bpf: Remove BPF_SKB_DELIVERY_TIME_NONE and rename s/delivery_time_/tstamp_/

This patch is to simplify the uapi bpf.h regarding to the tstamp type and use a similar way as the kernel to describe the value stored in __sk_buff->tstamp. My earlier thought was to avoid describing the semantic and clock base for the rcv timestamp until there is more clarity on the use case, so the __sk_buff->delivery_time_type naming instead of __sk_buff->tstamp_type. With some thoughts, it can reuse the UNSPEC naming. This patch first removes BPF_SKB_DELIVERY_TIME_NONE and also rename BPF_SKB_DELIVERY_TIME_UNSPEC to BPF_SKB_TSTAMP_UNSPEC and BPF_SKB_DELIVERY_TIME_MONO to BPF_SKB_TSTAMP_DELIVERY_MONO. The semantic of BPF_SKB_TSTAMP_DELIVERY_MONO is the same: __sk_buff->tstamp has delivery time in mono clock base. BPF_SKB_TSTAMP_UNSPEC means __sk_buff->tstamp has the (rcv) tstamp at ingress and the delivery time at egress. At egress, the clock base could be found from skb->sk->sk_clockid. __sk_buff->tstamp == 0 naturally means NONE, so NONE is not needed. With BPF_SKB_TSTAMP_UNSPEC for the rcv tstamp at ingress, the __sk_buff->delivery_time_type is also renamed to __sk_buff->tstamp_type which was also suggested in the earlier discussion: https://lore.kernel.org/bpf/b181acbe-caf8-502d-4b7b-7d96b9fc5d55@iogearbox.net/ The above will then make __sk_buff->tstamp and __sk_buff->tstamp_type the same as its kernel skb->tstamp and skb->mono_delivery_time counter part. The internal kernel function bpf_skb_convert_dtime_type_read() is then renamed to bpf_skb_convert_tstamp_type_read() and it can be simplified with the BPF_SKB_DELIVERY_TIME_NONE gone. A BPF_ALU32_IMM(BPF_AND) insn is also saved by using BPF_JMP32_IMM(BPF_JSET). The bpf helper bpf_skb_set_delivery_time() is also renamed to bpf_skb_set_tstamp(). The arg name is changed from dtime to tstamp also. It only allows setting tstamp 0 for BPF_SKB_TSTAMP_UNSPEC and it could be relaxed later if there is use case to change mono delivery time to non mono. prog->delivery_time_access is also renamed to prog->tstamp_type_access.

Martin KaFai Lau committed 4 years ago

Commit 9bb984f1 parent 9d90db94 files · +77 −93Browse files

Showing the changes to include/uapi (1 of 4 files). Show all

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include/uapi/linux/bpf.h+21−19

  *		0 on success, or a negative error in case of failure. On error
  *		*dst* buffer is zeroed out.
  *
- * long bpf_skb_set_delivery_time(struct sk_buff *skb, u64 dtime, u32 dtime_type)
+ * long bpf_skb_set_tstamp(struct sk_buff *skb, u64 tstamp, u32 tstamp_type)
  *	Description
- *		Set a *dtime* (delivery time) to the __sk_buff->tstamp and also
+ *		Change the __sk_buff->tstamp_type to *tstamp_type*
- *		change the __sk_buff->delivery_time_type to *dtime_type*.
+ *		and set *tstamp* to the __sk_buff->tstamp together.
  *
- *		When setting a delivery time (non zero *dtime*) to
+ *		If there is no need to change the __sk_buff->tstamp_type,
- *		__sk_buff->tstamp, only BPF_SKB_DELIVERY_TIME_MONO *dtime_type*
+ *		the tstamp value can be directly written to __sk_buff->tstamp
- *		is supported.  It is the only delivery_time_type that will be
- *		kept after bpf_redirect_*().
- *
- *		If there is no need to change the __sk_buff->delivery_time_type,
- *		the delivery time can be directly written to __sk_buff->tstamp
  *		instead.
  *
- *		*dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
+ *		BPF_SKB_TSTAMP_DELIVERY_MONO is the only tstamp that
- *		can be used to clear any delivery time stored in
+ *		will be kept during bpf_redirect_*().  A non zero
- *		__sk_buff->tstamp.
+ *		*tstamp* must be used with the BPF_SKB_TSTAMP_DELIVERY_MONO
+ *		*tstamp_type*.
+ *
+ *		A BPF_SKB_TSTAMP_UNSPEC *tstamp_type* can only be used
+ *		with a zero *tstamp*.
  *
  *		Only IPv4 and IPv6 skb->protocol are supported.
  *
  *	Return
  *		0 on success.
  *		**-EINVAL** for invalid input
- *		**-EOPNOTSUPP** for unsupported delivery_time_type and protocol
+ *		**-EOPNOTSUPP** for unsupported protocol
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
 	FN(xdp_load_bytes),		\
 	FN(xdp_store_bytes),		\
 	FN(copy_from_user_task),	\
-	FN(skb_set_delivery_time),      \
+	FN(skb_set_tstamp),		\
 	/* */
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
 } __attribute__((aligned(8)))
 enum {
-	BPF_SKB_DELIVERY_TIME_NONE,
+	BPF_SKB_TSTAMP_UNSPEC,
-	BPF_SKB_DELIVERY_TIME_UNSPEC,
+	BPF_SKB_TSTAMP_DELIVERY_MONO,	/* tstamp has mono delivery time */
-	BPF_SKB_DELIVERY_TIME_MONO,
+	/* For any BPF_SKB_TSTAMP_* that the bpf prog cannot handle,
+	 * the bpf prog should handle it like BPF_SKB_TSTAMP_UNSPEC
+	 * and try to deduce it by ingress, egress or skb->sk->sk_clockid.
+	 */
 };
 /* user accessible mirror of in-kernel sk_buff.
 	__u32 gso_segs;
 	__bpf_md_ptr(struct bpf_sock *, sk);
 	__u32 gso_size;
-	__u8  delivery_time_type;
+	__u8  tstamp_type;
 	__u32 :24;		/* Padding, future use. */
 	__u64 hwtstamp;
 };