mainlining shenanigans
762c400766
Before now, connection templates were ignored by the random dropentry procedure. But Michal Koutný suggests that we should add exception for connections under SYN attack. He provided patch that implements it for TCP: <quote> IPVS includes protection against filling the ip_vs_conn_tab by dropping 1/32 of feasible entries every second. The template entries (for persistent services) are never directly deleted by this mechanism but when a picked TCP connection entry is being dropped (1), the respective template entry is dropped too (realized by expiring 60 seconds after the connection entry being dropped). There is another mechanism that removes connection entries when they time out (2), in this case the associated template entry is not deleted. Under SYN flood template entries would accumulate (due to their entry longer timeout). The accumulation takes place also with drop_entry being enabled. Roughly 15% ((31/32)^60) of SYN_RECV connections survive the dropping mechanism (1) and are removed by the timeout mechanism (2)(defaults to 60 seconds for SYN_RECV), thus template entries would still accumulate. The patch ensures that when a connection entry times out, we also remove the template entry from the table. To prevent breaking persistent services (since the connection may time out in already established state) we add a new entry flag to protect templates what spawned at least one established TCP connection. </quote> We already added ASSURED flag for the templates in previous patch, so that we can use it now to decide which connection templates should be dropped under attack. But we also have some cases that need special handling. We modify the dropentry procedure as follows: - Linux timers currently use LIFO ordering but we can not rely on this to drop controlling connections. So, set cp->timeout to 0 to indicate that connection was dropped and that on expiration we should try to drop our controlling connections. As result, we can now avoid the ip_vs_conn_expire_now call. - move the cp->n_control check above, so that it avoids restarting the timer for controlling connections when not needed. - drop unassured connection templates here if they are not referred by any connections. On connection expiration: if connection was dropped (cp->timeout=0) try to drop our controlling connection except if it is a template in assured state. In ip_vs_conn_flush change order of ip_vs_conn_expire_now calls according to the LIFO timer expiration order. It should work faster for controlling connections with single controlled one. Suggested-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| 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.
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.