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

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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
This commit is contained in:
Martin KaFai Lau 2022-03-09 01:05:09 -08:00 • committed by Daniel Borkmann
parent 9d90db97e4
commit 9bb984f28d
4 changed files with 77 additions and 93 deletions
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2
include/linux/filter.h
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@ -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 */