c56716c69c
Multiple netfilter extensions store pointers to external data in their extension area struct. Examples: 1. Timeout policies 2. Connection tracking helpers. No references are taken for these. When a helper or timeout policy is removed, the conntrack table gets traversed and affected extensions are cleared. Conntrack entries not yet in the hashtable are referenced via a special list, the unconfirmed list. On removal of a policy or connection tracking helper, the unconfirmed list gets traversed an all entries are marked as dying, this prevents them from getting committed to the table at insertion time: core checks for dying bit, if set, the conntrack entry gets destroyed at confirm time. The disadvantage is that each new conntrack has to be added to the percpu unconfirmed list, and each insertion needs to remove it from this list. The list is only ever needed when a policy or helper is removed -- a rare occurrence. Add a generation ID count: Instead of adding to the list and then traversing that list on policy/helper removal, increment a counter that is stored in the extension area. For unconfirmed conntracks, the extension has the genid valid at ct allocation time. Removal of a helper/policy etc. increments the counter. At confirmation time, validate that ext->genid == global_id. If the stored number is not the same, do not allow the conntrack insertion, just like as if a confirmed-list traversal would have flagged the entry as dying. After insertion, the genid is no longer relevant (conntrack entries are now reachable via the conntrack table iterators and is set to 0. This allows removal of the percpu unconfirmed list. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| 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.