Re: [PATCH net-next v6 1/2] net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2024-09-09 02:54:57
Also in:
linux-doc
Jason Xing wrote:
From: Jason Xing <kernelxing@tencent.com> 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 <willemb@google.com> Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Willem de Bruijn <willemb@google.com> I really only suggested making this a new flag, not the main idea of filtering.
quoted hunk ↗ jump to hunk
--- v6 Link: https://lore.kernel.org/all/20240906095640.77533-1-kerneljasonxing@gmail.com/ (local) 1. add the description in doc provided by Willem 2. align the if statements (Willem) v5 Link: https://lore.kernel.org/all/20240905071738.3725-1-kerneljasonxing@gmail.com/ (local) 1. squash the hardware case patch into this one (Willem) 2. update corresponding commit message and doc (Willem) 3. remove the limitation in sock_set_timestamping() and restore the simplification branches. (Willem) v4 Link: https://lore.kernel.org/all/20240830153751.86895-2-kerneljasonxing@gmail.com/ (local) 1. revise the commit message and doc (Willem) 2. simplify the test statement (Jakub) 3. add Willem's reviewed-by tag (Willem) v3 1. Willem suggested this alternative way to solve the issue, so I added his Suggested-by tag here. Thanks! --- Documentation/networking/timestamping.rst | 17 +++++++++++++++++ include/uapi/linux/net_tstamp.h | 3 ++- net/ethtool/common.c | 1 + net/ipv4/tcp.c | 9 +++++++-- net/socket.c | 10 ++++++++-- 5 files changed, 35 insertions(+), 5 deletions(-)diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst index 9c7773271393..8199e6917671 100644 --- a/Documentation/networking/timestamping.rst +++ b/Documentation/networking/timestamping.rst@@ -267,6 +267,23 @@ SOF_TIMESTAMPING_OPT_TX_SWHW: two separate messages will be looped to the socket's error queue, each containing just one timestamp. +SOF_TIMESTAMPING_OPT_RX_FILTER: + Filter out spurious receive timestamps: report a receive timestamp + only if the matching timestamp generation flag is enabled. + + Receive timestamps are generated early in the ingress path, before a + packet's destination socket is known. If any socket enables receive + timestamps, packets for all socket will receive timestamped packets.
nit: s/packets for all socket/all sockets/ My error in my suggestion. Not important enough to respin.
+ Including those that request timestamp reporting with + SOF_TIMESTAMPING_SOFTWARE and/or SOF_TIMESTAMPING_RAW_HARDWARE, but + do not request receive timestamp generation. This can happen when + requesting transmit timestamps only.