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David Ahern says: ==================== net: Allow FIB notifiers to fail add and replace I wanted to revisit how resource overload is handled for hardware offload of FIB entries and rules. At the moment, the in-kernel fib notifier can tell a driver about a route or rule add, replace, and delete, but the notifier can not affect the action. Specifically, in the case of mlxsw if a route or rule add is going to overflow the ASIC resources the only recourse is to abort hardware offload. Aborting offload is akin to taking down the switch as the path from data plane to the control plane simply can not support the traffic bandwidth of the front panel ports. Further, the current state of FIB notifiers is inconsistent with other resources where a driver can affect a user request - e.g., enslavement of a port into a bridge or a VRF. As a result of the work done over the past 3+ years, I believe we are at a point where we can bring consistency to the stack and offloads, and reliably allow the FIB notifiers to fail a request, pushing an error along with a suitable error message back to the user. Rather than aborting offload when the switch is out of resources, userspace is simply prevented from adding more routes and has a clear indication of why. This set does not resolve the corner case where rules or routes not supported by the device are installed prior to the driver getting loaded and registering for FIB notifications. In that case, hardware offload has not been established and it can refuse to offload anything, sending errors back to userspace via extack. Since conceptually the driver owns the netdevices associated with its asic, this corner case mainly applies to unsupported rules and any races during the bringup phase. Patch 1 fixes call_fib_notifiers to extract the errno from the encoded response from handlers. Patches 2-5 allow the call to call_fib_notifiers to fail the add or replace of a route or rule. Patch 6 adds a simple resource controller to netdevsim to illustrate how a FIB resource controller can limit the number of route entries. Changes since RFC - correct return code for call_fib_notifier - dropped patch 6 exporting devlink symbols - limited example resource controller to init_net only - updated Kconfig for netdevsim to use MAY_USE_DEVLINK - updated cover letter regarding startup case noted by Ido ==================== Signed-off-by: David S. Miller <davem@davemloft.net> |
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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.