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Having MPLS packet stats is useful for observing network operation and for diagnosing network problems. In the absence of anything better, RFC2863 and RFC3813 are used for guidance for which stats to expose and the semantics of them. In particular rx_noroutes maps to in unknown protos in RFC2863. The stats are exposed to userspace via AF_MPLS attributes embedded in the IFLA_STATS_AF_SPEC attribute of RTM_GETSTATS messages. All the introduced fields are 64-bit, even error ones, to ensure no overflow with long uptimes. Per-CPU counters are used to avoid cache-line contention on the commonly used fields. The other fields have also been made per-CPU for code to avoid performance problems in error conditions on the assumption that on some platforms the cost of atomic operations could be more expensive than sending the packet (which is what would be done in the success case). If that's not the case, we could instead not use per-CPU counters for these fields. Only unicast and non-fragment are exposed at the moment, but other counters can be exposed in the future either by adding to the end of struct mpls_link_stats or by additional netlink attributes in the AF_MPLS IFLA_STATS_AF_SPEC nested attribute. Signed-off-by: Robert Shearman <rshearma@brocade.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.