dccp: Implement both feature-local and feature-remote Sequence Window feature

This adds full support for local/remote Sequence Window feature, from which the
  * sequence-number-validity (W) and
  * acknowledgment-number-validity (W') windows
derive as specified in RFC 4340, 7.5.3.

Specifically, the following is contained in this patch:
  * integrated new socket fields into dccp_sk;
  * updated the update_gsr/gss routines with regard to these fields;
  * updated handler code: the Sequence Window feature is located at the TX side,
    so the local feature is meant if the handler-rx flag is false;
  * the initialisation of `rcv_wnd' in reqsk is removed, since
    - rcv_wnd is not used by the code anywhere;
    - sequence number checks are not done in the LISTEN state (cf. 7.5.3);
    - dccp_check_req checks the Ack number validity more rigorously;
  * the `struct dccp_minisock' became empty and is now removed.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 67ffac9905f8..7303f79705d2 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -51,8 +51,17 @@ static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
 
 static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
 {
-        if (!rx)
-                dccp_msk(sk)->dccpms_sequence_window = seq_win;
+        struct dccp_sock *dp = dccp_sk(sk);
+
+        if (rx) {
+                dp->dccps_r_seq_win = seq_win;
+                /* propagate changes to update SWL/SWH */
+                dccp_update_gsr(sk, dp->dccps_gsr);
+        } else {
+                dp->dccps_l_seq_win = seq_win;
+                /* propagate changes to update AWL */
+                dccp_update_gss(sk, dp->dccps_gss);
+        }
         return 0;
 }