Make struct ifnet readable and comprehensible again by grouping

and ordering related variables, fields and locks next to each
other.  Add more comments to variables.

Over time 'ifnet' has accumlated a lot of additional pointers and
functionality in an unstructured way making it quite hard to read
and understand while obfuscating relationships between fields and
variables.

Quantify the structure size and how bloated it has become.

This is only a mechanical change in preparation for upcoming
work to make ifnet opaque to drivers and to separate out the
interface queuing.

Sponsored by:	The FreeBSD Foundation

1 files changed, 52 insertions, 48 deletions

diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 11eaadd..f918a39 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -96,19 +96,42 @@ VNET_DECLARE(struct pfil_head, link_pfil_hook);	/* packet filter hooks */
 /*
  * Structure defining a network interface.
  *
- * (Would like to call this struct ``if'', but C isn't PL/1.)
+ * Size ILP32:  592 (approx)
+ *	 LP64: 1048 (approx)
  */
-
 struct ifnet {
+	/* General book keeping of interface lists. */
+	TAILQ_ENTRY(ifnet) if_link; 	/* all struct ifnets are chained */
+	LIST_ENTRY(ifnet) if_clones;	/* interfaces of a cloner */
+	TAILQ_HEAD(, ifg_list) if_groups; /* linked list of groups per if */
+					/* protected by if_addr_lock */
+	u_char	if_alloctype;		/* if_type at time of allocation */
+
+	/* Driver and protocol specific information that remains stable. */
 	void	*if_softc;		/* pointer to driver state */
+	void	*if_llsoftc;		/* link layer softc */
 	void	*if_l2com;		/* pointer to protocol bits */
-	struct vnet *if_vnet;		/* pointer to network stack instance */
-	TAILQ_ENTRY(ifnet) if_link; 	/* all struct ifnets are chained */
-	char	if_xname[IFNAMSIZ];	/* external name (name + unit) */
 	const char *if_dname;		/* driver name */
 	int	if_dunit;		/* unit or IF_DUNIT_NONE */
+	u_short	if_index;		/* numeric abbreviation for this if  */
+	short	if_index_reserved;	/* spare space to grow if_index */
+	char	if_xname[IFNAMSIZ];	/* external name (name + unit) */
+	char	*if_description;	/* interface description */
+
+	/* Variable fields that are touched by the stack and drivers. */
+	int	if_flags;		/* up/down, broadcast, etc. */
+	int	if_capabilities;	/* interface features & capabilities */
+	int	if_capenable;		/* enabled features & capabilities */
+	void	*if_linkmib;		/* link-type-specific MIB data */
+	size_t	if_linkmiblen;		/* length of above data */
+	int	if_drv_flags;		/* driver-managed status flags */
 	u_int	if_refcount;		/* reference count */
-	struct	ifaddrhead if_addrhead;	/* linked list of addresses per if */
+	struct  ifaltq if_snd;		/* output queue (includes altq) */
+	struct	if_data if_data;	/* type information and statistics */
+	struct	task if_linktask;	/* task for link change events */
+
+	/* Addresses of different protocol families assigned to this if. */
+	struct	rwlock if_addr_lock;	/* lock to protect address lists */
 		/*
 		 * if_addrhead is the list of all addresses associated to
 		 * an interface.
@@ -119,21 +142,29 @@ struct ifnet {
 		 * However, access to the AF_LINK address through this
 		 * field is deprecated. Use if_addr or ifaddr_byindex() instead.
 		 */
-	int	if_pcount;		/* number of promiscuous listeners */
-	struct	carp_if *if_carp;	/* carp interface structure */
-	struct	bpf_if *if_bpf;		/* packet filter structure */
-	u_short	if_index;		/* numeric abbreviation for this if  */
-	short	if_index_reserved;	/* spare space to grow if_index */
-	struct  ifvlantrunk *if_vlantrunk; /* pointer to 802.1q data */
-	int	if_flags;		/* up/down, broadcast, etc. */
-	int	if_capabilities;	/* interface features & capabilities */
-	int	if_capenable;		/* enabled features & capabilities */
-	void	*if_linkmib;		/* link-type-specific MIB data */
-	size_t	if_linkmiblen;		/* length of above data */
-	struct	if_data if_data;
+	struct	ifaddrhead if_addrhead;	/* linked list of addresses per if */
 	struct	ifmultihead if_multiaddrs; /* multicast addresses configured */
 	int	if_amcount;		/* number of all-multicast requests */
-/* procedure handles */
+	struct	ifaddr	*if_addr;	/* pointer to link-level address */
+	const u_int8_t *if_broadcastaddr; /* linklevel broadcast bytestring */
+	struct	rwlock if_afdata_lock;
+	void	*if_afdata[AF_MAX];
+	int	if_afdata_initialized;
+
+	/* Additional features hung off the interface. */
+	u_int	if_fib;			/* interface FIB */
+	struct	vnet *if_vnet;		/* pointer to network stack instance */
+	struct	vnet *if_home_vnet;	/* where this ifnet originates from */
+	struct  ifvlantrunk *if_vlantrunk; /* pointer to 802.1q data */
+	struct	bpf_if *if_bpf;		/* packet filter structure */
+	int	if_pcount;		/* number of promiscuous listeners */
+	void	*if_bridge;		/* bridge glue */
+	void	*if_lagg;		/* lagg glue */
+	void	*if_pf_kif;		/* pf glue */
+	struct	carp_if *if_carp;	/* carp interface structure */
+	struct	label *if_label;	/* interface MAC label */
+
+	/* Various procedures of the layer2 encapsulation and drivers. */
 	int	(*if_output)		/* output routine (enqueue) */
 		(struct ifnet *, struct mbuf *, const struct sockaddr *,
 		     struct route *);
@@ -153,39 +184,12 @@ struct ifnet {
 		(struct ifnet *, struct mbuf *);
 	void	(*if_reassign)		/* reassign to vnet routine */
 		(struct ifnet *, struct vnet *, char *);
-	struct	vnet *if_home_vnet;	/* where this ifnet originates from */
-	struct	ifaddr	*if_addr;	/* pointer to link-level address */
-	void	*if_llsoftc;		/* link layer softc */
-	int	if_drv_flags;		/* driver-managed status flags */
-	struct  ifaltq if_snd;		/* output queue (includes altq) */
-	const u_int8_t *if_broadcastaddr; /* linklevel broadcast bytestring */
-
-	void	*if_bridge;		/* bridge glue */
-
-	struct	label *if_label;	/* interface MAC label */
-
-	/* these are only used by IPv6 */
-	void	*if_unused[2];
-	void	*if_afdata[AF_MAX];
-	int	if_afdata_initialized;
-	struct	rwlock if_afdata_lock;
-	struct	task if_linktask;	/* task for link change events */
-	struct	rwlock if_addr_lock;	/* lock to protect address lists */
-
-	LIST_ENTRY(ifnet) if_clones;	/* interfaces of a cloner */
-	TAILQ_HEAD(, ifg_list) if_groups; /* linked list of groups per if */
-					/* protected by if_addr_lock */
-	void	*if_pf_kif;
-	void	*if_lagg;		/* lagg glue */
-	char	*if_description;	/* interface description */
-	u_int	if_fib;			/* interface FIB */
-	u_char	if_alloctype;		/* if_type at time of allocation */
 
+	/* Stuff that's only temporary and doesn't belong here. */
 	u_int	if_hw_tsomax;		/* tso burst length limit, the minimum
 					 * is (IP_MAXPACKET / 8).
 					 * XXXAO: Have to find a better place
 					 * for it eventually. */
-
 	/*
 	 * Spare fields are added so that we can modify sensitive data
 	 * structures without changing the kernel binary interface, and must
@@ -193,6 +197,7 @@ struct ifnet {
 	 */
 	char	if_cspare[3];
 	int	if_ispare[4];
+	void	*if_unused[2];
 	void	*if_pspare[8];		/* 1 netmap, 7 TDB */
 };
 
@@ -521,5 +526,4 @@ void	if_deregister_com_alloc(u_char type);
     LLADDR((struct sockaddr_dl *)((ifp)->if_addr->ifa_addr))
 
 #endif /* _KERNEL */
-
 #endif /* !_NET_IF_VAR_H_ */