Commit 6b98ec7e authored by Jason Xing's avatar Jason Xing Committed by Martin KaFai Lau
Browse files

bpf: Add BPF_SOCK_OPS_TSTAMP_SCHED_CB callback 



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: default avatarJason Xing <kerneljasonxing@gmail.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-7-kerneljasonxing@gmail.com
parent aa290f93

include/linux/skbuff.h

+5 −1
Original line number Diff line number Diff line
@@ -489,10 +489,14 @@ enum { 


	/* generate software time stamp when entering packet scheduling */

	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    | \

				 SKBTX_SCHED_TSTAMP)

				 SKBTX_SCHED_TSTAMP | \

				 SKBTX_BPF)

#define SKBTX_ANY_TSTAMP	(SKBTX_HW_TSTAMP | \

				 SKBTX_HW_TSTAMP_USE_CYCLES | \

				 SKBTX_ANY_SW_TSTAMP)

include/uapi/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -7031,6 +7031,11 @@ enum { 
					 * by the kernel or the

					 * 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

net/core/dev.c

+2 −1
Original line number Diff line number Diff line
@@ -4501,7 +4501,8 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev) 
	skb_reset_mac_header(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);



	/* Disable soft irqs for various locks below. Also

net/core/skbuff.c

+20 −0
Original line number Diff line number Diff line
@@ -5556,6 +5556,23 @@ static bool skb_tstamp_tx_report_so_timestamping(struct sk_buff *skb, 
	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,

		     const struct sk_buff *ack_skb,

		     struct skb_shared_hwtstamps *hwtstamps,
@@ -5568,6 +5585,9 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb, 
	if (!sk)

		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))

		return;

tools/include/uapi/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -7031,6 +7031,11 @@ enum { 
					 * by the kernel or the

					 * 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