netdev - Re: [PATCH 2/6] vxlan: Group Policy extension

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Date:	Wed, 7 Jan 2015 23:27:40 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Jesse Gross <jesse@...ira.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Pravin Shelar <pshelar@...ira.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>
Subject: Re: [PATCH 2/6] vxlan: Group Policy extension

On 01/07/15 at 09:32am, Alexei Starovoitov wrote:
> I'm afraid 'union' style with first u8 flags working as selector
> won't work for the case you're describing, but since
>                       md.gbp = ntohs(vxh->gbp.policy_id);
>     2652:       41 0f b7 55 0a          movzwl 0xa(%r13),%edx
> then at least from performance side it's ok at least on x86.
> So this _packed stuff is fine, though not pretty.
> It's internal header, so we can improve it later.

I'm not sure I understand your first sentence but I'm not
married to the code as-is.

Would you like something like this?

 struct vxlanhdr_gbp {
 	__u8 vx_flags;
+#ifdef __LITTLE_ENDIAN_BITFIELD
+       __u8    reserved_flags1:3,
+               policy_applied:1,
+               reserved_flags2:2,
+               dont_learn:1,
+               reserved_flags3:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+       __u8    reserved_flags1:1,
+               dont_learn:1,
+               reserved_flags2:2,
+               policy_applied:1,
+               reserved_flags3:3;
+#else
+#error "Please fix <asm/byteorder.h>"
+#endif
+       __be16 policy_id;
+       __be32  vx_vni;
 };

 struct vxlanhdr {
+       union {
+               struct {
+#ifdef __LITTLE_ENDIAN_BITFIELD
+                       __u8    reserved_flags1:3,
+                               vni_present:1,
+                               reserved_flags2:3,
+                               gbp_present:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+                       __u8    gbp_present:1,
+                               reserved_flags2:3,
+                               vni_present:1,
+                               reserved_flags1:3;
+#else
+#error "Please fix <asm/byteorder.h>"
+#endif
+                       __u8    vx_reserved1;
+                       __be16  vx_reserved2;
+               };
+               __be32 vx_flags;
+       };
+       __be32  vx_vni;
 };




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