1 files changed, 25 insertions, 4 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index eaa9582779d0..4fee0424af7e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -346,8 +346,6 @@ static inline void tcp_dec_quickack_mode(struct sock *sk,
         }
 }
 
-extern void tcp_enter_quickack_mode(struct sock *sk);
-
 #define TCP_ECN_OK              1
 #define TCP_ECN_QUEUE_CWR       2
 #define TCP_ECN_DEMAND_CWR      4
@@ -475,8 +473,22 @@ 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;
 }
@@ -789,6 +801,15 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
 /* Use define here intentionally to get WARN_ON location shown at the caller */
 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
 
+/*
+ * Convert RFC 3390 larger initial window into an equivalent number of packets.
+ * This is based on the numbers specified in RFC 5681, 3.1.
+ */
+static inline u32 rfc3390_bytes_to_packets(const u32 smss)
+{
+        return smss <= 1095 ? 4 : (smss > 2190 ? 2 : 3);
+}
+
 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);