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Message-ID: <CA+FuTSe1DXY04rpwaaVvK0qFgq3owUtjTiRrVTTCUuUsR0UKyw@mail.gmail.com>
Date: Fri, 30 Aug 2024 17:07:32 -0400
From: Willem de Bruijn <willemb@...gle.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>, Vadim Fedorenko <vadfed@...a.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>,
Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] net_tstamp: add SCM_TS_OPT_ID to provide
OPT_ID in control message
On Fri, Aug 30, 2024 at 1:11 PM Vadim Fedorenko
<vadim.fedorenko@...ux.dev> wrote:
>
> On 30/08/2024 16:02, 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>
> >> ---
> >> include/net/inet_sock.h | 4 +++-
> >> include/net/sock.h | 1 +
> >> include/uapi/asm-generic/socket.h | 2 ++
> >> include/uapi/linux/net_tstamp.h | 1 +
> >> net/core/sock.c | 12 ++++++++++++
> >> net/ipv4/ip_output.c | 13 +++++++++++--
> >> net/ipv6/ip6_output.c | 13 +++++++++++--
> >> 7 files changed, 41 insertions(+), 5 deletions(-)
> >>
> >> 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 */
> >>
> >> 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
> >> +
> >> #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..081b40a55a2e 100644
> >> --- a/include/uapi/linux/net_tstamp.h
> >> +++ b/include/uapi/linux/net_tstamp.h
> >> @@ -32,6 +32,7 @@ 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_MASK = (SOF_TIMESTAMPING_LAST - 1) |
> >
> > Update SOF_TIMESTAMPING_LAST
>
> Got it
>
> >> 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;
> >> + 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:
> >> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> >> index b90d0f78ac80..65b5d9f53102 100644
> >> --- a/net/ipv4/ip_output.c
> >> +++ b/net/ipv4/ip_output.c
> >> @@ -1050,8 +1050,14 @@ static int __ip_append_data(struct sock *sk,
> >>
> >> hold_tskey = cork->tx_flags & SKBTX_ANY_TSTAMP &&
> >> READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID;
> >> - if (hold_tskey)
> >> - tskey = atomic_inc_return(&sk->sk_tskey) - 1;
> >> + if (hold_tskey) {
> >> + if (cork->flags & IPCORK_TS_OPT_ID) {
> >> + hold_tskey = false;
> >> + tskey = cork->ts_opt_id;
> >> + } else {
> >> + tskey = atomic_inc_return(&sk->sk_tskey) - 1;
> >> + }
> >> + }
> >>
> >> /* So, what's going on in the loop below?
> >> *
> >> @@ -1324,8 +1330,11 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
> >> cork->mark = ipc->sockc.mark;
> >> cork->priority = ipc->priority;
> >> cork->transmit_time = ipc->sockc.transmit_time;
> >> + cork->ts_opt_id = ipc->sockc.ts_opt_id;
> >> cork->tx_flags = 0;
> >> sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
> >> + if (ipc->sockc.tsflags & SOF_TIMESTAMPING_OPT_ID_CMSG)
> >> + cork->flags |= IPCORK_TS_OPT_ID;
> >>
> >> return 0;
> >> }
> >> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> >> index f26841f1490f..91eafef85c85 100644
> >> --- a/net/ipv6/ip6_output.c
> >> +++ b/net/ipv6/ip6_output.c
> >> @@ -1401,7 +1401,10 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
> >> cork->base.gso_size = ipc6->gso_size;
> >> cork->base.tx_flags = 0;
> >> cork->base.mark = ipc6->sockc.mark;
> >> + cork->base.ts_opt_id = ipc6->sockc.ts_opt_id;
> >> sock_tx_timestamp(sk, ipc6->sockc.tsflags, &cork->base.tx_flags);
> >> + if (ipc6->sockc.tsflags & SOF_TIMESTAMPING_OPT_ID_CMSG)
> >> + cork->base.flags |= IPCORK_TS_OPT_ID;
> >>
> >> cork->base.length = 0;
> >> cork->base.transmit_time = ipc6->sockc.transmit_time;
> >> @@ -1545,8 +1548,14 @@ static int __ip6_append_data(struct sock *sk,
> >>
> >> hold_tskey = cork->tx_flags & SKBTX_ANY_TSTAMP &&
> >> READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID;
> >> - if (hold_tskey)
> >> - tskey = atomic_inc_return(&sk->sk_tskey) - 1;
> >> + if (hold_tskey) {
> >> + if (cork->flags & IPCORK_TS_OPT_ID) {
> >> + hold_tskey = false;
> >> + tskey = cork->ts_opt_id;
> >> + } else {
> >> + tskey = atomic_inc_return(&sk->sk_tskey) - 1;
> >> + }
> >> + }
> >
> > Setting, then clearing hold_tskey is a bit weird. How about
> >
> > if (cork->tx_flags & SKBTX_ANY_TSTAMP &&
> > READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID) {
> > if (cork->flags & IPCORK_TS_OPT_ID) {
> > tskey = cork->ts_opt_id;
> > } else {
> > tskey = atomic_inc_return(&sk->sk_tskey) - 1;
> > hold_tskey = true;
> > }
> > }
>
> Yeah, looks ok, I'll change it this way, thanks!
>
> Can you please help me with kernel test robot report? I don't really get
> how can SCM_TS_OPT_ID be undefined if I added it the exact same place
> where other option are defined, like SCM_TXTIME or SO_MARK?
Both bot reports mention arch-alpha.
Take a look at the patch that introduced SCM_TXTIME. That is defined
and used in the same locations.
UAPI socket.h definitions need to be defined separate for various
archs. I also missed this.
Btw, for a next version please also document the new feature in
Documentation/networking/timestamping.rst
And let's keep it on the list.
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