diff options
| author | Martin KaFai Lau <kafai@fb.com> | 2022-03-09 10:04:56 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-03-10 22:57:05 +0100 |
| commit | 539de9328e3ab444efe51ddc7416ce2a3f0f23b2 (patch) | |
| tree | f072bd14ec814bc1f408d924b7c138a753c215be /net | |
| parent | bpf: net: Remove TC_AT_INGRESS_OFFSET and SKB_MONO_DELIVERY_TIME_OFFSET macro (diff) | |
| download | linux-539de9328e3ab444efe51ddc7416ce2a3f0f23b2.tar.xz linux-539de9328e3ab444efe51ddc7416ce2a3f0f23b2.zip | |
bpf: Simplify insn rewrite on BPF_READ __sk_buff->tstamp
The skb->tc_at_ingress and skb->mono_delivery_time are at the same
byte offset. Thus, only one BPF_LDX_MEM(BPF_B) is needed
and both bits can be tested together.
/* BPF_READ: a = __sk_buff->tstamp */
if (skb->tc_at_ingress && skb->mono_delivery_time)
a = 0;
else
a = skb->tstamp;
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220309090456.3711530-1-kafai@fb.com
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/filter.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 738a294a3c82..2c83d1f38704 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8956,21 +8956,22 @@ 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, + * the bpf prog is aware the tstamp could have delivery time. + * Thus, read skb->tstamp as is if delivery_time_access is true. + */ if (!prog->delivery_time_access) { + /* 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, 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, - 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); - /* skb->mono_delivery_time is set, read 0 as the (rcv) timestamp. */ + TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK); + *insn++ = BPF_JMP32_IMM(BPF_JNE, tmp_reg, + TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK, 2); + /* skb->tc_at_ingress && skb->mono_delivery_time, + * read 0 as the (rcv) timestamp. + */ *insn++ = BPF_MOV64_IMM(value_reg, 0); *insn++ = BPF_JMP_A(1); } |