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NIC drivers generally try to ensure that the "network header" is aligned to a 4-byte boundary. This is not always possible: When Ethernet frames are encapsulated in other packets with 4-byte aligned headers, the inner Ethernet header will have 4-byte alignment, and in consequence, the inner network header is aligned to 2, but not to 4 bytes. Most parts of batman-adv only care about 2-byte alignment; in particular, no unaligned accesses occur in performance-critical paths that handle actual payload data. This is not true for OGM handling: the seqno and crc fields are accessed as 32-bit values. To avoid these unaligned accesses, this patch reduces the expected packet alignment to 2 bytes for all of batadv's packet types. As no unaligned accesses existed on the performance-critical paths anyways, this chance does have any (positive or negative) effect on performance, but it still makes sense to avoid these accesses to prevent log noise when examining other unaligned accesses in the kernel while batman-adv is active. Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net> Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
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.