcu(&ft->list, &br->ftype_list);
> +}
> +
> +void br_del_frame(struct net_bridge *br, struct br_frame_type *ft)
> +{
> +	struct br_frame_type *tmp;
> +
> +	list_for_each_entry(tmp, &br->ftype_list, list)
> +		if (ft == tmp)
> +			list_del_rcu(&ft->list);
> +}
> diff --git a/net/bridge/br_mrp.c b/net/bridge/br_mrp.c
> index b36689e6e7cb..0428e1785041 100644
> --- a/net/bridge/br_mrp.c
> +++ b/net/bridge/br_mrp.c
> @@ -6,6 +6,13 @@
>  static const u8 mrp_test_dmac[ETH_ALEN] = { 0x1, 0x15, 0x4e, 0x0, 0x0, 0x1 };
>  static const u8 mrp_in_test_dmac[ETH_ALEN] = { 0x1, 0x15, 0x4e, 0x0, 0x0, 0x3 };
>  
> +static int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb);
> +
> +static struct br_frame_type mrp_frame_type __read_mostly = {
> +	.type = cpu_to_be16(ETH_P_MRP),
> +	.func = br_mrp_process,
> +};
> +
>  static bool br_mrp_is_ring_port(struct net_bridge_port *p_port,
>  				struct net_bridge_port *s_port,
>  				struct net_bridge_port *port)
> @@ -445,6 +452,9 @@ static void br_mrp_del_impl(struct net_bridge *br, struct br_mrp *mrp)
>  
>  	list_del_rcu(&mrp->list);
>  	kfree_rcu(mrp, rcu);
> +
> +	if (list_empty(&br->mrp_list))
> +		br_del_frame(br, &mrp_frame_type);
>  }
>  
>  /* Adds a new MRP instance.
> @@ -493,6 +503,9 @@ int br_mrp_add(struct net_bridge *br, struct br_mrp_instance *instance)
>  	spin_unlock_bh(&br->lock);
>  	rcu_assign_pointer(mrp->s_port, p);
>  
> +	if (list_empty(&br->mrp_list))
> +		br_add_frame(br, &mrp_frame_type);
> +
>  	INIT_DELAYED_WORK(&mrp->test_work, br_mrp_test_work_expired);
>  	INIT_DELAYED_WORK(&mrp->in_test_work, br_mrp_in_test_work_expired);
>  	list_add_tail_rcu(&mrp->list, &br->mrp_list);
> @@ -1172,15 +1185,13 @@ static int br_mrp_rcv(struct net_bridge_port *p,
>   * normal forwarding.
>   * note: already called with rcu_read_lock
>   */
> -int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb)
> +static int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb)
>  {
>  	/* If there is no MRP instance do normal forwarding */
>  	if (likely(!(p->flags & BR_MRP_AWARE)))
>  		goto out;
>  
> -	if (unlikely(skb->protocol == htons(ETH_P_MRP)))
> -		return br_mrp_rcv(p, skb, p->dev);
> -
> +	return br_mrp_rcv(p, skb, p->dev);
>  out:
>  	return 0;
>  }
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index baa1500f384f..e67c6d9e8bea 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -89,6 +89,13 @@ struct bridge_mcast_stats {
>  };
>  #endif
>  
> +struct br_frame_type {
> +	__be16			type;
> +	int			(*func)(struct net_bridge_port *port,
> +					struct sk_buff *skb);

Perhaps frame_handler or something similar would be a better name for the
callback ?

> +	struct list_head	list;
> +};
> +
>  struct br_vlan_stats {
>  	u64 rx_bytes;
>  	u64 rx_packets;
> @@ -433,6 +440,8 @@ struct net_bridge {
>  #endif
>  	struct hlist_head		fdb_list;
>  
> +	struct list_head		ftype_list;

Could you please expand this to frame_type_list ?

> +
>  #if IS_ENABLED(CONFIG_BRIDGE_MRP)
>  	struct list_head		mrp_list;
>  #endif
> @@ -708,6 +717,9 @@ int nbp_backup_change(struct net_bridge_port *p, struct net_device *backup_dev);
>  int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb);
>  rx_handler_func_t *br_get_rx_handler(const struct net_device *dev);
>  
> +void br_add_frame(struct net_bridge *br, struct br_frame_type *ft);
> +void br_del_frame(struct net_bridge *br, struct br_frame_type *ft);
> +
>  static inline bool br_rx_handler_check_rcu(const struct net_device *dev)
>  {
>  	return rcu_dereference(dev->rx_handler) == br_get_rx_handler(dev);
> @@ -1320,7 +1332,6 @@ extern int (*br_fdb_test_addr_hook)(struct net_device *dev, unsigned char *addr)
>  #if IS_ENABLED(CONFIG_BRIDGE_MRP)
>  int br_mrp_parse(struct net_bridge *br, struct net_bridge_port *p,
>  		 struct nlattr *attr, int cmd, struct netlink_ext_ack *extack);
> -int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb);
>  bool br_mrp_enabled(struct net_bridge *br);
>  void br_mrp_port_del(struct net_bridge *br, struct net_bridge_port *p);
>  int br_mrp_fill_info(struct sk_buff *skb, struct net_bridge *br);
> @@ -1332,11 +1343,6 @@ static inline int br_mrp_parse(struct net_bridge *br, struct net_bridge_port *p,
>  	return -EOPNOTSUPP;
>  }
>  
> -static inline int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb)
> -{
> -	return 0;
> -}
> -
>  static inline bool br_mrp_enabled(struct net_bridge *br)
>  {
>  	return false;