Dang Nabbit.  Now that you say it, I can see it. Don' t know why I couldn't see 
it before.

Anyway, thanks Martin. I'm appreciating both the information and the tone of 
your reply.


--
Ricky Charlet

-----Original Message-----
From: Martin Willi [mailto:[email protected]] 
Sent: Thursday, January 23, 2014 10:47 PM
To: Charlet, Ricky
Cc: [email protected]
Subject: Re: [strongSwan-dev] Q: is ikev1 dpd sensitive to ipsec traffic as 
proof of liveness?

Hi,

> My question is if ikev1 dpd is sensitive to ipsec-sa (those ipsec-sas 
> known to be children of 'this' ike-sa) traffic as a proof of peer 
> liveness.

Yes, a DPD check is omitted if any traffic has been received recently on one of 
the CHILD_SAs/Quick Modes.

>                 last_in = get_use_time(this, TRUE);
>                 now = time_monotonic(NULL);
>                 diff = now - last_in;
>                 if (!delay || diff >= delay)
>                 {

> The relevant call to get_use_time above looks at a stat named 
> STAT_INBOUND on the ike sa which records the last time traffic was 
> observed. The calls to set_statistic(STAT_INBOUND) only occur in ike 
> message processing, as far as I can tell.

That mentioned get_use_time() function also queries all CHILD_SAs for the last 
inbound traffic. Each CHILD_SA then queries the IPsec backend (the kernel) for 
the last SA use.

Regards
Martin

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