From bd89efc532fe41f867f848144cc8b42054ddf6f9 Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Fri, 12 May 2006 14:56:08 -0700 Subject: [NEIGH]: Fix IP-over-ATM and ARP interaction. The classical IP over ATM code maintains its own IPv4 <-> 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 lladdr 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 Signed-off-by: David S. Miller --- net/atm/clip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/atm') diff --git a/net/atm/clip.c b/net/atm/clip.c index 1a786bfaa416..72d852982664 100644 --- a/net/atm/clip.c +++ b/net/atm/clip.c @@ -963,7 +963,7 @@ static struct file_operations arp_seq_fops = { static int __init atm_clip_init(void) { struct proc_dir_entry *p; - neigh_table_init(&clip_tbl); + neigh_table_init_no_netlink(&clip_tbl); clip_tbl_hook = &clip_tbl; register_atm_ioctl(&clip_ioctl_ops); -- cgit v1.2.3