From 71bb49596bbf4e5a3328e1704d18604e822ba181 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Query supported CCIDs This provides a data structure to record which CCIDs are locally supported and three accessor functions: - a test function for internal use which is used to validate CCID requests made by the user; - a copy function so that the list can be used for feature-negotiation; - documented getsockopt() support so that the user can query capabilities. The data structure is a table which is filled in at compile-time with the list of available CCIDs (which in turn depends on the Kconfig choices). Using the copy function for cloning the list of supported CCIDs is useful for feature negotiation, since the negotiation is now with the full list of available CCIDs (e.g. {2, 3}) instead of the default value {2}. This means negotiation will not fail if the peer requests to use CCID3 instead of CCID2. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Documentation/networking/dccp.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 39131a3c78f..f0aeb20fa63 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -57,6 +57,10 @@ 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_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 -- cgit v1.2.3-18-g5258 From 17c30b40ed79e9f3955e884632c8f01e577b204a Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Deprecate Ack Ratio sysctl This patch deprecates the Ack Ratio sysctl, since * Ack Ratio is entirely ignored by CCID-3 and CCID-4, * Ack Ratio currently doesn't work in CCID-2 (i.e. is always set to 1); * even if it would work in CCID-2, there is no point for a user to change it: - Ack Ratio is constrained by cwnd (RFC 4341, 6.1.2), - if Ack Ratio > cwnd, the system resorts to spurious RTO timeouts (since waiting for Acks which will never arrive in this window), - cwnd is not a user-configurable value. The only reasonable place for Ack Ratio is to print it for debugging. It is planned to do this later on, as part of e.g. dccp_probe. With this patch Ack Ratio is now under full control of feature negotiation: * Ack Ratio is resolved as a dependency of the selected CCID; * if the chosen CCID supports it (i.e. CCID == CCID-2), Ack Ratio is set to the default of 2, following RFC 4340, 11.3 - "New connections start with Ack Ratio 2 for both endpoints"; * what happens then is part of another patch set, since it concerns the dynamic update of Ack Ratio while the connection is in full flight. Thanks to Tomasz Grobelny for discussion leading up to this patch. Signed-off-by: Gerrit Renker Acked-by: Arnaldo Carvalho de Melo --- Documentation/networking/dccp.txt | 3 --- 1 file changed, 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index f0aeb20fa63..43df4487379 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -125,9 +125,6 @@ send_ndp = 1 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. -- cgit v1.2.3-18-g5258 From fade756f18d42694e3acb00e3471ab43002cba16 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Set per-connection CCIDs via socket options With this patch, TX/RX CCIDs can now be changed on a per-connection basis, which overrides the defaults set by the global sysctl variables for TX/RX CCIDs. To make full use of this facility, the remaining patches of this patch set are needed, which track dependencies and activate negotiated feature values. Note on the maximum number of CCIDs that can be registered: ----------------------------------------------------------- The maximum number of CCIDs that can be registered on the socket is constrained by the space in a Confirm/Change feature negotiation option. The space in these in turn depends on the size of header options as defined in RFC 4340, 5.8. Since this is a recurring constant, it has been moved from ackvec.h into linux/dccp.h, clarifying its purpose. Relative to this size, the maximum number of CCID identifiers that can be present in a Confirm option (which always consumes 1 byte more than a Change option, cf. 6.1) is 2 bytes less than the maximum TLV size: one for the CCID-feature-type and one for the selected value. Signed-off-by: Gerrit Renker --- Documentation/networking/dccp.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 43df4487379..610083ff73f 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -61,6 +61,20 @@ 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 -- cgit v1.2.3-18-g5258 From 78673e24df27c76ec75565f4024d45c2c74ef148 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Remove obsolete parts of the old CCID interface The TX/RX CCIDs of the minisock are now redundant: similar to the Ack Vector case, their value equals initially that of the sysctl, but at the end of feature negotiation may be something different. The old interface removed by this patch thus has been replaced by the newer interface to dynamically query the currently loaded CCIDs earlier in this patch set. Also removed the constructors for the TX CCID and the RX CCID, since the switch rx/non-rx is done by the handler in minisocks.c (and the handler is the only place in the code where CCIDs are loaded). Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Documentation/networking/dccp.txt | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 610083ff73f..a203d132dbe 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -140,10 +140,11 @@ send_ackvec = 1 Whether or not to send Ack Vector options (sec. 11.5). 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). -- cgit v1.2.3-18-g5258 From 68e074bfcef269bc61006c2740d7f89ccbbd93d7 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Remove manual influence on NDP Count feature Updating the NDP count feature is handled automatically now: * for CCID-2 it is disabled, since the code does not use NDP counts; * for CCID-3 it is enabled, as NDP counts are used to determine loss lengths. Allowing the user to change NDP values leads to unpredictable and failing behaviour, since it is then possible to disable NDP counts even when they are needed (e.g. in CCID-3). This means that only those user settings are sensible that agree with the values for Send NDP Count implied by the choice of CCID. But those settings are already activated by the feature negotiation (CCID dependency tracking), hence this form of support is redundant. At startup the initialisation of the NDP count feature is with the default value of 0, which is done implicitly by the zeroing-out of the socket when it is allocated. If the choice of CCID or feature negotiation enables NDP count, this will then be updated via the NDP activation handler. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Documentation/networking/dccp.txt | 3 --- 1 file changed, 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index a203d132dbe..1403745ab40 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -133,9 +133,6 @@ 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). -- cgit v1.2.3-18-g5258 From b235dc4abbc1356284bd0dc730efa711f394e0e2 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp ccid-2: Phase out the use of boolean Ack Vector sysctl This removes the use of the sysctl and the minisock variable for the Send Ack Vector feature, which is now handled fully dynamically via feature negotiation; i.e. when CCID2 is enabled, Ack Vectors are automatically enabled (as per RFC 4341, 4.). Using a sysctl in parallel to this implementation would open the door to crashes, since much of the code relies on tests of the boolean minisock / sysctl variable. Thus, this patch replaces all tests of type if (dccp_msk(sk)->dccpms_send_ack_vector) /* ... */ with if (dp->dccps_hc_rx_ackvec != NULL) /* ... */ The dccps_hc_rx_ackvec is allocated by the dccp_hdlr_ackvec() when feature negotiation concluded that Ack Vectors are to be used on the half-connection. Otherwise, it is NULL (due to dccp_init_sock/dccp_create_openreq_child), so that the test is a valid one. The activation handler for Ack Vectors is called as soon as the feature negotiation has concluded at the * server when the Ack marking the transition RESPOND => OPEN arrives; * client after it has sent its ACK, marking the transition REQUEST => PARTOPEN. Adding the sequence number of the Response packet to the Ack Vector has been removed, since (a) connection establishment implies that the Response has been received; (b) the CCIDs only look at packets received in the (PART)OPEN state, i.e. this entry will always be ignored; (c) it can not be used for anything useful - to detect loss for instance, only packets received after the loss can serve as pseudo-dupacks. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Documentation/networking/dccp.txt | 3 --- 1 file changed, 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 1403745ab40..7a3bb1abb83 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -133,9 +133,6 @@ retries2 importance for retransmitted acknowledgments and feature negotiation, data packets are never retransmitted. Analogue of tcp_retries2. -send_ackvec = 1 - Whether or not to send Ack Vector options (sec. 11.5). - 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. -- cgit v1.2.3-18-g5258 From 51c7d4fa2675c106a980ddcdbe308b54b5151945 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Implement both feature-local and feature-remote Sequence Window feature This adds full support for local/remote Sequence Window feature, from which the * sequence-number-validity (W) and * acknowledgment-number-validity (W') windows derive as specified in RFC 4340, 7.5.3. Specifically, the following changes are introduced: * integrated new socket fields into dccp_sk; * updated the update_gsr/gss routines with regard to these fields; * updated handler code: the Sequence Window feature is located at the TX side, so the local feature is meant if the handler-rx flag is false; * the initialisation of `rcv_wnd' in reqsk is removed, since - rcv_wnd is not used by the code anywhere; - sequence number checks are not done in the LISTEN state (cf. 7.5.3); - dccp_check_req checks the Ack number validity more rigorously; * the `struct dccp_minisock' became empty and is now removed. Until the handshake completes with activating negotiated values, the local/remote Sequence-Window values are undefined and thus can not reliably be estimated. This issue is addressed in a separate patch. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Documentation/networking/dccp.txt | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index 7a3bb1abb83..b132e4a3cf0 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -141,7 +141,8 @@ rx_ccid = 2 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 -- cgit v1.2.3-18-g5258 From d6da3511d6b558d0b017777b61dc08b8fbc06ea4 Mon Sep 17 00:00:00 2001 From: Tomasz Grobelny Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: dccp: Policy-based packet dequeueing infrastructure This patch adds a generic infrastructure for policy-based dequeueing of TX packets and provides two policies: * a simple FIFO policy (which is the default) and * a priority based policy (set via socket options). Both policies honour the tx_qlen sysctl for the maximum size of the write queue (can be overridden via socket options). The priority policy uses skb->priority internally to assign an u32 priority identifier, using the same ranking as SO_PRIORITY. The skb->priority field is set to 0 when the packet leaves DCCP. The priority is supplied as ancillary data using cmsg(3), the patch also provides the requisite parsing routines. Signed-off-by: Tomasz Grobelny Signed-off-by: Gerrit Renker --- Documentation/networking/dccp.txt | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'Documentation') diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index b132e4a3cf0..fcfc1253442 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -45,6 +45,25 @@ http://linux-net.osdl.org/index.php/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, -- cgit v1.2.3-18-g5258