netdev - Re: [PATCH net-next v3 03/14] net-timestamp: open gate for bpf_setsockopt/

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Message-ID: <CAL+tcoCFBPmP7oGJSoF=_Vhaw3c7zKft8ooodNgx=S7GmVjqQw@mail.gmail.com>
Date: Tue, 29 Oct 2024 09:18:05 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemb@...gle.com, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, shuah@...nel.org, ykolal@...com, 
	bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v3 03/14] net-timestamp: open gate for bpf_setsockopt/_getsockopt

On Tue, Oct 29, 2024 at 8:59 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > For now, we support bpf_setsockopt to set or clear timestamps flags.
> >
> > Users can use something like this in bpf program to turn on the feature:
> > flags = SOF_TIMESTAMPING_TX_SCHED;
> > bpf_setsockopt(skops, SOL_SOCKET, SO_TIMESTAMPING, &flags, sizeof(flags));
> > The specific use cases can be seen in the bpf selftest in this series.
> >
> > Later, I will support each flags one by one based on this.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> >  include/net/sock.h              |  4 ++--
> >  include/uapi/linux/net_tstamp.h |  7 +++++++
> >  net/core/filter.c               |  7 +++++--
> >  net/core/sock.c                 | 34 ++++++++++++++++++++++++++-------
> >  net/ipv4/udp.c                  |  2 +-
> >  net/mptcp/sockopt.c             |  2 +-
> >  net/socket.c                    |  2 +-
> >  7 files changed, 44 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 5384f1e49f5c..062f405c744e 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -1775,7 +1775,7 @@ static inline void skb_set_owner_edemux(struct sk_buff *skb, struct sock *sk)
> >  #endif
> >
> >  int sk_setsockopt(struct sock *sk, int level, int optname,
> > -               sockptr_t optval, unsigned int optlen);
> > +               sockptr_t optval, unsigned int optlen, bool bpf_timetamping);
>
> timestamping, not timetamping

Oh, right...

>
> More importantly, is there perhaps a cleaner way to add a BPF
> setsockopt than to have to update the existing API and all its
> callers?

I've thought about that as well. As you may notice, this version
changes the prior implementation [1] that makes the code more clear
from my perspective.

[1]: https://lore.kernel.org/all/20241012040651.95616-3-kerneljasonxing@gmail.com/

The link here didn't support the bpf_setsockopt which requires more
strange modification in sol_socket_sockopt() and return earlier
compared to other uses of SO_xxx. That's why I changed here.

>
> >  int sock_setsockopt(struct socket *sock, int level, int op,
> >                   sockptr_t optval, unsigned int optlen);
> >  int do_sock_setsockopt(struct socket *sock, bool compat, int level,
> > @@ -1784,7 +1784,7 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level,
> >                      int optname, sockptr_t optval, sockptr_t optlen);
> >
> >  int sk_getsockopt(struct sock *sk, int level, int optname,
> > -               sockptr_t optval, sockptr_t optlen);
> > +               sockptr_t optval, sockptr_t optlen, bool bpf_timetamping);
> >  int sock_gettstamp(struct socket *sock, void __user *userstamp,
> >                  bool timeval, bool time32);
> >  struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
> > diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> > index 858339d1c1c4..0696699cf964 100644
> > --- a/include/uapi/linux/net_tstamp.h
> > +++ b/include/uapi/linux/net_tstamp.h
> > @@ -49,6 +49,13 @@ enum {
> >                                        SOF_TIMESTAMPING_TX_SCHED | \
> >                                        SOF_TIMESTAMPING_TX_ACK)
> >
> > +#define SOF_TIMESTAMPING_BPF_SUPPPORTED_MASK (SOF_TIMESTAMPING_SOFTWARE | \
> > +                                           SOF_TIMESTAMPING_TX_SCHED | \
> > +                                           SOF_TIMESTAMPING_TX_SOFTWARE | \
> > +                                           SOF_TIMESTAMPING_TX_ACK | \
> > +                                           SOF_TIMESTAMPING_OPT_ID | \
> > +                                           SOF_TIMESTAMPING_OPT_ID_TCP)
> > +
>
> We discussed the subtle distinction between OPT_ID and OPT_ID_TCP before.
>
> Basically, OPT_ID_TCP is a fix for OPT_ID on TCP sockets, and should always be
> passed. On a new API like this one, we can even require this.

Good idea. Will do it. Thanks.

>
> Not super important, only if it does not make the code more complex.

I need to ponder on this point more.

Thanks,
Jason