net/bpf: split VLAN_PRESENT bit handling from VLAN_TCI

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/filter.c

@@ -296,22 +296,21 @@ 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 */
+#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);
+		if (PKT_VLAN_PRESENT_BIT < 7)
 			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
-		}
 		break;
 	}
 
@@ -6140,19 +6139,22 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 		break;
 
 	case offsetof(struct __sk_buff, vlan_present):
-	case offsetof(struct __sk_buff, vlan_tci):
-		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
+		*target_size = 1;
+		*insn++ = BPF_LDX_MEM(BPF_B, si->dst_reg, si->src_reg,
+				      PKT_VLAN_PRESENT_OFFSET());
+		if (PKT_VLAN_PRESENT_BIT)
+			*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, PKT_VLAN_PRESENT_BIT);
+		if (PKT_VLAN_PRESENT_BIT < 7)
+			*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, 1);
+		break;
 
+	case offsetof(struct __sk_buff, vlan_tci):
 		*insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg,
 				      bpf_target_off(struct sk_buff, vlan_tci, 2,
 						     target_size));
-		if (si->off == offsetof(struct __sk_buff, vlan_tci)) {
-			*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg,
-						~VLAN_TAG_PRESENT);
-		} else {
-			*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, 12);
-			*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, 1);
-		}
+#ifdef VLAN_TAG_PRESENT
+		*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, ~VLAN_TAG_PRESENT);
+#endif
 		break;
 
 	case offsetof(struct __sk_buff, cb[0]) ...