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	32b293a53d
	
	
	
		
			
			During some debugging I needed to look into how /proc/net/ipv6_route
operated and in my digging I found its calling fib6_clean_all() which uses
"write_lock_bh(&table->tb6_lock)" before doing the walk of the table. I
found this on 2.6.32, but reading the code I believe the same basic idea
exists currently. Looking at the rtnetlink code they are only calling
"read_lock_bh(&table->tb6_lock);" via fib6_dump_table(). While I realize
reading from proc isn't the recommended way of fetching the ipv6 route
table; taking a write lock seems unnecessary and would probably cause
network performance issues.
To verify this I loaded up the ipv6 route table and then ran iperf in 3
cases:
  * doing nothing
  * reading ipv6 route table via proc
    (while :; do cat /proc/net/ipv6_route > /dev/null; done)
  * reading ipv6 route table via rtnetlink
    (while :; do ip -6 route show table all > /dev/null; done)
* Load the ipv6 route table up with:
  * for ((i = 0;i < 4000;i++)); do ip route add unreachable 2000::$i; done
* iperf commands:
  * client: iperf -i 1 -V -c <ipv6 addr>
  * server: iperf -V -s
* iperf results - 3 runs each (in Mbits/sec)
  * nothing: client: 927,927,927 server: 927,927,927
  * proc: client: 179,97,96,113 server: 142,112,133
  * iproute: client: 928,927,928 server: 927,927,927
lock_stat shows taking the write lock is causing the slowdown. Using this
info I decided to write a version of fib6_clean_all() which replaces
write_lock_bh(&table->tb6_lock) with read_lock_bh(&table->tb6_lock). With
this new function I see the same results as with my rtnetlink iperf test.
Signed-off-by: Josh Hunt <joshhunt00@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
		
	
			
		
			
				
	
	
		
			240 lines
		
	
	
	
		
			5.3 KiB
			
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			240 lines
		
	
	
	
		
			5.3 KiB
			
		
	
	
	
		
			C
		
	
	
	
	
	
| /*
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|  *	Linux INET6 implementation 
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|  *
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|  *	Authors:
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|  *	Pedro Roque		<roque@di.fc.ul.pt>	
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|  *
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|  *	This program is free software; you can redistribute it and/or
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|  *      modify it under the terms of the GNU General Public License
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|  *      as published by the Free Software Foundation; either version
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|  *      2 of the License, or (at your option) any later version.
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|  */
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| 
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| #ifndef _IP6_FIB_H
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| #define _IP6_FIB_H
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| 
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| #include <linux/ipv6_route.h>
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| #include <linux/rtnetlink.h>
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| #include <linux/spinlock.h>
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| #include <net/dst.h>
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| #include <net/flow.h>
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| #include <net/netlink.h>
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| #include <net/inetpeer.h>
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| 
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| #ifdef CONFIG_IPV6_MULTIPLE_TABLES
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| #define FIB6_TABLE_HASHSZ 256
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| #else
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| #define FIB6_TABLE_HASHSZ 1
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| #endif
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| 
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| struct rt6_info;
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| 
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| struct fib6_config {
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| 	u32		fc_table;
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| 	u32		fc_metric;
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| 	int		fc_dst_len;
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| 	int		fc_src_len;
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| 	int		fc_ifindex;
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| 	u32		fc_flags;
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| 	u32		fc_protocol;
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| 
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| 	struct in6_addr	fc_dst;
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| 	struct in6_addr	fc_src;
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| 	struct in6_addr	fc_prefsrc;
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| 	struct in6_addr	fc_gateway;
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| 
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| 	unsigned long	fc_expires;
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| 	struct nlattr	*fc_mx;
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| 	int		fc_mx_len;
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| 
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| 	struct nl_info	fc_nlinfo;
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| };
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| 
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| struct fib6_node {
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| 	struct fib6_node	*parent;
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| 	struct fib6_node	*left;
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| 	struct fib6_node	*right;
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| #ifdef CONFIG_IPV6_SUBTREES
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| 	struct fib6_node	*subtree;
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| #endif
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| 	struct rt6_info		*leaf;
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| 
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| 	__u16			fn_bit;		/* bit key */
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| 	__u16			fn_flags;
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| 	__u32			fn_sernum;
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| 	struct rt6_info		*rr_ptr;
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| };
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| 
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| #ifndef CONFIG_IPV6_SUBTREES
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| #define FIB6_SUBTREE(fn)	NULL
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| #else
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| #define FIB6_SUBTREE(fn)	((fn)->subtree)
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| #endif
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| 
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| /*
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|  *	routing information
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|  *
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|  */
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| 
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| struct rt6key {
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| 	struct in6_addr	addr;
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| 	int		plen;
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| };
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| 
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| struct fib6_table;
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| 
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| struct rt6_info {
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| 	struct dst_entry		dst;
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| 
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| 	/*
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| 	 * Tail elements of dst_entry (__refcnt etc.)
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| 	 * and these elements (rarely used in hot path) are in
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| 	 * the same cache line.
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| 	 */
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| 	struct fib6_table		*rt6i_table;
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| 	struct fib6_node		*rt6i_node;
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| 
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| 	struct in6_addr			rt6i_gateway;
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| 
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| 	atomic_t			rt6i_ref;
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| 
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| 	/* These are in a separate cache line. */
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| 	struct rt6key			rt6i_dst ____cacheline_aligned_in_smp;
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| 	u32				rt6i_flags;
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| 	struct rt6key			rt6i_src;
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| 	struct rt6key			rt6i_prefsrc;
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| 	u32				rt6i_metric;
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| 	u32				rt6i_peer_genid;
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| 
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| 	struct inet6_dev		*rt6i_idev;
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| 	struct inet_peer		*rt6i_peer;
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| 
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| #ifdef CONFIG_XFRM
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| 	u32				rt6i_flow_cache_genid;
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| #endif
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| 	/* more non-fragment space at head required */
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| 	unsigned short			rt6i_nfheader_len;
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| 
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| 	u8				rt6i_protocol;
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| };
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| 
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| static inline struct inet6_dev *ip6_dst_idev(struct dst_entry *dst)
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| {
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| 	return ((struct rt6_info *)dst)->rt6i_idev;
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| }
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| 
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| struct fib6_walker_t {
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| 	struct list_head lh;
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| 	struct fib6_node *root, *node;
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| 	struct rt6_info *leaf;
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| 	unsigned char state;
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| 	unsigned char prune;
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| 	unsigned int skip;
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| 	unsigned int count;
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| 	int (*func)(struct fib6_walker_t *);
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| 	void *args;
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| };
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| 
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| struct rt6_statistics {
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| 	__u32		fib_nodes;
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| 	__u32		fib_route_nodes;
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| 	__u32		fib_rt_alloc;		/* permanent routes	*/
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| 	__u32		fib_rt_entries;		/* rt entries in table	*/
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| 	__u32		fib_rt_cache;		/* cache routes		*/
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| 	__u32		fib_discarded_routes;
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| };
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| 
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| #define RTN_TL_ROOT	0x0001
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| #define RTN_ROOT	0x0002		/* tree root node		*/
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| #define RTN_RTINFO	0x0004		/* node with valid routing info	*/
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| 
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| /*
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|  *	priority levels (or metrics)
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|  *
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|  */
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| 
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| 
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| struct fib6_table {
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| 	struct hlist_node	tb6_hlist;
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| 	u32			tb6_id;
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| 	rwlock_t		tb6_lock;
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| 	struct fib6_node	tb6_root;
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| };
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| 
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| #define RT6_TABLE_UNSPEC	RT_TABLE_UNSPEC
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| #define RT6_TABLE_MAIN		RT_TABLE_MAIN
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| #define RT6_TABLE_DFLT		RT6_TABLE_MAIN
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| #define RT6_TABLE_INFO		RT6_TABLE_MAIN
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| #define RT6_TABLE_PREFIX	RT6_TABLE_MAIN
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| 
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| #ifdef CONFIG_IPV6_MULTIPLE_TABLES
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| #define FIB6_TABLE_MIN		1
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| #define FIB6_TABLE_MAX		RT_TABLE_MAX
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| #define RT6_TABLE_LOCAL		RT_TABLE_LOCAL
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| #else
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| #define FIB6_TABLE_MIN		RT_TABLE_MAIN
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| #define FIB6_TABLE_MAX		FIB6_TABLE_MIN
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| #define RT6_TABLE_LOCAL		RT6_TABLE_MAIN
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| #endif
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| 
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| typedef struct rt6_info *(*pol_lookup_t)(struct net *,
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| 					 struct fib6_table *,
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| 					 struct flowi6 *, int);
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| 
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| /*
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|  *	exported functions
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|  */
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| 
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| extern struct fib6_table        *fib6_get_table(struct net *net, u32 id);
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| extern struct fib6_table        *fib6_new_table(struct net *net, u32 id);
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| extern struct dst_entry         *fib6_rule_lookup(struct net *net,
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| 						  struct flowi6 *fl6, int flags,
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| 						  pol_lookup_t lookup);
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| 
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| extern struct fib6_node		*fib6_lookup(struct fib6_node *root,
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| 					     const struct in6_addr *daddr,
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| 					     const struct in6_addr *saddr);
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| 
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| struct fib6_node		*fib6_locate(struct fib6_node *root,
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| 					     const struct in6_addr *daddr, int dst_len,
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| 					     const struct in6_addr *saddr, int src_len);
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| 
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| extern void			fib6_clean_all_ro(struct net *net,
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| 					       int (*func)(struct rt6_info *, void *arg),
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| 					       int prune, void *arg);
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| 
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| extern void			fib6_clean_all(struct net *net,
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| 					       int (*func)(struct rt6_info *, void *arg),
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| 					       int prune, void *arg);
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| 
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| extern int			fib6_add(struct fib6_node *root,
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| 					 struct rt6_info *rt,
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| 					 struct nl_info *info);
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| 
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| extern int			fib6_del(struct rt6_info *rt,
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| 					 struct nl_info *info);
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| 
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| extern void			inet6_rt_notify(int event, struct rt6_info *rt,
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| 						struct nl_info *info);
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| 
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| extern void			fib6_run_gc(unsigned long expires,
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| 					    struct net *net);
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| 
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| extern void			fib6_gc_cleanup(void);
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| 
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| extern int			fib6_init(void);
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| 
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| #ifdef CONFIG_IPV6_MULTIPLE_TABLES
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| extern int			fib6_rules_init(void);
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| extern void			fib6_rules_cleanup(void);
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| #else
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| static inline int               fib6_rules_init(void)
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| {
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| 	return 0;
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| }
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| static inline void              fib6_rules_cleanup(void)
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| {
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| 	return ;
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| }
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| #endif
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| #endif
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