netdev - Re: [PATCH v2 net] tcp: consider recv buf for the initial window scale

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Date:	Sat, 30 Jul 2016 21:22:21 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	soheil.kdev@...il.com
Cc:	netdev@...r.kernel.org, edumazet@...gle.com, ycheng@...gle.com,
	ncardwell@...gle.com, soheil@...gle.com
Subject: Re: [PATCH v2 net] tcp: consider recv buf for the initial window
 scale

From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Date: Fri, 29 Jul 2016 09:34:02 -0400

> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> tcp_select_initial_window() intends to advertise a window
> scaling for the maximum possible window size. To do so,
> it considers the maximum of net.ipv4.tcp_rmem[2] and
> net.core.rmem_max as the only possible upper-bounds.
> However, users with CAP_NET_ADMIN can use SO_RCVBUFFORCE
> to set the socket's receive buffer size to values
> larger than net.ipv4.tcp_rmem[2] and net.core.rmem_max.
> Thus, SO_RCVBUFFORCE is effectively ignored by
> tcp_select_initial_window().
> 
> To fix this, consider the maximum of net.ipv4.tcp_rmem[2],
> net.core.rmem_max and socket's initial buffer space.
> 
> Fixes: b0573dea1fb3 ("[NET]: Introduce SO_{SND,RCV}BUFFORCE socket options")
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Suggested-by: Neal Cardwell <ncardwell@...gle.com>

Applied, thanks.