linux/net/dccp
Gerrit Renker 0c86962076 [DCCP]: Integrate state transitions for passive-close
This adds the necessary state transitions for the two forms of passive-close

 * PASSIVE_CLOSE    - which is entered when a host   receives a Close;
 * PASSIVE_CLOSEREQ - which is entered when a client receives a CloseReq.

Here is a detailed account of what the patch does in each state.

1) Receiving CloseReq

  The pseudo-code in 8.5 says:

     Step 13: Process CloseReq
          If P.type == CloseReq and S.state < CLOSEREQ,
              Generate Close
              S.state := CLOSING
              Set CLOSING timer.

  This means we need to address what to do in CLOSED, LISTEN, REQUEST, RESPOND, PARTOPEN, and OPEN.

   * CLOSED:         silently ignore - it may be a late or duplicate CloseReq;
   * LISTEN/RESPOND: will not appear, since Step 7 is performed first (we know we are the client);
   * REQUEST:        perform Step 13 directly (no need to enqueue packet);
   * OPEN/PARTOPEN:  enter PASSIVE_CLOSEREQ so that the application has a chance to process unread data.

  When already in PASSIVE_CLOSEREQ, no second CloseReq is enqueued. In any other state, the CloseReq is ignored.
  I think that this offers some robustness against rare and pathological cases: e.g. a simultaneous close where
  the client sends a Close and the server a CloseReq. The client will then be retransmitting its Close until it
  gets the Reset, so ignoring the CloseReq while in state CLOSING is sane.

2) Receiving Close

  The code below from 8.5 is unconditional.

     Step 14: Process Close
          If P.type == Close,
              Generate Reset(Closed)
              Tear down connection
              Drop packet and return

  Thus we need to consider all states:
   * CLOSED:           silently ignore, since this can happen when a retransmitted or late Close arrives;
   * LISTEN:           dccp_rcv_state_process() will generate a Reset ("No Connection");
   * REQUEST:          perform Step 14 directly (no need to enqueue packet);
   * RESPOND:          dccp_check_req() will generate a Reset ("Packet Error") -- left it at that;
   * OPEN/PARTOPEN:    enter PASSIVE_CLOSE so that application has a chance to process unread data;
   * CLOSEREQ:         server performed active-close -- perform Step 14;
   * CLOSING:          simultaneous-close: use a tie-breaker to avoid message ping-pong (see comment);
   * PASSIVE_CLOSEREQ: ignore - the peer has a bug (sending first a CloseReq and now a Close);
   * TIMEWAIT:         packet is ignored.

   Note that the condition of receiving a packet in state CLOSED here is different from the condition "there
   is no socket for such a connection": the socket still exists, but its state indicates it is unusable.

   Last, dccp_finish_passive_close sets either DCCP_CLOSED or DCCP_CLOSING = TCP_CLOSING, so that
   sk_stream_wait_close() will wait for the final Reset (which will trigger CLOSING => CLOSED).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:55:13 -08:00
..
ccids [TFRC]: Migrate TX history to singly-linked lis 2008-01-28 14:55:11 -08:00
ackvec.c [ACKVEC]: Reduce length of identifiers 2008-01-28 14:54:51 -08:00
ackvec.h [ACKVEC]: Reduce length of identifiers 2008-01-28 14:54:51 -08:00
ccid.c [DCCP]: fix theoretical ccids_{read,write}_lock() race 2007-08-13 22:52:09 -07:00
ccid.h [DCCP] ccid: Deprecate ccid_hc_tx_insert_options 2006-12-11 14:34:49 -08:00
dccp.h [DCCP]: Factor out common code for generating Resets 2007-10-10 16:52:44 -07:00
diag.c [INET]: Let inet_diag and friends autoload 2007-10-22 02:59:54 -07:00
feat.c [DCCP]: fix memory leak and clean up style - dccp_feat_empty_confirm() 2007-08-13 22:52:10 -07:00
feat.h [NET] DCCP: Fix whitespace errors. 2007-02-10 23:19:27 -08:00
input.c [DCCP]: Integrate state transitions for passive-close 2008-01-28 14:55:13 -08:00
ipv4.c [DCCP]: Use DEFINE_PROTO_INUSE infrastructure. 2007-11-07 04:09:01 -08:00
ipv6.c [DCCP]: Use DEFINE_PROTO_INUSE infrastructure. 2007-11-07 04:09:01 -08:00
ipv6.h Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
Kconfig [DCCP]: Promote CCID2 as default CCID 2008-01-28 14:54:46 -08:00
Makefile [DCCPv6]: Resolve conditional build problem 2006-12-02 21:22:28 -08:00
minisocks.c [DCCP]: Tidy-up -- minisock initialisation 2007-10-10 16:54:36 -07:00
options.c [DCCP]: Ignore Ack Vectors / Elapsed Time on DCCP-Request also 2008-01-28 14:54:47 -08:00
output.c [DCCP]: Use AF-independent rebuild_header routine 2008-01-28 14:55:12 -08:00
probe.c [NET]: Make /proc/net per network namespace 2007-10-10 16:49:06 -07:00
proto.c [DCCP]: Integrate state transitions for passive-close 2008-01-28 14:55:13 -08:00
sysctl.c [DCCP]: fix link error with !CONFIG_SYSCTL 2007-10-17 19:33:06 -07:00
timer.c [NET]: Convert init_timer into setup_timer 2008-01-28 14:53:35 -08:00