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b117e1e8a8
We want to add reference counting for FDB entries in cross-chip topologies, and in order for that to have any chance of working and not be unbalanced (leading to entries which are never deleted), we need to ensure that higher layers are sane, because if they aren't, it's garbage in, garbage out. For example, if we add a bridge FDB entry twice, the bridge properly errors out: $ bridge fdb add dev swp0 00:01:02:03:04:07 master static $ bridge fdb add dev swp0 00:01:02:03:04:07 master static RTNETLINK answers: File exists However, the same thing cannot be said about the bridge bypass operations: $ bridge fdb add dev swp0 00:01:02:03:04:07 $ bridge fdb add dev swp0 00:01:02:03:04:07 $ bridge fdb add dev swp0 00:01:02:03:04:07 $ bridge fdb add dev swp0 00:01:02:03:04:07 $ echo $? 0 But one 'bridge fdb del' is enough to remove the entry, no matter how many times it was added. The bridge bypass operations are impossible to maintain in these circumstances and lack of support for reference counting the cross-chip notifiers is holding us back from making further progress, so just drop support for them. The only way left for users to install static bridge FDB entries is the proper one, using the "master static" flags. With this change, rtnl_fdb_add() falls back to calling ndo_dflt_fdb_add() which uses the duplicate-exclusive variant of dev_uc_add(): dev_uc_add_excl(). Because DSA does not (yet) declare IFF_UNICAST_FLT, this results in us going to promiscuous mode: $ bridge fdb add dev swp0 00:01:02:03:04:05 [ 28.206743] device swp0 entered promiscuous mode $ bridge fdb add dev swp0 00:01:02:03:04:05 RTNETLINK answers: File exists So even if it does not completely fail, there is at least some indication that it is behaving differently from before, and closer to user space expectations, I would argue (the lack of a "local|static" specifier defaults to "local", or "host-only", so dev_uc_add() is a reasonable default implementation). If the generic implementation of .ndo_fdb_add provided by Vlad Yasevich is a proof of anything, it only proves that the implementation provided by DSA was always wrong, by not looking at "ndm->ndm_state & NUD_NOARP" (the "static" flag which means that the FDB entry points outwards) and "ndm->ndm_state & NUD_PERMANENT" (the "local" flag which means that the FDB entry points towards the host). It all used to mean the same thing to DSA. Update the documentation so that the users are not confused about what's going on. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.