3 files changed, 23 insertions, 8 deletions

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index afb66f9a8aff..f771034e8f27 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -72,6 +72,8 @@ DCCP_SOCKOPT_CCID_TX_INFO
         Returns a `struct tfrc_tx_info' in optval; the buffer for optval and
         optlen must be set to at least sizeof(struct tfrc_tx_info).
 
+On unidirectional connections it is useful to close the unused half-connection
+via shutdown (SHUT_WR or SHUT_RD): this will reduce per-packet processing costs.
 
 Sysctl variables
 ================
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 1ce101062824..df0fb2c149a6 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -103,6 +103,21 @@ static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
 }
 
+static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
+{
+        const struct dccp_sock *dp = dccp_sk(sk);
+
+        /* Don't deliver to RX CCID when node has shut down read end. */
+        if (!(sk->sk_shutdown & RCV_SHUTDOWN))
+                ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
+        /*
+         * Until the TX queue has been drained, we can not honour SHUT_WR, since
+         * we need received feedback as input to adjust congestion control.
+         */
+        if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
+                ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
+}
+
 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 {
         const struct dccp_hdr *dh = dccp_hdr(skb);
@@ -209,8 +224,9 @@ static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
         case DCCP_PKT_DATAACK:
         case DCCP_PKT_DATA:
                 /*
-                 * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
-                 * option if it is.
+                 * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
+                 * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
+                 * - sk_receive_queue is full, use Code 2, "Receive Buffer"
                  */
                 __skb_pull(skb, dh->dccph_doff * 4);
                 __skb_queue_tail(&sk->sk_receive_queue, skb);
@@ -300,9 +316,7 @@ int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
                             DCCP_SKB_CB(skb)->dccpd_seq,
                             DCCP_ACKVEC_STATE_RECEIVED))
                 goto discard;
-
-        ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
-        ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
+        dccp_deliver_input_to_ccids(sk, skb);
 
         return __dccp_rcv_established(sk, skb, dh, len);
 discard:
@@ -543,8 +557,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                                     DCCP_ACKVEC_STATE_RECEIVED))
                         goto discard;
 
-                ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
-                ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
+                dccp_deliver_input_to_ccids(sk, skb);
         }
 
         /*
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 7a3bea9c28c1..0aec73592124 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -981,7 +981,7 @@ EXPORT_SYMBOL_GPL(dccp_close);
 
 void dccp_shutdown(struct sock *sk, int how)
 {
-        dccp_pr_debug("entry\n");
+        dccp_pr_debug("called shutdown(%x)\n", how);
 }
 
 EXPORT_SYMBOL_GPL(dccp_shutdown);