mainlining shenanigans
c138806344
Switches work by learning the MAC address for each attached station by monitoring traffic from each station. When a station sends a packet, the switch records which port the MAC address is connected to. With IPv4 networking, before communication commences with a neighbour, an ARP packet is broadcasted to all stations asking for the MAC address corresponding with the IPv4. The desired station responds with an ARP reply, and the ARP reply causes the switch to learn which port the station is connected to. With IPv6 networking, the situation is rather different. Rather than broadcasting ARP packets, a "neighbour solicitation" is multicasted rather than broadcasted. This multicast needs to reach the intended station in order for the neighbour to be discovered. Once a neighbour has been discovered, and entered into the sending stations neighbour cache, communication can restart at a point later without sending a new neighbour solicitation, even if the entry in the neighbour cache is marked as stale. This can be after the MAC address has expired from the forwarding cache of the DSA switch - when that occurs, there is a long pause in communication. Our DSA implementation for mv88e6xxx switches disables flooding of multicast and unicast frames for bridged ports. As per the above description, this is fine for IPv4 networking, since the broadcasted ARP queries will be sent to and received by all stations on the same network. However, this breaks IPv6 very badly - blocking neighbour solicitations and later causing connections to stall. The defaults that the Linux bridge code expect from bridges are for unknown unicast and unknown multicast frames to be flooded to all ports on the bridge, which is at odds to the defaults adopted by our DSA implementation for mv88e6xxx switches. This commit enables by default flooding of both unknown unicast and unknown multicast frames whenever a port is added to a bridge, and disables the flooding when a port leaves the bridge. This means that mv88e6xxx DSA switches now behave as per the bridge(8) man page, and IPv6 works flawlessly through such a switch. Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.