[DCCP]: Perform SHUT_RD and SHUT_WR on receiving close

This patch performs two changes:

1) Close the write-end in addition to the read-end when a fin-like segment
  (Close or CloseReq) is received by DCCP. This accounts for the fact that DCCP,
  in contrast to TCP, does not have a half-close. RFC 4340 says in this respect
  that when a fin-like segment has been sent there is no guarantee at all that
  any   further data will be processed.
  Thus this patch performs SHUT_WR in addition to the SHUT_RD when a fin-like
  segment is encountered.

2) Minor change: I noted that code appears twice in different places and think it
   makes sense to put this into a self-contained function (dccp_enqueue()).

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>

1 files changed, 15 insertions, 7 deletions

diff --git a/net/dccp/input.c b/net/dccp/input.c
index decf2f21149b..dacd4fd3c63c 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -22,16 +22,27 @@
 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
 int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
 
-static void dccp_fin(struct sock *sk, struct sk_buff *skb)
+static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
 {
-        sk->sk_shutdown |= RCV_SHUTDOWN;
-        sock_set_flag(sk, SOCK_DONE);
         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
         __skb_queue_tail(&sk->sk_receive_queue, skb);
         skb_set_owner_r(skb, sk);
         sk->sk_data_ready(sk, 0);
 }
 
+static void dccp_fin(struct sock *sk, struct sk_buff *skb)
+{
+        /*
+         * On receiving Close/CloseReq, both RD/WR shutdown are performed.
+         * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
+         * receiving the closing segment, but there is no guarantee that such
+         * data will be processed at all.
+         */
+        sk->sk_shutdown = SHUTDOWN_MASK;
+        sock_set_flag(sk, SOCK_DONE);
+        dccp_enqueue_skb(sk, skb);
+}
+
 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
 {
         int queued = 0;
@@ -282,10 +293,7 @@ static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
                  * - 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);
-                skb_set_owner_r(skb, sk);
-                sk->sk_data_ready(sk, 0);
+                dccp_enqueue_skb(sk, skb);
                 return 0;
         case DCCP_PKT_ACK:
                 goto discard;