[NEIGH]: Fix IP-over-ATM and ARP interaction.
The classical IP over ATM code maintains its own IPv4 <-> <ATM stuff>
ARP table, using the standard neighbour-table code. The
neigh_table_init function adds this neighbour table to a linked list
of all neighbor tables which is used by the functions neigh_delete()
neigh_add() and neightbl_set(), all called by the netlink code.
Once the ATM neighbour table is added to the list, there are two
tables with family == AF_INET there, and ARP entries sent via netlink
go into the first table with matching family. This is indeterminate
and often wrong.
To see the bug, on a kernel with CLIP enabled, create a standard IPv4
ARP entry by pinging an unused address on a local subnet. Then attempt
to complete that entry by doing
ip neigh replace <ip address> lladdr <some mac address> nud reachable
Looking at the ARP tables by using
ip neigh show
will reveal two ARP entries for the same address. One of these can be
found in /proc/net/arp, and the other in /proc/net/atm/arp.
This patch adds a new function, neigh_table_init_no_netlink() which
does everything the neigh_table_init() does, except add the table to
the netlink all-arp-tables chain. In addition neigh_table_init() has a
check that all tables on the chain have a distinct address family.
The init call in clip.c is changed to call
neigh_table_init_no_netlink().
Since ATM ARP tables are rather more complicated than can currently be
handled by the available rtattrs in the netlink protocol, no
functionality is lost by this patch, and non-ATM ARP manipulation via
netlink is rescued. A more complete solution would involve a rtattr
for ATM ARP entries and some way for the netlink code to give
neigh_add and friends more information than just address family with
which to find the correct ARP table.
[ I've changed the assertion checking in neigh_table_init() to not
use BUG_ON() while holding neigh_tbl_lock. Instead we remember that
we found an existing tbl with the same family, and after dropping
the lock we'll give a diagnostic kernel log message and a stack dump.
-DaveM ]
Signed-off-by: Simon Kelley <simon@thekelleys.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4cf878e..50a8c73 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1326,8 +1326,7 @@
kfree(parms);
}
-
-void neigh_table_init(struct neigh_table *tbl)
+void neigh_table_init_no_netlink(struct neigh_table *tbl)
{
unsigned long now = jiffies;
unsigned long phsize;
@@ -1383,10 +1382,27 @@
tbl->last_flush = now;
tbl->last_rand = now + tbl->parms.reachable_time * 20;
+}
+
+void neigh_table_init(struct neigh_table *tbl)
+{
+ struct neigh_table *tmp;
+
+ neigh_table_init_no_netlink(tbl);
write_lock(&neigh_tbl_lock);
+ for (tmp = neigh_tables; tmp; tmp = tmp->next) {
+ if (tmp->family == tbl->family)
+ break;
+ }
tbl->next = neigh_tables;
neigh_tables = tbl;
write_unlock(&neigh_tbl_lock);
+
+ if (unlikely(tmp)) {
+ printk(KERN_ERR "NEIGH: Registering multiple tables for "
+ "family %d\n", tbl->family);
+ dump_stack();
+ }
}
int neigh_table_clear(struct neigh_table *tbl)
@@ -2657,6 +2673,7 @@
EXPORT_SYMBOL(neigh_resolve_output);
EXPORT_SYMBOL(neigh_table_clear);
EXPORT_SYMBOL(neigh_table_init);
+EXPORT_SYMBOL(neigh_table_init_no_netlink);
EXPORT_SYMBOL(neigh_update);
EXPORT_SYMBOL(neigh_update_hhs);
EXPORT_SYMBOL(pneigh_enqueue);