On Thu, Feb 13, 2025 at 7:49 AM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote:
>
> On 2/11/25 10:18 PM, Jason Xing wrote:
> > 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: Jason Xing <kerneljasonxing@xxxxxxxxx>
> > ---
> > kernel/bpf/btf.c | 1 +
> > net/core/filter.c | 32 +++++++++++++++++++++++++++++++-
> > 2 files changed, 32 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 9433b6467bbe..740210f883dc 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -8522,6 +8522,7 @@ 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;
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 7f56d0bbeb00..36793c68b125 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -12102,6 +12102,26 @@ __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;
> > + struct sock *sk;
> > +
> > + if (skops->op != BPF_SOCK_OPS_TS_SND_CB)
> > + return -EOPNOTSUPP;
>
> It still needs to test the "flags" such that it can be used in the future....
>
> if (flags)
> return -EINVAL;
Will add it.
> > +
> > + skb = skops->skb;
> > + sk = skops->sk;
> > + skb_shinfo(skb)->tx_flags |= SKBTX_BPF;
> > + if (sk_is_tcp(sk)) {
>
> Unnecessary check like this will only confuse reader. Remove it and revisit when
> UDP will be supported.
Okay.
Thanks,
Jason
>
> > + 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,
> > @@ -12135,6 +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,
> > @@ -12155,6 +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;
> > @@ -12173,7 +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);
> >
>
