[DCCP]: Dedicated auxiliary states to support passive-close

This adds two auxiliary states to deal with passive closes:
  * PASSIVE_CLOSE    (reached from OPEN via reception of Close)    and
  * PASSIVE_CLOSEREQ (reached from OPEN via reception of CloseReq)
as internal intermediate states.

These states are used to allow a receiver to process unread data before
acknowledging the received connection-termination-request (the Close/CloseReq).

Without such support, it will happen that passively-closed sockets enter CLOSED
state while there is still unprocessed data in the queue; leading to unexpected
and erratic API behaviour.

PASSIVE_CLOSE has been mapped into TCPF_CLOSE_WAIT, so that the code will
seamlessly work with inet_accept() (which tests for this state).

The state names are thanks to Arnaldo, who suggested this naming scheme
following an earlier revision of this patch.

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>

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index a0073268808ff8452e2035fcd40f3c9c9fffb8c6..8b3f9ad3cf0420331f6ef704a9928a6ce72b1e8d 100644 (file)
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -227,29 +227,51 @@ struct dccp_so_feat {
 #include <net/tcp_states.h>
 
 enum dccp_state {
-       DCCP_OPEN       = TCP_ESTABLISHED,
-       DCCP_REQUESTING = TCP_SYN_SENT,
-       DCCP_LISTEN     = TCP_LISTEN,
-       DCCP_RESPOND    = TCP_SYN_RECV,
-       DCCP_CLOSING    = TCP_CLOSING,
-       DCCP_TIME_WAIT  = TCP_TIME_WAIT,
-       DCCP_CLOSED     = TCP_CLOSE,
-       DCCP_PARTOPEN   = TCP_MAX_STATES,
+       DCCP_OPEN            = TCP_ESTABLISHED,
+       DCCP_REQUESTING      = TCP_SYN_SENT,
+       DCCP_LISTEN          = TCP_LISTEN,
+       DCCP_RESPOND         = TCP_SYN_RECV,
+       /*
+        * States involved in closing a DCCP connection:
+        * 1) ACTIVE_CLOSEREQ is entered by a server sending a CloseReq.
+        *
+        * 2) CLOSING can have three different meanings (RFC 4340, 8.3):
+        *  a. Client has performed active-close, has sent a Close to the server
+        *     from state OPEN or PARTOPEN, and is waiting for the final Reset
+        *     (in this case, SOCK_DONE == 1).
+        *  b. Client is asked to perform passive-close, by receiving a CloseReq
+        *     in (PART)OPEN state. It sends a Close and waits for final Reset
+        *     (in this case, SOCK_DONE == 0).
+        *  c. Server performs an active-close as in (a), keeps TIMEWAIT state.
+        *
+        * 3) The following intermediate states are employed to give passively
+        *    closing nodes a chance to process their unread data:
+        *    - PASSIVE_CLOSE    (from OPEN => CLOSED) and
+        *    - PASSIVE_CLOSEREQ (from (PART)OPEN to CLOSING; case (b) above).
+        */
+       DCCP_ACTIVE_CLOSEREQ = TCP_FIN_WAIT1,
+       DCCP_PASSIVE_CLOSE   = TCP_CLOSE_WAIT,  /* any node receiving a Close */
+       DCCP_CLOSING         = TCP_CLOSING,
+       DCCP_TIME_WAIT       = TCP_TIME_WAIT,
+       DCCP_CLOSED          = TCP_CLOSE,
+       DCCP_PARTOPEN        = TCP_MAX_STATES,
+       DCCP_PASSIVE_CLOSEREQ,                  /* clients receiving CloseReq */
        DCCP_MAX_STATES
 };
 
-#define DCCP_STATE_MASK 0xf
+#define DCCP_STATE_MASK 0x1f
 #define DCCP_ACTION_FIN (1<<7)
 
 enum {
-       DCCPF_OPEN       = TCPF_ESTABLISHED,
-       DCCPF_REQUESTING = TCPF_SYN_SENT,
-       DCCPF_LISTEN     = TCPF_LISTEN,
-       DCCPF_RESPOND    = TCPF_SYN_RECV,
-       DCCPF_CLOSING    = TCPF_CLOSING,
-       DCCPF_TIME_WAIT  = TCPF_TIME_WAIT,
-       DCCPF_CLOSED     = TCPF_CLOSE,
-       DCCPF_PARTOPEN   = 1 << DCCP_PARTOPEN,
+       DCCPF_OPEN            = TCPF_ESTABLISHED,
+       DCCPF_REQUESTING      = TCPF_SYN_SENT,
+       DCCPF_LISTEN          = TCPF_LISTEN,
+       DCCPF_RESPOND         = TCPF_SYN_RECV,
+       DCCPF_ACTIVE_CLOSEREQ = TCPF_FIN_WAIT1,
+       DCCPF_CLOSING         = TCPF_CLOSING,
+       DCCPF_TIME_WAIT       = TCPF_TIME_WAIT,
+       DCCPF_CLOSED          = TCPF_CLOSE,
+       DCCPF_PARTOPEN        = (1 << DCCP_PARTOPEN),
 };
 
 static inline struct dccp_hdr *dccp_hdr(const struct sk_buff *skb)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 73006b74767854bcb7b00bbcb9b8498ce69fa3bb..3489d3f21f5049dd67a6517c31802bd4f4847e53 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -60,8 +60,7 @@ void dccp_set_state(struct sock *sk, const int state)
 {
        const int oldstate = sk->sk_state;
 
-       dccp_pr_debug("%s(%p) %-10.10s -> %s\n",
-                     dccp_role(sk), sk,
+       dccp_pr_debug("%s(%p)  %s  -->  %s\n", dccp_role(sk), sk,
                      dccp_state_name(oldstate), dccp_state_name(state));
        WARN_ON(state == oldstate);
 
@@ -134,14 +133,17 @@ EXPORT_SYMBOL_GPL(dccp_packet_name);
 const char *dccp_state_name(const int state)
 {
        static char *dccp_state_names[] = {
-       [DCCP_OPEN]       = "OPEN",
-       [DCCP_REQUESTING] = "REQUESTING",
-       [DCCP_PARTOPEN]   = "PARTOPEN",
-       [DCCP_LISTEN]     = "LISTEN",
-       [DCCP_RESPOND]    = "RESPOND",
-       [DCCP_CLOSING]    = "CLOSING",
-       [DCCP_TIME_WAIT]  = "TIME_WAIT",
-       [DCCP_CLOSED]     = "CLOSED",
+       [DCCP_OPEN]             = "OPEN",
+       [DCCP_REQUESTING]       = "REQUESTING",
+       [DCCP_PARTOPEN]         = "PARTOPEN",
+       [DCCP_LISTEN]           = "LISTEN",
+       [DCCP_RESPOND]          = "RESPOND",
+       [DCCP_CLOSING]          = "CLOSING",
+       [DCCP_ACTIVE_CLOSEREQ]  = "CLOSEREQ",
+       [DCCP_PASSIVE_CLOSE]    = "PASSIVE_CLOSE",
+       [DCCP_PASSIVE_CLOSEREQ] = "PASSIVE_CLOSEREQ",
+       [DCCP_TIME_WAIT]        = "TIME_WAIT",
+       [DCCP_CLOSED]           = "CLOSED",
        };
 
        if (state >= DCCP_MAX_STATES)