netdev - Re: [PATCH net] sk_buff: drop all skb extensions on free and skb scrubbing

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Date:   Thu, 26 Sep 2019 10:24:37 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Cc:     steffen.klassert@...unet.com, paulb@...lanox.com,
        vladbu@...lanox.com
Subject: Re: [PATCH net] sk_buff: drop all skb extensions on free and skb
 scrubbing



On 9/26/19 7:18 AM, Florian Westphal wrote:
> Now that we have a 3rd extension, add a new helper that drops the
> extension space and use it when we need to scrub an sk_buff.
> 
> At this time, scrubbing clears secpath and bridge netfilter data, but
> retains the tc skb extension, after this patch all three get cleared.
> 
> NAPI reuse/free assumes we can only have a secpath attached to skb, but
> it seems better to clear all extensions there as well.
> 
> Fixes: 95a7233c452a ("net: openvswitch: Set OvS recirc_id from tc chain index")
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  include/linux/skbuff.h | 9 +++++++++
>  net/core/dev.c         | 4 ++--
>  net/core/skbuff.c      | 2 +-
>  3 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 907209c0794e..4debdd58a0ce 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -4144,8 +4144,17 @@ static inline void *skb_ext_find(const struct sk_buff *skb, enum skb_ext_id id)
>  
>  	return NULL;
>  }
> +
> +static inline void skb_ext_reset(struct sk_buff *skb)
> +{
> +	if (skb->active_extensions) {

This deserves an unlikely(skb->active_extensions) hint here ?

> +		__skb_ext_put(skb->extensions);
> +		skb->active_extensions = 0;
> +	}
> +}
>  #else
>  static inline void skb_ext_put(struct sk_buff *skb) {}
> +static inline void skb_ext_reset(struct sk_buff *skb) {}
>  static inline void skb_ext_del(struct sk_buff *skb, int unused) {}
>  static inline void __skb_ext_copy(struct sk_buff *d, const struct sk_buff *s) {}
>  static inline void skb_ext_copy(struct sk_buff *dst, const struct sk_buff *s) {}
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 71b18e80389f..bf3ed413abaf 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5666,7 +5666,7 @@ EXPORT_SYMBOL(gro_find_complete_by_type);
>  static void napi_skb_free_stolen_head(struct sk_buff *skb)
>  {
>  	skb_dst_drop(skb);
> -	secpath_reset(skb);
> +	skb_ext_put(skb);
>  	kmem_cache_free(skbuff_head_cache, skb);
>  }
>  
> @@ -5733,7 +5733,7 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
>  	skb->encapsulation = 0;
>  	skb_shinfo(skb)->gso_type = 0;
>  	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
> -	secpath_reset(skb);
> +	skb_ext_reset(skb);
>  
>  	napi->skb = skb;
>  }
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index f12e8a050edb..01d65206f4fb 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5119,7 +5119,7 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)
>  	skb->skb_iif = 0;
>  	skb->ignore_df = 0;
>  	skb_dst_drop(skb);
> -	secpath_reset(skb);
> +	skb_ext_reset(skb);
>  	nf_reset(skb);
>  	nf_reset_trace(skb);
>  
>