netdev - [PATCH 1/2 net-next] vxlan: Be liberal on receive and only require the I bit to be set

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Date:	Fri, 11 Jul 2014 18:59:49 +0200
From:	Thomas Graf <tgraf@...g.ch>
To:	netdev@...r.kernel.org
Cc:	stephen@...workplumber.org, therbert@...gle.com,
	nicolas.dichtel@...nd.com, pshelar@...ira.com,
	xiyou.wangcong@...il.com, ogerlitz@...lanox.com,
	dborkman@...hat.com,
	"Pritesh Kothari (pritkoth)" <pritkoth@...co.com>,
	Madhu Challa <challa@...ronetworks.com>
Subject: [PATCH 1/2 net-next] vxlan: Be liberal on receive and only require the I bit to be set

The VXLAN receive code is currently conservative in what it accepts and
will reject any frame that uses any of the reserved fields. The VXLAN
draft specifies that "reserved fields MUST be set to zero on transmit
and ignored on receive." though.

Be liberal in only requiring the I bit to allow for VXLAN extensions
to be implemented.

Cc: Pritesh Kothari (pritkoth) <pritkoth@...co.com>
Cc: Madhu Challa <challa@...ronetworks.com>
Signed-off-by: Thomas Graf <tgraf@...g.ch>
---
 drivers/net/vxlan.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 10 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index e6808f7..2e9fbcc 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -63,12 +63,43 @@
 #define VXLAN_VID_MASK	(VXLAN_N_VID - 1)
 #define VXLAN_HLEN (sizeof(struct udphdr) + sizeof(struct vxlanhdr))
 
-#define VXLAN_FLAGS 0x08000000	/* struct vxlanhdr.vx_flags required value. */
-
+/* Base VXLAN header:
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |R|R|R|R|I|R|R|R|               Reserved                        |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                VXLAN Network Identifier (VNI) |   Reserved    |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * I = 1	VXLAN Network Identifier (VNI) present
+ */
 /* VXLAN protocol header */
 struct vxlanhdr {
-	__be32 vx_flags;
-	__be32 vx_vni;
+#ifdef __LITTLE_ENDIAN_BITFIELD
+	__u8	reserved_flags1:3,
+		vni_present:1,
+		reserved_flags2:4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	__u8	reserved_flags2:4,
+		vni_present:1,
+		reserved_flags1:3;
+#else
+#error	"Please fix <asm/byteorder.h>"
+#endif
+	__u8	vx_reserved1;
+	__be16	vx_reserved2;
+	__be32	vx_vni;
+};
+
+union vxlan_oct_hdr {
+	struct vxlanhdr	hdr;
+	__u8		octets[8];
+};
+
+#define vxlan_flags(vxh) (((union vxlan_oct_hdr *)(vxh))->octets[0])
+
+enum {
+	VXLAN_FLAG_VNI		= 0x08,
+	VXLAN_FLAG_RESERVED	= 0xF7,
 };
 
 /* UDP port for VXLAN traffic.
@@ -1141,12 +1172,10 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	if (!pskb_may_pull(skb, VXLAN_HLEN))
 		goto error;
 
-	/* Return packets with reserved bits set */
 	vxh = (struct vxlanhdr *)(udp_hdr(skb) + 1);
-	if (vxh->vx_flags != htonl(VXLAN_FLAGS) ||
-	    (vxh->vx_vni & htonl(0xff))) {
+	if (!vxh->vni_present) {
 		netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
-			   ntohl(vxh->vx_flags), ntohl(vxh->vx_vni));
+			   vxlan_flags(vxh), ntohl(vxh->vx_vni));
 		goto error;
 	}
 
@@ -1617,7 +1646,9 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
 	}
 
 	vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
-	vxh->vx_flags = htonl(VXLAN_FLAGS);
+	vxlan_flags(vxh) = VXLAN_FLAG_VNI;
+	vxh->vx_reserved1 = 0;
+	vxh->vx_reserved2 = 0;
 	vxh->vx_vni = vni;
 
 	__skb_push(skb, sizeof(*uh));
@@ -1689,7 +1720,9 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
 	}
 
 	vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
-	vxh->vx_flags = htonl(VXLAN_FLAGS);
+	vxlan_flags(vxh) = VXLAN_FLAG_VNI;
+	vxh->vx_reserved1 = 0;
+	vxh->vx_reserved2 = 0;
 	vxh->vx_vni = vni;
 
 	__skb_push(skb, sizeof(*uh));
-- 
1.9.3

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