On Sat, Mar 15, 2025 at 4:31 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Thu, Mar 13, 2025 at 12:03 PM Amery Hung <ameryhung@xxxxxxxxx> wrote:
> >
> > Do not allow users to attach bpf qdiscs to classful qdiscs. This is to
> > prevent accidentally breaking existings classful qdiscs if they rely on
> > some data in the child qdisc. This restriction can potentially be lifted
> > in the future. Note that, we still allow bpf qdisc to be attached to mq.
> >
> > Signed-off-by: Amery Hung <ameryhung@xxxxxxxxx>
> > ---
> > net/sched/bpf_qdisc.c | 20 +++++++++++++++++++-
> > 1 file changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
> > index e4e7a5879869..c2f33cd35674 100644
> > --- a/net/sched/bpf_qdisc.c
> > +++ b/net/sched/bpf_qdisc.c
> > @@ -170,8 +170,11 @@ static int bpf_qdisc_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
> > return 0;
> >
> > *insn++ = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
> > + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 16);
> > *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
>
> Both loads need a comment.
> It's st_ops callback specific and not obvious what ends up in r1 and r2.
>
Got it. I will clarify this in the comment.
> > *insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_init_prologue_ids[0]);
> > + *insn++ = BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1);
> > + *insn++ = BPF_EXIT_INSN();
> > *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_6);
> > *insn++ = prog->insnsi[0];
> >
> > @@ -239,11 +242,26 @@ __bpf_kfunc void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire, u64
> > }
> >
> > /* bpf_qdisc_init_prologue - Hidden kfunc called in prologue of .init. */
> > -__bpf_kfunc void bpf_qdisc_init_prologue(struct Qdisc *sch)
> > +__bpf_kfunc int bpf_qdisc_init_prologue(struct Qdisc *sch,
> > + struct netlink_ext_ack *extack)
> > {
> > struct bpf_sched_data *q = qdisc_priv(sch);
> > + struct net_device *dev = qdisc_dev(sch);
> > + struct Qdisc *p;
> > +
> > + if (sch->parent != TC_H_ROOT) {
> > + p = qdisc_lookup(dev, TC_H_MAJ(sch->parent));
> > + if (!p)
> > + return -ENOENT;
> > +
> > + if (!(p->flags & TCQ_F_MQROOT)) {
> > + NL_SET_ERR_MSG(extack, "BPF qdisc only supported on root or mq");
> > + return -EINVAL;
> > + }
> > + }
> >
> > qdisc_watchdog_init(&q->watchdog, sch);
> > + return 0;
> > }
> >
> > /* bpf_qdisc_reset_destroy_epilogue - Hidden kfunc called in epilogue of .reset
> > --
> > 2.47.1
> >
