Subject: Re: [PATCH net-next 1/4] flow_keys: include thoff into flow_keys for later usage

From: Daniel Borkmann <[email-masked]>
Date: Tue, 19 Mar 2013 15:01:24 +0100

On 03/19/2013 02:55 PM, Eric Dumazet wrote:
> On Tue, 2013-03-19 at 14:28 +0100, Daniel Borkmann wrote:
>> In skb_flow_dissect(), we perform a dissection of a skbuff. Since we're
>> doing the work here anyway, also store thoff for a later usage, e.g. in
>> the BPF filter. We need to reorder choke_skb_cb a bit, though. Also, by
>> having thoff 16 Bit, we do not need to pack flow_keys.
>>
>> Suggested-by: Eric Dumazet <[email-masked]>
>> Signed-off-by: Daniel Borkmann <[email-masked]>
>> ---
>>   include/net/flow_keys.h   | 1 +
>>   net/core/flow_dissector.c | 5 ++++-
>>   net/sched/sch_choke.c     | 4 ++--
>>   3 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
>> index 80461c1..bb8271d 100644
>> --- a/include/net/flow_keys.h
>> +++ b/include/net/flow_keys.h
>> @@ -9,6 +9,7 @@ struct flow_keys {
>>   		__be32 ports;
>>   		__be16 port16[2];
>>   	};
>> +	u16 thoff;
>>   	u8 ip_proto;
>>   };
>>
>> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>> index f8d9e03..eb9dde1 100644
>> --- a/net/core/flow_dissector.c
>> +++ b/net/core/flow_dissector.c
>> @@ -23,7 +23,8 @@ static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *i
>>
>>   bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
>>   {
>> -	int poff, nhoff = skb_network_offset(skb);
>> +	int poff;
>> +	u16 nhoff = skb_network_offset(skb);
>>   	u8 ip_proto;
>>   	__be16 proto = skb->protocol;
>>
>> @@ -151,6 +152,8 @@ ipv6:
>>   			flow->ports = *ports;
>>   	}
>>
>> +	flow->thoff = nhoff;
>> +
>>   	return true;
>>   }
>>   EXPORT_SYMBOL(skb_flow_dissect);
>> diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
>> index cc37dd5..9854c2b 100644
>> --- a/net/sched/sch_choke.c
>> +++ b/net/sched/sch_choke.c
>> @@ -141,9 +141,9 @@ static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
>>   }
>>
>>   struct choke_skb_cb {
>> -	u16			classid;
>> -	u8			keys_valid;
>>   	struct flow_keys	keys;
>> +	u8			keys_valid;
>> +	u16			classid;
>>   };
>>
>>   static inline struct choke_skb_cb *choke_skb_cb(const struct sk_buff *skb)
>
> Hmm, we dont need to change choke_skb_cb, as the sizeof(keys) didnt
> change
>
> (its aligned on 4 bytes)
>
> The first version of the patch needed this because we were using an u32
> field for thoff

You're right. I will send a version 2 of this set in a while.