wireless: support internal statically compiled regulatory database

[safe/jmp/linux-2.6] / Documentation / networking / dccp.txt

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index fdc93be..b132e4a 100644 (file)
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -14,8 +14,15 @@ Introduction
 ============
 
 Datagram Congestion Control Protocol (DCCP) is an unreliable, connection
-based protocol designed to solve issues present in UDP and TCP particularly
-for real time and multimedia traffic.
+oriented protocol designed to solve issues present in UDP and TCP, particularly
+for real-time and multimedia (streaming) traffic.
+It divides into a base protocol (RFC 4340) and plugable congestion control
+modules called CCIDs. Like plugable TCP congestion control, at least one CCID
+needs to be enabled in order for the protocol to function properly. In the Linux
+implementation, this is the TCP-like CCID2 (RFC 4341). Additional CCIDs, such as
+the TCP-friendly CCID3 (RFC 4342), are optional.
+For a brief introduction to CCIDs and suggestions for choosing a CCID to match
+given applications, see section 10 of RFC 4340.
 
 It has a base protocol and pluggable congestion control IDs (CCIDs).
 
@@ -50,6 +57,30 @@ can be set before calling bind().
 DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet
 size (application payload size) in bytes, see RFC 4340, section 14.
 
+DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs
+supported by the endpoint (see include/linux/dccp.h for symbolic constants).
+The caller needs to provide a sufficiently large (> 2) array of type uint8_t.
+
+DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same
+time, combining the operation of the next two socket options. This option is
+preferrable over the latter two, since often applications will use the same
+type of CCID for both directions; and mixed use of CCIDs is not currently well
+understood. This socket option takes as argument at least one uint8_t value, or
+an array of uint8_t values, which must match available CCIDS (see above). CCIDs
+must be registered on the socket before calling connect() or listen().
+
+DCCP_SOCKOPT_TX_CCID is read/write. It returns the current CCID (if set) or sets
+the preference list for the TX CCID, using the same format as DCCP_SOCKOPT_CCID.
+Please note that the getsockopt argument type here is `int', not uint8_t.
+
+DCCP_SOCKOPT_RX_CCID is analogous to DCCP_SOCKOPT_TX_CCID, but for the RX CCID.
+
+DCCP_SOCKOPT_SERVER_TIMEWAIT enables the server (listening socket) to hold
+timewait state when closing the connection (RFC 4340, 8.3). The usual case is
+that the closing server sends a CloseReq, whereupon the client holds timewait
+state. When this boolean socket option is on, the server sends a Close instead
+and will enter TIMEWAIT. This option must be set after accept() returns.
+
 DCCP_SOCKOPT_SEND_CSCOV and DCCP_SOCKOPT_RECV_CSCOV are used for setting the
 partial checksum coverage (RFC 4340, sec. 9.2). The default is that checksums
 always cover the entire packet and that only fully covered application data is
@@ -102,23 +133,16 @@ retries2
        importance for retransmitted acknowledgments and feature negotiation,
        data packets are never retransmitted. Analogue of tcp_retries2.
 
-send_ndp = 1
-       Whether or not to send NDP count options (sec. 7.7.2).
-
-send_ackvec = 1
-       Whether or not to send Ack Vector options (sec. 11.5).
-
-ack_ratio = 2
-       The default Ack Ratio (sec. 11.3) to use.
-
 tx_ccid = 2
-       Default CCID for the sender-receiver half-connection.
+       Default CCID for the sender-receiver half-connection. Depending on the
+       choice of CCID, the Send Ack Vector feature is enabled automatically.
 
 rx_ccid = 2
-       Default CCID for the receiver-sender half-connection.
+       Default CCID for the receiver-sender half-connection; see tx_ccid.
 
 seq_window = 100
-       The initial sequence window (sec. 7.5.2).
+       The initial sequence window (sec. 7.5.2) of the sender. This influences
+       the local ackno validity and the remote seqno validity windows (7.5.1).
 
 tx_qlen = 5
        The size of the transmit buffer in packets. A value of 0 corresponds
@@ -129,6 +153,12 @@ sync_ratelimit = 125 ms
        sequence-invalid packets on the same socket (RFC 4340, 7.5.4). The unit
        of this parameter is milliseconds; a value of 0 disables rate-limiting.
 
+IOCTLS
+======
+FIONREAD
+       Works as in udp(7): returns in the `int' argument pointer the size of
+       the next pending datagram in bytes, or 0 when no datagram is pending.
+
 Notes
 =====