From: Oliver Hartkopp <socketcan@hartkopp•net>
To: Jiri Pirko <jiri@resnulli•us>
Cc: David Miller <davem@davemloft•net>,
Linux Netdev List <netdev@vger•kernel.org>
Subject: Re: [RFC davem] revert: net: Make skb->skb_iif always track skb->dev
Date: Sat, 12 Jan 2013 21:14:25 +0100 [thread overview]
Message-ID: <50F1C421.7080501@hartkopp.net> (raw)
In-Reply-To: <20130112193728.GB1567@minipsycho.orion>
On 12.01.2013 20:37, Jiri Pirko wrote:
> Sat, Jan 12, 2013 at 07:40:33PM CET, socketcan@hartkopp•net wrote:
>> An there i wanted to add this code to omit sending the CAN frame on the
>> originating interface:
>>
>> @@ .. @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data
>>
>> if (!(gwj->dst.dev->flags & IFF_UP)) {
>> gwj->dropped_frames++;
>> return;
>> }
>>
>> + /* is sending the skb back to the incoming interface allowed? */
>> + if (!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK) &&
>> + skb->skb_iif == gwj->dst.dev->ifindex)
>> + return;
>> +
>> /*
>> * clone the given skb, which has not been done in can_rcv()
>> *
>>
>> This works fine, when the patch from Dave is reverted.
>>
>> I did not find any good solution to preserve the originating netdev over
>> several netif_receive_skb() calls - but this skb_iif which has been made
>> unusable ...
>
>
>
> Well, look at struct receiver in net/can/af_can.h:
>
> struct receiver {
> struct hlist_node list;
> struct rcu_head rcu;
> canid_t can_id;
> canid_t mask;
> unsigned long matches;
> void (*func)(struct sk_buff *, void *);
> void *data;
> char *ident;
> };
>
> your can_can_gw_rcv() is callback registered as ->func here.
> This ->func is called from chain can_rcv->can_receive->can_rcv_filter->deliver
>
> So just extend
> ->func to something like:
>
> void (*func)(struct sk_buff *, struct neti_device *orig_dev, void *);
> and pass the orig_dev all the way through the chain.
>
Passing the information up to the can-gw once is not the problem.
But when this skb has to be routed to another CAN netdev it is cloned and goes
down from can_can_gw_rcv() to
-> can_send(cloned_skb) -> dev_queue_xmit(cloned_skb)
And when it has been sent successfully on the CAN bus the cloned_skb is echoed
back into the system via netif_rx_ni(cloned_skb).
(see http://lxr.linux.no/#linux+v3.7.2/Documentation/networking/can.txt#L177 )
This entire path - using dev_queue_xmit() / netif_rx_ni() - is reduced to a
skb structure and can not deal with any orig_dev pointer.
Therefore storing the first incoming interface in skb_iif is relevant for this
use-case.
Regards,
Oliver
next prev parent reply other threads:[~2013-01-12 20:14 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-12 13:48 [RFC davem] revert: net: Make skb->skb_iif always track skb->dev Oliver Hartkopp
2013-01-12 18:13 ` Jiri Pirko
2013-01-12 18:40 ` Oliver Hartkopp
2013-01-12 19:37 ` Jiri Pirko
2013-01-12 20:14 ` Oliver Hartkopp [this message]
2013-01-12 21:23 ` David Miller
2013-01-12 21:36 ` David Miller
2013-01-13 3:06 ` [PATCH net-next] pkt_sched: namespace aware ifb Eric Dumazet
2013-01-13 3:50 ` Benjamin LaHaise
2013-01-13 5:49 ` Eric Dumazet
2013-01-13 14:44 ` Jamal Hadi Salim
2013-01-13 16:41 ` Benjamin LaHaise
2013-01-13 16:57 ` Eric Dumazet
2013-01-13 17:25 ` Jamal Hadi Salim
2013-01-14 5:40 ` Eric Dumazet
2013-01-13 17:46 ` [PATCH net-next] ifb: dont hard code inet_net use Eric Dumazet
2013-01-14 13:13 ` Jamal Hadi Salim
2013-01-14 15:15 ` [PATCH net-next] pkt_sched: namespace aware act_mirred Benjamin LaHaise
2013-01-14 20:10 ` David Miller
2013-01-14 20:13 ` [PATCH net-next] ifb: dont hard code inet_net use David Miller
2013-01-13 14:59 ` [PATCH net-next] pkt_sched: namespace aware ifb Benjamin LaHaise
2013-01-13 16:35 ` Eric Dumazet
2013-01-13 11:01 ` [RFC davem] revert: net: Make skb->skb_iif always track skb->dev Oliver Hartkopp
2013-01-13 13:20 ` David Miller
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