Persistently store NIC's hardware MAC address, and add a way to retrive it

jhb pointed out that (struct ifnet) is part of the network driver KBI, and
thus the offsets of internal fields must not change. Therefore, move the new
"if_hw_addr" field to the end, and consume one of the "if_pspare"s; that's
what they're there for. The new field replaces the *last* element of that
array; that way, offsetof(if_pspare) and offsetof(if_ispare) are unchanged
compared to before r318397.

PR:		194386
Reviewed by:	jhb
Pointyhat to:	rpokala
Sponsored by:	Panasas

(cherry picked from commit 53168a58b2d5e27ea918b00e0398e6629c91864c)

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 3eba221..569465b 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -241,7 +241,6 @@ struct ifnet {
 	struct	ifmultihead if_multiaddrs; /* multicast addresses configured */
 	int	if_amcount;		/* number of all-multicast requests */
 	struct	ifaddr	*if_addr;	/* pointer to link-level address */
-	void	*if_hw_addr;		/* hardware link-level address */
 	const u_int8_t *if_broadcastaddr; /* linklevel broadcast bytestring */
 	struct	rwlock if_afdata_lock;
 	void	*if_afdata[AF_MAX];
@@ -312,7 +311,8 @@ struct ifnet {
 	 * that structure can be enhanced without changing the kernel
 	 * binary interface.
 	 */
-	void	*if_pspare[4];		/* packet pacing / general use */
+	void	*if_pspare[3];		/* packet pacing / general use */
+	void	*if_hw_addr;		/* hardware link-level address */
 	int	if_ispare[4];		/* packet pacing / general use */
 };