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bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time()

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* __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
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41
include/uapi/linux/bpf.h
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@@ -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;
};