This patch makes a stylistic improvement by removing CFM protocol
information from cfm.h. In the process it changes
cfm_compose_ccm() to populate an ofpbuf instead of a struct ccm.
In an effort to make CFM easier to understand and configure, this
patch removes the Maintenance_Point and Monitor tables from the
database. As a consequence, users will only be able to configure
one remote maintenance point. Furthermore, before this patch each
remote maintenance point maintained its own separate fault flag in
the database. This flag is no longer reported, users will need to
infer the fault status from the global CFM fault flag.
These settings added complexity to the database and CFM module
interface with negligible benefit. This patch removes them in such
a way that they can easily be re-added in the (unlikely) event that
we need them in the future.
This patch moves the cfm/show unixctl show command from the bridge
to the CFM module. This is more in line with how LACP does it, and
will make future patches easier to implement.
Ben pointed out that an attacker could cause OVS to use infinite
memory by sending a series of CCMs with different MAIDs. Each
message would cause a remote_maid to be allocated and stored for
several seconds.
Since Commit 1c2e2d2fc8 (cfm: Don't report unexpected remote
endpoints) no longer reports unexpected remote MAIDS and MPs in the
database, the only reason to keep track of this information is for
debugging purposes. In my judgment, it provides negligible useful
debugging information at the expense of significantly increased
code complexity. This commit rips it out entirely.
Before this patch, CFM would report unexpected remote maintenance
points in the database. This commit no longer exposes this
information.
Information about precisely why a link is faulty is more interesting
to a system administrator debugging a problem than a controller
which will generally only care about whether or not a link is
faulty. For simplicity sake, this commit removes this information
from the database where it was somewhat awkwardly placed. In the
future it may be valuable to report the information through
ovs-appctl commands for debugging purposes.
It doesn't really make sense for the CFM code to be composing
packets. Its caller is better placed to compose the appropriate
L2 header. This commit pulls that logic out of the CFM library.
This commit implements a subset of the 802.1ag specification for
Connectivity Fault Management (CFM) using Continuity Check Messages
(CCM). When CFM is configured on an interface CCMs are broadcast
at regular intervals to detect missing or unexpected connectivity.
