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bpf: Remove BPF_SKB_DELIVERY_TIME_NONE and rename s/delivery_time_/ts…
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…tamp_/

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: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220309090509.3712315-1-kafai@fb.com
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@iamkafai @borkmann
iamkafai authored and borkmann committed Mar 10, 2022
1 parent 9d90db9 commit 9bb984f
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Showing 4 changed files with 77 additions and 93 deletions.
2 changes: 1 addition & 1 deletion include/linux/filter.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down
40 changes: 21 additions & 19 deletions include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
*
Expand All @@ -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), \
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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.
Expand Down Expand Up @@ -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;
};
Expand Down
88 changes: 34 additions & 54 deletions net/core/filter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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:
Expand Down Expand Up @@ -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);
}

Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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):
Expand Down
40 changes: 21 additions & 19 deletions tools/include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
*
Expand All @@ -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), \
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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.
Expand Down Expand Up @@ -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;
};
Expand Down

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