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Message-ID: <66d77459a0df1_ce32f2947c@willemb.c.googlers.com.notmuch>
Date: Tue, 03 Sep 2024 16:40:57 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Willem de Bruijn <willemb@...gle.com>
Cc: netdev@...r.kernel.org,
Jakub Kicinski <kuba@...nel.org>,
Jason Xing <kerneljasonxing@...il.com>,
Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH net-next v2 1/2] net_tstamp: add SCM_TS_OPT_ID to provide
OPT_ID in control message
Vadim Fedorenko wrote:
> On 02/09/2024 15:29, Willem de Bruijn wrote:
> > Vadim Fedorenko wrote:
> >> SOF_TIMESTAMPING_OPT_ID socket option flag gives a way to correlate TX
> >> timestamps and packets sent via socket. Unfortunately, there is no way
> >> to reliably predict socket timestamp ID value in case of error returned
> >> by sendmsg. For UDP sockets it's impossible because of lockless
> >> nature of UDP transmit, several threads may send packets in parallel. In
> >> case of RAW sockets MSG_MORE option makes things complicated. More
> >> details are in the conversation [1].
> >> This patch adds new control message type to give user-space
> >> software an opportunity to control the mapping between packets and
> >> values by providing ID with each sendmsg. This works fine for UDP
> >> sockets only, and explicit check is added to control message parser.
> >>
> >> [1] https://lore.kernel.org/netdev/CALCETrU0jB+kg0mhV6A8mrHfTE1D1pr1SD_B9Eaa9aDPfgHdtA@mail.gmail.com/
> >>
> >> Signed-off-by: Vadim Fedorenko <vadfed@...a.com>
> >> ---
> >> Documentation/networking/timestamping.rst | 14 ++++++++++++++
> >> arch/alpha/include/uapi/asm/socket.h | 4 +++-
> >> arch/mips/include/uapi/asm/socket.h | 2 ++
> >> arch/parisc/include/uapi/asm/socket.h | 2 ++
> >> arch/sparc/include/uapi/asm/socket.h | 2 ++
> >> include/net/inet_sock.h | 4 +++-
> >> include/net/sock.h | 1 +
> >> include/uapi/asm-generic/socket.h | 2 ++
> >> include/uapi/linux/net_tstamp.h | 3 ++-
> >> net/core/sock.c | 12 ++++++++++++
> >> net/ethtool/common.c | 1 +
> >> net/ipv4/ip_output.c | 16 ++++++++++++----
> >> net/ipv6/ip6_output.c | 16 ++++++++++++----
> >> 13 files changed, 68 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst
> >> index 5e93cd71f99f..93b0901e4e8e 100644
> >> --- a/Documentation/networking/timestamping.rst
> >> +++ b/Documentation/networking/timestamping.rst
> >> @@ -193,6 +193,20 @@ SOF_TIMESTAMPING_OPT_ID:
> >> among all possibly concurrently outstanding timestamp requests for
> >> that socket.
> >>
> >> + With this option enabled user-space application can provide custom
> >> + ID for each message sent via UDP socket with control message with
> >> + type set to SCM_TS_OPT_ID::
> >> +
> >> + struct msghdr *msg;
> >> + ...
> >> + cmsg = CMSG_FIRSTHDR(msg);
> >> + cmsg->cmsg_level = SOL_SOCKET;
> >> + cmsg->cmsg_type = SO_TIMESTAMPING;
> >> + cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
> >> + *((__u32 *) CMSG_DATA(cmsg)) = opt_id;
> >> + err = sendmsg(fd, msg, 0);
> >> +
> >
> > Please make it clear that this CMSG is optional.
> >
> > The process can optionally override the default generated ID, by
> > passing a specific ID with control message SCM_TS_OPT_ID:
>
> Ok, I'll re-phrase it this way, thanks!
>
>
> >> SOF_TIMESTAMPING_OPT_ID_TCP:
> >> Pass this modifier along with SOF_TIMESTAMPING_OPT_ID for new TCP
> >> timestamping applications. SOF_TIMESTAMPING_OPT_ID defines how the
> >> diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> >> index e94f621903fe..0698e6662cdf 100644
> >> --- a/arch/alpha/include/uapi/asm/socket.h
> >> +++ b/arch/alpha/include/uapi/asm/socket.h
> >> @@ -10,7 +10,7 @@
> >> * Note: we only bother about making the SOL_SOCKET options
> >> * same as OSF/1, as that's all that "normal" programs are
> >> * likely to set. We don't necessarily want to be binary
> >> - * compatible with _everything_.
> >> + * compatible with _everything_.
> >
> > Is this due to a checkpatch warning? If so, please add a brief comment
> > to the commit message to show that this change is intentional. If not,
> > please don't touch unrelated code.
>
> I'll remove it, because it looks like it was some unhappy linter...
>
> >> */
> >> #define SOL_SOCKET 0xffff
> >>
> >> @@ -140,6 +140,8 @@
> >> #define SO_PASSPIDFD 76
> >> #define SO_PEERPIDFD 77
> >>
> >> +#define SCM_TS_OPT_ID 78
> >> +
> >> #if !defined(__KERNEL__)
> >>
> >> #if __BITS_PER_LONG == 64
> >> diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
> >> index 60ebaed28a4c..bb3dc8feb205 100644
> >> --- a/arch/mips/include/uapi/asm/socket.h
> >> +++ b/arch/mips/include/uapi/asm/socket.h
> >> @@ -151,6 +151,8 @@
> >> #define SO_PASSPIDFD 76
> >> #define SO_PEERPIDFD 77
> >>
> >> +#define SCM_TS_OPT_ID 78
> >> +
> >> #if !defined(__KERNEL__)
> >>
> >> #if __BITS_PER_LONG == 64
> >> diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
> >> index be264c2b1a11..c3ab3b3289eb 100644
> >> --- a/arch/parisc/include/uapi/asm/socket.h
> >> +++ b/arch/parisc/include/uapi/asm/socket.h
> >> @@ -132,6 +132,8 @@
> >> #define SO_PASSPIDFD 0x404A
> >> #define SO_PEERPIDFD 0x404B
> >>
> >> +#define SCM_TS_OPT_ID 0x404C
> >> +
> >> #if !defined(__KERNEL__)
> >>
> >> #if __BITS_PER_LONG == 64
> >> diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
> >> index 682da3714686..9b40f0a57fbc 100644
> >> --- a/arch/sparc/include/uapi/asm/socket.h
> >> +++ b/arch/sparc/include/uapi/asm/socket.h
> >> @@ -133,6 +133,8 @@
> >> #define SO_PASSPIDFD 0x0055
> >> #define SO_PEERPIDFD 0x0056
> >>
> >> +#define SCM_TS_OPT_ID 0x0057
> >> +
> >> #if !defined(__KERNEL__)
> >>
> >>
> >> diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
> >> index 394c3b66065e..2161d50cf0fd 100644
> >> --- a/include/net/inet_sock.h
> >> +++ b/include/net/inet_sock.h
> >> @@ -174,6 +174,7 @@ struct inet_cork {
> >> __s16 tos;
> >> char priority;
> >> __u16 gso_size;
> >> + u32 ts_opt_id;
> >> u64 transmit_time;
> >> u32 mark;
> >> };
> >> @@ -241,7 +242,8 @@ struct inet_sock {
> >> struct inet_cork_full cork;
> >> };
> >>
> >> -#define IPCORK_OPT 1 /* ip-options has been held in ipcork.opt */
> >> +#define IPCORK_OPT 1 /* ip-options has been held in ipcork.opt */
> >> +#define IPCORK_TS_OPT_ID 2 /* timestmap opt id has been provided in cmsg */
> >
> > typo: timestamp
> >
> > And maybe more relevant: /* ts_opt_id field is valid, overriding sk_tskey */
>
> I'll change it
>
> >> enum {
> >> INET_FLAGS_PKTINFO = 0,
> >> diff --git a/include/net/sock.h b/include/net/sock.h
> >> index f51d61fab059..73e21dad5660 100644
> >> --- a/include/net/sock.h
> >> +++ b/include/net/sock.h
> >> @@ -1794,6 +1794,7 @@ struct sockcm_cookie {
> >> u64 transmit_time;
> >> u32 mark;
> >> u32 tsflags;
> >> + u32 ts_opt_id;
> >> };
> >>
> >> static inline void sockcm_init(struct sockcm_cookie *sockc,
> >> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> >> index 8ce8a39a1e5f..db3df3e74b01 100644
> >> --- a/include/uapi/asm-generic/socket.h
> >> +++ b/include/uapi/asm-generic/socket.h
> >> @@ -135,6 +135,8 @@
> >> #define SO_PASSPIDFD 76
> >> #define SO_PEERPIDFD 77
> >>
> >> +#define SCM_TS_OPT_ID 78
> >
> > nit: different indentation
>
> Hmm... that's interesting, it's ok in the code, there no spaces before
> #define. I'll re-check it in the patch in v3.
>
> >> +
> >> #if !defined(__KERNEL__)
> >>
> >> #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
> >> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> >> index a2c66b3d7f0f..e2f145e3f3a1 100644
> >> --- a/include/uapi/linux/net_tstamp.h
> >> +++ b/include/uapi/linux/net_tstamp.h
> >> @@ -32,8 +32,9 @@ enum {
> >> SOF_TIMESTAMPING_OPT_TX_SWHW = (1<<14),
> >> SOF_TIMESTAMPING_BIND_PHC = (1 << 15),
> >> SOF_TIMESTAMPING_OPT_ID_TCP = (1 << 16),
> >> + SOF_TIMESTAMPING_OPT_ID_CMSG = (1 << 17),
> >>
> >> - SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID_TCP,
> >> + SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID_CMSG,
> >> SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
> >> SOF_TIMESTAMPING_LAST
> >> };
> >> diff --git a/net/core/sock.c b/net/core/sock.c
> >> index 468b1239606c..560b075765fa 100644
> >> --- a/net/core/sock.c
> >> +++ b/net/core/sock.c
> >> @@ -2859,6 +2859,18 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
> >> return -EINVAL;
> >> sockc->transmit_time = get_unaligned((u64 *)CMSG_DATA(cmsg));
> >> break;
> >> + case SCM_TS_OPT_ID:
> >> + /* allow this option for UDP sockets only */
> >> + if (!sk_is_udp(sk))
> >> + return -EINVAL;
> >
> > Let's relax the restriction that this is only for UDP.
> >
> > At least to also support SOCK_RAW. I don't think that requires any
> > additional code at all?
>
> RAW sockets use skb_setup_tx_timestamps which does atomic operation of
> incrementing sk_tskey when in _sock_tx_timestamp. So I'll have to
> convert all spots (can, ipv4/raw, ipv6/raw, 3 x af_packet) to use the
> same logic as in udp path (sock_tx_timestamp) and add conditions.
> Or change skb_setup_tx_timestamps to do the logic and take different
> arguments. It may look as a big refactoring, so I would like to make
> it as a follow-up series.
You're referring to passing the whole sockcm_cookie through these
functions, right?
Agreed that that is a lot of churn and best left for a separate patch.
Would still be good to have it merged together in a single series, but
not a hard requirement.
Other than that it seems a small change in _sock_tx_timestamp.
@@ -2668,8 +2668,12 @@ static inline void _sock_tx_timestamp(struct sock *sk, __u16 tsflags,
if (unlikely(tsflags)) {
- __sock_tx_timestamp(tsflags, tx_flags);
+ __sock_tx_timestamp(sockc->tsflags, tx_flags);
if (tsflags & SOF_TIMESTAMPING_OPT_ID && tskey &&
- tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK)
- *tskey = atomic_inc_return(&sk->sk_tskey) - 1;
+ tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK) {
+ if (tsflags & SOF_TIMESTAMPING_OPT_ID_CMSG)
+ *tskey = sockc->ts_opt_id;
+ else
+ *tskey = atomic_inc_return(&sk->sk_tskey) - 1;
+ }
> > Extending to TCP should be straightforward too, just a branch
> > on sockc in tcp_tx_timestamp.
>
> TCP part looks a bit easier, as you said, I have to adjust
> tcp_tx_timestamp and the logic is straightforward. I still have to
> provide a pointer to sock coockie instead of flags, but there is only
> one caller of this function and it's much easier than with RAW sockets.
Yeah, the two are intermingled. If you want to pass sockc to
_sock_tx_timestamp then all callers have to pass it. And TCP
currently does not.
> > If so, let's support all. It makes for a simpler API if it is
> > supported uniformly wherever OPT_ID is.
>
> If you think that the way I explained for RAW sockets is good enough,
> I can send all of them as a single patcheset. Otherwise I would like to
> add RAW sockets in follow-up series.
>
> >> + tsflags = READ_ONCE(sk->sk_tsflags);
> >> + if (!(tsflags & SOF_TIMESTAMPING_OPT_ID))
> >> + return -EINVAL;
> >> + if (cmsg->cmsg_len != CMSG_LEN(sizeof(u32)))
> >> + return -EINVAL;
> >> + sockc->ts_opt_id = *(u32 *)CMSG_DATA(cmsg);
> >> + sockc->tsflags |= SOF_TIMESTAMPING_OPT_ID_CMSG;
> >> + break;
> >> /* SCM_RIGHTS and SCM_CREDENTIALS are semantically in SOL_UNIX. */
> >> case SCM_RIGHTS:
> >> case SCM_CREDENTIALS:
>
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