43c3e95746
[ Upstream commit ce5e098f7a10b4bf8e948c12fa350320c5c3afad ]
Default remotes are stored as FDB entries with an Ethernet address of
00:00:00:00:00:00. When a request is made to change a remote address of
a VXLAN device, vxlan_changelink() first deletes the existing default
remote, and then creates a new FDB entry.
This works well as long as the list of default remotes matches exactly
the configuration of a VXLAN remote address. Thus when the VXLAN device
has a remote of X, there should be exactly one default remote FDB entry
X. If the VXLAN device has no remote address, there should be no such
entry.
Besides using "ip link set", it is possible to manipulate the list of
default remotes by using the "bridge fdb". It is therefore easy to break
the above condition. Under such circumstances, the __vxlan_fdb_delete()
call doesn't delete the FDB entry itself, but just one remote. The
following vxlan_fdb_create() then creates a new FDB entry, leading to a
situation where two entries exist for the address 00:00:00:00:00:00,
each with a different subset of default remotes.
An even more obvious breakage rooted in the same cause can be observed
when a remote address is configured for a VXLAN device that did not have
one before. In that case vxlan_changelink() doesn't remove any remote,
and just creates a new FDB entry for the new address:
$ ip link add name vx up type vxlan id 2000 dstport 4789
$ bridge fdb ap dev vx 00:00:00:00:00:00 dst 192.0.2.20 self permanent
$ bridge fdb ap dev vx 00:00:00:00:00:00 dst 192.0.2.30 self permanent
$ ip link set dev vx type vxlan remote 192.0.2.30
$ bridge fdb sh dev vx | grep 00:00:00:00:00:00
00:00:00:00:00:00 dst 192.0.2.30 self permanent <- new entry, 1 rdst
00:00:00:00:00:00 dst 192.0.2.20 self permanent <- orig. entry, 2 rdsts
00:00:00:00:00:00 dst 192.0.2.30 self permanent
To fix this, instead of calling vxlan_fdb_create() directly, defer to
vxlan_fdb_update(). That has logic to handle the duplicates properly.
Additionally, it also handles notifications, so drop that call from
changelink as well.
Fixes: 0241b836732f ("vxlan: fix default fdb entry netlink notify ordering during netdev create")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.