Re: [PATCH bpf-next 1/3] net: skbuff: rename __pkt_vlan_present_offset to __mono_tc_offset

Martin KaFai Lau
2023-03-09T01:16:53Z

On 3/7/23 4:31 PM, Jakub Kicinski wrote:
> vlan_present is gone since
> commit 354259fa73e2 ("net: remove skb->vlan_present")
> rename the offset field to what BPF is currently looking
> for in this byte - mono_delivery_time and tc_at_ingress.
>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> include/linux/skbuff.h | 4 ++--
> net/core/filter.c | 8 ++++----
> tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c | 6 +++---
> 3 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index ff7ad331fb82..004009b3930f 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -956,7 +956,7 @@ struct sk_buff {
> __u8 csum_valid:1;
>
> /* private: */
> - __u8 __pkt_vlan_present_offset[0];
> + __u8 __mono_tc_offset[0];
> /* public: */
> __u8 remcsum_offload:1;
> __u8 csum_complete_sw:1;
> @@ -1080,7 +1080,7 @@ struct sk_buff {
> #define TC_AT_INGRESS_MASK (1 << 7)
> #define SKB_MONO_DELIVERY_TIME_MASK (1 << 5)
> #endif
> -#define PKT_VLAN_PRESENT_OFFSET offsetof(struct sk_buff, __pkt_vlan_present_offset)
> +#define SKB_BF_MONO_TC_OFFSET offsetof(struct sk_buff, __mono_tc_offset)
>
> #ifdef __KERNEL__
> /*
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 50f649f1b4a9..3370efad1dda 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -9185,7 +9185,7 @@ static struct bpf_insn *bpf_convert_tstamp_type_read(const struct bpf_insn *si,
> __u8 tmp_reg = BPF_REG_AX;
>
> *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
> - PKT_VLAN_PRESENT_OFFSET);
> + SKB_BF_MONO_TC_OFFSET);
> *insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg,
> SKB_MONO_DELIVERY_TIME_MASK, 2);
> *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_UNSPEC);
> @@ -9232,7 +9232,7 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog,
> /* 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_LDX_MEM(BPF_B, tmp_reg, skb_reg, SKB_BF_MONO_TC_OFFSET);
> *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
> TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK);
> *insn++ = BPF_JMP32_IMM(BPF_JNE, tmp_reg,
> @@ -9267,14 +9267,14 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
> 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);
> + *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, SKB_BF_MONO_TC_OFFSET);
> /* Writing __sk_buff->tstamp as ingress, goto <clear> */
> *insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg, TC_AT_INGRESS_MASK, 1);
> /* goto <store> */
> *insn++ = BPF_JMP_A(2);
> /* <clear>: mono_delivery_time */
> *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, ~SKB_MONO_DELIVERY_TIME_MASK);
> - *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, PKT_VLAN_PRESENT_OFFSET);
> + *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, SKB_BF_MONO_TC_OFFSET);
> }
> #endif
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c b/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> index d5fe3d4b936c..ae7b6e50e405 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> @@ -68,17 +68,17 @@ static struct test_case test_cases[] = {
> #if defined(__x86_64__) || defined(__aarch64__)
> {
> N(SCHED_CLS, struct __sk_buff, tstamp),
> - .read = "r11 = *(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset);"
> + .read = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
> "w11 &= 160;"

The mask needs to be adjusted also after patch 3. This selftest is failing:
https://github.com/kernel-patches/bpf/actions/runs/4369844423/jobs/7644281598

> "if w11 != 0xa0 goto pc+2;"
> "$dst = 0;"
> "goto pc+1;"
> "$dst = *(u64 *)($ctx + sk_buff::tstamp);",
> - .write = "r11 = *(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset);"
> + .write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
> "if w11 & 0x80 goto pc+1;"

It probably needs to adjust here also

> "goto pc+2;"
> "w11 &= -33;"

and here.

> - "*(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset) = r11;"
> + "*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
> "*(u64 *)($ctx + sk_buff::tstamp) = $src;",
> },
> #endif