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[PATCH net-next 23/27] net/bpf: split VLAN_PRESENT bit handling from VLAN_TCI

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  [PATCH net-next 23/27] net/bpf: split VLAN_PRESENT bit handling from  VLAN_TCI Michał Mirosław <mirq-linux@rere.qmqm.pl> - 2016-12-13 01:20 +0100

#1540756 — [PATCH net-next 23/27] net/bpf: split VLAN_PRESENT bit handling from VLAN_TCI

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
 net/core/filter.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index b146170..c3321f1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -188,22 +188,20 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
 		break;
 
 	case SKF_AD_VLAN_TAG:
-	case SKF_AD_VLAN_TAG_PRESENT:
 		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
-		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
 
 		/* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */
 		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
 				      offsetof(struct sk_buff, vlan_tci));
-		if (skb_field == SKF_AD_VLAN_TAG) {
-			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,
-						~VLAN_TAG_PRESENT);
-		} else {
-			/* dst_reg >>= 12 */
-			*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);
-			/* dst_reg &= 1 */
-			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
-		}
+#ifdef VLAN_TAG_PRESENT
+		*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, ~VLAN_TAG_PRESENT);
+#endif
+		break;
+	case SKF_AD_VLAN_TAG_PRESENT:
+		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET());
+		if (PKT_VLAN_PRESENT_BIT)
+			*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, PKT_VLAN_PRESENT_BIT);
+		*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
 		break;
 	}
 
-- 
2.10.2

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