From: Martin KaFai Lau <kafai@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>,
<netdev@vger.kernel.org>
Subject: [PATCH bpf-next 2/5] bpf: Simplify insn rewrite on BPF_READ __sk_buff->tstamp
Date: Wed, 9 Mar 2022 01:04:56 -0800 [thread overview]
Message-ID: <20220309090456.3711530-1-kafai@fb.com> (raw)
In-Reply-To: <20220309090444.3710464-1-kafai@fb.com>
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>
---
net/core/filter.c | 21 +++++++++++----------
1 file 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);
}
--
2.30.2
next prev parent reply other threads:[~2022-03-09 9:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 9:04 [PATCH bpf-next 0/5] bpf: Follow up on bpf __sk_buff->tstamp Martin KaFai Lau
2022-03-09 9:04 ` [PATCH bpf-next 1/5] bpf: net: Remove TC_AT_INGRESS_OFFSET and SKB_MONO_DELIVERY_TIME_OFFSET macro Martin KaFai Lau
2022-03-09 9:04 ` Martin KaFai Lau [this message]
2022-03-09 9:05 ` [PATCH bpf-next 3/5] bpf: Simplify insn rewrite on BPF_WRITE __sk_buff->tstamp Martin KaFai Lau
2022-03-09 9:05 ` [PATCH bpf-next 4/5] bpf: Remove BPF_SKB_DELIVERY_TIME_NONE and rename s/delivery_time_/tstamp_/ Martin KaFai Lau
2022-03-09 9:05 ` [PATCH bpf-next 5/5] bpf: selftests: Update tests after s/delivery_time/tstamp/ change in bpf.h Martin KaFai Lau
2022-03-10 22:00 ` [PATCH bpf-next 0/5] bpf: Follow up on bpf __sk_buff->tstamp patchwork-bot+netdevbpf
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