netdev - Re: [PATCH net v2] skbuff: Release nfct refcount on napi stolen or re-used skbs

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Date:   Mon, 5 Jul 2021 11:13:49 +0300
From:   Mika Penttilä <mika.penttila@...tfour.com>
To:     Paul Blakey <paulb@...dia.com>, netdev@...r.kernel.org,
        Eric Dumazet <eric.dumazet@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Oz Shlomo <ozsh@...dia.com>, Roi Dayan <roid@...dia.com>,
        Vlad Buslov <vladbu@...dia.com>
Subject: Re: [PATCH net v2] skbuff: Release nfct refcount on napi stolen or
 re-used skbs

Hi!

On 5.7.2021 10.49, Paul Blakey wrote:
> When multiple SKBs are merged to a new skb under napi GRO,
> or SKB is re-used by napi, if nfct was set for them in the
> driver, it will not be released while freeing their stolen
> head state or on re-use.
>
> Release nfct on napi's stolen or re-used SKBs, and
> in gro_list_prepare, check conntrack metadata diff.
>
> Fixes: 5c6b94604744 ("net/mlx5e: CT: Handle misses after executing CT action")
> Reviewed-by: Roi Dayan <roid@...dia.com>
> Signed-off-by: Paul Blakey <paulb@...dia.com>
> ---
> Changelog:
> 	v1->v2:
> 	 Check for different flows based on CT and chain metadata in gro_list_prepare
>
>   net/core/dev.c    | 13 +++++++++++++
>   net/core/skbuff.c |  1 +
>   2 files changed, 14 insertions(+)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 439faadab0c2..bf62cb2ec6da 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5981,6 +5981,18 @@ static void gro_list_prepare(const struct list_head *head,
>   			diffs = memcmp(skb_mac_header(p),
>   				       skb_mac_header(skb),
>   				       maclen);
> +
> +		diffs |= skb_get_nfct(p) ^ skb_get_nfct(skb);
> +
> +		if (!diffs) {
> +			struct tc_skb_ext *skb_ext = skb_ext_find(skb, TC_SKB_EXT);
> +			struct tc_skb_ext *p_ext = skb_ext_find(p, TC_SKB_EXT);
> +
> +			diffs |= (!!p_ext) ^ (!!skb_ext);
> +			if (!diffs && unlikely(skb_ext))
> +				diffs |= p_ext->chain ^ skb_ext->chain;
> +		}
> +
>   		NAPI_GRO_CB(p)->same_flow = !diffs;
>   	}
>   }
> @@ -6243,6 +6255,7 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
>   	skb_shinfo(skb)->gso_type = 0;
>   	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
>   	skb_ext_reset(skb);
> +	nf_reset_ct(skb);
>   
>   	napi->skb = skb;
>   }
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index bbc3b4b62032..239eb2fba255 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -939,6 +939,7 @@ void __kfree_skb_defer(struct sk_buff *skb)
>   
>   void napi_skb_free_stolen_head(struct sk_buff *skb)
>   {
> +	nf_conntrack_put(skb_nfct(skb));

Should this be  nf_reset_ct() to clear the skb->_nfct and not leave a 
uncounted reference?

>   	skb_dst_drop(skb);
>   	skb_ext_put(skb);
>   	napi_skb_cache_put(skb);