dccp tfrc: Let dccp_tfrc_lib do the sampling work

This migrates more TFRC-related code into the dccp_tfrc_lib:
 * sampling of the packet size `s' (which is only needed until the first
   loss interval is computed (ccid3_first_li));
 * updating the byte-counter `bytes_recvd' in between sending feedbacks.
The result is a better separation of CCID-3 specific and TFRC specific
code, which aids future integration with ECN and e.g. CCID-4.

Further changes:
----------------
 * replaced magic number of 536 with equivalent constant TCP_MIN_RCVMSS;
   (this constant is also used when no estimate for `s' is available).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 50dac01e48c5e20c3c5434c9bfebfc9477004458..8744590acb34532aaf6c9bce5ce30536453b0959 100644 (file)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -590,12 +590,9 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
                         * would bring X down to s/t_mbi. That is why we return
                         * X_recv according to rfc3448bis-06 for the moment.
                         */
-                       u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT, s = hcrx->s;
+                       u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT,
+                           s   = tfrc_rx_hist_packet_size(&hcrx->hist);
 
-                       if (s == 0) {
-                               DCCP_WARN("No sample for s, using fallback\n");
-                               s = TCP_MIN_RCVMSS;
-                       }
                        hcrx->x_recv = scaled_div32(s, 2 * rtt);
                        break;
                }
@@ -617,7 +614,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
                if (delta <= 0)
                        DCCP_BUG("delta (%ld) <= 0", (long)delta);
                else
-                       hcrx->x_recv = scaled_div32(hcrx->bytes_recv, delta);
+                       hcrx->x_recv = scaled_div32(hcrx->hist.bytes_recvd, delta);
                break;
        default:
                return;
@@ -628,7 +625,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
 
        hcrx->tstamp_last_feedback = now;
        hcrx->last_counter         = dccp_hdr(skb)->dccph_ccval;
-       hcrx->bytes_recv           = 0;
+       hcrx->hist.bytes_recvd     = 0;
 
        dp->dccps_hc_rx_insert_options = 1;
        dccp_send_ack(sk);
@@ -669,7 +666,8 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
 static u32 ccid3_first_li(struct sock *sk)
 {
        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
-       u32 x_recv, p, delta;
+       u32 x_recv, p, delta,
+           s = tfrc_rx_hist_packet_size(&hcrx->hist);
        u64 fval;
 
        /*
@@ -686,7 +684,7 @@ static u32 ccid3_first_li(struct sock *sk)
        }
 
        delta = ktime_to_us(net_timedelta(hcrx->tstamp_last_feedback));
-       x_recv = scaled_div32(hcrx->bytes_recv, delta);
+       x_recv = scaled_div32(hcrx->hist.bytes_recvd, delta);
        if (x_recv == 0) {              /* would also trigger divide-by-zero */
                DCCP_WARN("X_recv==0\n");
                if (hcrx->x_recv == 0) {
@@ -696,8 +694,7 @@ static u32 ccid3_first_li(struct sock *sk)
                x_recv = hcrx->x_recv;
        }
 
-       fval = scaled_div(hcrx->s, hcrx->rtt);
-       fval = scaled_div32(fval, x_recv);
+       fval = scaled_div32(scaled_div(s, hcrx->rtt), x_recv);
        p = tfrc_calc_x_reverse_lookup(fval);
 
        ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
@@ -724,31 +721,12 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 
        if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
                if (is_data_packet) {
-                       const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
                        do_feedback = CCID3_FBACK_INITIAL;
                        ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
-                       hcrx->s = payload;
-                       /*
-                        * Not necessary to update bytes_recv here,
-                        * since X_recv = 0 for the first feedback packet (cf.
-                        * RFC 3448, 6.3) -- gerrit
-                        */
                }
                goto update_records;
        }
 
-       if (tfrc_rx_hist_duplicate(&hcrx->hist, skb))
-               return; /* done receiving */
-
-       if (is_data_packet) {
-               const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
-               /*
-                * Update moving-average of s and the sum of received payload bytes
-                */
-               hcrx->s = tfrc_ewma(hcrx->s, payload, 9);
-               hcrx->bytes_recv += payload;
-       }
-
        if (tfrc_rx_hist_loss_pending(&hcrx->hist))
                return; /* done receiving */
 

diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h
index 1773a8dd36d8323076a7920015f6a9cbeba48124..0c4fadd85f9416447e40e2c43cff540a7c4a0de2 100644 (file)
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -124,25 +124,21 @@ enum ccid3_hc_rx_states {
  *
  *  @last_counter  -  Tracks window counter (RFC 4342, 8.1)
  *  @state  -  Receiver state, one of %ccid3_hc_rx_states
- *  @bytes_recv  -  Total sum of DCCP payload bytes
  *  @x_recv  -  Receiver estimate of send rate (RFC 3448, sec. 4.3)
  *  @rtt  -  Receiver estimate of RTT
  *  @tstamp_last_feedback  -  Time at which last feedback was sent
  *  @hist  -  Packet history (loss detection + RTT sampling)
  *  @li_hist  -  Loss Interval database
- *  @s  -  Received packet size in bytes
  *  @p_inverse  -  Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
  */
 struct ccid3_hc_rx_sock {
        u8                              last_counter:4;
        enum ccid3_hc_rx_states         state:8;
-       u32                             bytes_recv;
        u32                             x_recv;
        u32                             rtt;
        ktime_t                         tstamp_last_feedback;
        struct tfrc_rx_hist             hist;
        struct tfrc_loss_hist           li_hist;
-       u16                             s;
 #define p_inverse                      li_hist.i_mean
 };
 

diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 8ea96903033ddd318e7ceebdcd5b8ff0d76b23e0..ee34b4564242d49c51e2e776e175d34563b65d4f 100644 (file)
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -352,6 +352,16 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
                __three_after_loss(h);
        }
 
+       /*
+        * Update moving-average of `s' and the sum of received payload bytes.
+        */
+       if (dccp_data_packet(skb)) {
+               const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
+
+               h->packet_size = tfrc_ewma(h->packet_size, payload, 9);
+               h->bytes_recvd += payload;
+       }
+
        /* RFC 3448, 6.1: update I_0, whose growth implies p <= p_prev */
        if (!is_new_loss)
                tfrc_lh_update_i_mean(lh, skb);

diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index e9d8097947d585602007440a5cba7f5681aa7602..b7c87a1a27208222806ab32073354ac47d283afc 100644 (file)
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -91,12 +91,16 @@ struct tfrc_rx_hist_entry {
  * @loss_count:                Number of entries in circular history
  * @loss_start:                Movable index (for loss detection)
  * @rtt_sample_prev:   Used during RTT sampling, points to candidate entry
+ * @packet_size:       Packet size in bytes (as per RFC 3448, 3.1)
+ * @bytes_recvd:       Number of bytes received since last sending feedback
  */
 struct tfrc_rx_hist {
        struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
        u8                        loss_count:2,
                                  loss_start:2;
 #define rtt_sample_prev                  loss_start
+       u32                       packet_size,
+                                 bytes_recvd;
 };
 
 /**
@@ -140,6 +144,18 @@ static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
        return h->loss_count > 0;
 }
 
+/*
+ * Accessor functions to retrieve parameters sampled by the RX history
+ */
+static inline u32 tfrc_rx_hist_packet_size(const struct tfrc_rx_hist *h)
+{
+       if (h->packet_size == 0) {
+               DCCP_WARN("No sample for s, using fallback\n");
+               return TCP_MIN_RCVMSS;
+       }
+       return h->packet_size;
+}
+
 extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
                                    const struct sk_buff *skb, const u64 ndp);
 

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index a3caa11aa8365c804f2703637bd87c73ef38da0d..ecf3be961e11218894661af68996e4154e5a9854 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -185,7 +185,7 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
        sk->sk_state            = DCCP_CLOSED;
        sk->sk_write_space      = dccp_write_space;
        icsk->icsk_sync_mss     = dccp_sync_mss;
-       dp->dccps_mss_cache     = 536;
+       dp->dccps_mss_cache     = TCP_MIN_RCVMSS;
        dp->dccps_rate_last     = jiffies;
        dp->dccps_role          = DCCP_ROLE_UNDEFINED;
        dp->dccps_service       = DCCP_SERVICE_CODE_IS_ABSENT;