dccp tfrc: Receiver history initialisation routine

This patch 
 1) separates history allocation and initialisation, to facilitate early
    loss detection (implemented by a subsequent patch);

 2) removes duplication by using the existing tfrc_rx_hist_purge() if the
    allocation fails. This is now possible, since the initialisation routine
 3) zeroes out the entire history before using it. 

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

3 files changed, 32 insertions, 24 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 5470a978be02..36f4992f3c38 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -766,7 +766,7 @@ static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
 
         hcrx->state = TFRC_RSTATE_NO_DATA;
         tfrc_lh_init(&hcrx->li_hist);
-        return tfrc_rx_hist_alloc(&hcrx->hist);
+        return tfrc_rx_hist_init(&hcrx->hist, sk);
 }
 
 static void ccid3_hc_rx_exit(struct sock *sk)
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 5c4450866904..5b4e1cf8439d 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -352,28 +352,6 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
 }
 EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
 
-int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
-{
-        int i;
-
-        for (i = 0; i <= TFRC_NDUPACK; i++) {
-                h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
-                if (h->ring[i] == NULL)
-                        goto out_free;
-        }
-
-        h->loss_count = h->loss_start = 0;
-        return 0;
-
-out_free:
-        while (i-- != 0) {
-                kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
-                h->ring[i] = NULL;
-        }
-        return -ENOBUFS;
-}
-EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
-
 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 {
         int i;
@@ -386,6 +364,36 @@ void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 }
 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 
+static int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
+{
+        int i;
+
+        memset(h, 0, sizeof(*h));
+
+        for (i = 0; i <= TFRC_NDUPACK; i++) {
+                h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
+                if (h->ring[i] == NULL) {
+                        tfrc_rx_hist_purge(h);
+                        return -ENOBUFS;
+                }
+        }
+        return 0;
+}
+
+int tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk)
+{
+        if (tfrc_rx_hist_alloc(h))
+                return -ENOBUFS;
+        /*
+         * Initialise first entry with GSR to start loss detection as early as
+         * possible. Code using this must not use any other fields. The entry
+         * will be overwritten once the CCID updates its received packets.
+         */
+        tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno = dccp_sk(sk)->dccps_gsr;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_init);
+
 /**
  * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
  */
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index 221d8102da51..e9d8097947d5 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -153,7 +153,7 @@ extern int  tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
                                 struct sock *sk);
 extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
                                    const struct sk_buff *skb);
-extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
+extern int  tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk);
 extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
 
 #endif /* _DCCP_PKT_HIST_ */