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Wed, 09 Apr 2025 14:46:12 -0700 (PDT) Received: from localhost ([2a03:2880:ff::]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b02a0cf38dasm1497117a12.23.2025.04.09.14.46.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Apr 2025 14:46:12 -0700 (PDT) From: Amery Hung To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, edumazet@google.com, kuba@kernel.org, xiyou.wangcong@gmail.com, jhs@mojatatu.com, martin.lau@kernel.org, jiri@resnulli.us, stfomichev@gmail.com, toke@redhat.com, sinquersw@gmail.com, ekarani.silvestre@ccc.ufcg.edu.br, yangpeihao@sjtu.edu.cn, yepeilin.cs@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v7 04/10] bpf: net_sched: Add a qdisc watchdog timer Date: Wed, 9 Apr 2025 14:46:00 -0700 Message-ID: <20250409214606.2000194-5-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250409214606.2000194-1-ameryhung@gmail.com> References: <20250409214606.2000194-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Amery Hung 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. The implementation relies on struct_ops gen_prologue/epilogue to patch bpf programs provided by users. Operator specific prologue/epilogue kfuncs are introduced instead of watchdog kfuncs so that it is easier to extend prologue/epilogue in the future (writing C vs BPF bytecode). Signed-off-by: Amery Hung Acked-by: Toke Høiland-Jørgensen --- net/sched/bpf_qdisc.c | 106 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 105 insertions(+), 1 deletion(-) diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c index d812a72ca032..5f4ab4877535 100644 --- a/net/sched/bpf_qdisc.c +++ b/net/sched/bpf_qdisc.c @@ -13,6 +13,10 @@ 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; }; @@ -142,6 +146,56 @@ 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 (prog->aux->attach_st_ops_member_off != offsetof(struct Qdisc_ops, init)) + return 0; + + /* r6 = r1; // r6 will be "u64 *ctx". r1 is "u64 *ctx". + * r1 = r1[0]; // r1 will be "struct Qdisc *sch" + * r0 = bpf_qdisc_init_prologue(r1); + * r1 = r6; // r1 will be "u64 *ctx". + */ + *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 (prog->aux->attach_st_ops_member_off != offsetof(struct Qdisc_ops, reset) && + prog->aux->attach_st_ops_member_off != offsetof(struct Qdisc_ops, destroy)) + return 0; + + /* r1 = stack[ctx_stack_off]; // r1 will be "u64 *ctx" + * r1 = r1[0]; // r1 will be "struct Qdisc *sch" + * r0 = bpf_qdisc_reset_destroy_epilogue(r1); + * BPF_EXIT; + */ + *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. @@ -170,6 +224,36 @@ __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) @@ -177,6 +261,9 @@ 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) @@ -187,16 +274,22 @@ 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) + enum qdisc_ops_kf_flags { QDISC_OPS_KF_COMMON = 0, QDISC_OPS_KF_ENQUEUE = 1 << 0, + QDISC_OPS_KF_DEQUEUE = 1 << 1, }; static const u32 qdisc_ops_context_flags[] = { [QDISC_OP_IDX(enqueue)] = QDISC_OPS_KF_ENQUEUE, - [QDISC_OP_IDX(dequeue)] = QDISC_OPS_KF_COMMON, + [QDISC_OP_IDX(dequeue)] = QDISC_OPS_KF_DEQUEUE, [QDISC_OP_IDX(init)] = QDISC_OPS_KF_COMMON, [QDISC_OP_IDX(reset)] = QDISC_OPS_KF_COMMON, [QDISC_OP_IDX(destroy)] = QDISC_OPS_KF_COMMON, @@ -219,6 +312,10 @@ static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id) btf_id_set_contains(&qdisc_enqueue_kfunc_set, kfunc_id)) return 0; + if ((flags & QDISC_OPS_KF_DEQUEUE) && + btf_id_set_contains(&qdisc_dequeue_kfunc_set, kfunc_id)) + return 0; + if (btf_id_set_contains(&qdisc_common_kfunc_set, kfunc_id)) return 0; @@ -235,6 +332,8 @@ static const struct bpf_verifier_ops bpf_qdisc_verifier_ops = { .get_func_proto = bpf_base_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, @@ -250,6 +349,11 @@ 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; -- 2.47.1