netdev - Re: [PATCH net v2] ipv4: try to cache dst_entries which would cause a redirect

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Message-ID: <alpine.LFD.2.11.1501222135140.2572@ja.home.ssi.bg>
Date:	Thu, 22 Jan 2015 21:57:14 +0200 (EET)
From:	Julian Anastasov <ja@....bg>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
cc:	netdev@...r.kernel.org, Marcelo Leitner <mleitner@...hat.com>,
	Florian Westphal <fw@...len.de>
Subject: Re: [PATCH net v2] ipv4: try to cache dst_entries which would cause
 a redirect


	Hello,

On Thu, 22 Jan 2015, Hannes Frederic Sowa wrote:

> I would try to not introduce this complexity. I am currently researching
> if this change does improve things:
> 
>         do_cache = res->fi && !itag;
> -       if (out_dev == in_dev && err && IN_DEV_TX_REDIRECTS(out_dev) &&
> -           (IN_DEV_SHARED_MEDIA(out_dev) ||
> -            inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res)))) {
> -               flags |= RTCF_DOREDIRECT;
> -               do_cache = false;
> +       if (skb->protocol == htons(ETH_P_IP)) {
> +               if (out_dev == in_dev && err && IN_DEV_TX_REDIRECTS(out_dev) &&
> +                   skb->protocol == htons(ETH_P_IP) &&

	Above is duplicate. Or better to remove first
and to keep this second check if flag is not cleared below...

> +                   (IN_DEV_SHARED_MEDIA(out_dev) ||
> +                    inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res))))
> +                       IPCB(skb)->flags |= IPSKB_DOREDIRECT;
> +               else if (IPCB(skb)->flags & IPSKB_DOREDIRECT)
> +                       IPCB(skb)->flags &= ~IPSKB_DOREDIRECT;

	It seems we do not need to clear the flag for
ip_options_rcv_srr purposes because ip_route_input is called
only if initial rt_type is RTN_LOCAL, so the flag should be
unset. ip_mkroute_input/__mkroute_input is called only for
forwarding.

	In ip_options_rcv_srr we have RTN_LOCAL ... [RTN_LOCAL]
and may be final RTN_UNICAST. The flag can be set and used
only for RTN_UNICAST and that is the final ip_route_input
called there. Lets keep it just with the 2nd ETH_P_IP check?

Regards

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