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bpf: Add BPF_SOCK_OPS_TSTAMP_SCHED_CB callback

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Support SCM_TSTAMP_SCHED case for bpf timestamping.

Add a new sock_ops callback, BPF_SOCK_OPS_TSTAMP_SCHED_CB. This
callback will occur at the same timestamping point as the user
space's SCM_TSTAMP_SCHED. The BPF program can use it to get the
same SCM_TSTAMP_SCHED timestamp without modifying the user-space
application.

A new SKBTX_BPF flag is added to mark skb_shinfo(skb)->tx_flags,
ensuring that the new BPF timestamping and the current user
space's SO_TIMESTAMPING do not interfere with each other.

Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-7-kerneljasonxing@gmail.com
This commit is contained in:
Jason Xing 2025-02-20 15:29:34 +08:00 • committed by Martin KaFai Lau
parent aa290f93a4
commit 6b98ec7e88
5 changed files with 37 additions and 2 deletions
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6
include/linux/skbuff.h
View file

@ -489,10 +489,14 @@ enum {
/* generate software time stamp when entering packet scheduling */ /* generate software time stamp when entering packet scheduling */
SKBTX_SCHED_TSTAMP = 1 << 6, SKBTX_SCHED_TSTAMP = 1 << 6,
/* used for bpf extension when a bpf program is loaded */
SKBTX_BPF = 1 << 7,
}; };
#define SKBTX_ANY_SW_TSTAMP (SKBTX_SW_TSTAMP | \ #define SKBTX_ANY_SW_TSTAMP (SKBTX_SW_TSTAMP | \
SKBTX_SCHED_TSTAMP) SKBTX_SCHED_TSTAMP | \
SKBTX_BPF)
#define SKBTX_ANY_TSTAMP (SKBTX_HW_TSTAMP | \ #define SKBTX_ANY_TSTAMP (SKBTX_HW_TSTAMP | \
SKBTX_HW_TSTAMP_USE_CYCLES | \ SKBTX_HW_TSTAMP_USE_CYCLES | \
SKBTX_ANY_SW_TSTAMP) SKBTX_ANY_SW_TSTAMP)

5
include/uapi/linux/bpf.h
View file

@ -7031,6 +7031,11 @@ enum {
* by the kernel or the * by the kernel or the
* earlier bpf-progs. * earlier bpf-progs.
*/ */
BPF_SOCK_OPS_TSTAMP_SCHED_CB, /* Called when skb is passing
* through dev layer when
* SK_BPF_CB_TX_TIMESTAMPING
* feature is on.
*/
}; };
/* List of TCP states. There is a build check in net/ipv4/tcp.c to detect /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect

3
net/core/dev.c
View file

@ -4501,7 +4501,8 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
skb_reset_mac_header(skb); skb_reset_mac_header(skb);
skb_assert_len(skb); skb_assert_len(skb);
if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP)) if (unlikely(skb_shinfo(skb)->tx_flags &
(SKBTX_SCHED_TSTAMP | SKBTX_BPF)))
__skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED); __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);
/* Disable soft irqs for various locks below. Also /* Disable soft irqs for various locks below. Also

20
net/core/skbuff.c
View file

@ -5556,6 +5556,23 @@ static bool skb_tstamp_tx_report_so_timestamping(struct sk_buff *skb,
return false; return false;
} }
static void skb_tstamp_tx_report_bpf_timestamping(struct sk_buff *skb,
struct sock *sk,
int tstype)
{
int op;
switch (tstype) {
case SCM_TSTAMP_SCHED:
op = BPF_SOCK_OPS_TSTAMP_SCHED_CB;
break;
default:
return;
}
bpf_skops_tx_timestamping(sk, skb, op);
}
void __skb_tstamp_tx(struct sk_buff *orig_skb, void __skb_tstamp_tx(struct sk_buff *orig_skb,
const struct sk_buff *ack_skb, const struct sk_buff *ack_skb,
struct skb_shared_hwtstamps *hwtstamps, struct skb_shared_hwtstamps *hwtstamps,
@ -5568,6 +5585,9 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
if (!sk) if (!sk)
return; return;
if (skb_shinfo(orig_skb)->tx_flags & SKBTX_BPF)
skb_tstamp_tx_report_bpf_timestamping(orig_skb, sk, tstype);
if (!skb_tstamp_tx_report_so_timestamping(orig_skb, hwtstamps, tstype)) if (!skb_tstamp_tx_report_so_timestamping(orig_skb, hwtstamps, tstype))
return; return;

5
tools/include/uapi/linux/bpf.h
View file

@ -7031,6 +7031,11 @@ enum {
* by the kernel or the * by the kernel or the
* earlier bpf-progs. * earlier bpf-progs.
*/ */
BPF_SOCK_OPS_TSTAMP_SCHED_CB, /* Called when skb is passing
* through dev layer when
* SK_BPF_CB_TX_TIMESTAMPING
* feature is on.
*/
}; };
/* List of TCP states. There is a build check in net/ipv4/tcp.c to detect /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect