linux/include/net/snmp.h

/*
 *
 *		SNMP MIB entries for the IP subsystem.
 *		
 *		Alan Cox <gw4pts@gw4pts.ampr.org>
 *
 *		We don't chose to implement SNMP in the kernel (this would
 *		be silly as SNMP is a pain in the backside in places). We do
 *		however need to collect the MIB statistics and export them
 *		out of /proc (eventually)
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 */
 
#ifndef _SNMP_H
#define _SNMP_H

#include <linux/cache.h>
#include <linux/snmp.h>
#include <linux/smp.h>

/*
 * Mibs are stored in array of unsigned long.
 */
/*
 * struct snmp_mib{}
 *  - list of entries for particular API (such as /proc/net/snmp)
 *  - name of entries.
 */
struct snmp_mib {
	const char *name;
	int entry;
};

#define SNMP_MIB_ITEM(_name,_entry)	{	\
	.name = _name,				\
	.entry = _entry,			\
}

#define SNMP_MIB_SENTINEL {	\
	.name = NULL,		\
	.entry = 0,		\
}

/*
 * We use all unsigned longs. Linux will soon be so reliable that even 
 * these will rapidly get too small 8-). Seriously consider the IpInReceives 
 * count on the 20Gb/s + networks people expect in a few years time!
 */

/* 
 * The rule for padding: 
 * Best is power of two because then the right structure can be found by a 
 * simple shift. The structure should be always cache line aligned.
 * gcc needs n=alignto(cachelinesize, popcnt(sizeof(bla_mib))) shift/add 
 * instructions to emulate multiply in case it is not power-of-two. 
 * Currently n is always <=3 for all sizes so simple cache line alignment 
 * is enough. 
 * 
 * The best solution would be a global CPU local area , especially on 64 
 * and 128byte cacheline machine it makes a *lot* of sense -AK
 */ 

#define __SNMP_MIB_ALIGN__	____cacheline_aligned

/* IPstats */
#define IPSTATS_MIB_MAX	__IPSTATS_MIB_MAX
struct ipstats_mib {
	unsigned long	mibs[IPSTATS_MIB_MAX];
} __SNMP_MIB_ALIGN__;

/* ICMP */
#define ICMP_MIB_DUMMY	__ICMP_MIB_MAX
#define ICMP_MIB_MAX	(__ICMP_MIB_MAX + 1)

struct icmp_mib {
	unsigned long	mibs[ICMP_MIB_MAX];
} __SNMP_MIB_ALIGN__;

#define ICMPMSG_MIB_MAX	__ICMPMSG_MIB_MAX
struct icmpmsg_mib {
	unsigned long	mibs[ICMPMSG_MIB_MAX];
} __SNMP_MIB_ALIGN__;

/* ICMP6 (IPv6-ICMP) */
#define ICMP6_MIB_MAX	__ICMP6_MIB_MAX
struct icmpv6_mib {
	unsigned long	mibs[ICMP6_MIB_MAX];
} __SNMP_MIB_ALIGN__;

#define ICMP6MSG_MIB_MAX  __ICMP6MSG_MIB_MAX
struct icmpv6msg_mib {
	unsigned long	mibs[ICMP6MSG_MIB_MAX];
} __SNMP_MIB_ALIGN__;


/* TCP */
#define TCP_MIB_MAX	__TCP_MIB_MAX
struct tcp_mib {
	unsigned long	mibs[TCP_MIB_MAX];
} __SNMP_MIB_ALIGN__;

/* UDP */
#define UDP_MIB_MAX	__UDP_MIB_MAX
struct udp_mib {
	unsigned long	mibs[UDP_MIB_MAX];
} __SNMP_MIB_ALIGN__;

/* Linux */
#define LINUX_MIB_MAX	__LINUX_MIB_MAX
struct linux_mib {
	unsigned long	mibs[LINUX_MIB_MAX];
};

/* Linux Xfrm */
#define LINUX_MIB_XFRMMAX	__LINUX_MIB_XFRMMAX
struct linux_xfrm_mib {
	unsigned long	mibs[LINUX_MIB_XFRMMAX];
};

/* 
 * FIXME: On x86 and some other CPUs the split into user and softirq parts
 * is not needed because addl $1,memory is atomic against interrupts (but 
 * atomic_inc would be overkill because of the lock cycles). Wants new 
 * nonlocked_atomic_inc() primitives -AK
 */ 
#define DEFINE_SNMP_STAT(type, name)	\
	__typeof__(type) *name[2]
#define DECLARE_SNMP_STAT(type, name)	\
	extern __typeof__(type) *name[2]

#define SNMP_STAT_BHPTR(name)	(name[0])
#define SNMP_STAT_USRPTR(name)	(name[1])

#define SNMP_INC_STATS_BH(mib, field)	\
			__this_cpu_inc(mib[0]->mibs[field])
#define SNMP_INC_STATS_USER(mib, field)	\
			this_cpu_inc(mib[1]->mibs[field])
#define SNMP_INC_STATS(mib, field)	\
			this_cpu_inc(mib[!in_softirq()]->mibs[field])
#define SNMP_DEC_STATS(mib, field)	\
			this_cpu_dec(mib[!in_softirq()]->mibs[field])
#define SNMP_ADD_STATS_BH(mib, field, addend)	\
			__this_cpu_add(mib[0]->mibs[field], addend)
#define SNMP_ADD_STATS_USER(mib, field, addend)	\
			this_cpu_add(mib[1]->mibs[field], addend)
#define SNMP_UPD_PO_STATS(mib, basefield, addend)	\
	do { \
		__typeof__(mib[0]) ptr; \
		preempt_disable(); \
		ptr = this_cpu_ptr((mib)[!in_softirq()]); \
		ptr->mibs[basefield##PKTS]++; \
		ptr->mibs[basefield##OCTETS] += addend;\
		preempt_enable(); \
	} while (0)
#define SNMP_UPD_PO_STATS_BH(mib, basefield, addend)	\
	do { \
		__typeof__(mib[0]) ptr = \
			__this_cpu_ptr((mib)[!in_softirq()]); \
		ptr->mibs[basefield##PKTS]++; \
		ptr->mibs[basefield##OCTETS] += addend;\
	} while (0)
#endif