Commit f626300a authored by Soheil Hassas Yeganeh's avatar Soheil Hassas Yeganeh Committed by David S. Miller
Browse files

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

To fix this, consider the maximum of net.ipv4.tcp_rmem[2],
net.core.rmem_max and socket's initial buffer space.

Fixes: b0573dea

 ("[NET]: Introduce SO_{SND,RCV}BUFFORCE socket options")
Signed-off-by: default avatarSoheil Hassas Yeganeh <>
Suggested-by: default avatarNeal Cardwell <>
Acked-by: default avatarNeal Cardwell <>
Signed-off-by: default avatarDavid S. Miller <>
parent c27bdce2
......@@ -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;
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