diff options
Diffstat (limited to 'Documentation/networking/dccp.txt')
| -rw-r--r-- | Documentation/networking/dccp.txt | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 271d524a4c8d..d718bc2ff1cf 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -38,15 +38,35 @@ The Linux DCCP implementation does not currently support all the features that a specified in RFCs 4340...42. The known bugs are at: - http://linux-net.osdl.org/index.php/TODO#DCCP + http://www.linuxfoundation.org/collaborate/workgroups/networking/todo#DCCP For more up-to-date versions of the DCCP implementation, please consider using the experimental DCCP test tree; instructions for checking this out are on: -http://linux-net.osdl.org/index.php/DCCP_Testing#Experimental_DCCP_source_tree +http://www.linuxfoundation.org/collaborate/workgroups/networking/dccp_testing#Experimental_DCCP_source_tree Socket options ============== +DCCP_SOCKOPT_QPOLICY_ID sets the dequeuing policy for outgoing packets. It takes +a policy ID as argument and can only be set before the connection (i.e. changes +during an established connection are not supported). Currently, two policies are +defined: the "simple" policy (DCCPQ_POLICY_SIMPLE), which does nothing special, +and a priority-based variant (DCCPQ_POLICY_PRIO). The latter allows to pass an +u32 priority value as ancillary data to sendmsg(), where higher numbers indicate +a higher packet priority (similar to SO_PRIORITY). This ancillary data needs to +be formatted using a cmsg(3) message header filled in as follows: + cmsg->cmsg_level = SOL_DCCP; + cmsg->cmsg_type = DCCP_SCM_PRIORITY; + cmsg->cmsg_len = CMSG_LEN(sizeof(uint32_t)); /* or CMSG_LEN(4) */ + +DCCP_SOCKOPT_QPOLICY_TXQLEN sets the maximum length of the output queue. A zero +value is always interpreted as unbounded queue length. If different from zero, +the interpretation of this parameter depends on the current dequeuing policy +(see above): the "simple" policy will enforce a fixed queue size by returning +EAGAIN, whereas the "prio" policy enforces a fixed queue length by dropping the +lowest-priority packet first. The default value for this parameter is +initialised from /proc/sys/net/dccp/default/tx_qlen. + DCCP_SOCKOPT_SERVICE sets the service. The specification mandates use of service codes (RFC 4340, sec. 8.1.2); if this socket option is not set, the socket will fall back to 0 (which means that no meaningful service code @@ -147,6 +167,7 @@ rx_ccid = 2 seq_window = 100 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). + Values in the range Wmin = 32 (RFC 4340, 7.5.2) up to 2^32-1 can be set. tx_qlen = 5 The size of the transmit buffer in packets. A value of 0 corresponds |