SCTP: calculate RTO / RTT and RTTVAR as per RFC
This patch addresses the need to calculate the RTO / RTT and RTTVAR
according to the rules depicted by the RFC4960 at section 6.3.1
Change-Id: I1d346f3c67610070b3f602f32c7738d58b99ffed
Signed-off-by: Marco Varlese <marco.varlese@suse.com>
diff --git a/src/vnet/sctp/sctp.h b/src/vnet/sctp/sctp.h
index 8f80d84..0634f01 100644
--- a/src/vnet/sctp/sctp.h
+++ b/src/vnet/sctp/sctp.h
@@ -79,9 +79,11 @@
u32 cwnd; /**< The current congestion window. */
u32 ssthresh; /**< The current ssthresh value. */
+ u32 rtt_ts; /**< USED to hold the timestamp of when the packet has been sent */
+
u32 RTO; /**< The current retransmission timeout value. */
u32 SRTT; /**< The current smoothed round-trip time. */
- u32 RTTVAR; /**< The current RTT variation. */
+ f32 RTTVAR; /**< The current RTT variation. */
u32 partially_acked_bytes; /**< The tracking method for increase of cwnd when in
congestion avoidance mode (see Section 7.2.2).*/
@@ -195,9 +197,6 @@
u32 rcv_a_rwnd; /**< LOCAL max seg size that includes options. To be updated by congestion algos, etc. */
u32 snd_a_rwnd; /**< REMOTE max seg size that includes options. To be updated if peer pushes back on window, etc.*/
- u32 rtt_ts;
- u32 rtt_seq;
-
u8 overall_sending_status; /**< 0 indicates first fragment of a user message
1 indicates normal stream
2 indicates last fragment of a user message */
@@ -523,7 +522,7 @@
SCTP_TIMER_HANDLE_INVALID);
sctp_sub_connection_t *sub = &tc->sub_conn[conn_idx];
- tc->sub_conn[conn_idx].timers[timer_id] =
+ sub->timers[timer_id] =
tw_timer_start_16t_2w_512sl (&sctp_main.timer_wheels[sub->c_thread_index],
sub->c_c_index, timer_id, interval);
}
@@ -542,15 +541,6 @@
sub->timers[timer_id] = SCTP_TIMER_HANDLE_INVALID;
}
-always_inline void
-sctp_update_time (f64 now, u32 thread_index)
-{
- sctp_set_time_now (thread_index);
- tw_timer_expire_timers_16t_2w_512sl (&sctp_main.timer_wheels[thread_index],
- now);
- sctp_flush_frames_to_output (thread_index);
-}
-
/**
* Try to cleanup half-open connection
*
@@ -599,6 +589,61 @@
return sctp_main.time_now[vlib_get_thread_index ()];
}
+#define ABS(x) ((x) > 0) ? (x) : -(x);
+
+always_inline void
+sctp_calculate_rto (sctp_connection_t * sctp_conn, u8 conn_idx)
+{
+ /* See RFC4960, 6.3.1. RTO Calculation */
+ u32 RTO = 0;
+ f32 RTTVAR = 0;
+ u32 now = sctp_time_now ();
+ u32 prev_ts = sctp_conn->sub_conn[conn_idx].rtt_ts;
+ u32 R = prev_ts - now;
+
+ if (sctp_conn->sub_conn[conn_idx].RTO == 0) // C1: Let's initialize our RTO
+ {
+ sctp_conn->sub_conn[conn_idx].RTO = SCTP_RTO_MIN;
+ return;
+ }
+
+ if (sctp_conn->sub_conn[conn_idx].RTO == SCTP_RTO_MIN && sctp_conn->sub_conn[conn_idx].SRTT == 0) // C2: First RTT calculation
+ {
+ sctp_conn->sub_conn[conn_idx].SRTT = R;
+ RTTVAR = R / 2;
+
+ if (RTTVAR == 0)
+ RTTVAR = 100e-3; /* 100 ms */
+
+ sctp_conn->sub_conn[conn_idx].RTTVAR = RTTVAR;
+ }
+ else // C3: RTT already exists; let's recalculate
+ {
+ RTTVAR = (1 - SCTP_RTO_BETA) * sctp_conn->sub_conn[conn_idx].RTTVAR +
+ SCTP_RTO_BETA * ABS (sctp_conn->sub_conn[conn_idx].SRTT - R);
+
+ if (RTTVAR == 0)
+ RTTVAR = 100e-3; /* 100 ms */
+
+ sctp_conn->sub_conn[conn_idx].RTTVAR = RTTVAR;
+
+ sctp_conn->sub_conn[conn_idx].SRTT =
+ (1 - SCTP_RTO_ALPHA) * sctp_conn->sub_conn[conn_idx].SRTT +
+ SCTP_RTO_ALPHA * R;
+ }
+
+ RTO =
+ sctp_conn->sub_conn[conn_idx].SRTT +
+ 4 * sctp_conn->sub_conn[conn_idx].RTTVAR;
+ if (RTO < SCTP_RTO_MIN) // C6
+ RTO = SCTP_RTO_MIN;
+
+ if (RTO > SCTP_RTO_MAX) // C7
+ RTO = SCTP_RTO_MAX;
+
+ sctp_conn->sub_conn[conn_idx].RTO = RTO;
+}
+
always_inline void
sctp_timer_update (sctp_connection_t * tc, u8 conn_idx, u8 timer_id,
u32 interval)