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From: Arnd Bergmann <arnd@arndb.de>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Bluez mailing list <linux-bluetooth@vger.kernel.org>,
	y2038 Mailman List <y2038@lists.linaro.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Deepa Dinamani <deepa.kernel@gmail.com>,
	Rich Felker <dalias@libc.org>, Guy Harris <guy@alum.mit.edu>
Subject: Re: [RFC] y2038: HCI_TIME_STAMP with time64
Date: Fri, 10 Jan 2020 17:08:23 +0100	[thread overview]
Message-ID: <CAK8P3a1K79zGvi3hc4aw4vcsni1cx4u121OBHgWiaFSPxpA6ZQ@mail.gmail.com> (raw)
In-Reply-To: <5E8DACB3-3B53-4E22-A834-4CEDFC6A1757@holtmann.org>

On Fri, Jan 10, 2020 at 4:44 PM Marcel Holtmann <marcel@holtmann.org> wrote:
> > I noticed earlier this week that the HCI_CMSG_TSTAMP/HCI_TIME_STAMP
> > interface has no time64 equivalent, as we apparently missed that when
> > converting the normal socket timestamps to support both time32 and time64
> > variants of the sockopt and cmsg data.
...
> > When using HCI_TIME_STAMP on a 32-bit system with a time64
> > libc, users will interpret the { s32 tv_sec; s32 tv_usec } layout of
> > the kernel as { s64 tv_sec; ... }, which puts complete garbage
> > into the timestamp regardless of whether this code runs before or
> > after y2038. From looking at codesearch.debian.org, I found two
> > users of this: libpcap and hcidump. There are probably others that
> > are not part of Debian.
...
> > 3. Add support for the normal SO_TIMESTAMPNS_NEW sockopt in
> >   HCI, providing timestamps in the unambiguous { long long tv_sec;
> >   long long tv_nsec; } format to user space, and change applications
> >   to use that if supported by the kernel.
>
> I have added SO_TIMESTAMP* to every Bluetooth socket a while back. And that should be used by the majority of the tools. One exception might by hcidump which has been replaced by btmon already anyway.
>
> So I would not bother with HCI_TIME_STAMP fixing. We can do 2) if someone really still wants to use that socket option. However I am under the impression that 3) should be already possible.

Ok, excellent, I had not realized this works already.

I have now also checked
https://github.com/the-tcpdump-group/libpcap/blob/master/pcap-bt-monitor-linux.c
which uses SO_TIMESTAMP and then should work. I guess this is similar
to what btmon does.

For libpcap that leaves
https://github.com/the-tcpdump-group/libpcap/blob/master/pcap-bt-linux.c#L358

which needs a fairly simply fix on 32-bit architectures to copy the
two 32-bit fields
into the longer pkth.ts fields individually rather than using a memcpy.
I've added Guy Harris to Cc, he seems to be the maintainer for this file
according to the git history.

The same change is needed for
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/tools/hcidump.c#n233
if there are any remaining users. I can send you a patch if you want.

        Arnd

  reply	other threads:[~2020-01-10 16:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 10:11 [RFC] y2038: HCI_TIME_STAMP with time64 Arnd Bergmann
2020-01-10 15:44 ` Marcel Holtmann
2020-01-10 16:08   ` Arnd Bergmann [this message]
2020-01-10 17:52     ` Marcel Holtmann

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