Commit 59422464 authored by Jason Xing's avatar Jason Xing Committed by Martin KaFai Lau
Browse files

bpf: Support selective sampling for bpf timestamping 



Add the bpf_sock_ops_enable_tx_tstamp kfunc to allow BPF programs to
selectively enable TX timestamping on a skb during tcp_sendmsg().

For example, BPF program will limit tracking X numbers of packets
and then will stop there instead of tracing all the sendmsgs of
matched flow all along. It would be helpful for users who cannot
afford to calculate latencies from every sendmsg call probably
due to the performance or storage space consideration.

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/20250220072940.99994-12-kerneljasonxing@gmail.com
parent c9525d24

kernel/bpf/btf.c

+1 −0
Original line number Diff line number Diff line
@@ -8524,6 +8524,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type) 
	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:

	case BPF_PROG_TYPE_CGROUP_SOCKOPT:

	case BPF_PROG_TYPE_CGROUP_SYSCTL:

	case BPF_PROG_TYPE_SOCK_OPS:

		return BTF_KFUNC_HOOK_CGROUP;

	case BPF_PROG_TYPE_SCHED_ACT:

		return BTF_KFUNC_HOOK_SCHED_ACT;

net/core/filter.c

+30 −1
Original line number Diff line number Diff line
@@ -12103,6 +12103,25 @@ __bpf_kfunc int bpf_sk_assign_tcp_reqsk(struct __sk_buff *s, struct sock *sk, 
#endif

}



__bpf_kfunc int bpf_sock_ops_enable_tx_tstamp(struct bpf_sock_ops_kern *skops,

					      u64 flags)

{

	struct sk_buff *skb;



	if (skops->op != BPF_SOCK_OPS_TSTAMP_SENDMSG_CB)

		return -EOPNOTSUPP;



	if (flags)

		return -EINVAL;



	skb = skops->skb;

	skb_shinfo(skb)->tx_flags |= SKBTX_BPF;

	TCP_SKB_CB(skb)->txstamp_ack |= TSTAMP_ACK_BPF;

	skb_shinfo(skb)->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;



	return 0;

}



__bpf_kfunc_end_defs();



int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
@@ -12136,6 +12155,10 @@ BTF_KFUNCS_START(bpf_kfunc_check_set_tcp_reqsk) 
BTF_ID_FLAGS(func, bpf_sk_assign_tcp_reqsk, KF_TRUSTED_ARGS)

BTF_KFUNCS_END(bpf_kfunc_check_set_tcp_reqsk)



BTF_KFUNCS_START(bpf_kfunc_check_set_sock_ops)

BTF_ID_FLAGS(func, bpf_sock_ops_enable_tx_tstamp, KF_TRUSTED_ARGS)

BTF_KFUNCS_END(bpf_kfunc_check_set_sock_ops)



static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {

	.owner = THIS_MODULE,

	.set = &bpf_kfunc_check_set_skb,
@@ -12156,6 +12179,11 @@ static const struct btf_kfunc_id_set bpf_kfunc_set_tcp_reqsk = { 
	.set = &bpf_kfunc_check_set_tcp_reqsk,

};



static const struct btf_kfunc_id_set bpf_kfunc_set_sock_ops = {

	.owner = THIS_MODULE,

	.set = &bpf_kfunc_check_set_sock_ops,

};



static int __init bpf_kfunc_init(void)

{

	int ret;
@@ -12174,7 +12202,8 @@ static int __init bpf_kfunc_init(void) 
	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);

	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,

					       &bpf_kfunc_set_sock_addr);

	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_tcp_reqsk);

	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_tcp_reqsk);

	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SOCK_OPS, &bpf_kfunc_set_sock_ops);

}

late_initcall(bpf_kfunc_init);