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[76.146.13.146]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-737116b0e8asm12175596b3a.158.2025.03.19.14.54.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Mar 2025 14:54:12 -0700 (PDT) From: Amery Hung To: netdev@vger.kernel.org Cc: bpf@vger.kernel.org, daniel@iogearbox.net, andrii@kernel.org, alexei.starovoitov@gmail.com, martin.lau@kernel.org, kuba@kernel.org, edumazet@google.com, xiyou.wangcong@gmail.com, jhs@mojatatu.com, sinquersw@gmail.com, toke@redhat.com, juntong.deng@outlook.com, jiri@resnulli.us, stfomichev@gmail.com, ekarani.silvestre@ccc.ufcg.edu.br, yangpeihao@sjtu.edu.cn, yepeilin.cs@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v6 04/11] bpf: net_sched: Add basic bpf qdisc kfuncs Date: Wed, 19 Mar 2025 14:53:51 -0700 Message-ID: <20250319215358.2287371-5-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250319215358.2287371-1-ameryhung@gmail.com> References: <20250319215358.2287371-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Amery Hung Add basic kfuncs for working on skb in qdisc. Both bpf_qdisc_skb_drop() and bpf_kfree_skb() can be used to release a reference to an skb. However, bpf_qdisc_skb_drop() can only be called in .enqueue where a to_free skb list is available from kernel to defer the release. bpf_kfree_skb() should be used elsewhere. It is also used in bpf_obj_free_fields() when cleaning up skb in maps and collections. bpf_skb_get_hash() returns the flow hash of an skb, which can be used to build flow-based queueing algorithms. Finally, allow users to create read-only dynptr via bpf_dynptr_from_skb(). Signed-off-by: Amery Hung Acked-by: Toke Høiland-Jørgensen --- net/sched/bpf_qdisc.c | 111 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 110 insertions(+), 1 deletion(-) diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c index 7eca556a3782..d812a72ca032 100644 --- a/net/sched/bpf_qdisc.c +++ b/net/sched/bpf_qdisc.c @@ -8,6 +8,9 @@ #include #include +#define QDISC_OP_IDX(op) (offsetof(struct Qdisc_ops, op) / sizeof(void (*)(void))) +#define QDISC_MOFF_IDX(moff) (moff / sizeof(void (*)(void))) + static struct bpf_struct_ops bpf_Qdisc_ops; struct bpf_sk_buff_ptr { @@ -139,6 +142,95 @@ static int bpf_qdisc_btf_struct_access(struct bpf_verifier_log *log, return 0; } +__bpf_kfunc_start_defs(); + +/* bpf_skb_get_hash - Get the flow hash of an skb. + * @skb: The skb to get the flow hash from. + */ +__bpf_kfunc u32 bpf_skb_get_hash(struct sk_buff *skb) +{ + return skb_get_hash(skb); +} + +/* bpf_kfree_skb - Release an skb's reference and drop it immediately. + * @skb: The skb whose reference to be released and dropped. + */ +__bpf_kfunc void bpf_kfree_skb(struct sk_buff *skb) +{ + kfree_skb(skb); +} + +/* bpf_qdisc_skb_drop - Drop an skb by adding it to a deferred free list. + * @skb: The skb whose reference to be released and dropped. + * @to_free_list: The list of skbs to be dropped. + */ +__bpf_kfunc void bpf_qdisc_skb_drop(struct sk_buff *skb, + struct bpf_sk_buff_ptr *to_free_list) +{ + __qdisc_drop(skb, (struct sk_buff **)to_free_list); +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(qdisc_kfunc_ids) +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_KFUNCS_END(qdisc_kfunc_ids) + +BTF_SET_START(qdisc_common_kfunc_set) +BTF_ID(func, bpf_skb_get_hash) +BTF_ID(func, bpf_kfree_skb) +BTF_ID(func, bpf_dynptr_from_skb) +BTF_SET_END(qdisc_common_kfunc_set) + +BTF_SET_START(qdisc_enqueue_kfunc_set) +BTF_ID(func, bpf_qdisc_skb_drop) +BTF_SET_END(qdisc_enqueue_kfunc_set) + +enum qdisc_ops_kf_flags { + QDISC_OPS_KF_COMMON = 0, + QDISC_OPS_KF_ENQUEUE = 1 << 0, +}; + +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(init)] = QDISC_OPS_KF_COMMON, + [QDISC_OP_IDX(reset)] = QDISC_OPS_KF_COMMON, + [QDISC_OP_IDX(destroy)] = QDISC_OPS_KF_COMMON, +}; + +static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id) +{ + u32 moff, flags; + + if (!btf_id_set8_contains(&qdisc_kfunc_ids, kfunc_id)) + return 0; + + if (prog->aux->st_ops != &bpf_Qdisc_ops) + return -EACCES; + + moff = prog->aux->attach_st_ops_member_off; + flags = qdisc_ops_context_flags[QDISC_MOFF_IDX(moff)]; + + if ((flags & QDISC_OPS_KF_ENQUEUE) && + btf_id_set_contains(&qdisc_enqueue_kfunc_set, kfunc_id)) + return 0; + + if (btf_id_set_contains(&qdisc_common_kfunc_set, kfunc_id)) + return 0; + + return -EACCES; +} + +static const struct btf_kfunc_id_set bpf_qdisc_kfunc_set = { + .owner = THIS_MODULE, + .set = &qdisc_kfunc_ids, + .filter = bpf_qdisc_kfunc_filter, +}; + 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, @@ -225,8 +317,25 @@ static struct bpf_struct_ops bpf_Qdisc_ops = { .owner = THIS_MODULE, }; +BTF_ID_LIST(bpf_sk_buff_dtor_ids) +BTF_ID(func, bpf_kfree_skb) + static int __init bpf_qdisc_kfunc_init(void) { - return register_bpf_struct_ops(&bpf_Qdisc_ops, Qdisc_ops); + int ret; + const struct btf_id_dtor_kfunc skb_kfunc_dtors[] = { + { + .btf_id = bpf_sk_buff_ids[0], + .kfunc_btf_id = bpf_sk_buff_dtor_ids[0] + }, + }; + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_qdisc_kfunc_set); + ret = ret ?: register_btf_id_dtor_kfuncs(skb_kfunc_dtors, + ARRAY_SIZE(skb_kfunc_dtors), + THIS_MODULE); + ret = ret ?: register_bpf_struct_ops(&bpf_Qdisc_ops, Qdisc_ops); + + return ret; } late_initcall(bpf_qdisc_kfunc_init);