With the new y2038 safe timestamping options added, update the documentation to reflect the changes.
Signed-off-by: Deepa Dinamani deepa.kernel@gmail.com Acked-by: Willem de Bruijn willemb@google.com --- Documentation/networking/timestamping.txt | 43 ++++++++++++++++++++--- 1 file changed, 38 insertions(+), 5 deletions(-)
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index 1be0b6f9e0cb..67e4ab3cdb86 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -6,11 +6,21 @@ The interfaces for receiving network packages timestamps are: * SO_TIMESTAMP Generates a timestamp for each incoming packet in (not necessarily monotonic) system time. Reports the timestamp via recvmsg() in a - control message as struct timeval (usec resolution). + control message in usec resolution. + SO_TIMESTAMP is defined as SO_TIMESTAMP_NEW or SO_TIMESTAMP_OLD + based on the architecture type and time_t representation of libc. + Control message format is in struct __kernel_old_timeval for + SO_TIMESTAMP_OLD and in struct __kernel_sock_timeval for + SO_TIMESTAMP_NEW options respectively.
* SO_TIMESTAMPNS Same timestamping mechanism as SO_TIMESTAMP, but reports the - timestamp as struct timespec (nsec resolution). + timestamp as struct timespec in nsec resolution. + SO_TIMESTAMPNS is defined as SO_TIMESTAMPNS_NEW or SO_TIMESTAMPNS_OLD + based on the architecture type and time_t representation of libc. + Control message format is in struct timespec for SO_TIMESTAMPNS_OLD + and in struct __kernel_timespec for SO_TIMESTAMPNS_NEW options + respectively.
* IP_MULTICAST_LOOP + SO_TIMESTAMP[NS] Only for multicast:approximate transmit timestamp obtained by @@ -22,7 +32,7 @@ The interfaces for receiving network packages timestamps are: timestamps for stream sockets.
-1.1 SO_TIMESTAMP: +1.1 SO_TIMESTAMP (also SO_TIMESTAMP_OLD and SO_TIMESTAMP_NEW):
This socket option enables timestamping of datagrams on the reception path. Because the destination socket, if any, is not known early in @@ -31,15 +41,25 @@ same is true for all early receive timestamp options.
For interface details, see `man 7 socket`.
+Always use SO_TIMESTAMP_NEW timestamp to always get timestamp in +struct __kernel_sock_timeval format.
-1.2 SO_TIMESTAMPNS: +SO_TIMESTAMP_OLD returns incorrect timestamps after the year 2038 +on 32 bit machines. + +1.2 SO_TIMESTAMPNS (also SO_TIMESTAMPNS_OLD and SO_TIMESTAMPNS_NEW):
This option is identical to SO_TIMESTAMP except for the returned data type. Its struct timespec allows for higher resolution (ns) timestamps than the timeval of SO_TIMESTAMP (ms).
+Always use SO_TIMESTAMPNS_NEW timestamp to always get timestamp in +struct __kernel_timespec format. + +SO_TIMESTAMPNS_OLD returns incorrect timestamps after the year 2038 +on 32 bit machines.
-1.3 SO_TIMESTAMPING: +1.3 SO_TIMESTAMPING (also SO_TIMESTAMPING_OLD and SO_TIMESTAMPING_NEW):
Supports multiple types of timestamp requests. As a result, this socket option takes a bitmap of flags, not a boolean. In @@ -323,10 +343,23 @@ SO_TIMESTAMP and SO_TIMESTAMPNS records can be retrieved. These timestamps are returned in a control message with cmsg_level SOL_SOCKET, cmsg_type SCM_TIMESTAMPING, and payload of type
+For SO_TIMESTAMPING_OLD: + struct scm_timestamping { struct timespec ts[3]; };
+For SO_TIMESTAMPING_NEW: + +struct scm_timestamping64 { + struct __kernel_timespec ts[3]; + +Always use SO_TIMESTAMPING_NEW timestamp to always get timestamp in +struct scm_timestamping64 format. + +SO_TIMESTAMPING_OLD returns incorrect timestamps after the year 2038 +on 32 bit machines. + The structure can return up to three timestamps. This is a legacy feature. At least one field is non-zero at any time. Most timestamps are passed in ts[0]. Hardware timestamps are passed in ts[2].