linux-toradex.git/Documentation/networking/timestamping.txt, branch v4.14-rc4

net: Fix minor code bug in timestamping.txt

2017-07-11T20:34:54+00:00

Passing (void*)val instead of &val would make a pointer out of an integer
and cause sock_setsockopt to -EFAULT.

See tools/testing/selftests/networking/timestamping/timestamping.c
for a working example.

Cc: David S. Miller 
Cc: netdev@vger.kernel.org
Signed-off-by: Ahmad Fatoum 
Signed-off-by: David S. Miller

net: allow simultaneous SW and HW transmit timestamping

2017-05-21T17:37:32+00:00

Add SOF_TIMESTAMPING_OPT_TX_SWHW option to allow an outgoing packet to
be looped to the socket's error queue with a software timestamp even
when a hardware transmit timestamp is expected to be provided by the
driver.

Applications using this option will receive two separate messages from
the error queue, one with a software timestamp and the other with a
hardware timestamp. As the hardware timestamp is saved to the shared skb
info, which may happen before the first message with software timestamp
is received by the application, the hardware timestamp is copied to the
SCM_TIMESTAMPING control message only when the skb has no software
timestamp or it is an incoming packet.

While changing sw_tx_timestamp(), inline it in skb_tx_timestamp() as
there are no other users.

CC: Richard Cochran 
CC: Willem de Bruijn 
Signed-off-by: Miroslav Lichvar 
Acked-by: Willem de Bruijn 
Signed-off-by: David S. Miller

net: fix documentation of struct scm_timestamping

2017-05-21T17:37:32+00:00

The scm_timestamping struct may return multiple non-zero fields, e.g.
when both software and hardware RX timestamping is enabled, or when the
SO_TIMESTAMP(NS) option is combined with SCM_TIMESTAMPING and a false
software timestamp is generated in the recvmsg() call in order to always
return a SCM_TIMESTAMP(NS) message.

CC: Richard Cochran 
CC: Willem de Bruijn 
Signed-off-by: Miroslav Lichvar 
Acked-by: Willem de Bruijn 
Signed-off-by: David S. Miller

net: add new control message for incoming HW-timestamped packets

2017-05-21T17:37:32+00:00

Add SOF_TIMESTAMPING_OPT_PKTINFO option to request a new control message
for incoming packets with hardware timestamps. It contains the index of
the real interface which received the packet and the length of the
packet at layer 2.

The index is useful with bonding, bridges and other interfaces, where
IP_PKTINFO doesn't allow applications to determine which PHC made the
timestamp. With the L2 length (and link speed) it is possible to
transpose preamble timestamps to trailer timestamps, which are used in
the NTP protocol.

While this information could be provided by two new socket options
independently from timestamping, it doesn't look like they would be very
useful. With this option any performance impact is limited to hardware
timestamping.

Use dev_get_by_napi_id() to get the device and its index. On kernels
with disabled CONFIG_NET_RX_BUSY_POLL or drivers not using NAPI, a zero
index will be returned in the control message.

CC: Richard Cochran 
Acked-by: Willem de Bruijn 
Signed-off-by: Miroslav Lichvar 
Signed-off-by: David S. Miller

tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING

2016-11-30T15:04:25+00:00

This patch exports the sender chronograph stats via the socket
SO_TIMESTAMPING channel. Currently we can instrument how long a
particular application unit of data was queued in TCP by tracking
SOF_TIMESTAMPING_TX_SOFTWARE and SOF_TIMESTAMPING_TX_SCHED. Having
these sender chronograph stats exported simultaneously along with
these timestamps allow further breaking down the various sender
limitation.  For example, a video server can tell if a particular
chunk of video on a connection takes a long time to deliver because
TCP was experiencing small receive window. It is not possible to
tell before this patch without packet traces.

To prepare these stats, the user needs to set
SOF_TIMESTAMPING_OPT_STATS and SOF_TIMESTAMPING_OPT_TSONLY flags
while requesting other SOF_TIMESTAMPING TX timestamps. When the
timestamps are available in the error queue, the stats are returned
in a separate control message of type SCM_TIMESTAMPING_OPT_STATS,
in a list of TLVs (struct nlattr) of types: TCP_NLA_BUSY_TIME,
TCP_NLA_RWND_LIMITED, TCP_NLA_SNDBUF_LIMITED. Unit is microsecond.

Signed-off-by: Francis Yan 
Signed-off-by: Yuchung Cheng 
Signed-off-by: Soheil Hassas Yeganeh 
Acked-by: Neal Cardwell 
Signed-off-by: David S. Miller

sock: document timestamping via cmsg in Documentation

2016-04-04T19:50:30+00:00

Update docs and add code snippet for using cmsg for timestamping.

Signed-off-by: Soheil Hassas Yeganeh 
Acked-by: Willem de Bruijn 
Signed-off-by: David S. Miller

clarify implementation of ethtool's get_ts_info op

2015-07-18T02:59:04+00:00

This patch adds some clarification about the intended way to implement
both SIOCSHWTSTAMP and ethtool's get_ts_info. The HWTSTAMP API has
several Rx filters which are very specific, as well as more general
filters. The specific filters really only exist to support some broken
hardware which can't fully implement the generic filters. This patch
adds clarification that it is okay to support the specific filters in
SIOCSHWTSTAMP by upscaling them to the generic filters. In addition,
update the header for ethtool_ts_info to specify that drivers ought to
only report the filters they support without upscaling in this manner.

Signed-off-by: Jacob Keller 
Acked-by: Richard Cochran 
Tested-by: Phil Schmitt 
Reviewed-by: Aaron Brown 
Signed-off-by: Jeff Kirsher

net-timestamp: no-payload option

2015-02-03T02:46:51+00:00

Add timestamping option SOF_TIMESTAMPING_OPT_TSONLY. For transmit
timestamps, this loops timestamps on top of empty packets.

Doing so reduces the pressure on SO_RCVBUF. Payload inspection and
cmsg reception (aside from timestamps) are no longer possible. This
works together with a follow on patch that allows administrators to
only allow tx timestamping if it does not loop payload or metadata.

Signed-off-by: Willem de Bruijn 

----

Changes (rfc -> v1)
  - add documentation
  - remove unnecessary skb->len test (thanks to Richard Cochran)
Signed-off-by: David S. Miller

net-timestamp: expand documentation and test

2014-12-09T01:20:48+00:00

Documentation:
  expand explanation of timestamp counter

Test:
  new: flag -I requests and prints PKTINFO
  new: flag -x prints payload (possibly truncated)
  fix: remove pretty print that breaks common flag '-l 1'

Signed-off-by: Willem de Bruijn 
Signed-off-by: David S. Miller

net-timestamp: allow reading recv cmsg on errqueue with origin tstamp

2014-12-09T01:20:48+00:00

Allow reading of timestamps and cmsg at the same time on all relevant
socket families. One use is to correlate timestamps with egress
device, by asking for cmsg IP_PKTINFO.

on AF_INET sockets, call the relevant function (ip_cmsg_recv). To
avoid changing legacy expectations, only do so if the caller sets a
new timestamping flag SOF_TIMESTAMPING_OPT_CMSG.

on AF_INET6 sockets, IPV6_PKTINFO and all other recv cmsg are already
returned for all origins. only change is to set ifindex, which is
not initialized for all error origins.

In both cases, only generate the pktinfo message if an ifindex is
known. This is not the case for ACK timestamps.

The difference between the protocol families is probably a historical
accident as a result of the different conditions for generating cmsg
in the relevant ip(v6)_recv_error function:

ipv4:        if (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP) {
ipv6:        if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL) {

At one time, this was the same test bar for the ICMP/ICMP6
distinction. This is no longer true.

Signed-off-by: Willem de Bruijn 

----

Changes
  v1 -> v2
    large rewrite
    - integrate with existing pktinfo cmsg generation code
    - on ipv4: only send with new flag, to maintain legacy behavior
    - on ipv6: send at most a single pktinfo cmsg
    - on ipv6: initialize fields if not yet initialized

The recv cmsg interfaces are also relevant to the discussion of
whether looping packet headers is problematic. For v6, cmsgs that
identify many headers are already returned. This patch expands
that to v4. If it sounds reasonable, I will follow with patches

1. request timestamps without payload with SOF_TIMESTAMPING_OPT_TSONLY
   (http://patchwork.ozlabs.org/patch/366967/)
2. sysctl to conditionally drop all timestamps that have payload or
   cmsg from users without CAP_NET_RAW.
Signed-off-by: David S. Miller