tcp: improve timestamp rtt accuracy

- switch to using vlib_time as reference for timestamps
- use us precision ticks for tcp but keep using ms precision for
timestamps. As a result, srtt, rttvar and rto are now measured in us
instead of ms. MRTT samples from timestamps are converted from ms to
us (not accurate under ms) while high precision samples are used with us
precision, i.e., they're no longer converted to ms precision samples.

Type: improvement

Change-Id: Ibda559575d9b4fdc85b0985264f7c865ff367e34
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/src/vnet/tcp/tcp.h b/src/vnet/tcp/tcp.h
index 91783a6e025..bc6e353b60e 100644
--- a/src/vnet/tcp/tcp.h
+++ b/src/vnet/tcp/tcp.h
@@ -91,7 +91,7 @@ typedef struct tcp_worker_ctx_
   /** convenience pointer to this thread's vlib main */
   vlib_main_t *vm;
 
-  /** worker time */
+  /** Time measured in @ref TCP_TSTAMP_TICK used for time stamps */
   u32 time_now;
 
   /* Max timers to be handled per dispatch loop */
@@ -209,8 +209,6 @@ typedef struct _tcp_main
   /* Pool of listeners. */
   tcp_connection_t *listener_pool;
 
-  f64 tstamp_ticks_per_clock;
-
   /** vlib buffer size */
   u32 bytes_per_buffer;