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.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220309090509.3712315-1-kafai@fb.com

include/linux/filter.h

@@ -573,7 +573,7 @@ struct bpf_prog {
 				enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
 				call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
 				call_get_func_ip:1, /* Do we call get_func_ip() */
-				delivery_time_access:1; /* Accessed __sk_buff->delivery_time_type */
+				tstamp_type_access:1; /* Accessed __sk_buff->tstamp_type */
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	enum bpf_attach_type	expected_attach_type; /* For some prog types */
 	u32			len;		/* Number of filter blocks */

include/uapi/linux/bpf.h

@@ -5090,23 +5090,22 @@ union bpf_attr {
  *		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->delivery_time_type to *dtime_type*.
+ *		Change the __sk_buff->tstamp_type to *tstamp_type*
+ *		and set *tstamp* to the __sk_buff->tstamp together.
  *
- *		When setting a delivery time (non zero *dtime*) to
- *		__sk_buff->tstamp, only BPF_SKB_DELIVERY_TIME_MONO *dtime_type*
- *		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
+ *		If there is no need to change the __sk_buff->tstamp_type,
+ *		the tstamp value can be directly written to __sk_buff->tstamp
  *		instead.
  *
- *		*dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
- *		can be used to clear any delivery time stored in
- *		__sk_buff->tstamp.
+ *		BPF_SKB_TSTAMP_DELIVERY_MONO is the only tstamp that
+ *		will be kept during bpf_redirect_*().  A non zero
+ *		*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.
  *
@@ -5119,7 +5118,7 @@ union bpf_attr {
  *	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),			\
@@ -5314,7 +5313,7 @@ union bpf_attr {
 	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
@@ -5505,9 +5504,12 @@ union {					\
 } __attribute__((aligned(8)))
 
 enum {
-	BPF_SKB_DELIVERY_TIME_NONE,
-	BPF_SKB_DELIVERY_TIME_UNSPEC,
-	BPF_SKB_DELIVERY_TIME_MONO,
+	BPF_SKB_TSTAMP_UNSPEC,
+	BPF_SKB_TSTAMP_DELIVERY_MONO,	/* tstamp has mono delivery time */
+	/* 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.
@@ -5550,7 +5552,7 @@ struct __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;
 };

net/core/filter.c

@@ -7388,36 +7388,36 @@ static const struct bpf_func_proto bpf_sock_ops_reserve_hdr_opt_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
-BPF_CALL_3(bpf_skb_set_delivery_time, struct sk_buff *, skb,
-	   u64, dtime, u32, dtime_type)
+BPF_CALL_3(bpf_skb_set_tstamp, struct sk_buff *, skb,
+	   u64, tstamp, u32, tstamp_type)
 {
 	/* skb_clear_delivery_time() is done for inet protocol */
 	if (skb->protocol != htons(ETH_P_IP) &&
 	    skb->protocol != htons(ETH_P_IPV6))
 		return -EOPNOTSUPP;
 
-	switch (dtime_type) {
-	case BPF_SKB_DELIVERY_TIME_MONO:
-		if (!dtime)
+	switch (tstamp_type) {
+	case BPF_SKB_TSTAMP_DELIVERY_MONO:
+		if (!tstamp)
 			return -EINVAL;
-		skb->tstamp = dtime;
+		skb->tstamp = tstamp;
 		skb->mono_delivery_time = 1;
 		break;
-	case BPF_SKB_DELIVERY_TIME_NONE:
-		if (dtime)
+	case BPF_SKB_TSTAMP_UNSPEC:
+		if (tstamp)
 			return -EINVAL;
 		skb->tstamp = 0;
 		skb->mono_delivery_time = 0;
 		break;
 	default:
-		return -EOPNOTSUPP;
+		return -EINVAL;
 	}
 
 	return 0;
 }
 
-static const struct bpf_func_proto bpf_skb_set_delivery_time_proto = {
-	.func           = bpf_skb_set_delivery_time,
+static const struct bpf_func_proto bpf_skb_set_tstamp_proto = {
+	.func           = bpf_skb_set_tstamp,
 	.gpl_only       = false,
 	.ret_type       = RET_INTEGER,
 	.arg1_type      = ARG_PTR_TO_CTX,
@@ -7786,8 +7786,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_tcp_gen_syncookie_proto;
 	case BPF_FUNC_sk_assign:
 		return &bpf_sk_assign_proto;
-	case BPF_FUNC_skb_set_delivery_time:
-		return &bpf_skb_set_delivery_time_proto;
+	case BPF_FUNC_skb_set_tstamp:
+		return &bpf_skb_set_tstamp_proto;
 #endif
 	default:
 		return bpf_sk_base_func_proto(func_id);
@@ -8127,9 +8127,9 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
 			return false;
 		info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL;
 		break;
-	case offsetof(struct __sk_buff, delivery_time_type):
+	case offsetof(struct __sk_buff, tstamp_type):
 		return false;
-	case offsetofend(struct __sk_buff, delivery_time_type) ... offsetof(struct __sk_buff, hwtstamp) - 1:
+	case offsetofend(struct __sk_buff, tstamp_type) ... offsetof(struct __sk_buff, hwtstamp) - 1:
 		/* Explicitly prohibit access to padding in __sk_buff. */
 		return false;
 	default:
@@ -8484,14 +8484,14 @@ static bool tc_cls_act_is_valid_access(int off, int size,
 		break;
 	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
 		return false;
-	case offsetof(struct __sk_buff, delivery_time_type):
+	case offsetof(struct __sk_buff, tstamp_type):
 		/* The convert_ctx_access() on reading and writing
 		 * __sk_buff->tstamp depends on whether the bpf prog
-		 * has used __sk_buff->delivery_time_type or not.
-		 * Thus, we need to set prog->delivery_time_access
+		 * has used __sk_buff->tstamp_type or not.
+		 * Thus, we need to set prog->tstamp_type_access
 		 * earlier during is_valid_access() here.
 		 */
-		((struct bpf_prog *)prog)->delivery_time_access = 1;
+		((struct bpf_prog *)prog)->tstamp_type_access = 1;
 		return size == sizeof(__u8);
 	}
 
@@ -8888,42 +8888,22 @@ static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type,
 	return insn - insn_buf;
 }
 
-static struct bpf_insn *bpf_convert_dtime_type_read(const struct bpf_insn *si,
-						    struct bpf_insn *insn)
+static struct bpf_insn *bpf_convert_tstamp_type_read(const struct bpf_insn *si,
+						     struct bpf_insn *insn)
 {
 	__u8 value_reg = si->dst_reg;
 	__u8 skb_reg = si->src_reg;
+	/* AX is needed because src_reg and dst_reg could be the same */
 	__u8 tmp_reg = BPF_REG_AX;
 
 	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
 			      PKT_VLAN_PRESENT_OFFSET);
-	*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
-				SKB_MONO_DELIVERY_TIME_MASK);
-	*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
-	/* value_reg = BPF_SKB_DELIVERY_TIME_MONO */
-	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_MONO);
-	*insn++ = BPF_JMP_A(IS_ENABLED(CONFIG_NET_CLS_ACT) ? 10 : 5);
-
-	*insn++ = BPF_LDX_MEM(BPF_DW, tmp_reg, skb_reg,
-			      offsetof(struct sk_buff, tstamp));
-	*insn++ = BPF_JMP_IMM(BPF_JNE, tmp_reg, 0, 2);
-	/* value_reg = BPF_SKB_DELIVERY_TIME_NONE */
-	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_NONE);
-	*insn++ = BPF_JMP_A(IS_ENABLED(CONFIG_NET_CLS_ACT) ? 6 : 1);
-
-#ifdef CONFIG_NET_CLS_ACT
-	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);
-	*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
-	*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
-	/* At ingress, value_reg = 0 */
-	*insn++ = BPF_MOV32_IMM(value_reg, 0);
+	*insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg,
+				SKB_MONO_DELIVERY_TIME_MASK, 2);
+	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_UNSPEC);
 	*insn++ = BPF_JMP_A(1);
-#endif
-
-	/* value_reg = BPF_SKB_DELIVERYT_TIME_UNSPEC */
-	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_UNSPEC);
+	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_DELIVERY_MONO);
 
-	/* 15 insns with CONFIG_NET_CLS_ACT */
 	return insn;
 }
 
@@ -8956,11 +8936,11 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog,
 	__u8 skb_reg = si->src_reg;
 
 #ifdef CONFIG_NET_CLS_ACT
-	/* If the delivery_time_type is read,
+	/* If the tstamp_type is read,
 	 * the bpf prog is aware the tstamp could have delivery time.
-	 * Thus, read skb->tstamp as is if delivery_time_access is true.
+	 * Thus, read skb->tstamp as is if tstamp_type_access is true.
 	 */
-	if (!prog->delivery_time_access) {
+	if (!prog->tstamp_type_access) {
 		/* AX is needed because src_reg and dst_reg could be the same */
 		__u8 tmp_reg = BPF_REG_AX;
 
@@ -8990,13 +8970,13 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
 	__u8 skb_reg = si->dst_reg;
 
 #ifdef CONFIG_NET_CLS_ACT
-	/* If the delivery_time_type is read,
+	/* If the tstamp_type is read,
 	 * the bpf prog is aware the tstamp could have delivery time.
-	 * Thus, write skb->tstamp as is if delivery_time_access is true.
+	 * Thus, write skb->tstamp as is if tstamp_type_access is true.
 	 * Otherwise, writing at ingress will have to clear the
 	 * mono_delivery_time bit also.
 	 */
-	if (!prog->delivery_time_access) {
+	if (!prog->tstamp_type_access) {
 		__u8 tmp_reg = BPF_REG_AX;
 
 		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);
@@ -9329,8 +9309,8 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 			insn = bpf_convert_tstamp_read(prog, si, insn);
 		break;
 
-	case offsetof(struct __sk_buff, delivery_time_type):
-		insn = bpf_convert_dtime_type_read(si, insn);
+	case offsetof(struct __sk_buff, tstamp_type):
+		insn = bpf_convert_tstamp_type_read(si, insn);
 		break;
 
 	case offsetof(struct __sk_buff, gso_segs):

tools/include/uapi/linux/bpf.h

@@ -5090,23 +5090,22 @@ union bpf_attr {
  *		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->delivery_time_type to *dtime_type*.
+ *		Change the __sk_buff->tstamp_type to *tstamp_type*
+ *		and set *tstamp* to the __sk_buff->tstamp together.
  *
- *		When setting a delivery time (non zero *dtime*) to
- *		__sk_buff->tstamp, only BPF_SKB_DELIVERY_TIME_MONO *dtime_type*
- *		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
+ *		If there is no need to change the __sk_buff->tstamp_type,
+ *		the tstamp value can be directly written to __sk_buff->tstamp
  *		instead.
  *
- *		*dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
- *		can be used to clear any delivery time stored in
- *		__sk_buff->tstamp.
+ *		BPF_SKB_TSTAMP_DELIVERY_MONO is the only tstamp that
+ *		will be kept during bpf_redirect_*().  A non zero
+ *		*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.
  *
@@ -5119,7 +5118,7 @@ union bpf_attr {
  *	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),			\
@@ -5314,7 +5313,7 @@ union bpf_attr {
 	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
@@ -5505,9 +5504,12 @@ union {					\
 } __attribute__((aligned(8)))
 
 enum {
-	BPF_SKB_DELIVERY_TIME_NONE,
-	BPF_SKB_DELIVERY_TIME_UNSPEC,
-	BPF_SKB_DELIVERY_TIME_MONO,
+	BPF_SKB_TSTAMP_UNSPEC,
+	BPF_SKB_TSTAMP_DELIVERY_MONO,	/* tstamp has mono delivery time */
+	/* 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.
@@ -5550,7 +5552,7 @@ struct __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;
 };