netdev - Re: [net-next] tipc: fix node keep alive interval calculation

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Message-Id: <20181205.205252.715914017447325382.davem@davemloft.net>
Date:   Wed, 05 Dec 2018 20:52:52 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     hoang.h.le@...tech.com.au
Cc:     tipc-discussion@...ts.sourceforge.net, jon.maloy@...csson.com,
        maloy@...jonn.com, ying.xue@...driver.com, netdev@...r.kernel.org
Subject: Re: [net-next] tipc: fix node keep alive interval calculation

From: Hoang Le <hoang.h.le@...tech.com.au>
Date: Thu,  6 Dec 2018 09:00:09 +0700

> When setting LINK tolerance, node timer interval will be calculated
> base on the LINK with lowest tolerance.
> 
> But when calculated, the old node timer interval only updated if current
> setting value (tolerance/4) less than old ones regardless of number of
> links as well as links' lowest tolerance value.
> 
> This caused to two cases missing if tolerance changed as following:
> Case 1:
> 1.1/ There is one link (L1) available in the system
> 1.2/ Set L1's tolerance from 1500ms => lower (i.e 500ms)
> 1.3/ Then, fallback to default (1500ms) or higher (i.e 2000ms)
> 
> Expected:
>     node timer interval is 1500/4=375ms after 1.3
> 
> Result:
> node timer interval will not being updated after changing tolerance at 1.3
> since its value 1500/4=375ms is not less than 500/4=125ms at 1.2.
> 
> Case 2:
> 2.1/ There are two links (L1, L2) available in the system
> 2.2/ L1 and L2 tolerance value are 2000ms as initial
> 2.3/ Set L2's tolerance from 2000ms => lower 1500ms
> 2.4/ Disable link L2 (bring down its bearer)
> 
> Expected:
>     node timer interval is 2000ms/4=500ms after 2.4
> 
> Result:
> node timer interval will not being updated after disabling L2 since
> its value 2000ms/4=500ms is still not less than 1500/4=375ms at 2.3
> although L2 is already not available in the system.
> 
> To fix this, we start the node interval calculation by initializing it to
> a value larger than any conceivable calculated value. This way, the link
> with the lowest tolerance will always determine the calculated value.
> 
> Acked-by: Jon Maloy <jon.maloy@...csson.com>
> Signed-off-by: Hoang Le <hoang.h.le@...tech.com.au>

Applied, thank you.