netdev - Re: [PATCH net-next 1/4] flow_dissector: add meaningful comments

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Date:   Wed, 23 Oct 2019 11:57:15 +0200
From:   Simon Horman <simon.horman@...ronome.com>
To:     Matteo Croce <mcroce@...hat.com>
Cc:     netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S . Miller " <davem@...emloft.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Paul Blakey <paulb@...lanox.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/4] flow_dissector: add meaningful comments

On Mon, Oct 21, 2019 at 10:09:45PM +0200, Matteo Croce wrote:
> Documents two piece of code which can't be understood at a glance.
> 
> Signed-off-by: Matteo Croce <mcroce@...hat.com>

Reviewed-by: Simon Horman <simon.horman@...ronome.com>

> ---
>  include/net/flow_dissector.h | 1 +
>  net/core/flow_dissector.c    | 6 ++++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> index 90bd210be060..7747af3cc500 100644
> --- a/include/net/flow_dissector.h
> +++ b/include/net/flow_dissector.h
> @@ -282,6 +282,7 @@ struct flow_keys {
>  	struct flow_dissector_key_vlan cvlan;
>  	struct flow_dissector_key_keyid keyid;
>  	struct flow_dissector_key_ports ports;
> +	/* 'addrs' must be the last member */
>  	struct flow_dissector_key_addrs addrs;
>  };
>  
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 7c09d87d3269..affde70dad47 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -1374,6 +1374,9 @@ static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
>  {
>  	size_t diff = FLOW_KEYS_HASH_OFFSET + sizeof(flow->addrs);
>  	BUILD_BUG_ON((sizeof(*flow) - FLOW_KEYS_HASH_OFFSET) % sizeof(u32));
> +	/* flow.addrs MUST be the last member in struct flow_keys because
> +	 * different L3 protocols have different address length
> +	 */
>  	BUILD_BUG_ON(offsetof(typeof(*flow), addrs) !=
>  		     sizeof(*flow) - sizeof(flow->addrs));
>  
> @@ -1421,6 +1424,9 @@ __be32 flow_get_u32_dst(const struct flow_keys *flow)
>  }
>  EXPORT_SYMBOL(flow_get_u32_dst);
>  
> +/* Sort the source and destination IP (and the ports if the IP are the same),
> + * to have consistent hash within the two directions
> + */
>  static inline void __flow_hash_consistentify(struct flow_keys *keys)
>  {
>  	int addr_diff, i;
> -- 
> 2.21.0
>