mainlining shenanigans
4d5c32ec75
David Ahern says: ==================== nexthops: Fix 2 fundamental flaws with nexthop groups Nik's torture tests have exposed 2 fundamental mistakes with the initial nexthop code for groups. First, the nexthops entries and num_nh in the nh_grp struct should not be modified once the struct is set under rcu. Doing so has major affects on the datapath seeing valid nexthop entries. Second, the helpers in the header file were convenient for not repeating code, but they cause datapath walks to potentially see 2 different group structs after an rcu replace, disrupting a walk of the path objects. This second problem applies solely to IPv4 as I re-used too much of the existing code in walking legs of a multipath route. Patches 1 is refactoring change to simplify the overhead of reviewing and understanding the change in patch 2 which fixes the update of nexthop groups when a compnent leg is removed. Patches 3-5 address the second problem. Patch 3 inlines the multipath check such that the mpath lookup and subsequent calls all use the same nh_grp struct. Patches 4 and 5 fix datapath uses of fib_info_num_path with iterative calls to fib_info_nhc. fib_info_num_path can be used in control plane path in a 'for loop' with subsequent fib_info_nhc calls to get each leg since the nh_grp struct is only changed while holding the rtnl; the combination can not be used in the data plane with external nexthops as it involves repeated dereferences of nh_grp struct which can change between calls. Similarly, nexthop_is_multipath can be used for branching decisions in the datapath since the nexthop type can not be changed (a group can not be converted to standalone and vice versa). Patch set developed in coordination with Nikolay Aleksandrov. He did a lot of work creating a good reproducer, discussing options to fix it and testing iterations. I have adapted Nik's commands into additional tests in the nexthops selftest script which I will send against -next. v2 - fixed whitespace errors ==================== Signed-off-by: David S. Miller <davem@davemloft.net> |
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| kernel | ||
| lib | ||
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| .clang-format | ||
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| .get_maintainer.ignore | ||
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| 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.