1 files changed, 21 insertions, 11 deletions

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index 39131a3c78f8..7a3bb1abb830 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -57,6 +57,24 @@ 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
@@ -115,20 +133,12 @@ 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).