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ipv4: fib: Allow for consistent FIB dumping 

The next patch will enable listeners of the FIB notification chain to
request a dump of the FIB tables. However, since RTNL isn't taken during
the dump, it's possible for the FIB tables to change mid-dump, which
will result in inconsistency between the listener's table and the
kernel's.

Allow listeners to know about changes that occurred mid-dump, by adding
a change sequence counter to each net namespace. The counter is
incremented just before a notification is sent in the FIB chain.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ido Schimmel 2016-12-03 16:45:06 +01:00 committed by David S. Miller
parent d3f706f68e
commit cacaad11f4
3 changed files with 6 additions and 0 deletions
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3
include/net/netns/ipv4.h
View File

@ -135,6 +135,9 @@ struct netns_ipv4 {
#ifdef CONFIG_IP_ROUTE_MULTIPATH
int sysctl_fib_multipath_use_neigh;
#endif
unsigned int fib_seq; /* protected by rtnl_mutex */
atomic_t rt_genid;
};
#endif

2
net/ipv4/fib_frontend.c
View File

@ -1219,6 +1219,8 @@ static int __net_init ip_fib_net_init(struct net *net)
int err;
size_t size = sizeof(struct hlist_head) * FIB_TABLE_HASHSZ;
net->ipv4.fib_seq = 0;
/* Avoid false sharing : Use at least a full cache line */
size = max_t(size_t, size, L1_CACHE_BYTES);

1
net/ipv4/fib_trie.c
View File

@ -101,6 +101,7 @@ EXPORT_SYMBOL(unregister_fib_notifier);
int call_fib_notifiers(struct net *net, enum fib_event_type event_type,
struct fib_notifier_info *info)
{
net->ipv4.fib_seq++;
info->net = net;
return atomic_notifier_call_chain(&fib_chain, event_type, info);
}