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net_tstamp: add SCM_TS_OPT_ID to provide OPT_ID in control message

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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 for UDP sockets.
The documentation is also added in this patch.

[1] https://lore.kernel.org/netdev/CALCETrU0jB+kg0mhV6A8mrHfTE1D1pr1SD_B9Eaa9aDPfgHdtA@mail.gmail.com/

Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Link: https://patch.msgid.link/20241001125716.2832769-2-vadfed@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vadim Fedorenko 2024-10-01 05:57:14 -07:00 committed by Jakub Kicinski
parent 34ea1df802
commit 4aecca4c76
11 changed files with 75 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
Documentation/networking/timestamping.rst
View File

@ -194,6 +194,20 @@ SOF_TIMESTAMPING_OPT_ID:
among all possibly concurrently outstanding timestamp requests for
that socket.
The process can optionally override the default generated ID, by
passing a specific ID with control message SCM_TS_OPT_ID (not
supported for TCP sockets)::
struct msghdr *msg;
...
cmsg = CMSG_FIRSTHDR(msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_TS_OPT_ID;
cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
*((__u32 *) CMSG_DATA(cmsg)) = opt_id;
err = sendmsg(fd, msg, 0);
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

2
arch/alpha/include/uapi/asm/socket.h
View File

@ -146,6 +146,8 @@
#define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
#define SO_DEVMEM_DONTNEED 80
#define SCM_TS_OPT_ID 81
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/mips/include/uapi/asm/socket.h
View File

@ -157,6 +157,8 @@
#define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
#define SO_DEVMEM_DONTNEED 80
#define SCM_TS_OPT_ID 81
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/parisc/include/uapi/asm/socket.h
View File

@ -138,6 +138,8 @@
#define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
#define SO_DEVMEM_DONTNEED 80
#define SCM_TS_OPT_ID 0x404C
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/sparc/include/uapi/asm/socket.h
View File

@ -139,6 +139,8 @@
#define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
#define SO_DEVMEM_DONTNEED 0x0059
#define SCM_TS_OPT_ID 0x005a
#if !defined(__KERNEL__)

4
include/net/inet_sock.h
View File

@ -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 /* ts_opt_id field is valid, overriding sk_tskey */
enum {
INET_FLAGS_PKTINFO = 0,

7
include/net/sock.h
View File

@ -954,6 +954,12 @@ enum sock_flags {
};
#define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))
/*
* The highest bit of sk_tsflags is reserved for kernel-internal
* SOCKCM_FLAG_TS_OPT_ID. There is a check in core/sock.c to control that
* SOF_TIMESTAMPING* values do not reach this reserved area
*/
#define SOCKCM_FLAG_TS_OPT_ID BIT(31)
static inline void sock_copy_flags(struct sock *nsk, const struct sock *osk)
{
@ -1796,6 +1802,7 @@ struct sockcm_cookie {
u64 transmit_time;
u32 mark;
u32 tsflags;
u32 ts_opt_id;
};
static inline void sockcm_init(struct sockcm_cookie *sockc,

2
include/uapi/asm-generic/socket.h
View File

@ -141,6 +141,8 @@
#define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
#define SO_DEVMEM_DONTNEED 80
#define SCM_TS_OPT_ID 81
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))

13
net/core/sock.c
View File

@ -2899,6 +2899,8 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
{
u32 tsflags;
BUILD_BUG_ON(SOF_TIMESTAMPING_LAST == (1 << 31));
switch (cmsg->cmsg_type) {
case SO_MARK:
if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) &&
@ -2927,6 +2929,17 @@ 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:
if (sk_is_tcp(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 |= SOCKCM_FLAG_TS_OPT_ID;
break;
/* SCM_RIGHTS and SCM_CREDENTIALS are semantically in SOL_UNIX. */
case SCM_RIGHTS:
case SCM_CREDENTIALS:

19
net/ipv4/ip_output.c
View File

@ -973,7 +973,7 @@ static int __ip_append_data(struct sock *sk,
unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
int csummode = CHECKSUM_NONE;
struct rtable *rt = dst_rtable(cork->dst);
bool paged, hold_tskey, extra_uref = false;
bool paged, hold_tskey = false, extra_uref = false;
unsigned int wmem_alloc_delta = 0;
u32 tskey = 0;
@ -1049,10 +1049,15 @@ static int __ip_append_data(struct sock *sk,
cork->length += length;
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 (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;
}
}
/* So, what's going on in the loop below?
*
@ -1327,6 +1332,10 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
cork->transmit_time = ipc->sockc.transmit_time;
cork->tx_flags = 0;
sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
if (ipc->sockc.tsflags & SOCKCM_FLAG_TS_OPT_ID) {
cork->flags |= IPCORK_TS_OPT_ID;
cork->ts_opt_id = ipc->sockc.ts_opt_id;
}
return 0;
}

20
net/ipv6/ip6_output.c
View File

@ -1402,7 +1402,10 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
cork->base.tx_flags = 0;
cork->base.mark = ipc6->sockc.mark;
sock_tx_timestamp(sk, ipc6->sockc.tsflags, &cork->base.tx_flags);
if (ipc6->sockc.tsflags & SOCKCM_FLAG_TS_OPT_ID) {
cork->base.flags |= IPCORK_TS_OPT_ID;
cork->base.ts_opt_id = ipc6->sockc.ts_opt_id;
}
cork->base.length = 0;
cork->base.transmit_time = ipc6->sockc.transmit_time;
@ -1433,7 +1436,7 @@ static int __ip6_append_data(struct sock *sk,
bool zc = false;
u32 tskey = 0;
struct rt6_info *rt = dst_rt6_info(cork->dst);
bool paged, hold_tskey, extra_uref = false;
bool paged, hold_tskey = false, extra_uref = false;
struct ipv6_txoptions *opt = v6_cork->opt;
int csummode = CHECKSUM_NONE;
unsigned int maxnonfragsize, headersize;
@ -1543,10 +1546,15 @@ static int __ip6_append_data(struct sock *sk,
flags &= ~MSG_SPLICE_PAGES;
}
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 (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;
}
}
/*
* Let's try using as much space as possible.