Documentation/networking/dccp.rst

1 .. SPDX-License-Identifier: GPL-2.0
9    - Introduction
10    - Missing features
11    - Socket options
12    - Sysctl variables
13    - IOCTLs
14    - Other tunables
15    - Notes
22 for real-time and multimedia (streaming) traffic.
26 implementation, this is the TCP-like CCID2 (RFC 4341). Additional CCIDs, such as
27 the TCP-friendly CCID3 (RFC 4342), are optional.
34 is at http://www.ietf.org/html.charters/dccp-charter.html
46 For more up-to-date versions of the DCCP implementation, please consider using
57 and a priority-based variant (DCCPQ_POLICY_PRIO). The latter allows to pass an
58 u32 priority value as ancillary data to sendmsg(), where higher numbers indicate
59 a higher packet priority (similar to SO_PRIORITY). This ancillary data needs to
62 	cmsg->cmsg_level = SOL_DCCP;
63 	cmsg->cmsg_type	 = DCCP_SCM_PRIORITY;
64 	cmsg->cmsg_len	 = CMSG_LEN(sizeof(uint32_t));	/* or CMSG_LEN(4) */
71 lowest-priority packet first. The default value for this parameter is
78 than one code has no effect (all subsequent service codes are ignored). The
82 DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet
85 DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs
89 built-in CCIDs.
91 DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same
122 	sets a threshold, where again values 0..15 are acceptable. The default
125 	coverage value are also acceptable. The higher the number, the more
129 The following two options apply to CCID 3 exclusively and are getsockopt()-only.
140 On unidirectional connections it is useful to close the unused half-connection
141 via shutdown (SHUT_WR or SHUT_RD): this will reduce per-packet processing costs.
156 	than 0, suggested is less than 10. Analogue of tcp_syn_retries.
168 	Default CCID for the sender-receiver half-connection. Depending on the
172 	Default CCID for the receiver-sender half-connection; see tx_ccid.
177 	Values in the range Wmin = 32 (RFC 4340, 7.5.2) up to 2^32-1 can be set.
184 	The timeout between subsequent DCCP-Sync packets sent in response to
185 	sequence-invalid packets on the same socket (RFC 4340, 7.5.4). The unit
186 	of this parameter is milliseconds; a value of 0 disables rate-limiting.
201 Per-route rto_min support
202 	CCID-2 supports the RTAX_RTO_MIN per-route setting for the minimum value
210 	CCID-3 also supports the rto_min setting: it is used to define the lower
218 because the checksum covers the pseudo-header as per TCP and UDP. Linux NAT