Merge branch 'for_rmk' of git://git.linaro.org/kernel/linux-linaro-next into devel-stable

1 files changed, 16 insertions, 2 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index eaa9582779d0..3e4b33e36602 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -475,8 +475,22 @@ extern unsigned int tcp_current_mss(struct sock *sk);
 /* Bound MSS / TSO packet size with the half of the window */
 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
 {
-        if (tp->max_window && pktsize > (tp->max_window >> 1))
-                return max(tp->max_window >> 1, 68U - tp->tcp_header_len);
+        int cutoff;
+
+        /* When peer uses tiny windows, there is no use in packetizing
+         * to sub-MSS pieces for the sake of SWS or making sure there
+         * are enough packets in the pipe for fast recovery.
+         *
+         * On the other hand, for extremely large MSS devices, handling
+         * smaller than MSS windows in this way does make sense.
+         */
+        if (tp->max_window >= 512)
+                cutoff = (tp->max_window >> 1);
+        else
+                cutoff = tp->max_window;
+
+        if (cutoff && pktsize > cutoff)
+                return max_t(int, cutoff, 68U - tp->tcp_header_len);
         else
                 return pktsize;
 }