diff mbox series

[bpf-next,v2,08/14] bpf: net_sched: Add a qdisc watchdog timer

Message ID 20241220195619.2022866-9-amery.hung@gmail.com (mailing list archive)
State New, archived
Delegated to: BPF
Headers show
Series bpf qdisc | expand

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bpf/vmtest-bpf-next-PR success PR summary
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Commit Message

Amery Hung Dec. 20, 2024, 7:55 p.m. UTC
From: Amery Hung <amery.hung@bytedance.com>

Add a watchdog timer to bpf qdisc. The watchdog can be used to schedule
the execution of qdisc through kfunc, bpf_qdisc_schedule(). It can be
useful for building traffic shaping scheduling algorithm, where the time
the next packet will be dequeued is known.

Signed-off-by: Amery Hung <amery.hung@bytedance.com>
---
 include/linux/filter.h | 10 +++++
 net/sched/bpf_qdisc.c  | 92 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

Comments

Martin KaFai Lau Jan. 9, 2025, 12:20 a.m. UTC | #1
On 12/20/24 11:55 AM, Amery Hung wrote:
> diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
> index 1c92bfcc3847..bbe7aded6f24 100644
> --- a/net/sched/bpf_qdisc.c
> +++ b/net/sched/bpf_qdisc.c
> @@ -8,6 +8,10 @@
>   
>   static struct bpf_struct_ops bpf_Qdisc_ops;
>   
> +struct bpf_sched_data {
> +	struct qdisc_watchdog watchdog;
> +};
> +
>   struct bpf_sk_buff_ptr {
>   	struct sk_buff *skb;
>   };
> @@ -108,6 +112,46 @@ static int bpf_qdisc_btf_struct_access(struct bpf_verifier_log *log,
>   	return 0;
>   }
>   
> +BTF_ID_LIST(bpf_qdisc_init_prologue_ids)
> +BTF_ID(func, bpf_qdisc_init_prologue)
> +
> +static int bpf_qdisc_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
> +				  const struct bpf_prog *prog)
> +{
> +	struct bpf_insn *insn = insn_buf;
> +
> +	if (strcmp(prog->aux->attach_func_name, "init"))
> +		return 0;
> +
> +	*insn++ = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
> +	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
> +	*insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_init_prologue_ids[0]);

I was wondering if patch 7 is needed if BPF_EMIT_CALL() and BPF_CALL_1() were 
used, so it looks more like a bpf helper instead of kfunc. I tried but failed at 
the "fn = env->ops->get_func_proto(insn->imm, env->prog);" in do_misc_fixups(). 
I think the change in patch 7 is simple enough instead of getting 
get_func_proto() works for this case.

> +	*insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_6);
> +	*insn++ = prog->insnsi[0];
> +
> +	return insn - insn_buf;
> +}
> +
> +BTF_ID_LIST(bpf_qdisc_reset_destroy_epilogue_ids)
> +BTF_ID(func, bpf_qdisc_reset_destroy_epilogue)
> +
> +static int bpf_qdisc_gen_epilogue(struct bpf_insn *insn_buf, const struct bpf_prog *prog,
> +				  s16 ctx_stack_off)
> +{
> +	struct bpf_insn *insn = insn_buf;
> +
> +	if (strcmp(prog->aux->attach_func_name, "reset") &&
> +	    strcmp(prog->aux->attach_func_name, "destroy"))
> +		return 0;
> +
> +	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_FP, ctx_stack_off);
> +	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
> +	*insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_reset_destroy_epilogue_ids[0]);
> +	*insn++ = BPF_EXIT_INSN();
> +
> +	return insn - insn_buf;
> +}
> +
Amery Hung Jan. 9, 2025, 3 p.m. UTC | #2
On Wed, Jan 8, 2025 at 4:20 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 12/20/24 11:55 AM, Amery Hung wrote:
> > diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
> > index 1c92bfcc3847..bbe7aded6f24 100644
> > --- a/net/sched/bpf_qdisc.c
> > +++ b/net/sched/bpf_qdisc.c
> > @@ -8,6 +8,10 @@
> >
> >   static struct bpf_struct_ops bpf_Qdisc_ops;
> >
> > +struct bpf_sched_data {
> > +     struct qdisc_watchdog watchdog;
> > +};
> > +
> >   struct bpf_sk_buff_ptr {
> >       struct sk_buff *skb;
> >   };
> > @@ -108,6 +112,46 @@ static int bpf_qdisc_btf_struct_access(struct bpf_verifier_log *log,
> >       return 0;
> >   }
> >
> > +BTF_ID_LIST(bpf_qdisc_init_prologue_ids)
> > +BTF_ID(func, bpf_qdisc_init_prologue)
> > +
> > +static int bpf_qdisc_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
> > +                               const struct bpf_prog *prog)
> > +{
> > +     struct bpf_insn *insn = insn_buf;
> > +
> > +     if (strcmp(prog->aux->attach_func_name, "init"))
> > +             return 0;
> > +
> > +     *insn++ = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
> > +     *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
> > +     *insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_init_prologue_ids[0]);
>
> I was wondering if patch 7 is needed if BPF_EMIT_CALL() and BPF_CALL_1() were
> used, so it looks more like a bpf helper instead of kfunc. I tried but failed at
> the "fn = env->ops->get_func_proto(insn->imm, env->prog);" in do_misc_fixups().
> I think the change in patch 7 is simple enough instead of getting
> get_func_proto() works for this case.
>

Yeah. Making BPF_EMIT_CALL + BPF_CALL_xxx work in
gen_prologue/epilogue doesn't seem trivial to me at least when
compared with BPF_CALL_KFUNC.

> > +     *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_6);
> > +     *insn++ = prog->insnsi[0];
> > +
> > +     return insn - insn_buf;
> > +}
> > +
> > +BTF_ID_LIST(bpf_qdisc_reset_destroy_epilogue_ids)
> > +BTF_ID(func, bpf_qdisc_reset_destroy_epilogue)
> > +
> > +static int bpf_qdisc_gen_epilogue(struct bpf_insn *insn_buf, const struct bpf_prog *prog,
> > +                               s16 ctx_stack_off)
> > +{
> > +     struct bpf_insn *insn = insn_buf;
> > +
> > +     if (strcmp(prog->aux->attach_func_name, "reset") &&
> > +         strcmp(prog->aux->attach_func_name, "destroy"))
> > +             return 0;
> > +
> > +     *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_FP, ctx_stack_off);
> > +     *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
> > +     *insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_reset_destroy_epilogue_ids[0]);
> > +     *insn++ = BPF_EXIT_INSN();
> > +
> > +     return insn - insn_buf;
> > +}
> > +
diff mbox series

Patch

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0477254bc2d3..3bc9b741a120 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -469,6 +469,16 @@  static inline bool insn_is_cast_user(const struct bpf_insn *insn)
 		.off   = 0,					\
 		.imm   = BPF_CALL_IMM(FUNC) })
 
+/* Kfunc call */
+
+#define BPF_CALL_KFUNC(OFF, IMM)				\
+	((struct bpf_insn) {					\
+		.code  = BPF_JMP | BPF_CALL,			\
+		.dst_reg = 0,					\
+		.src_reg = BPF_PSEUDO_KFUNC_CALL,		\
+		.off   = OFF,					\
+		.imm   = IMM })
+
 /* Raw code statement block */
 
 #define BPF_RAW_INSN(CODE, DST, SRC, OFF, IMM)			\
diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
index 1c92bfcc3847..bbe7aded6f24 100644
--- a/net/sched/bpf_qdisc.c
+++ b/net/sched/bpf_qdisc.c
@@ -8,6 +8,10 @@ 
 
 static struct bpf_struct_ops bpf_Qdisc_ops;
 
+struct bpf_sched_data {
+	struct qdisc_watchdog watchdog;
+};
+
 struct bpf_sk_buff_ptr {
 	struct sk_buff *skb;
 };
@@ -108,6 +112,46 @@  static int bpf_qdisc_btf_struct_access(struct bpf_verifier_log *log,
 	return 0;
 }
 
+BTF_ID_LIST(bpf_qdisc_init_prologue_ids)
+BTF_ID(func, bpf_qdisc_init_prologue)
+
+static int bpf_qdisc_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
+				  const struct bpf_prog *prog)
+{
+	struct bpf_insn *insn = insn_buf;
+
+	if (strcmp(prog->aux->attach_func_name, "init"))
+		return 0;
+
+	*insn++ = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
+	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
+	*insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_init_prologue_ids[0]);
+	*insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_6);
+	*insn++ = prog->insnsi[0];
+
+	return insn - insn_buf;
+}
+
+BTF_ID_LIST(bpf_qdisc_reset_destroy_epilogue_ids)
+BTF_ID(func, bpf_qdisc_reset_destroy_epilogue)
+
+static int bpf_qdisc_gen_epilogue(struct bpf_insn *insn_buf, const struct bpf_prog *prog,
+				  s16 ctx_stack_off)
+{
+	struct bpf_insn *insn = insn_buf;
+
+	if (strcmp(prog->aux->attach_func_name, "reset") &&
+	    strcmp(prog->aux->attach_func_name, "destroy"))
+		return 0;
+
+	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_FP, ctx_stack_off);
+	*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
+	*insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_reset_destroy_epilogue_ids[0]);
+	*insn++ = BPF_EXIT_INSN();
+
+	return insn - insn_buf;
+}
+
 __bpf_kfunc_start_defs();
 
 /* bpf_skb_get_hash - Get the flow hash of an skb.
@@ -136,6 +180,36 @@  __bpf_kfunc void bpf_qdisc_skb_drop(struct sk_buff *skb,
 	__qdisc_drop(skb, (struct sk_buff **)to_free_list);
 }
 
+/* bpf_qdisc_watchdog_schedule - Schedule a qdisc to a later time using a timer.
+ * @sch: The qdisc to be scheduled.
+ * @expire: The expiry time of the timer.
+ * @delta_ns: The slack range of the timer.
+ */
+__bpf_kfunc void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire, u64 delta_ns)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_schedule_range_ns(&q->watchdog, expire, delta_ns);
+}
+
+/* bpf_qdisc_init_prologue - Hidden kfunc called in prologue of .init. */
+__bpf_kfunc void bpf_qdisc_init_prologue(struct Qdisc *sch)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_init(&q->watchdog, sch);
+}
+
+/* bpf_qdisc_reset_destroy_epilogue - Hidden kfunc called in epilogue of .reset
+ * and .destroy
+ */
+__bpf_kfunc void bpf_qdisc_reset_destroy_epilogue(struct Qdisc *sch)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_cancel(&q->watchdog);
+}
+
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(qdisc_kfunc_ids)
@@ -143,6 +217,9 @@  BTF_ID_FLAGS(func, bpf_skb_get_hash, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_kfree_skb, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_qdisc_skb_drop, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_dynptr_from_skb, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_qdisc_watchdog_schedule, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_qdisc_init_prologue, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_qdisc_reset_destroy_epilogue, KF_TRUSTED_ARGS)
 BTF_KFUNCS_END(qdisc_kfunc_ids)
 
 BTF_SET_START(qdisc_common_kfunc_set)
@@ -152,8 +229,13 @@  BTF_SET_END(qdisc_common_kfunc_set)
 
 BTF_SET_START(qdisc_enqueue_kfunc_set)
 BTF_ID(func, bpf_qdisc_skb_drop)
+BTF_ID(func, bpf_qdisc_watchdog_schedule)
 BTF_SET_END(qdisc_enqueue_kfunc_set)
 
+BTF_SET_START(qdisc_dequeue_kfunc_set)
+BTF_ID(func, bpf_qdisc_watchdog_schedule)
+BTF_SET_END(qdisc_dequeue_kfunc_set)
+
 static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id)
 {
 	if (bpf_Qdisc_ops.type != btf_type_by_id(prog->aux->attach_btf,
@@ -170,6 +252,9 @@  static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id)
 	if (!strcmp(prog->aux->attach_func_name, "enqueue")) {
 		if (btf_id_set_contains(&qdisc_enqueue_kfunc_set, kfunc_id))
 		       return 0;
+	} else if (!strcmp(prog->aux->attach_func_name, "dequeue")) {
+		if (btf_id_set_contains(&qdisc_dequeue_kfunc_set, kfunc_id))
+		       return 0;
 	}
 
 	return btf_id_set_contains(&qdisc_common_kfunc_set, kfunc_id) ? 0 : -EACCES;
@@ -185,6 +270,8 @@  static const struct bpf_verifier_ops bpf_qdisc_verifier_ops = {
 	.get_func_proto		= bpf_qdisc_get_func_proto,
 	.is_valid_access	= bpf_qdisc_is_valid_access,
 	.btf_struct_access	= bpf_qdisc_btf_struct_access,
+	.gen_prologue		= bpf_qdisc_gen_prologue,
+	.gen_epilogue		= bpf_qdisc_gen_epilogue,
 };
 
 static int bpf_qdisc_init_member(const struct btf_type *t,
@@ -200,6 +287,11 @@  static int bpf_qdisc_init_member(const struct btf_type *t,
 
 	moff = __btf_member_bit_offset(t, member) / 8;
 	switch (moff) {
+	case offsetof(struct Qdisc_ops, priv_size):
+		if (uqdisc_ops->priv_size)
+			return -EINVAL;
+		qdisc_ops->priv_size = sizeof(struct bpf_sched_data);
+		return 1;
 	case offsetof(struct Qdisc_ops, peek):
 		qdisc_ops->peek = qdisc_peek_dequeued;
 		return 0;