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authorSoheil Hassas Yeganeh <soheil@google.com>2016-07-29 09:34:02 -0400
committerDavid S. Miller <davem@davemloft.net>2016-07-30 21:21:57 -0700
commitf626300a3e776ccc9671b0dd94698fb3aa315966 (patch)
tree032f554f8c42e31904c8c11856945c70244441cb /net
parentc27bdce2b916b01c27615467c69d357d3426c42f (diff)
downloadlinux-f626300a3e776ccc9671b0dd94698fb3aa315966.tar.gz
tcp: consider recv buf for the initial window scale
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>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_output.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b26aa870adc0..bdaef7fd6e47 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;