On 4/23/21 5:05 PM, Kumar Kartikeya Dwivedi wrote:
[...]
tools/lib/bpf/libbpf.h | 92 ++++++++
tools/lib/bpf/libbpf.map | 5 +
tools/lib/bpf/netlink.c | 478 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 574 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index bec4e6a6e31d..1c717c07b66e 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -775,6 +775,98 @@ LIBBPF_API int bpf_linker__add_file(struct bpf_linker *linker, const char *filen
LIBBPF_API int bpf_linker__finalize(struct bpf_linker *linker);
LIBBPF_API void bpf_linker__free(struct bpf_linker *linker);
+enum bpf_tc_attach_point {
+ BPF_TC_INGRESS,
+ BPF_TC_EGRESS,
+ BPF_TC_CUSTOM_PARENT,
+ _BPF_TC_PARENT_MAX,
I don't think we need to expose _BPF_TC_PARENT_MAX as part of the API, I would drop
the latter.
+};
+
+/* The opts structure is also used to return the created filters attributes
+ * (e.g. in case the user left them unset). Some of the options that were left
+ * out default to a reasonable value, documented below.
+ *
+ * protocol - ETH_P_ALL
+ * chain index - 0
+ * class_id - 0 (can be set by bpf program using skb->tc_classid)
+ * bpf_flags - TCA_BPF_FLAG_ACT_DIRECT (direct action mode)
+ * bpf_flags_gen - 0
+ *
+ * The user must fulfill documented requirements for each function.
Not sure if this is overly relevant as part of the bpf_tc_opts in here. For the
2nd part, I would probably just mention that libbpf internally attaches the bpf
programs with direct action mode. The hw offload may be future todo, and the other
bits are little used anyway; mentioning them here, what value does it have to
libbpf users? I'd rather just drop the 2nd part and/or simplify this paragraph
just stating that the progs are attached in direct action mode.
+ */
+struct bpf_tc_opts {
+ size_t sz;
+ __u32 handle;
+ __u32 parent;
+ __u16 priority;
+ __u32 prog_id;
+ bool replace;
+ size_t :0;
+};
+
+#define bpf_tc_opts__last_field replace
+
+struct bpf_tc_ctx;
+
+struct bpf_tc_ctx_opts {
+ size_t sz;
+};
+
+#define bpf_tc_ctx_opts__last_field sz
+
+/* Requirements */
+/*
+ * @ifindex: Must be > 0.
+ * @parent: Must be one of the enum constants < _BPF_TC_PARENT_MAX
+ * @opts: Can be NULL, currently no options are supported.
+ */
Up to Andrii, but we don't have such API doc in general inside libbpf.h, I
would drop it for the time being to be consistent with the rest (same for
others below).
+LIBBPF_API struct bpf_tc_ctx *bpf_tc_ctx_init(__u32 ifindex,
nit: in user space s/__u32 ifindex/int ifindex/
+ enum bpf_tc_attach_point parent,
+ struct bpf_tc_ctx_opts *opts);
Should we enforce opts being NULL or non-NULL here, or drop the arg from here
for now altogether? (And if later versions of the functions show up this could
be mapped to the right one?)
+/*
+ * @ctx: Can be NULL, if not, must point to a valid object.
+ * If the qdisc was attached during ctx_init, it will be deleted if no
+ * filters are attached to it.
+ * When ctx == NULL, this is a no-op.
+ */
+LIBBPF_API int bpf_tc_ctx_destroy(struct bpf_tc_ctx *ctx);
+/*
+ * @ctx: Cannot be NULL.
+ * @fd: Must be >= 0.
+ * @opts: Cannot be NULL, prog_id must be unset, all other fields can be
+ * optionally set. All fields except replace will be set as per created
+ * filter's attributes. parent must only be set when attach_point of ctx is
+ * BPF_TC_CUSTOM_PARENT, otherwise parent must be unset.
+ *
+ * Fills the following fields in opts:
+ * handle
+ * parent
+ * priority
+ * prog_id
+ */
+LIBBPF_API int bpf_tc_attach(struct bpf_tc_ctx *ctx, int fd,
+ struct bpf_tc_opts *opts);
+/*
+ * @ctx: Cannot be NULL.
+ * @opts: Cannot be NULL, replace and prog_id must be unset, all other fields
+ * must be set.
+ */
+LIBBPF_API int bpf_tc_detach(struct bpf_tc_ctx *ctx,
+ const struct bpf_tc_opts *opts);
One thing that I find a bit odd from this API is that BPF_TC_INGRESS / BPF_TC_EGRESS
needs to be set each time via bpf_tc_ctx_init(). So whenever a specific program would
be attached to both we need to 're-init' in between just to change from hook a to b,
whereas when you have BPF_TC_CUSTOM_PARENT, you could just use a different opts->parent
without going this detour (unless the clsact wasn't loaded there in the first place).
Could we add a BPF_TC_UNSPEC to enum bpf_tc_attach_point, which the user would pass to
bpf_tc_ctx_init(), so that opts.direction = BPF_TC_INGRESS with subsequent bpf_tc_attach()
can be called, and same opts.direction = BPF_TC_EGRESS with bpf_tc_attach() for different
fd. The only thing we cared about in bpf_tc_ctx_init() resp. the ctx was that qdisc was
ready.
+/*
+ * @ctx: Cannot be NULL.
+ * @opts: Cannot be NULL, replace and prog_id must be unset, all other fields
+ * must be set.
+ *
+ * Fills the following fields in opts:
+ * handle
+ * parent
+ * priority
+ * prog_id
+ */
+LIBBPF_API int bpf_tc_query(struct bpf_tc_ctx *ctx,
+ struct bpf_tc_opts *opts);
+
#ifdef __cplusplus
} /* extern "C" */
#endif
