* [PATCH v2 net] tcp: consider recv buf for the initial window scale
@ 2016-07-29 13:34 Soheil Hassas Yeganeh
2016-07-29 13:39 ` Neal Cardwell
2016-07-31 4:22 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Soheil Hassas Yeganeh @ 2016-07-29 13:34 UTC (permalink / raw)
To: davem, netdev; +Cc: edumazet, ycheng, ncardwell, Soheil Hassas Yeganeh
From: Soheil Hassas Yeganeh <soheil@google.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@google.com>
Suggested-by: Neal Cardwell <ncardwell@google.com>
---
net/ipv4/tcp_output.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b26aa87..bdaef7f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -236,7 +236,8 @@ void tcp_select_initial_window(int __space, __u32 mss,
/* Set window scaling on max possible window
* See RFC1323 for an explanation of the limit to 14
*/
- space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
+ space = max_t(u32, space, sysctl_tcp_rmem[2]);
+ space = max_t(u32, space, sysctl_rmem_max);
space = min_t(u32, space, *window_clamp);
while (space > 65535 && (*rcv_wscale) < 14) {
space >>= 1;
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 net] tcp: consider recv buf for the initial window scale
2016-07-29 13:34 [PATCH v2 net] tcp: consider recv buf for the initial window scale Soheil Hassas Yeganeh
@ 2016-07-29 13:39 ` Neal Cardwell
2016-07-31 4:22 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Neal Cardwell @ 2016-07-29 13:39 UTC (permalink / raw)
To: Soheil Hassas Yeganeh
Cc: David Miller, Netdev, Eric Dumazet, Yuchung Cheng, Soheil Hassas Yeganeh
On Fri, Jul 29, 2016 at 9:34 AM, Soheil Hassas Yeganeh
<soheil.kdev@gmail.com> wrote:
> 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@google.com>
> Suggested-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Thanks, Soheil.
neal
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 net] tcp: consider recv buf for the initial window scale
2016-07-29 13:34 [PATCH v2 net] tcp: consider recv buf for the initial window scale Soheil Hassas Yeganeh
2016-07-29 13:39 ` Neal Cardwell
@ 2016-07-31 4:22 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2016-07-31 4:22 UTC (permalink / raw)
To: soheil.kdev; +Cc: netdev, edumazet, ycheng, ncardwell, soheil
From: Soheil Hassas Yeganeh <soheil.kdev@gmail.com>
Date: Fri, 29 Jul 2016 09:34:02 -0400
> From: Soheil Hassas Yeganeh <soheil@google.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@google.com>
> Suggested-by: Neal Cardwell <ncardwell@google.com>
Applied, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-07-29 13:34 [PATCH v2 net] tcp: consider recv buf for the initial window scale Soheil Hassas Yeganeh
2016-07-29 13:39 ` Neal Cardwell
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