diff mbox series

[net,v2,2/2] socket: don't clear SOCK_TSTAMP_NEW when SO_TIMESTAMPNS is disabled

Message ID 20201012093542.15504-2-ceggers@arri.de
State Accepted
Delegated to: David Miller
Headers show
Series [net,v2,1/2] socket: fix option SO_TIMESTAMPING_NEW | expand

Commit Message

Christian Eggers Oct. 12, 2020, 9:35 a.m. UTC
SOCK_TSTAMP_NEW (timespec64 instead of timespec) is also used for
hardware time stamps (configured via SO_TIMESTAMPING_NEW).

User space (ptp4l) first configures hardware time stamping via
SO_TIMESTAMPING_NEW which sets SOCK_TSTAMP_NEW. In the next step, ptp4l
disables SO_TIMESTAMPNS(_NEW) (software time stamps), but this must not
switch hardware time stamps back to "32 bit mode".

This problem happens on 32 bit platforms were the libc has already
switched to struct timespec64 (from SO_TIMExxx_OLD to SO_TIMExxx_NEW
socket options). ptp4l complains with "missing timestamp on transmitted
peer delay request" because the wrong format is received (and

Fixes: 887feae36aee ("socket: Add SO_TIMESTAMP[NS]_NEW")
Fixes: 783da70e8396 ("net: add sock_enable_timestamps")
Signed-off-by: Christian Eggers <ceggers@arri.de>
Acked-by: Willem de Bruijn <willemb@google.com>
Acked-by: Deepa Dinamani <deepa.kernel@gmail.com>
- Added ACKs from Willem and Deepa

On Saturday, 10 October 2020, 05:38:56 CEST, Deepa Dinamani wrote:
> On Fri, Oct 9, 2020 at 5:35 PM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote:
> > As this commit message shows, with SO_TIMESTAMP(NS) and
> > SO_TIMESTAMPING that can be independently turned on and off, disabling
> > one can incorrectly switch modes while the other is still active.
> This will not help the case when a child process that inherits the fd
> and then sets SO_TIMESTAMP*_OLD/NEW on it, while the parent uses the
> other version.
> One of the two processes might still be surprised. But, child and
> parent actively using the same socket fd might be expecting trouble
> already.

Usually the decision between SO_TIMESTAMP*_OLD/NEW  will be done at compile
time (trough the system C library headers). For a typical "distribution" it
should be quite unlikely that two programs will be compiled using different

 net/core/sock.c | 1 -
 1 file changed, 1 deletion(-)
diff mbox series


diff --git a/net/core/sock.c b/net/core/sock.c
index 669cf9b8bb44..f4236c7512b5 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -757,7 +757,6 @@  static void __sock_set_timestamps(struct sock *sk, bool val, bool new, bool ns)
 	} else {
 		sock_reset_flag(sk, SOCK_RCVTSTAMP);
 		sock_reset_flag(sk, SOCK_RCVTSTAMPNS);
-		sock_reset_flag(sk, SOCK_TSTAMP_NEW);