[DCCP]: Support for server holding timewait state

This adds a socket option and signalling support for the case where the server
holds timewait state on closing the connection, as described in RFC 4340, 8.3.

Since holding timewait state at the server is the non-usual case, it is enabled
via a socket option. Documentation for this socket option has been added.

The setsockopt statement has been made resilient against different possible cases
of expressing boolean `true' values using a suggestion by Ian McDonald.

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, 3 insertions, 0 deletions

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 312b989c7edb..c676021603f5 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -205,6 +205,7 @@ struct dccp_so_feat {
 #define DCCP_SOCKOPT_CHANGE_L           3
 #define DCCP_SOCKOPT_CHANGE_R           4
 #define DCCP_SOCKOPT_GET_CUR_MPS        5
+#define DCCP_SOCKOPT_SERVER_TIMEWAIT    6
 #define DCCP_SOCKOPT_SEND_CSCOV         10
 #define DCCP_SOCKOPT_RECV_CSCOV         11
 #define DCCP_SOCKOPT_CCID_RX_INFO       128
@@ -492,6 +493,7 @@ struct dccp_ackvec;
  * @dccps_role - role of this sock, one of %dccp_role
  * @dccps_hc_rx_insert_options - receiver wants to add options when acking
  * @dccps_hc_tx_insert_options - sender wants to add options when sending
+ * @dccps_server_timewait - server holds timewait state on close (RFC 4340, 8.3)
  * @dccps_xmit_timer - timer for when CCID is not ready to send
  * @dccps_syn_rtt - RTT sample from Request/Response exchange (in usecs)
  */
@@ -528,6 +530,7 @@ struct dccp_sock {
         enum dccp_role                  dccps_role:2;
         __u8                            dccps_hc_rx_insert_options:1;
         __u8                            dccps_hc_tx_insert_options:1;
+        __u8                            dccps_server_timewait:1;
         struct timer_list               dccps_xmit_timer;
 };