netdev - Re: Receive offloads, small RCVBUF and zero TCP window

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Message-Id: <20161128.155459.1527519991492144879.davem@davemloft.net>
Date:   Mon, 28 Nov 2016 15:54:59 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     alexandre.sidorenko@....com
Cc:     netdev@...r.kernel.org
Subject: Re: Receive offloads, small RCVBUF and zero TCP window

From: Alex Sidorenko <alexandre.sidorenko@....com>
Date: Mon, 28 Nov 2016 15:49:26 -0500

> Now the question is whether is is OK to have icsk->icsk_ack.rcv_mss
> larger than MTU.

It absolutely is not OK.

If VMWare wants to receive large frames for batching purposes it must
use GRO or similar to achieve that, not just send vanilla frames into
the stack which are larger than the device MTU.