From: Amery Hung <amery.hung@xxxxxxxxxxxxx>
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 <amery.hung@xxxxxxxxxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/bpf_struct_ops.c | 2 +
net/sched/bpf_qdisc.c | 92 ++++++++++++++++++++++++++++++++++++-
3 files changed, 94 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2556f8043276..87ecee12af21 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1809,6 +1809,7 @@ struct bpf_struct_ops {
void *cfi_stubs;
struct module *owner;
const char *name;
+ const struct btf_type *type;
struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
};
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 27d4a170df84..65542d8f064c 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -442,6 +442,8 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
goto errout;
}
+ st_ops->type = t;
+
return 0;
errout:
diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
index 4b7d013f4f5c..1c92bfcc3847 100644
--- a/net/sched/bpf_qdisc.c
+++ b/net/sched/bpf_qdisc.c
@@ -108,6 +108,79 @@ 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_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)
+
+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,
+ prog->aux->attach_btf_id))
+ return 0;
+
+ /* Skip the check when prog->attach_func_name is not yet available
+ * during check_cfg().
+ */
+ if (!btf_id_set8_contains(&qdisc_kfunc_ids, kfunc_id) ||
+ !prog->aux->attach_func_name)
+ return 0;
+
+ if (!strcmp(prog->aux->attach_func_name, "enqueue")) {
+ if (btf_id_set_contains(&qdisc_enqueue_kfunc_set, kfunc_id))
+ return 0;
+ }
+
+ return btf_id_set_contains(&qdisc_common_kfunc_set, kfunc_id) ? 0 : -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_qdisc_get_func_proto,
.is_valid_access = bpf_qdisc_is_valid_access,
@@ -200,8 +273,25 @@ 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);
--
2.47.0
