netdev - Re: [PATCH net] net: ipv4: use a dedicated counter for icmp

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Date:   Fri, 08 Feb 2019 21:50:51 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     lorenzo.bianconi@...hat.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] net: ipv4: use a dedicated counter for icmp_v4
 redirect packets

From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Date: Wed,  6 Feb 2019 19:18:04 +0100

> According to the algorithm described in the comment block at the
> beginning of ip_rt_send_redirect, the host should try to send
> 'ip_rt_redirect_number' ICMP redirect packets with an exponential
> backoff and then stop sending them at all assuming that the destination
> ignores redirects.
> If the device has previously sent some ICMP error packets that are
> rate-limited (e.g TTL expired) and continues to receive traffic,
> the redirect packets will never be transmitted. This happens since
> peer->rate_tokens will be typically greater than 'ip_rt_redirect_number'
> and so it will never be reset even if the redirect silence timeout
> (ip_rt_redirect_silence) has elapsed without receiving any packet
> requiring redirects.
> 
> Fix it by using a dedicated counter for the number of ICMP redirect
> packets that has been sent by the host
> 
> I have not been able to identify a given commit that introduced the
> issue since ip_rt_send_redirect implements the same rate-limiting
> algorithm from commit 1da177e4c3f4 ("Linux-2.6.12-rc2")
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>

Applied and queued up for -stable, thanks.