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
180 is derived from a per-socket u32 counter (that wraps). For datagram
207 a timestamp with counter N-1. SOF_TIMESTAMPING_OPT_ID_TCP
257 received the packet and its length at layer 2. A valid (non-zero)
263 Request both hardware and software timestamps for outgoing packets
265 are enabled at the same time. If both timestamps are generated,
292 cmsg->cmsg_level = SOL_SOCKET;
293 cmsg->cmsg_type = SO_TIMESTAMPING;
294 cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
312 -------------------------
322 correlating a timestamp with data is non-trivial. A range of bytes
340 bytestreams, we chose that a timestamp is generated only when all
351 relevant sequence number in skb_shinfo(skb)->tskey. Because an skbuff
352 has only one such field, only one timestamp can be generated.
362 These precautions ensure that the timestamp is generated only when all
376 page (`man 7 socket`) describes how timestamps generated with
381 ----------------------------
404 feature. At least one field is non-zero at any time. Most timestamps
411 as linuxptp. For the PTP clock API, see Documentation/driver-api/ptp.rst.
415 software timestamp will be generated in the recvmsg() call and passed
416 in ts[0] when a real software timestamp is missing. This happens also
448 is the first if ts[2] is non-zero, the second otherwise, in which
476 Reading from the error queue is always a non-blocking operation. To
491 implicitly defined. ts[0] holds a software timestamp if set, ts[1]
512 the requested fine-grained filtering for incoming packets is not
539 /* possible values for hwtstamp_config->tx_type */
557 /* possible values for hwtstamp_config->rx_filter */
577 --------------------------------------------------------
595 Time stamps for outgoing packets are to be generated as follows:
597 - In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
598 is set no-zero. If yes, then the driver is expected to do hardware time
600 - If this is possible for the skb and requested, then declare
602 SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with::
604 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
609 software generated time stamps by the network subsystem.
610 - Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware
611 as possible. skb_tx_timestamp() provides a software time stamp if requested
613 - As soon as the driver has sent the packet and/or obtained a
619 should not fall back to software time stamping. The rationale is that
621 software time stamping and therefore could lead to unexpected deltas
625 ----------------------------------------------------------
666 - ``.port_txtstamp()``: a hook called prior to the transmission of
668 This is required for two-step timestamping, since the hardware
671 packet so that it can re-enqueue the packet back into the socket's
674 in skb->cb and enqueue a tx skb queue. Typically, a switch will have a
677 key-value pairs of PTP sequence ID/message type/domain number and the
685 One-step TX timestamping do not require packet cloning, since there is
686 no follow-up message required by the PTP protocol (because the
689 to be re-enqueued into its socket's error queue.
691 - ``.port_rxtstamp()``: On RX, the BPF classifier is run by DSA to
696 timestamps might either be available in-band (through metadata in the
697 DSA header, or attached in other ways to the packet), or out-of-band
713 mii_timestamper`` and add a pointer to it in ``phydev->mii_ts``. The presence
721 - Checking, in ``.ndo_eth_ioctl``, whether ``phy_has_hwtstamp(netdev->phydev)``
725 - On RX, special intervention may or may not be needed, depending on the
728 ``skb_defer_rx_timestamp(skb)`` is necessary or not - and if it is, don't
730 enabled, and ``skb->dev->phydev->mii_ts`` exists, its ``.rxtstamp()`` hook
741 - On TX, again, special intervention might or might not be needed. The
742 function that calls the ``mii_ts->txtstamp()`` hook is named
746 drivers already perform for software timestamping purposes. Therefore, if a
747 MAC supports software timestamping, it does not need to do anything further
763 Stacked PHCs, especially DSA (but not only) - since that doesn't require any
765 all possible code paths - is that they uncover bugs which were impossible to
769 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
780 the ``.ndo_eth_ioctl`` ("``priv->hwtstamp_tx_enabled == true``") and the
781 current skb requires a TX timestamp ("``skb_shinfo(skb)->tx_flags &
783 "``skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS``" flag. Note: as
791 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``" was set. With a stacked
798 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``", but also for
799 "``priv->hwtstamp_tx_enabled == true``". Because the rest of the system ensures