netdev - Re: [net-next PATCH 0/2] GENEVE/VXLAN: Enable outer Tx checksum by default

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Message-Id: <20160224.104130.944927463190990372.davem@davemloft.net>
Date:	Wed, 24 Feb 2016 10:41:30 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	David.Laight@...LAB.COM
Cc:	jesse@...nel.org, tom@...bertland.com, ecree@...arflare.com,
	aduyck@...antis.com, netdev@...r.kernel.org,
	alexander.duyck@...il.com
Subject: Re: [net-next PATCH 0/2] GENEVE/VXLAN: Enable outer Tx checksum by
 default

From: David Laight <David.Laight@...LAB.COM>
Date: Wed, 24 Feb 2016 09:58:03 +0000

> From: David Miller
>> Sent: 23 February 2016 18:25
>> 
>> From: Jesse Gross <jesse@...nel.org>
>> Date: Tue, 23 Feb 2016 09:31:09 -0800
>> 
>> > Most OSs (including Linux with connected TCP sockets) use non-zero IP
>> > IDs so requiring this would effectively disable GRO.
>> 
>> +1
>> 
>> Any OS that wants to work with SLHC, as I mentioned, has to emit
>> monotonically increasing IP ID values in all packets, even those with
>> DF set.
> 
> Doesn't that leak a lot of info about the sending system?
> ISTR one OS deliberately randomising the IP ID values in order
> to avoid giving out information about the number of packets being sent.

The ID generater is per-flow, therefore I don't think this is an
issue.

And if it is an issue, then it exists for fragmented traffic on
every machine on the planet.