@@ -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);
}
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(-)