Lines Matching +full:software +full:- +full:generated
1 .. SPDX-License-Identifier: GPL-2.0
43 -------------------------------------------------------------
59 -------------------------------------------------------------------
72 ----------------------------------------------------------------------
97 Timestamps may also be generated for reasons other than being
102 Request rx timestamps generated by the network adapter.
106 are generated just after a device driver hands a packet to the
110 Request tx timestamps generated by the network adapter. This flag
115 are generated in the device driver as close as possible, but always
130 a timestamp is generated at each layer. This allows for fine
138 over-report measurement, because the timestamp is generated when all
148 generated control message. Changes to the bits take immediate
154 Report any software timestamps when available.
160 Report hardware timestamps as generated by
181 is derived from a per-socket u32 counter (that wraps). For datagram
197 The process can optionally override the default generated ID, by
204 cmsg->cmsg_level = SOL_SOCKET;
205 cmsg->cmsg_type = SCM_TS_OPT_ID;
206 cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
222 a timestamp with counter N-1. SOF_TIMESTAMPING_OPT_ID_TCP
272 received the packet and its length at layer 2. A valid (non-zero)
278 Request both hardware and software timestamps for outgoing packets
280 are enabled at the same time. If both timestamps are generated,
288 Receive timestamps are generated early in the ingress path, before a
297 ignore the unexpected non-zero value. But it makes behavior subtly
324 cmsg->cmsg_level = SOL_SOCKET;
325 cmsg->cmsg_type = SO_TIMESTAMPING;
326 cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
344 -------------------------
354 correlating a timestamp with data is non-trivial. A range of bytes
372 bytestreams, we chose that a timestamp is generated only when all
383 relevant sequence number in skb_shinfo(skb)->tskey. Because an skbuff
384 has only one such field, only one timestamp can be generated.
392 autocork. After linux-4.7, a better way to prevent coalescing is
395 These precautions ensure that the timestamp is generated only when all
409 page (`man 7 socket`) describes how timestamps generated with
414 ----------------------------
437 feature. At least one field is non-zero at any time. Most timestamps
444 as linuxptp. For the PTP clock API, see Documentation/driver-api/ptp.rst.
448 software timestamp will be generated in the recvmsg() call and passed
449 in ts[0] when a real software timestamp is missing. This happens also
481 is the first if ts[2] is non-zero, the second otherwise, in which
509 Reading from the error queue is always a non-blocking operation. To
524 implicitly defined. ts[0] holds a software timestamp if set, ts[1]
574 If the requested fine-grained filtering for incoming packets is not
581 /* possible values for hwtstamp_config->tx_type */
599 /* possible values for hwtstamp_config->rx_filter */
619 --------------------------------------------------------
638 Time stamps for outgoing packets are to be generated as follows:
640 - In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
641 is set no-zero. If yes, then the driver is expected to do hardware time
643 - If this is possible for the skb and requested, then declare
645 SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with::
647 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
652 software generated time stamps by the network subsystem.
653 - Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware
654 as possible. skb_tx_timestamp() provides a software time stamp if requested
656 - As soon as the driver has sent the packet and/or obtained a
662 should not fall back to software time stamping. The rationale is that
664 software time stamping and therefore could lead to unexpected deltas
668 ----------------------------------------------------------
709 - ``.port_txtstamp()``: a hook called prior to the transmission of
711 This is required for two-step timestamping, since the hardware
714 packet so that it can re-enqueue the packet back into the socket's
717 in skb->cb and enqueue a tx skb queue. Typically, a switch will have a
720 key-value pairs of PTP sequence ID/message type/domain number and the
728 One-step TX timestamping do not require packet cloning, since there is
729 no follow-up message required by the PTP protocol (because the
732 to be re-enqueued into its socket's error queue.
734 - ``.port_rxtstamp()``: On RX, the BPF classifier is run by DSA to
739 timestamps might either be available in-band (through metadata in the
740 DSA header, or attached in other ways to the packet), or out-of-band
756 mii_timestamper`` and add a pointer to it in ``phydev->mii_ts``. The presence
764 - Checking, in ``.ndo_eth_ioctl``, whether ``phy_has_hwtstamp(netdev->phydev)``
768 - On RX, special intervention may or may not be needed, depending on the
771 ``skb_defer_rx_timestamp(skb)`` is necessary or not - and if it is, don't
773 enabled, and ``skb->dev->phydev->mii_ts`` exists, its ``.rxtstamp()`` hook
784 - On TX, again, special intervention might or might not be needed. The
785 function that calls the ``mii_ts->txtstamp()`` hook is named
789 drivers already perform for software timestamping purposes. Therefore, if a
790 MAC supports software timestamping, it does not need to do anything further
806 Stacked PHCs, especially DSA (but not only) - since that doesn't require any
808 all possible code paths - is that they uncover bugs which were impossible to
812 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
823 the ``.ndo_eth_ioctl`` ("``priv->hwtstamp_tx_enabled == true``") and the
824 current skb requires a TX timestamp ("``skb_shinfo(skb)->tx_flags &
826 "``skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS``" flag. Note: as
834 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``" was set. With a stacked
841 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``", but also for
842 "``priv->hwtstamp_tx_enabled == true``". Because the rest of the system ensures