Re: [RFC PATCH 6/7] net: allow simultaneous SW and HW transmit timestamping

[Willem de Bruijn]

On Thu, Apr 13, 2017 at 11:24 AM, Keller, Jacob E
 wrote:
>
>
>> -Original Message-
>> From: Miroslav Lichvar [mailto:mlich...@redhat.com]
>> Sent: Thursday, April 13, 2017 8:00 AM
>>
>> Oh, I see. I was struggling to find a good name for this option.
>>
>> > The name for this option is therefore not very descriptive. Perhaps
>> > SOF_TIMESTAMPING_OPT_BOTH_SW_HW.
>>
>> Simultaneous SW/HW timestamping was already possible for incoming
>> packets. Maybe _OPT_TX_SWHW would be better?
>>
>
> This sounds more accurate to me.

Agreed.

RE: [RFC PATCH 6/7] net: allow simultaneous SW and HW transmit timestamping

[Keller, Jacob E]

> -Original Message-
> From: Miroslav Lichvar [mailto:mlich...@redhat.com]
> Sent: Thursday, April 13, 2017 8:00 AM
>
> Oh, I see. I was struggling to find a good name for this option.
> 
> > The name for this option is therefore not very descriptive. Perhaps
> > SOF_TIMESTAMPING_OPT_BOTH_SW_HW.
> 
> Simultaneous SW/HW timestamping was already possible for incoming
> packets. Maybe _OPT_TX_SWHW would be better?
>

This sounds more accurate to me.

Thanks,
Jake
 
> --
> Miroslav Lichvar

Re: [RFC PATCH 6/7] net: allow simultaneous SW and HW transmit timestamping

[Miroslav Lichvar]

On Thu, Apr 13, 2017 at 10:30:32AM -0400, Willem de Bruijn wrote:
> On Wed, Apr 12, 2017 at 10:17 AM, Miroslav Lichvar  
> wrote:
> > +SOF_TIMESTAMPING_OPT_MULTIMSG:
> > +
> > +  Allow outgoing packets to be looped multiple times to the socket's
> > +  error queue in order to receive both software and hardware transmit
> > +  timestamps.
> > +
> 
> It is already possible to receive multiple copies of the same message.
> Timestamps of type SCM_TSTAMP_SCHED will be passed for every
> device, virtual or physical, such as bonding. With TCP retransmits,
> multiple SCM_TSTAMP_SND can be observed.

Oh, I see. I was struggling to find a good name for this option.

> The name for this option is therefore not very descriptive. Perhaps
> SOF_TIMESTAMPING_OPT_BOTH_SW_HW.

Simultaneous SW/HW timestamping was already possible for incoming
packets. Maybe _OPT_TX_SWHW would be better?

-- 
Miroslav Lichvar

Re: [RFC PATCH 6/7] net: allow simultaneous SW and HW transmit timestamping

[Willem de Bruijn]

On Wed, Apr 12, 2017 at 10:17 AM, Miroslav Lichvar  wrote:
> Add SOF_TIMESTAMPING_OPT_MULTIMSG option to allow looping the outgoing
> packet 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.
>
> CC: Richard Cochran 
> CC: Willem de Bruijn 
> Signed-off-by: Miroslav Lichvar 
> ---
>  Documentation/networking/timestamping.txt | 12 ++--
>  include/linux/skbuff.h|  3 +--
>  include/uapi/linux/net_tstamp.h   |  3 ++-
>  net/core/skbuff.c |  4 
>  net/socket.c  |  6 ++
>  5 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/networking/timestamping.txt 
> b/Documentation/networking/timestamping.txt
> index ed04aaa..8f30385 100644
> --- a/Documentation/networking/timestamping.txt
> +++ b/Documentation/networking/timestamping.txt
> @@ -201,6 +201,12 @@ SOF_TIMESTAMPING_OPT_PKTINFO:
>this information, it will be attached in struct scm_ts_pktinfo as
>a separate control message of type SCM_TIMESTAMPING_PKTINFO.
>
> +SOF_TIMESTAMPING_OPT_MULTIMSG:
> +
> +  Allow outgoing packets to be looped multiple times to the socket's
> +  error queue in order to receive both software and hardware transmit
> +  timestamps.
> +

It is already possible to receive multiple copies of the same message.
Timestamps of type SCM_TSTAMP_SCHED will be passed for every
device, virtual or physical, such as bonding. With TCP retransmits,
multiple SCM_TSTAMP_SND can be observed.

The name for this option is therefore not very descriptive. Perhaps
SOF_TIMESTAMPING_OPT_BOTH_SW_HW.

>  New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to
>  disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate
>  regardless of the setting of sysctl net.core.tstamp_allow_data.
> @@ -320,8 +326,10 @@ struct scm_timestamping {
>  };
>
>  The structure can return up to three timestamps. This is a legacy
> -feature. Only one field is non-zero at any time. Most timestamps
> -are passed in ts[0]. Hardware timestamps are passed in ts[2].
> +feature. Most timestamps are passed in ts[0]. Hardware timestamps
> +are passed in ts[2]. Incoming packets may have timestamps in both
> +ts[0] and ts[2], but for outgoing packets only one field is non-zero
> +at any time.
>
>  ts[1] used to hold hardware timestamps converted to system time.
>  Instead, expose the hardware clock device on the NIC directly as
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index e91685a..0387c4b 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3302,8 +3302,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
>
>  static inline void sw_tx_timestamp(struct sk_buff *skb)
>  {
> -   if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
> -   !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
> +   if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP)
> skb_tstamp_tx(skb, NULL);
>  }
>
> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> index 8397ecd..887e3ff 100644
> --- a/include/uapi/linux/net_tstamp.h
> +++ b/include/uapi/linux/net_tstamp.h
> @@ -27,8 +27,9 @@ enum {
> SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),
> SOF_TIMESTAMPING_OPT_STATS = (1<<12),
> SOF_TIMESTAMPING_OPT_PKTINFO = (1<<13),
> +   SOF_TIMESTAMPING_OPT_MULTIMSG = (1<<14),
>
> -   SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_PKTINFO,
> +   SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_MULTIMSG,
> SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
>  SOF_TIMESTAMPING_LAST
>  };
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 7ca251f..d3df8ff 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3863,6 +3863,10 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> if (!sk)
> return;
>
> +   if (!hwtstamps && !(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_MULTIMSG) &&
> +   skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
> +   return;
> +
> tsonly = sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TSONLY;
> if (!skb_may_tx_timestamp(sk, tsonly))
> return;
> diff --git a/net/socket.c b/net/socket.c
> index 32e78de..5c9f2eb 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -695,12 +695,18 @@ void