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bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time() 

* __sk_buff->delivery_time_type:
This patch adds __sk_buff->delivery_time_type.  It tells if the
delivery_time is stored in __sk_buff->tstamp or not.

It will be most useful for ingress to tell if the __sk_buff->tstamp
has the (rcv) timestamp or delivery_time.  If delivery_time_type
is 0 (BPF_SKB_DELIVERY_TIME_NONE), it has the (rcv) timestamp.

Two non-zero types are defined for the delivery_time_type,
BPF_SKB_DELIVERY_TIME_MONO and BPF_SKB_DELIVERY_TIME_UNSPEC.  For UNSPEC,
it can only happen in egress because only mono delivery_time can be
forwarded to ingress now.  The clock of UNSPEC delivery_time
can be deduced from the skb->sk->sk_clockid which is how
the sch_etf doing it also.

* Provide forwarded delivery_time to tc-bpf@ingress:
With the help of the new delivery_time_type, the tc-bpf has a way
to tell if the __sk_buff->tstamp has the (rcv) timestamp or
the delivery_time.  During bpf load time, the verifier will learn if
the bpf prog has accessed the new __sk_buff->delivery_time_type.
If it does, it means the tc-bpf@ingress is expecting the
skb->tstamp could have the delivery_time.  The kernel will then
read the skb->tstamp as-is during bpf insn rewrite without
checking the skb->mono_delivery_time.  This is done by adding a
new prog->delivery_time_access bit.  The same goes for
writing skb->tstamp.

* bpf_skb_set_delivery_time():
The bpf_skb_set_delivery_time() helper is added to allow setting both
delivery_time and the delivery_time_type at the same time.  If the
tc-bpf does not need to change the delivery_time_type, it can directly
write to the __sk_buff->tstamp as the existing tc-bpf has already been
doing.  It will be most useful at ingress to change the
__sk_buff->tstamp from the (rcv) timestamp to
a mono delivery_time and then bpf_redirect_*().

bpf only has mono clock helper (bpf_ktime_get_ns), and
the current known use case is the mono EDT for fq, and
only mono delivery time can be kept during forward now,
so bpf_skb_set_delivery_time() only supports setting
BPF_SKB_DELIVERY_TIME_MONO.  It can be extended later when use cases
come up and the forwarding path also supports other clock bases.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2022-03-02 11:56:34 -08:00 committed by David S. Miller
parent 7449197d60
commit 8d21ec0e46
4 changed files with 214 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/filter.h
View File

@ -572,7 +572,8 @@ struct bpf_prog {
has_callchain_buf:1, /* callchain buffer allocated? */
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() */
call_get_func_ip:1, /* Do we call get_func_ip() */
delivery_time_access:1; /* Accessed __sk_buff->delivery_time_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 */

41
include/uapi/linux/bpf.h
View File

@ -5086,6 +5086,37 @@ union bpf_attr {
* Return
* 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)
* Description
* Set a *dtime* (delivery time) to the __sk_buff->tstamp and also
* change the __sk_buff->delivery_time_type to *dtime_type*.
*
* 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
* instead.
*
* *dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
* can be used to clear any delivery time stored in
* __sk_buff->tstamp.
*
* Only IPv4 and IPv6 skb->protocol are supported.
*
* This function is most useful when it needs to set a
* mono delivery time to __sk_buff->tstamp and then
* bpf_redirect_*() to the egress of an iface. For example,
* changing the (rcv) timestamp in __sk_buff->tstamp at
* ingress to a mono delivery time and then bpf_redirect_*()
* to sch_fq@phy-dev.
* Return
* 0 on success.
* **-EINVAL** for invalid input
* **-EOPNOTSUPP** for unsupported delivery_time_type and protocol
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5280,6 +5311,7 @@ union bpf_attr {
FN(xdp_load_bytes), \
FN(xdp_store_bytes), \
FN(copy_from_user_task), \
FN(skb_set_delivery_time), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@ -5469,6 +5501,12 @@ union { \
__u64 :64; \
} __attribute__((aligned(8)))
enum {
BPF_SKB_DELIVERY_TIME_NONE,
BPF_SKB_DELIVERY_TIME_UNSPEC,
BPF_SKB_DELIVERY_TIME_MONO,
};
/* user accessible mirror of in-kernel sk_buff.
* new fields can only be added to the end of this structure
*/
@ -5509,7 +5547,8 @@ struct __sk_buff {
__u32 gso_segs;
__bpf_md_ptr(struct bpf_sock *, sk);
__u32 gso_size;
__u32 :32; /* Padding, future use. */
__u8 delivery_time_type;
__u32 :24; /* Padding, future use. */
__u64 hwtstamp;
};

165
net/core/filter.c
View File

@ -7388,6 +7388,43 @@ 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)
{
/* 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)
return -EINVAL;
skb->tstamp = dtime;
skb->mono_delivery_time = 1;
break;
case BPF_SKB_DELIVERY_TIME_NONE:
if (dtime)
return -EINVAL;
skb->tstamp = 0;
skb->mono_delivery_time = 0;
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
static const struct bpf_func_proto bpf_skb_set_delivery_time_proto = {
.func = bpf_skb_set_delivery_time,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_ANYTHING,
};
#endif /* CONFIG_INET */
bool bpf_helper_changes_pkt_data(void *func)
@ -7749,6 +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;
#endif
default:
return bpf_sk_base_func_proto(func_id);
@ -8088,7 +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 offsetofend(struct __sk_buff, gso_size) ... offsetof(struct __sk_buff, hwtstamp) - 1:
case offsetof(struct __sk_buff, delivery_time_type):
return false;
case offsetofend(struct __sk_buff, delivery_time_type) ... offsetof(struct __sk_buff, hwtstamp) - 1:
/* Explicitly prohibit access to padding in __sk_buff. */
return false;
default:
@ -8443,6 +8484,15 @@ 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):
/* 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
* earlier during is_valid_access() here.
*/
((struct bpf_prog *)prog)->delivery_time_access = 1;
return size == sizeof(__u8);
}
return bpf_skb_is_valid_access(off, size, type, prog, info);
@ -8838,6 +8888,45 @@ 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)
{
__u8 value_reg = si->dst_reg;
__u8 skb_reg = si->src_reg;
__u8 tmp_reg = BPF_REG_AX;
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
SKB_MONO_DELIVERY_TIME_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, TC_AT_INGRESS_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_JMP_A(1);
#endif
/* value_reg = BPF_SKB_DELIVERYT_TIME_UNSPEC */
*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_UNSPEC);
/* 15 insns with CONFIG_NET_CLS_ACT */
return insn;
}
static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
struct bpf_insn *insn)
{
@ -8859,29 +8948,32 @@ static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
return insn;
}
static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_insn *si,
static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog,
const struct bpf_insn *si,
struct bpf_insn *insn)
{
__u8 value_reg = si->dst_reg;
__u8 skb_reg = si->src_reg;
#ifdef CONFIG_NET_CLS_ACT
__u8 tmp_reg = BPF_REG_AX;
if (!prog->delivery_time_access) {
__u8 tmp_reg = BPF_REG_AX;
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 5);
/* @ingress, read __sk_buff->tstamp as the (rcv) timestamp,
* so check the skb->mono_delivery_time.
*/
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
SKB_MONO_DELIVERY_TIME_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
/* skb->mono_delivery_time is set, read 0 as the (rcv) timestamp. */
*insn++ = BPF_MOV64_IMM(value_reg, 0);
*insn++ = BPF_JMP_A(1);
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 5);
/* @ingress, read __sk_buff->tstamp as the (rcv) timestamp,
* so check the skb->mono_delivery_time.
*/
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
SKB_MONO_DELIVERY_TIME_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
/* skb->mono_delivery_time is set, read 0 as the (rcv) timestamp. */
*insn++ = BPF_MOV64_IMM(value_reg, 0);
*insn++ = BPF_JMP_A(1);
}
#endif
*insn++ = BPF_LDX_MEM(BPF_DW, value_reg, skb_reg,
@ -8889,27 +8981,30 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_insn *si,
return insn;
}
static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_insn *si,
static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
const struct bpf_insn *si,
struct bpf_insn *insn)
{
__u8 value_reg = si->src_reg;
__u8 skb_reg = si->dst_reg;
#ifdef CONFIG_NET_CLS_ACT
__u8 tmp_reg = BPF_REG_AX;
if (!prog->delivery_time_access) {
__u8 tmp_reg = BPF_REG_AX;
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3);
/* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.
* Clear the skb->mono_delivery_time.
*/
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
~SKB_MONO_DELIVERY_TIME_MASK);
*insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3);
/* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.
* Clear the skb->mono_delivery_time.
*/
*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
~SKB_MONO_DELIVERY_TIME_MASK);
*insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg,
SKB_MONO_DELIVERY_TIME_OFFSET);
}
#endif
/* skb->tstamp = tstamp */
@ -9226,9 +9321,13 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
BUILD_BUG_ON(sizeof_field(struct sk_buff, tstamp) != 8);
if (type == BPF_WRITE)
insn = bpf_convert_tstamp_write(si, insn);
insn = bpf_convert_tstamp_write(prog, si, insn);
else
insn = bpf_convert_tstamp_read(si, insn);
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);
break;
case offsetof(struct __sk_buff, gso_segs):

41
tools/include/uapi/linux/bpf.h
View File

@ -5086,6 +5086,37 @@ union bpf_attr {
* Return
* 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)
* Description
* Set a *dtime* (delivery time) to the __sk_buff->tstamp and also
* change the __sk_buff->delivery_time_type to *dtime_type*.
*
* 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
* instead.
*
* *dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
* can be used to clear any delivery time stored in
* __sk_buff->tstamp.
*
* Only IPv4 and IPv6 skb->protocol are supported.
*
* This function is most useful when it needs to set a
* mono delivery time to __sk_buff->tstamp and then
* bpf_redirect_*() to the egress of an iface. For example,
* changing the (rcv) timestamp in __sk_buff->tstamp at
* ingress to a mono delivery time and then bpf_redirect_*()
* to sch_fq@phy-dev.
* Return
* 0 on success.
* **-EINVAL** for invalid input
* **-EOPNOTSUPP** for unsupported delivery_time_type and protocol
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5280,6 +5311,7 @@ union bpf_attr {
FN(xdp_load_bytes), \
FN(xdp_store_bytes), \
FN(copy_from_user_task), \
FN(skb_set_delivery_time), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@ -5469,6 +5501,12 @@ union { \
__u64 :64; \
} __attribute__((aligned(8)))
enum {
BPF_SKB_DELIVERY_TIME_NONE,
BPF_SKB_DELIVERY_TIME_UNSPEC,
BPF_SKB_DELIVERY_TIME_MONO,
};
/* user accessible mirror of in-kernel sk_buff.
* new fields can only be added to the end of this structure
*/
@ -5509,7 +5547,8 @@ struct __sk_buff {
__u32 gso_segs;
__bpf_md_ptr(struct bpf_sock *, sk);
__u32 gso_size;
__u32 :32; /* Padding, future use. */
__u8 delivery_time_type;
__u32 :24; /* Padding, future use. */
__u64 hwtstamp;
};