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| author | Alejandro Colomar <colomar.6.4.3@gmail.com> | 2020-04-06 09:30:55 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2020-04-06 10:07:04 +0200 |
| commit | a47d370bb356ad40ce0eaa21c48c81a8aba801e4 (patch) | |
| tree | ec8ff3e7ec7a34e8eddbbb5ade405610c97656a4 /man7/socket.7 | |
| parent | f3c29937e678c3baf89b138d822e6edd46af7009 (diff) | |
| download | man-pages-a47d370bb356ad40ce0eaa21c48c81a8aba801e4.tar.gz | |
socket.7: Document SO_TIMESTAMPNS
===========
DESCRIPTION
===========
I added a paragraph for ``SO_TIMESTAMP``, and modified the
paragraph for ``SIOCGSTAMP`` in relation to ``SO_TIMESTAMPNS``.
I based the documentation on the existing ``SO_TIMESTAMP``
documentation, and
on my experience using ``SO_TIMESTAMPNS``.
I asked a question on stackoverflow, which helped me understand
``SO_TIMESTAMPNS``:
https://stackoverflow.com/q/60971556/6872717
Testing of the feature being documented
=======================================
I wrote a simple server and client test.
In the client side, I connected a socket specifying
``SOCK_STREAM`` and ``"tcp"``.
Then I enabled timestamp in ns:
.. code-block:: c
int enable = 1;
if (setsockopt(sd, SOL_SOCKET, SO_TIMESTAMPNS, &enable,
sizeof(enable)))
goto err;
Then I prepared the msg header:
.. code-block:: c
char buf[BUFSIZ];
char cbuf[BUFSIZ];
struct msghdr msg;
struct iovec iov;
memset(buf, 0, ARRAY_BYTES(buf));
iov.iov_len = ARRAY_BYTES(buf) - 1;
iov.iov_base = buf;
msg.msg_name = NULL;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cbuf;
msg.msg_controllen = ARRAY_BYTES(cbuf);
And got some times before and after receiving the msg:
.. code-block:: c
struct timespec tm_before, tm_recvmsg, tm_after, tm_msg;
clock_gettime(CLOCK_REALTIME, &tm_before);
usleep(500000);
clock_gettime(CLOCK_REALTIME, &tm_recvmsg);
n = recvmsg(sd, &msg, MSG_WAITALL);
if (n < 0)
goto err;
usleep(1000000);
clock_gettime(CLOCK_REALTIME, &tm_after);
After that I read the timestamp of the msg:
.. code-block:: c
struct cmsghdr *cmsg;
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg;
cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SO_TIMESTAMPNS) {
memcpy(&tm_msg, CMSG_DATA(cmsg), sizeof(tm_msg));
break;
}
}
if (!cmsg)
goto err;
And finally printed the results:
.. code-block:: c
double tdiff;
printf("%s\n", buf);
tdiff = timespec_diff_ms(&tm_before, &tm_recvmsg);
printf("tm_r - tm_b = %lf ms\n", tdiff);
tdiff = timespec_diff_ms(&tm_before, &tm_after);
printf("tm_a - tm_b = %lf ms\n", tdiff);
tdiff = timespec_diff_ms(&tm_before, &tm_msg);
printf("tm_m - tm_b = %lf ms\n", tdiff);
Which printed:
::
asdasdfasdfasdfadfgdfghfthgujty 6, 0;
tm_r - tm_b = 500.000000 ms
tm_a - tm_b = 1500.000000 ms
tm_m - tm_b = 18.000000 ms
System:
::
Linux debian 5.4.0-4-amd64 #1 SMP Debian 5.4.19-1 (2020-02-13) x86_64
GNU/Linux
gcc (Debian 9.3.0-8) 9.3.0
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Diffstat (limited to 'man7/socket.7')
| -rw-r--r-- | man7/socket.7 | 33 |
1 files changed, 25 insertions, 8 deletions
diff --git a/man7/socket.7 b/man7/socket.7 index 7f309cb8ea..ee551dbcfd 100644 --- a/man7/socket.7 +++ b/man7/socket.7 @@ -26,11 +26,6 @@ .\" Seems to do something similar to getpeername(), but then .\" why is it necessary / how does it differ? .\" -.\" SO_TIMESTAMPNS (2.6.22) -.\" Documentation/networking/timestamping.txt -.\" commit 92f37fd2ee805aa77925c1e64fd56088b46094fc -.\" Author: Eric Dumazet <dada1@cosmosbay.com> -.\" .\" SO_TIMESTAMPING (2.6.30) .\" Documentation/networking/timestamping.txt .\" commit cb9eff097831007afb30d64373f29d99825d0068 @@ -946,6 +941,24 @@ See .BR cmsg (3) for details on control messages. .TP +.B SO_TIMESTAMPNS +Enable or disable the receiving of the +.B SO_TIMESTAMPNS +control message. +The timestamp control message is sent with level +.B SOL_SOCKET +and the +.I cmsg_data +field is a +.I "struct timespec" +indicating the +reception time of the last packet passed to the user in this call. +The clock used for the timestamp is +.BR CLOCK_REALTIME . +See +.BR cmsg (3) +for details on control messages. +.TP .B SO_TYPE Gets the socket type as an integer (e.g., .BR SOCK_STREAM ). @@ -1075,13 +1088,17 @@ See for a description of .IR "struct timeval" . .\" -This ioctl should be used only if the socket option +This ioctl should be used only if the socket options .B SO_TIMESTAMP -is not set on the socket. +and +.B SO_TIMESTAMPNS +are not set on the socket. Otherwise, it returns the timestamp of the last packet that was received while .B SO_TIMESTAMP -was not set, or it fails if no such packet has been received, +and +.B SO_TIMESTAMPNS +were not set, or it fails if no such packet has been received, (i.e., .BR ioctl (2) returns \-1 with |