kernel.git/Documentation/networking/timestamping.rst, branch linux-rolling-lts

docs: networking: timestamping: improve stacked PHC sentence

2025-05-13T22:40:54Z

The first paragraph makes no grammatical sense. I suppose a portion of the intended sentece is missing: "[The challenge with ] stacked PHCs (...) is that they uncover bugs". Rephrase, and at the same time simplify the structure of the sentence a little bit, it is not easy to follow. Fixes: 94d9f78f4d64 ("docs: networking: timestamping: add section for stacked PHC devices") Signed-off-by: Vladimir Oltean Acked-by: Richard Cochran Link: https://patch.msgid.link/20250512131751.320283-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski

net-timestamp: COMPLETION timestamp on packet tx completion

2025-03-25T16:48:05Z

Add SOF_TIMESTAMPING_TX_COMPLETION, for requesting a software timestamp when hardware reports a packet completed. Completion tstamp is useful for Bluetooth, as hardware timestamps do not exist in the HCI specification except for ISO packets, and the hardware has a queue where packets may wait. In this case the software SND timestamp only reflects the kernel-side part of the total latency (usually small) and queue length (usually 0 unless HW buffers congested), whereas the completion report time is more informative of the true latency. It may also be useful in other cases where HW TX timestamps cannot be obtained and user wants to estimate an upper bound to when the TX probably happened. Signed-off-by: Pauli Virtanen Reviewed-by: Willem de Bruijn Signed-off-by: Luiz Augusto von Dentz

net: ethtool: Add support for tsconfig command to get/set hwtstamp config

2024-12-16T12:51:41Z

Introduce support for ETHTOOL_MSG_TSCONFIG_GET/SET ethtool netlink socket to read and configure hwtstamp configuration of a PHC provider. Note that simultaneous hwtstamp isn't supported; configuring a new one disables the previous setting. Signed-off-by: Kory Maincent Signed-off-by: David S. Miller

net_tstamp: add SCM_TS_OPT_ID to provide OPT_ID in control message

2024-10-04T18:52:19Z

SOF_TIMESTAMPING_OPT_ID socket option flag gives a way to correlate TX timestamps and packets sent via socket. Unfortunately, there is no way to reliably predict socket timestamp ID value in case of error returned by sendmsg. For UDP sockets it's impossible because of lockless nature of UDP transmit, several threads may send packets in parallel. In case of RAW sockets MSG_MORE option makes things complicated. More details are in the conversation [1]. This patch adds new control message type to give user-space software an opportunity to control the mapping between packets and values by providing ID with each sendmsg for UDP sockets. The documentation is also added in this patch. [1] https://lore.kernel.org/netdev/CALCETrU0jB+kg0mhV6A8mrHfTE1D1pr1SD_B9Eaa9aDPfgHdtA@mail.gmail.com/ Reviewed-by: Willem de Bruijn Reviewed-by: Jason Xing Signed-off-by: Vadim Fedorenko Link: https://patch.msgid.link/20241001125716.2832769-2-vadfed@meta.com Signed-off-by: Jakub Kicinski

net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag

2024-09-10T23:55:23Z

introduce a new flag SOF_TIMESTAMPING_OPT_RX_FILTER in the receive path. User can set it with SOF_TIMESTAMPING_SOFTWARE to filter out rx software timestamp report, especially after a process turns on netstamp_needed_key which can time stamp every incoming skb. Previously, we found out if an application starts first which turns on netstamp_needed_key, then another one only passing SOF_TIMESTAMPING_SOFTWARE could also get rx timestamp. Now we handle this case by introducing this new flag without breaking users. Quoting Willem to explain why we need the flag: "why a process would want to request software timestamp reporting, but not receive software timestamp generation. The only use I see is when the application does request SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_TX_SOFTWARE." Similarly, this new flag could also be used for hardware case where we can set it with SOF_TIMESTAMPING_RAW_HARDWARE, then we won't receive hardware receive timestamp. Another thing about errqueue in this patch I have a few words to say: In this case, we need to handle the egress path carefully, or else reporting the tx timestamp will fail. Egress path and ingress path will finally call sock_recv_timestamp(). We have to distinguish them. Errqueue is a good indicator to reflect the flow direction. Suggested-by: Willem de Bruijn Signed-off-by: Jason Xing Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20240909015612.3856-2-kerneljasonxing@gmail.com Signed-off-by: Jakub Kicinski

net-timestamp: correct the use of SOF_TIMESTAMPING_RAW_HARDWARE

2024-09-10T23:55:08Z

SOF_TIMESTAMPING_RAW_HARDWARE is a report flag which passes the timestamps generated by either SOF_TIMESTAMPING_TX_HARDWARE or SOF_TIMESTAMPING_RX_HARDWARE to the userspace all the time. So let us revise the doc here. Link: https://lore.kernel.org/all/66d8c21d3042a_163d93294cb@willemb.c.googlers.com.notmuch/ Suggested-by: Willem de Bruijn Reviewed-by: Willem de Bruijn Signed-off-by: Jason Xing Link: https://patch.msgid.link/20240908124141.39628-1-kerneljasonxing@gmail.com Signed-off-by: Jakub Kicinski

docs: networking: timestamping: mention MSG_EOR flag

2023-12-14T02:19:39Z

TCP got MSG_EOR support in linux-4.7. This is a canonical way of making sure no coalescing will be performed on the skb, even if it could not be immediately sent. Signed-off-by: Eric Dumazet Cc: Martin KaFai Lau Acked-by: Willem de Bruijn Link: https://lore.kernel.org/r/20231212110608.3673677-1-edumazet@google.com Signed-off-by: Jakub Kicinski

net_tstamp: add SOF_TIMESTAMPING_OPT_ID_TCP

2022-12-09T03:49:21Z

Add an option to initialize SOF_TIMESTAMPING_OPT_ID for TCP from write_seq sockets instead of snd_una. This should have been the behavior from the start. Because processes may now exist that rely on the established behavior, do not change behavior of the existing option, but add the right behavior with a new flag. It is encouraged to always set SOF_TIMESTAMPING_OPT_ID_TCP on stream sockets along with the existing SOF_TIMESTAMPING_OPT_ID. Intuitively the contract is that the counter is zero after the setsockopt, so that the next write N results in a notification for the last byte N - 1. On idle sockets snd_una == write_seq and this holds for both. But on sockets with data in transmission, snd_una records the unacked offset in the stream. This depends on the ACK response from the peer. A process cannot learn this in a race free manner (ioctl SIOCOUTQ is one racy approach). write_seq records the offset at the last byte written by the process. This is a better starting point. It matches the intuitive contract in all circumstances, unaffected by external behavior. The new timestamp flag necessitates increasing sk_tsflags to 32 bits. Move the field in struct sock to avoid growing the socket (for some common CONFIG variants). The UAPI interface so_timestamping.flags is already int, so 32 bits wide. Reported-by: Sotirios Delimanolis Signed-off-by: Willem de Bruijn Link: https://lore.kernel.org/r/20221207143701.29861-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski

docs: networking: Use netif_rx().

2022-03-04T12:02:19Z

Since commit baebdf48c3600 ("net: dev: Makes sure netif_rx() can be invoked in any context.") the function netif_rx() can be used in preemptible/thread context as well as in interrupt context. Use netif_rx(). Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

docs: networking: replace skb_hwtstamp_tx with skb_tstamp_tx

2021-12-21T02:47:11Z

Tiny doc fix. The hardware transmit function was called skb_tstamp_tx from its introduction in commit ac45f602ee3d ("net: infrastructure for hardware time stamping") in the same series as this documentation. Fixes: cb9eff097831 ("net: new user space API for time stamping of incoming and outgoing packets") Signed-off-by: Willem de Bruijn Link: https://lore.kernel.org/r/20211220144608.2783526-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski