net: TCP thin-stream detection

Inline function to dynamically detect thin streams based on
the number of packets in flight. Used to dynamically trigger
thin-stream mechanisms if enabled by ioctl or sysctl.

Signed-off-by: Andreas Petlund <apetlund@simula.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 75a00c80bdda..0bdc3f640247 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1386,6 +1386,14 @@ static inline void tcp_highest_sack_combine(struct sock *sk,
                 tcp_sk(sk)->highest_sack = new;
 }
 
+/* Determines whether this is a thin stream (which may suffer from
+ * increased latency). Used to trigger latency-reducing mechanisms.
+ */
+static inline unsigned int tcp_stream_is_thin(struct tcp_sock *tp)
+{
+        return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
+}
+
 /* /proc */
 enum tcp_seq_states {
         TCP_SEQ_STATE_LISTENING,