Re: [RFC PATCH net-next v3 2/5] flow_dissector: Add L2TPv3 dissectors

[Guillaume Nault <gnault@redhat.com>]

On Thu, Sep 01, 2022 at 02:01:28PM +0200, Wojciech Drewek wrote:
> Allow to dissect L2TPv3 specific field which is:
> - session ID (32 bits)
> 
> L2TPv3 might be transported over IP or over UDP,
> this ipmplementation is only about L2TPv3 over IP.
> IP protocold carries L2TPv3 when ip_proto is

Nit: you didn't fix the spelling of "protocold". It's probably not
worth to send a new version just because of this typo though.

> Acked-by: Guillaume Nault <gnault@redhat.com>
> Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
> ---
> v3: move !dissector_uses_key() check before calling
>     __skb_header_pointer
> ---
>  include/net/flow_dissector.h |  9 +++++++++
>  net/core/flow_dissector.c    | 28 ++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> index 6c74812d64b2..5ccf52ef8809 100644
> --- a/include/net/flow_dissector.h
> +++ b/include/net/flow_dissector.h
> @@ -289,6 +289,14 @@ struct flow_dissector_key_pppoe {
>  	__be16 type;
>  };
>  
> +/**
> + * struct flow_dissector_key_l2tpv3:
> + * @session_id: identifier for a l2tp session
> + */
> +struct flow_dissector_key_l2tpv3 {
> +	__be32 session_id;
> +};
> +
>  enum flow_dissector_key_id {
>  	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
>  	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
> @@ -320,6 +328,7 @@ enum flow_dissector_key_id {
>  	FLOW_DISSECTOR_KEY_HASH, /* struct flow_dissector_key_hash */
>  	FLOW_DISSECTOR_KEY_NUM_OF_VLANS, /* struct flow_dissector_key_num_of_vlans */
>  	FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe */
> +	FLOW_DISSECTOR_KEY_L2TPV3, /* struct flow_dissector_key_l2tpv3 */
>  
>  	FLOW_DISSECTOR_KEY_MAX,
>  };
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 764c4cb3fe8f..8180e65ab8e2 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -204,6 +204,30 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
>  	skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen);
>  }
>  
> +static void __skb_flow_dissect_l2tpv3(const struct sk_buff *skb,
> +				      struct flow_dissector *flow_dissector,
> +				      void *target_container, const void *data,
> +				      int nhoff, int hlen)
> +{
> +	struct flow_dissector_key_l2tpv3 *key_l2tpv3;
> +	struct {
> +		__be32 session_id;
> +	} *hdr, _hdr;
> +
> +	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_L2TPV3))
> +		return;
> +
> +	hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
> +	if (!hdr)
> +		return;
> +
> +	key_l2tpv3 = skb_flow_dissector_target(flow_dissector,
> +					       FLOW_DISSECTOR_KEY_L2TPV3,
> +					       target_container);
> +
> +	key_l2tpv3->session_id = hdr->session_id;
> +}
> +
>  void skb_flow_dissect_meta(const struct sk_buff *skb,
>  			   struct flow_dissector *flow_dissector,
>  			   void *target_container)
> @@ -1497,6 +1521,10 @@ bool __skb_flow_dissect(const struct net *net,
>  		__skb_flow_dissect_icmp(skb, flow_dissector, target_container,
>  					data, nhoff, hlen);
>  		break;
> +	case IPPROTO_L2TP:
> +		__skb_flow_dissect_l2tpv3(skb, flow_dissector, target_container,
> +					  data, nhoff, hlen);
> +		break;
>  
>  	default:
>  		break;
> -- 
> 2.31.1
>