€•¶‘      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ#/translations/zh_CN/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ#/translations/zh_TW/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ#/translations/it_IT/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ#/translations/ja_JP/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ#/translations/ko_KR/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ#/translations/sp_SP/networking/dccp”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒ=/var/lib/git/docbuild/linux/Documentation/networking/dccp.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒDCCP protocol”h]”hŒDCCP protocol”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubh¢)”}”(hŒpContents
- Introduction
- Missing features
- Socket options
- Sysctl variables
- IOCTLs
- Other tunables
- Notes”h]”hŒpContents
- Introduction
- Missing features
- Socket options
- Sysctl variables
- IOCTLs
- Other tunables
- Notes”…””}”hhÉsbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1h¡hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒIntroduction”h]”hŒIntroduction”…””}”(hhÚhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh×hžhhŸh³h KubhŒ	paragraph”“”)”}”(hX·  Datagram Congestion Control Protocol (DCCP) is an unreliable, connection
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 pluggable congestion control
modules called CCIDs. Like pluggable 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.”h]”hX·  Datagram Congestion Control Protocol (DCCP) is an unreliable, connection
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 pluggable congestion control
modules called CCIDs. Like pluggable 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.”…””}”(hhêhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Khh×hžhubhé)”}”(hŒDIt has a base protocol and pluggable congestion control IDs (CCIDs).”h]”hŒDIt has a base protocol and pluggable congestion control IDs (CCIDs).”…””}”(hhøhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Khh×hžhubhé)”}”(hŒ‰DCCP is a Proposed Standard (RFC 2026), and the homepage for DCCP as a protocol
is at http://www.ietf.org/html.charters/dccp-charter.html”h]”(hŒVDCCP is a Proposed Standard (RFC 2026), and the homepage for DCCP as a protocol
is at ”…””}”(hj  hžhhŸNh NubhŒ	reference”“”)”}”(hŒ3http://www.ietf.org/html.charters/dccp-charter.html”h]”hŒ3http://www.ietf.org/html.charters/dccp-charter.html”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j  uh1j  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K!hh×hžhubeh}”(h]”Œintroduction”ah ]”h"]”Œintroduction”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒMissing features”h]”hŒMissing features”…””}”(hj0  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj-  hžhhŸh³h K&ubhé)”}”(hŒoThe Linux DCCP implementation does not currently support all the features that are
specified in RFCs 4340...42.”h]”hŒoThe Linux DCCP implementation does not currently support all the features that are
specified in RFCs 4340...42.”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K'hj-  hžhubhé)”}”(hŒThe known bugs are at:”h]”hŒThe known bugs are at:”…””}”(hjL  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K*hj-  hžhubhŒblock_quote”“”)”}”(hŒKhttp://www.linuxfoundation.org/collaborate/workgroups/networking/todo#DCCP
”h]”hé)”}”(hŒJhttp://www.linuxfoundation.org/collaborate/workgroups/networking/todo#DCCP”h]”j  )”}”(hjb  h]”hŒJhttp://www.linuxfoundation.org/collaborate/workgroups/networking/todo#DCCP”…””}”(hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jb  uh1j  hj`  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K,hj\  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jZ  hŸh³h K,hj-  hžhubhé)”}”(hX  For more up-to-date versions of the DCCP implementation, please consider using
the experimental DCCP test tree; instructions for checking this out are on:
http://www.linuxfoundation.org/collaborate/workgroups/networking/dccp_testing#Experimental_DCCP_source_tree”h]”(hŒ›For more up-to-date versions of the DCCP implementation, please consider using
the experimental DCCP test tree; instructions for checking this out are on:
”…””}”(hj~  hžhhŸNh Nubj  )”}”(hŒkhttp://www.linuxfoundation.org/collaborate/workgroups/networking/dccp_testing#Experimental_DCCP_source_tree”h]”hŒkhttp://www.linuxfoundation.org/collaborate/workgroups/networking/dccp_testing#Experimental_DCCP_source_tree”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jˆ  uh1j  hj~  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K.hj-  hžhubeh}”(h]”Œmissing-features”ah ]”h"]”Œmissing features”ah$]”h&]”uh1h´hh¶hžhhŸh³h K&ubhµ)”}”(hhh]”(hº)”}”(hŒSocket options”h]”hŒSocket options”…””}”(hj¦  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj£  hžhhŸh³h K4ubhé)”}”(hXt  DCCP_SOCKOPT_QPOLICY_ID sets the dequeuing policy for outgoing packets. It takes
a policy ID as argument and can only be set before the connection (i.e. changes
during an established connection are not supported). Currently, two policies are
defined: the "simple" policy (DCCPQ_POLICY_SIMPLE), which does nothing special,
and a priority-based variant (DCCPQ_POLICY_PRIO). The latter allows to pass an
u32 priority value as ancillary data to sendmsg(), where higher numbers indicate
a higher packet priority (similar to SO_PRIORITY). This ancillary data needs to
be formatted using a cmsg(3) message header filled in as follows::”h]”hXw  DCCP_SOCKOPT_QPOLICY_ID sets the dequeuing policy for outgoing packets. It takes
a policy ID as argument and can only be set before the connection (i.e. changes
during an established connection are not supported). Currently, two policies are
defined: the â€œsimpleâ€ policy (DCCPQ_POLICY_SIMPLE), which does nothing special,
and a priority-based variant (DCCPQ_POLICY_PRIO). The latter allows to pass an
u32 priority value as ancillary data to sendmsg(), where higher numbers indicate
a higher packet priority (similar to SO_PRIORITY). This ancillary data needs to
be formatted using a cmsg(3) message header filled in as follows:”…””}”(hj´  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K5hj£  hžhubhŒliteral_block”“”)”}”(hŒ‡cmsg->cmsg_level = SOL_DCCP;
cmsg->cmsg_type  = DCCP_SCM_PRIORITY;
cmsg->cmsg_len   = CMSG_LEN(sizeof(uint32_t));  /* or CMSG_LEN(4) */”h]”hŒ‡cmsg->cmsg_level = SOL_DCCP;
cmsg->cmsg_type  = DCCP_SCM_PRIORITY;
cmsg->cmsg_len   = CMSG_LEN(sizeof(uint32_t));  /* or CMSG_LEN(4) */”…””}”hjÄ  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jÂ  hŸh³h K>hj£  hžhubhé)”}”(hX  DCCP_SOCKOPT_QPOLICY_TXQLEN sets the maximum length of the output queue. A zero
value is always interpreted as unbounded queue length. If different from zero,
the interpretation of this parameter depends on the current dequeuing policy
(see above): the "simple" policy will enforce a fixed queue size by returning
EAGAIN, whereas the "prio" policy enforces a fixed queue length by dropping the
lowest-priority packet first. The default value for this parameter is
initialised from /proc/sys/net/dccp/default/tx_qlen.”h]”hX  DCCP_SOCKOPT_QPOLICY_TXQLEN sets the maximum length of the output queue. A zero
value is always interpreted as unbounded queue length. If different from zero,
the interpretation of this parameter depends on the current dequeuing policy
(see above): the â€œsimpleâ€ policy will enforce a fixed queue size by returning
EAGAIN, whereas the â€œprioâ€ policy enforces a fixed queue length by dropping the
lowest-priority packet first. The default value for this parameter is
initialised from /proc/sys/net/dccp/default/tx_qlen.”…””}”(hjÒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KBhj£  hžhubhé)”}”(hXæ  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
is present). On active sockets this is set before connect(); specifying more
than one code has no effect (all subsequent service codes are ignored). The
case is different for passive sockets, where multiple service codes (up to 32)
can be set before calling bind().”h]”hXæ  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
is present). On active sockets this is set before connect(); specifying more
than one code has no effect (all subsequent service codes are ignored). The
case is different for passive sockets, where multiple service codes (up to 32)
can be set before calling bind().”…””}”(hjà  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KJhj£  hžhubhé)”}”(hŒ’DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet
size (application payload size) in bytes, see RFC 4340, section 14.”h]”hŒ’DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet
size (application payload size) in bytes, see RFC 4340, section 14.”…””}”(hjî  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KRhj£  hžhubhé)”}”(hX>  DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs
supported by the endpoint. The option value is an array of type uint8_t whose
size is passed as option length. The minimum array size is 4 elements, the
value returned in the optlen argument always reflects the true number of
built-in CCIDs.”h]”hX>  DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs
supported by the endpoint. The option value is an array of type uint8_t whose
size is passed as option length. The minimum array size is 4 elements, the
value returned in the optlen argument always reflects the true number of
built-in CCIDs.”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KUhj£  hžhubhé)”}”(hX  DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same
time, combining the operation of the next two socket options. This option is
preferable over the latter two, since often applications will use the same
type of CCID for both directions; and mixed use of CCIDs is not currently well
understood. This socket option takes as argument at least one uint8_t value, or
an array of uint8_t values, which must match available CCIDS (see above). CCIDs
must be registered on the socket before calling connect() or listen().”h]”hX  DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same
time, combining the operation of the next two socket options. This option is
preferable over the latter two, since often applications will use the same
type of CCID for both directions; and mixed use of CCIDs is not currently well
understood. This socket option takes as argument at least one uint8_t value, or
an array of uint8_t values, which must match available CCIDS (see above). CCIDs
must be registered on the socket before calling connect() or listen().”…””}”(hj
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K[hj£  hžhubhé)”}”(hŒíDCCP_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.”h]”(hŒØDCCP_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 ”…””}”(hj  hžhhŸNh NubhŒliteral”“”)”}”(hŒ``int``”h]”hŒint”…””}”(hj"  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j   hj  ubhŒ, not uint8_t.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kchj£  hžhubhé)”}”(hŒODCCP_SOCKOPT_RX_CCID is analogous to DCCP_SOCKOPT_TX_CCID, but for the RX CCID.”h]”hŒODCCP_SOCKOPT_RX_CCID is analogous to DCCP_SOCKOPT_TX_CCID, but for the RX CCID.”…””}”(hj:  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kghj£  hžhubhé)”}”(hX~  DCCP_SOCKOPT_SERVER_TIMEWAIT enables the server (listening socket) to hold
timewait state when closing the connection (RFC 4340, 8.3). The usual case is
that the closing server sends a CloseReq, whereupon the client holds timewait
state. When this boolean socket option is on, the server sends a Close instead
and will enter TIMEWAIT. This option must be set after accept() returns.”h]”hX~  DCCP_SOCKOPT_SERVER_TIMEWAIT enables the server (listening socket) to hold
timewait state when closing the connection (RFC 4340, 8.3). The usual case is
that the closing server sends a CloseReq, whereupon the client holds timewait
state. When this boolean socket option is on, the server sends a Close instead
and will enter TIMEWAIT. This option must be set after accept() returns.”…””}”(hjH  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kihj£  hžhubhé)”}”(hXx  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
accepted by the receiver. Hence, when using this feature on the sender, it must
be enabled at the receiver, too with suitable choice of CsCov.”h]”hXx  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
accepted by the receiver. Hence, when using this feature on the sender, it must
be enabled at the receiver, too with suitable choice of CsCov.”…””}”(hjV  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kohj£  hžhubhŒdefinition_list”“”)”}”(hhh]”(hŒdefinition_list_item”“”)”}”(hŒ¿DCCP_SOCKOPT_SEND_CSCOV sets the sender checksum coverage. Values in the
range 0..15 are acceptable. The default setting is 0 (full coverage),
values between 1..15 indicate partial coverage.
”h]”(hŒterm”“”)”}”(hŒHDCCP_SOCKOPT_SEND_CSCOV sets the sender checksum coverage. Values in the”h]”hŒHDCCP_SOCKOPT_SEND_CSCOV sets the sender checksum coverage. Values in the”…””}”(hjq  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h Kwhjk  ubhŒ
definition”“”)”}”(hhh]”hé)”}”(hŒurange 0..15 are acceptable. The default setting is 0 (full coverage),
values between 1..15 indicate partial coverage.”h]”hŒurange 0..15 are acceptable. The default setting is 0 (full coverage),
values between 1..15 indicate partial coverage.”…””}”(hj„  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kvhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjk  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h Kwhjf  ubjj  )”}”(hXç  DCCP_SOCKOPT_RECV_CSCOV is for the receiver and has a different meaning: it
sets a threshold, where again values 0..15 are acceptable. The default
of 0 means that all packets with a partial coverage will be discarded.
Values in the range 1..15 indicate that packets with minimally such a
coverage value are also acceptable. The higher the number, the more
restrictive this setting (see [RFC 4340, sec. 9.2.1]). Partial coverage
settings are inherited to the child socket after accept().
”h]”(jp  )”}”(hŒKDCCP_SOCKOPT_RECV_CSCOV is for the receiver and has a different meaning: it”h]”hŒKDCCP_SOCKOPT_RECV_CSCOV is for the receiver and has a different meaning: it”…””}”(hj¢  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h Khjž  ubj€  )”}”(hhh]”hé)”}”(hXš  sets a threshold, where again values 0..15 are acceptable. The default
of 0 means that all packets with a partial coverage will be discarded.
Values in the range 1..15 indicate that packets with minimally such a
coverage value are also acceptable. The higher the number, the more
restrictive this setting (see [RFC 4340, sec. 9.2.1]). Partial coverage
settings are inherited to the child socket after accept().”h]”hXš  sets a threshold, where again values 0..15 are acceptable. The default
of 0 means that all packets with a partial coverage will be discarded.
Values in the range 1..15 indicate that packets with minimally such a
coverage value are also acceptable. The higher the number, the more
restrictive this setting (see [RFC 4340, sec. 9.2.1]). Partial coverage
settings are inherited to the child socket after accept().”…””}”(hj³  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Kzhj°  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjž  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h Khjf  hžhubeh}”(h]”h ]”h"]”h$]”h&]”uh1jd  hj£  hžhhŸh³h Nubhé)”}”(hŒœThe following two options apply to CCID 3 exclusively and are getsockopt()-only.
In either case, a TFRC info struct (defined in <linux/tfrc.h>) is returned.”h]”hŒœThe following two options apply to CCID 3 exclusively and are getsockopt()-only.
In either case, a TFRC info struct (defined in <linux/tfrc.h>) is returned.”…””}”(hjÓ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h Khj£  hžhubje  )”}”(hhh]”(jj  )”}”(hŒDCCP_SOCKOPT_CCID_RX_INFO
Returns a ``struct tfrc_rx_info`` in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_rx_info).
”h]”(jp  )”}”(hŒDCCP_SOCKOPT_CCID_RX_INFO”h]”hŒDCCP_SOCKOPT_CCID_RX_INFO”…””}”(hjè  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K†hjä  ubj€  )”}”(hhh]”hé)”}”(hŒ‚Returns a ``struct tfrc_rx_info`` in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_rx_info).”h]”(hŒ
Returns a ”…””}”(hjù  hžhhŸNh Nubj!  )”}”(hŒ``struct tfrc_rx_info``”h]”hŒstruct tfrc_rx_info”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j   hjù  ubhŒa in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_rx_info).”…””}”(hjù  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K…hjö  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjä  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K†hjá  ubjj  )”}”(hŒDCCP_SOCKOPT_CCID_TX_INFO
Returns a ``struct tfrc_tx_info`` in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_tx_info).
”h]”(jp  )”}”(hŒDCCP_SOCKOPT_CCID_TX_INFO”h]”hŒDCCP_SOCKOPT_CCID_TX_INFO”…””}”(hj)  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h KŠhj%  ubj€  )”}”(hhh]”hé)”}”(hŒ‚Returns a ``struct tfrc_tx_info`` in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_tx_info).”h]”(hŒ
Returns a ”…””}”(hj:  hžhhŸNh Nubj!  )”}”(hŒ``struct tfrc_tx_info``”h]”hŒstruct tfrc_tx_info”…””}”(hjB  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j   hj:  ubhŒa in optval; the buffer for optval and
optlen must be set to at least sizeof(struct tfrc_tx_info).”…””}”(hj:  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K‰hj7  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj%  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h KŠhjá  hžhubeh}”(h]”h ]”h"]”h$]”h&]”uh1jd  hj£  hžhhŸh³h Nubhé)”}”(hŒŸOn unidirectional connections it is useful to close the unused half-connection
via shutdown (SHUT_WR or SHUT_RD): this will reduce per-packet processing costs.”h]”hŒŸOn unidirectional connections it is useful to close the unused half-connection
via shutdown (SHUT_WR or SHUT_RD): this will reduce per-packet processing costs.”…””}”(hjl  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KŒhj£  hžhubeh}”(h]”Œsocket-options”ah ]”h"]”Œsocket options”ah$]”h&]”uh1h´hh¶hžhhŸh³h K4ubhµ)”}”(hhh]”(hº)”}”(hŒSysctl variables”h]”hŒSysctl variables”…””}”(hj…  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj‚  hžhhŸh³h K‘ubhé)”}”(hŒ€Several DCCP default parameters can be managed by the following sysctls
(sysctl net.dccp.default or /proc/sys/net/dccp/default):”h]”hŒ€Several DCCP default parameters can be managed by the following sysctls
(sysctl net.dccp.default or /proc/sys/net/dccp/default):”…””}”(hj“  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K’hj‚  hžhubje  )”}”(hhh]”(jj  )”}”(hXæ  request_retries
The number of active connection initiation retries (the number of
Requests minus one) before timing out. In addition, it also governs
the behaviour of the other, passive side: this variable also sets
the number of times DCCP repeats sending a Response when the initial
handshake does not progress from RESPOND to OPEN (i.e. when no Ack
is received after the initial Request).  This value should be greater
than 0, suggested is less than 10. Analogue of tcp_syn_retries.
”h]”(jp  )”}”(hŒrequest_retries”h]”hŒrequest_retries”…””}”(hj¨  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h Kœhj¤  ubj€  )”}”(hhh]”hé)”}”(hXÕ  The number of active connection initiation retries (the number of
Requests minus one) before timing out. In addition, it also governs
the behaviour of the other, passive side: this variable also sets
the number of times DCCP repeats sending a Response when the initial
handshake does not progress from RESPOND to OPEN (i.e. when no Ack
is received after the initial Request).  This value should be greater
than 0, suggested is less than 10. Analogue of tcp_syn_retries.”h]”hXÕ  The number of active connection initiation retries (the number of
Requests minus one) before timing out. In addition, it also governs
the behaviour of the other, passive side: this variable also sets
the number of times DCCP repeats sending a Response when the initial
handshake does not progress from RESPOND to OPEN (i.e. when no Ack
is received after the initial Request).  This value should be greater
than 0, suggested is less than 10. Analogue of tcp_syn_retries.”…””}”(hj¹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K–hj¶  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj¤  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h Kœhj¡  ubjj  )”}”(hŒretries1
How often a DCCP Response is retransmitted until the listening DCCP
side considers its connecting peer dead. Analogue of tcp_retries1.
”h]”(jp  )”}”(hŒretries1”h]”hŒretries1”…””}”(hj×  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K hjÓ  ubj€  )”}”(hhh]”hé)”}”(hŒ†How often a DCCP Response is retransmitted until the listening DCCP
side considers its connecting peer dead. Analogue of tcp_retries1.”h]”hŒ†How often a DCCP Response is retransmitted until the listening DCCP
side considers its connecting peer dead. Analogue of tcp_retries1.”…””}”(hjè  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KŸhjå  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjÓ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K hj¡  hžhubjj  )”}”(hŒÔretries2
The number of times a general DCCP packet is retransmitted. This has
importance for retransmitted acknowledgments and feature negotiation,
data packets are never retransmitted. Analogue of tcp_retries2.
”h]”(jp  )”}”(hŒretries2”h]”hŒretries2”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K¥hj  ubj€  )”}”(hhh]”hé)”}”(hŒÊThe number of times a general DCCP packet is retransmitted. This has
importance for retransmitted acknowledgments and feature negotiation,
data packets are never retransmitted. Analogue of tcp_retries2.”h]”hŒÊThe number of times a general DCCP packet is retransmitted. This has
importance for retransmitted acknowledgments and feature negotiation,
data packets are never retransmitted. Analogue of tcp_retries2.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K£hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K¥hj¡  hžhubjj  )”}”(hŒ™tx_ccid = 2
Default CCID for the sender-receiver half-connection. Depending on the
choice of CCID, the Send Ack Vector feature is enabled automatically.
”h]”(jp  )”}”(hŒtx_ccid = 2”h]”hŒtx_ccid = 2”…””}”(hj5  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K©hj1  ubj€  )”}”(hhh]”hé)”}”(hŒŒDefault CCID for the sender-receiver half-connection. Depending on the
choice of CCID, the Send Ack Vector feature is enabled automatically.”h]”hŒŒDefault CCID for the sender-receiver half-connection. Depending on the
choice of CCID, the Send Ack Vector feature is enabled automatically.”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K¨hjC  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj1  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K©hj¡  hžhubjj  )”}”(hŒOrx_ccid = 2
Default CCID for the receiver-sender half-connection; see tx_ccid.
”h]”(jp  )”}”(hŒrx_ccid = 2”h]”hŒrx_ccid = 2”…””}”(hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K¬hj`  ubj€  )”}”(hhh]”hé)”}”(hŒBDefault CCID for the receiver-sender half-connection; see tx_ccid.”h]”hŒBDefault CCID for the receiver-sender half-connection; see tx_ccid.”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K¬hjr  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj`  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K¬hj¡  hžhubjj  )”}”(hŒêseq_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.
”h]”(jp  )”}”(hŒseq_window = 100”h]”hŒseq_window = 100”…””}”(hj“  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K±hj  ubj€  )”}”(hhh]”hé)”}”(hŒØThe initial sequence window (sec. 7.5.2) of the sender. This influences
the local ackno validity and the remote seqno validity windows (7.5.1).
Values in the range Wmin = 32 (RFC 4340, 7.5.2) up to 2^32-1 can be set.”h]”hŒØThe initial sequence window (sec. 7.5.2) of the sender. This influences
the local ackno validity and the remote seqno validity windows (7.5.1).
Values in the range Wmin = 32 (RFC 4340, 7.5.2) up to 2^32-1 can be set.”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K¯hj¡  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K±hj¡  hžhubjj  )”}”(hŒrtx_qlen = 5
The size of the transmit buffer in packets. A value of 0 corresponds
to an unbounded transmit buffer.
”h]”(jp  )”}”(hŒtx_qlen = 5”h]”hŒtx_qlen = 5”…””}”(hjÂ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h Kµhj¾  ubj€  )”}”(hhh]”hé)”}”(hŒeThe size of the transmit buffer in packets. A value of 0 corresponds
to an unbounded transmit buffer.”h]”hŒeThe size of the transmit buffer in packets. A value of 0 corresponds
to an unbounded transmit buffer.”…””}”(hjÓ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K´hjÐ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj¾  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h Kµhj¡  hžhubjj  )”}”(hŒîsync_ratelimit = 125 ms
The timeout between subsequent DCCP-Sync packets sent in response to
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.

”h]”(jp  )”}”(hŒsync_ratelimit = 125 ms”h]”hŒsync_ratelimit = 125 ms”…””}”(hjñ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h K»hjí  ubj€  )”}”(hhh]”hé)”}”(hŒÔThe timeout between subsequent DCCP-Sync packets sent in response to
sequence-invalid packets on the same socket (RFC 4340, 7.5.4). The unit
of this parameter is milliseconds; a value of 0 disables rate-limiting.”h]”hŒÔThe timeout between subsequent DCCP-Sync packets sent in response to
sequence-invalid packets on the same socket (RFC 4340, 7.5.4). The unit
of this parameter is milliseconds; a value of 0 disables rate-limiting.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h K¸hjÿ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjí  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h K»hj¡  hžhubeh}”(h]”h ]”h"]”h$]”h&]”uh1jd  hj‚  hžhhŸh³h Nubeh}”(h]”Œsysctl-variables”ah ]”h"]”Œsysctl variables”ah$]”h&]”uh1h´hh¶hžhhŸh³h K‘ubhµ)”}”(hhh]”(hº)”}”(hŒIOCTLS”h]”hŒIOCTLS”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj*  hžhhŸh³h K¾ubje  )”}”(hhh]”(jj  )”}”(hŒ—FIONREAD
Works as in udp(7): returns in the ``int`` argument pointer the size of
the next pending datagram in bytes, or 0 when no datagram is pending.
”h]”(jp  )”}”(hŒFIONREAD”h]”hŒFIONREAD”…””}”(hjB  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h KÁhj>  ubj€  )”}”(hhh]”hé)”}”(hŒ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.”h]”(hŒ#Works as in udp(7): returns in the ”…””}”(hjS  hžhhŸNh Nubj!  )”}”(hŒ``int``”h]”hŒint”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j   hjS  ubhŒc argument pointer the size of
the next pending datagram in bytes, or 0 when no datagram is pending.”…””}”(hjS  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KÀhjP  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj>  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h KÁhj;  ubjj  )”}”(hŒˆSIOCOUTQ
Returns the number of unsent data bytes in the socket send queue as ``int``
into the buffer specified by the argument pointer.
”h]”(jp  )”}”(hŒSIOCOUTQ”h]”hŒSIOCOUTQ”…””}”(hjƒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h KÅhj  ubj€  )”}”(hhh]”hé)”}”(hŒ~Returns the number of unsent data bytes in the socket send queue as ``int``
into the buffer specified by the argument pointer.”h]”(hŒDReturns the number of unsent data bytes in the socket send queue as ”…””}”(hj”  hžhhŸNh Nubj!  )”}”(hŒ``int``”h]”hŒint”…””}”(hjœ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j   hj”  ubhŒ3
into the buffer specified by the argument pointer.”…””}”(hj”  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KÄhj‘  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h KÅhj;  hžhubeh}”(h]”h ]”h"]”h$]”h&]”uh1jd  hj*  hžhhŸh³h Nubeh}”(h]”Œioctls”ah ]”h"]”Œioctls”ah$]”h&]”uh1h´hh¶hžhhŸh³h K¾ubhµ)”}”(hhh]”(hº)”}”(hŒOther tunables”h]”hŒOther tunables”…””}”(hjÑ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjÎ  hžhhŸh³h KÈubje  )”}”(hhh]”jj  )”}”(hX/  Per-route rto_min support
CCID-2 supports the RTAX_RTO_MIN per-route setting for the minimum value
of the RTO timer. This setting can be modified via the 'rto_min' option
of iproute2; for example::

        > ip route change 10.0.0.0/24   rto_min 250j dev wlan0
        > ip route add    10.0.0.254/32 rto_min 800j dev wlan0
        > ip route show dev wlan0

CCID-3 also supports the rto_min setting: it is used to define the lower
bound for the expiry of the nofeedback timer. This can be useful on LANs
with very low RTTs (e.g., loopback, Gbit ethernet).

”h]”(jp  )”}”(hŒPer-route rto_min support”h]”hŒPer-route rto_min support”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jo  hŸh³h KÕhjâ  ubj€  )”}”(hhh]”(hé)”}”(hŒ«CCID-2 supports the RTAX_RTO_MIN per-route setting for the minimum value
of the RTO timer. This setting can be modified via the 'rto_min' option
of iproute2; for example::”h]”hŒ®CCID-2 supports the RTAX_RTO_MIN per-route setting for the minimum value
of the RTO timer. This setting can be modified via the â€˜rto_minâ€™ option
of iproute2; for example:”…””}”(hj÷  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KÊhjô  ubjÃ  )”}”(hŒ‡> ip route change 10.0.0.0/24   rto_min 250j dev wlan0
> ip route add    10.0.0.254/32 rto_min 800j dev wlan0
> ip route show dev wlan0”h]”hŒ‡> ip route change 10.0.0.0/24   rto_min 250j dev wlan0
> ip route add    10.0.0.254/32 rto_min 800j dev wlan0
> ip route show dev wlan0”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jÂ  hŸh³h KÎhjô  ubhé)”}”(hŒÅCCID-3 also supports the rto_min setting: it is used to define the lower
bound for the expiry of the nofeedback timer. This can be useful on LANs
with very low RTTs (e.g., loopback, Gbit ethernet).”h]”hŒÅCCID-3 also supports the rto_min setting: it is used to define the lower
bound for the expiry of the nofeedback timer. This can be useful on LANs
with very low RTTs (e.g., loopback, Gbit ethernet).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KÒhjô  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hjâ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ji  hŸh³h KÕhjß  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jd  hjÎ  hžhhŸh³h Nubeh}”(h]”Œother-tunables”ah ]”h"]”Œother tunables”ah$]”h&]”uh1h´hh¶hžhhŸh³h KÈubhµ)”}”(hhh]”(hº)”}”(hŒNotes”h]”hŒNotes”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj;  hžhhŸh³h KØubhé)”}”(hŒ¼DCCP does not travel through NAT successfully at present on many boxes. This is
because the checksum covers the pseudo-header as per TCP and UDP. Linux NAT
support for DCCP has been added.”h]”hŒ¼DCCP does not travel through NAT successfully at present on many boxes. This is
because the checksum covers the pseudo-header as per TCP and UDP. Linux NAT
support for DCCP has been added.”…””}”(hjL  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hèhŸh³h KÙhj;  hžhubeh}”(h]”Œnotes”ah ]”h"]”Œnotes”ah$]”h&]”uh1h´hh¶hžhhŸh³h KØubeh}”(h]”Œdccp-protocol”ah ]”h"]”Œdccp protocol”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jg  jd  j*  j'  j   j  j  j|  j'  j$  jË  jÈ  j8  j5  j_  j\  uŒ	nametypes”}”(jg  ‰j*  ‰j   ‰j  ‰j'  ‰jË  ‰j8  ‰j_  ‰uh}”(jd  h¶j'  h×j  j-  j|  j£  j$  j‚  jÈ  j*  j5  jÎ  j\  j;  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.