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Message-ID: <66d5cbbba9669_6138829497@willemb.c.googlers.com.notmuch>
Date: Mon, 02 Sep 2024 10:29:15 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Vadim Fedorenko <vadfed@...a.com>,
Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
Willem de Bruijn <willemb@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...nel.org>,
Jason Xing <kerneljasonxing@...il.com>
Cc: Vadim Fedorenko <vadfed@...a.com>,
netdev@...r.kernel.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:
> 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:
> 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.
> */
> #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 */
> 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
> +
> #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?
Extending to TCP should be straightforward too, just a branch
on sockc in tcp_tx_timestamp.
If so, let's support all. It makes for a simpler API if it is
supported uniformly wherever OPT_ID is.
> + 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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