[SCTP]: Fix receive buffer accounting.

When doing receiver buffer accounting, we always used skb->truesize.
This is problematic when processing bundled DATA chunks because for
every DATA chunk that could be small part of one large skb, we would
charge the size of the entire skb.  The new approach is to store the
size of the DATA chunk we are accounting for in the sctp_ulpevent
structure and use that stored value for accounting.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 4 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 3fe906d..9deec43 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5362,6 +5362,20 @@ static void sctp_wfree(struct sk_buff *skb)
 	sctp_association_put(asoc);
 }
 
+/* Do accounting for the receive space on the socket.
+ * Accounting for the association is done in ulpevent.c
+ * We set this as a destructor for the cloned data skbs so that
+ * accounting is done at the correct time.
+ */
+void sctp_sock_rfree(struct sk_buff *skb)
+{
+	struct sock *sk = skb->sk;
+	struct sctp_ulpevent *event = sctp_skb2event(skb);
+
+	atomic_sub(event->rmem_len, &sk->sk_rmem_alloc);
+}
+
+
 /* Helper function to wait for space in the sndbuf.  */
 static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
 				size_t msg_len)
@@ -5634,10 +5648,10 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 	sctp_skb_for_each(skb, &oldsk->sk_receive_queue, tmp) {
 		event = sctp_skb2event(skb);
 		if (event->asoc == assoc) {
-			sock_rfree(skb);
+			sctp_sock_rfree(skb);
 			__skb_unlink(skb, &oldsk->sk_receive_queue);
 			__skb_queue_tail(&newsk->sk_receive_queue, skb);
-			skb_set_owner_r(skb, newsk);
+			sctp_skb_set_owner_r(skb, newsk);
 		}
 	}
 
@@ -5665,10 +5679,10 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 		sctp_skb_for_each(skb, &oldsp->pd_lobby, tmp) {
 			event = sctp_skb2event(skb);
 			if (event->asoc == assoc) {
-				sock_rfree(skb);
+				sctp_sock_rfree(skb);
 				__skb_unlink(skb, &oldsp->pd_lobby);
 				__skb_queue_tail(queue, skb);
-				skb_set_owner_r(skb, newsk);
+				sctp_skb_set_owner_r(skb, newsk);
 			}
 		}