Re: [PATCH net-next] net: openvswitch: Set OvS recirc_id from tc chain index

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Wed, Aug 07, 2019 at 03:08:42PM +0300, Paul Blakey wrote:
> Offloaded OvS datapath rules are translated one to one to tc rules,
> for example the following simplified OvS rule:
> 
> recirc_id(0),in_port(dev1),eth_type(0x0800),ct_state(-trk) actions:ct(),recirc(2)
> 
> Will be translated to the following tc rule:
> 
> $ tc filter add dev dev1 ingress \
> 	    prio 1 chain 0 proto ip \
> 		flower tcp ct_state -trk \
> 		action ct pipe \
> 		action goto chain 2
> 
> Received packets will first travel though tc, and if they aren't stolen
> by it, like in the above rule, they will continue to OvS datapath.
> Since we already did some actions (action ct in this case) which might
> modify the packets, and updated action stats, we would like to continue
> the proccessing with the correct recirc_id in OvS (here recirc_id(2))
> where we left off.
> 
> To support this, introduce a new skb extension for tc, which
> will be used for translating tc chain to ovs recirc_id to
> handle these miss cases. Last tc chain index will be set
> by tc goto chain action and read by OvS datapath.
> 
> Signed-off-by: Paul Blakey <paulb@mellanox.com>
> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
> Acked-by: Jiri Pirko <jiri@mellanox.com>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

> ---
>  include/linux/skbuff.h    | 13 +++++++++++++
>  include/net/sch_generic.h |  5 ++++-
>  net/core/skbuff.c         |  6 ++++++
>  net/openvswitch/flow.c    |  9 +++++++++
>  net/sched/Kconfig         | 13 +++++++++++++
>  net/sched/act_api.c       |  1 +
>  net/sched/cls_api.c       | 12 ++++++++++++
>  7 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 3aef8d8..fb2a792 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -279,6 +279,16 @@ struct nf_bridge_info {
>  };
>  #endif
>  
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +/* Chain in tc_skb_ext will be used to share the tc chain with
> + * ovs recirc_id. It will be set to the current chain by tc
> + * and read by ovs to recirc_id.
> + */
> +struct tc_skb_ext {
> +	__u32 chain;
> +};
> +#endif
> +
>  struct sk_buff_head {
>  	/* These two members must be first. */
>  	struct sk_buff	*next;
> @@ -4050,6 +4060,9 @@ enum skb_ext_id {
>  #ifdef CONFIG_XFRM
>  	SKB_EXT_SEC_PATH,
>  #endif
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +	TC_SKB_EXT,
> +#endif
>  	SKB_EXT_NUM, /* must be last */
>  };
>  
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index 6b6b012..871feea 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -275,7 +275,10 @@ struct tcf_result {
>  			unsigned long	class;
>  			u32		classid;
>  		};
> -		const struct tcf_proto *goto_tp;
> +		struct {
> +			const struct tcf_proto *goto_tp;
> +			u32 goto_index;
> +		};
>  
>  		/* used in the skb_tc_reinsert function */
>  		struct {
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index ea8e8d3..2b40b5a 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -4087,6 +4087,9 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
>  #ifdef CONFIG_XFRM
>  	[SKB_EXT_SEC_PATH] = SKB_EXT_CHUNKSIZEOF(struct sec_path),
>  #endif
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +	[TC_SKB_EXT] = SKB_EXT_CHUNKSIZEOF(struct tc_skb_ext),
> +#endif
>  };
>  
>  static __always_inline unsigned int skb_ext_total_length(void)
> @@ -4098,6 +4101,9 @@ static __always_inline unsigned int skb_ext_total_length(void)
>  #ifdef CONFIG_XFRM
>  		skb_ext_type_len[SKB_EXT_SEC_PATH] +
>  #endif
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +		skb_ext_type_len[TC_SKB_EXT] +
> +#endif
>  		0;
>  }
>  
> diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
> index bc89e16..0287ead 100644
> --- a/net/openvswitch/flow.c
> +++ b/net/openvswitch/flow.c
> @@ -816,6 +816,9 @@ static int key_extract_mac_proto(struct sk_buff *skb)
>  int ovs_flow_key_extract(const struct ip_tunnel_info *tun_info,
>  			 struct sk_buff *skb, struct sw_flow_key *key)
>  {
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +	struct tc_skb_ext *tc_ext;
> +#endif
>  	int res, err;
>  
>  	/* Extract metadata from packet. */
> @@ -848,7 +851,13 @@ int ovs_flow_key_extract(const struct ip_tunnel_info *tun_info,
>  	if (res < 0)
>  		return res;
>  	key->mac_proto = res;
> +
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +	tc_ext = skb_ext_find(skb, TC_SKB_EXT);
> +	key->recirc_id = tc_ext ? tc_ext->chain : 0;
> +#else
>  	key->recirc_id = 0;
> +#endif
>  
>  	err = key_extract(skb, key);
>  	if (!err)
> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
> index afd2ba1..b3faafe 100644
> --- a/net/sched/Kconfig
> +++ b/net/sched/Kconfig
> @@ -963,6 +963,19 @@ config NET_IFE_SKBTCINDEX
>          tristate "Support to encoding decoding skb tcindex on IFE action"
>          depends on NET_ACT_IFE
>  
> +config NET_TC_SKB_EXT
> +	bool "TC recirculation support"
> +	depends on NET_CLS_ACT
> +	default y if NET_CLS_ACT
> +	select SKB_EXTENSIONS
> +
> +	help
> +	  Say Y here to allow tc chain misses to continue in OvS datapath in
> +	  the correct recirc_id, and hardware chain misses to continue in
> +	  the correct chain in tc software datapath.
> +
> +	  Say N here if you won't be using tc<->ovs offload or tc chains offload.
> +
>  endif # NET_SCHED
>  
>  config NET_SCH_FIFO
> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> index 3397122..c393604 100644
> --- a/net/sched/act_api.c
> +++ b/net/sched/act_api.c
> @@ -27,6 +27,7 @@ static void tcf_action_goto_chain_exec(const struct tc_action *a,
>  {
>  	const struct tcf_chain *chain = rcu_dereference_bh(a->goto_chain);
>  
> +	res->goto_index = chain->index;
>  	res->goto_tp = rcu_dereference_bh(chain->filter_chain);
>  }
>  
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 3565d9a..b0b829a 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -1660,6 +1660,18 @@ int tcf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
>  			goto reset;
>  		} else if (unlikely(TC_ACT_EXT_CMP(err, TC_ACT_GOTO_CHAIN))) {
>  			first_tp = res->goto_tp;
> +
> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
> +			{
> +				struct tc_skb_ext *ext;
> +
> +				ext = skb_ext_add(skb, TC_SKB_EXT);
> +				if (WARN_ON_ONCE(!ext))
> +					return TC_ACT_SHOT;
> +
> +				ext->chain = res->goto_index;
> +			}
> +#endif
>  			goto reset;
>  		}
>  #endif
> -- 
> 1.8.3.1
>