netdev - Re: [PATCH v3] ipv4: Early TCP socket demux.

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Date:	Wed, 20 Jun 2012 10:00:37 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	David Miller <davem@...emloft.net>
cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v3] ipv4: Early TCP socket demux.


	Hello,

On Tue, 19 Jun 2012, David Miller wrote:

> +		if (sk->sk_state != TCP_TIME_WAIT) {
> +			struct dst_entry *dst = sk->sk_rx_dst;
> +			if (dst)
> +				dst = dst_check(dst, 0);

	What about checking rp_filter here or before dst_check:

			rcu_read_lock();
			in_dev = __in_dev_get_rcu(dst->dev);
			if (skb->dev != dst->dev &&
			    (!in_dev || IN_DEV_RPFILTER(in_dev)))
				dst = NULL;
			rcu_read_unlock();

	But may be it is a bad idea to return cached dst
that is with different dev. May be it is better a simple
check instead:

			if (skb->dev != dst->dev)
				dst = NULL;

	It will work for the common case of traffic using
same dev.

> +			if (dst) {
> +				skb_dst_set_noref(skb, dst);
> +				err = 0;
> +			}

	Also, is it a good idea to hide such optimizations
in a bit mask:

sysctl_net_optimizations & 1: optimize for end host
sysctl_net_optimizations & 2: optimize for router
...

Regards

--
Julian Anastasov <ja@....bg>
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