BPF_JMP32_IMM(BPF_JSET) is used to save a BPF_ALU32_IMM(BPF_AND).
The skb->tc_at_ingress and skb->mono_delivery_time are at the same
offset, so only one BPF_LDX_MEM(BPF_B) is needed.
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
net/core/filter.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 2c83d1f38704..f914e4b13b18 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8990,25 +8990,27 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
__u8 skb_reg = si->dst_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, write skb->tstamp as is if delivery_time_access is true.
+ * Otherwise, writing at ingress will have to clear the
+ * mono_delivery_time bit also.
+ */
if (!prog->delivery_time_access) {
__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, 3);
- /* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.
- * Clear 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_STX_MEM(BPF_B, skb_reg, tmp_reg,
- PKT_VLAN_PRESENT_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);
}
#endif
- /* skb->tstamp = tstamp */
+ /* <store>: skb->tstamp = tstamp */
*insn++ = BPF_STX_MEM(BPF_DW, skb_reg, value_reg,
offsetof(struct sk_buff, tstamp));
return insn;
--
2.30.2
