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Message-ID: <932f7ff3-6087-47cf-91ec-2601da38ebec@linux.dev>
Date: Mon, 2 Sep 2024 22:07:44 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: 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
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.
> 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.
> 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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