netdev - [PATCH net-next 6/6] net/bpf: split VLAN_PRESENT bit handling from VLAN

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Message-Id: <c7085e3873520f23eefa4d38622a66b6f4294ae7.1483492355.git.mirq-linux@rere.qmqm.pl>
Date:   Wed,  4 Jan 2017 02:18:27 +0100 (CET)
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Thomas Graf <tgraf@...g.ch>, Martin KaFai Lau <kafai@...com>,
        Craig Gallek <kraig@...gle.com>
Subject: [PATCH net-next 6/6] net/bpf: split VLAN_PRESENT bit handling from
 VLAN_TCI

Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
v2: save an insn on big-endiands

 net/core/filter.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 1969b3f118c1..7caf0bbbd092 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -188,22 +188,21 @@ 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;
 	}
 
-- 
2.11.0