[CCID3]: Accurately determine idle & application-limited periods

This fixes/updates the handling of idle and application-limited periods in CCID3,
which currently is broken: there is no detection as to how long a sender has been
idle - there is only one flag which is toggled in between function calls.

Being obsolete now, the `idle' flag is removed.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 10 insertions, 10 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index c025236ce49b..94a322863844 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -119,6 +119,13 @@ static inline void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx)
 
 }
 
+static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
+{
+        u32 delta = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count);
+
+        return delta / hctx->ccid3hctx_rtt;
+}
+
 /**
  * ccid3_hc_tx_update_x  -  Update allowed sending rate X
  * @stamp: most recent time if available - can be left NULL.
@@ -139,10 +146,11 @@ static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
 
         /*
          * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
-         * when idling [RFC 4342, 5.1]. See also draft-ietf-dccp-rfc3448bis.
+         * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
+         * a sender is idle if it has not sent anything over a 2-RTT-period.
          * For consistency with X and X_recv, min_rate is also scaled by 2^6.
          */
-        if (unlikely(hctx->ccid3hctx_idle)) {
+        if (ccid3_hc_tx_idle_rtt(hctx, now) >= 2) {
                 min_rate = rfc3390_initial_rate(sk);
                 min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
         }
@@ -228,8 +236,6 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
         ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
                        ccid3_tx_state_name(hctx->ccid3hctx_state));
 
-        hctx->ccid3hctx_idle = 1;
-
         switch (hctx->ccid3hctx_state) {
         case TFRC_SSTATE_NO_FBACK:
                 /* RFC 3448, 4.4: Halve send rate directly */
@@ -372,7 +378,6 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
         /* prepare to send now (add options etc.) */
         dp->dccps_hc_tx_insert_options = 1;
         DCCP_SKB_CB(skb)->dccpd_ccval = hctx->ccid3hctx_last_win_count;
-        hctx->ccid3hctx_idle = 0;
 
         /* set the nominal send time for the next following packet */
         hctx->ccid3hctx_t_nom = ktime_add_us(hctx->ccid3hctx_t_nom,
@@ -531,9 +536,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 
                 sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
                                    jiffies + usecs_to_jiffies(t_nfb));
-
-                /* set idle flag */
-                hctx->ccid3hctx_idle = 1;
                 break;
         case TFRC_SSTATE_NO_SENT:       /* fall through */
         case TFRC_SSTATE_TERM:          /* ignore feedback when closing */
diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h
index 83467c34ed2b..36eca34228f0 100644
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -88,7 +88,6 @@ enum ccid3_hc_tx_states {
  * @ccid3hctx_t_last_win_count - Timestamp of earliest packet
  *                               with last_win_count value sent
  * @ccid3hctx_no_feedback_timer - Handle to no feedback timer
- * @ccid3hctx_idle - Flag indicating that sender is idling
  * @ccid3hctx_t_ld - Time last doubled during slow start
  * @ccid3hctx_t_nom - Nominal send time of next packet
  * @ccid3hctx_delta - Send timer delta (RFC 3448, 4.6) in usecs
@@ -107,7 +106,6 @@ struct ccid3_hc_tx_sock {
         u16                             ccid3hctx_s;
         enum ccid3_hc_tx_states         ccid3hctx_state:8;
         u8                              ccid3hctx_last_win_count;
-        u8                              ccid3hctx_idle;
         ktime_t                         ccid3hctx_t_last_win_count;
         struct timer_list               ccid3hctx_no_feedback_timer;
         ktime_t                         ccid3hctx_t_ld;