Pablo Neira Ayuso says:
====================
Netfilter updates for net-next
A final pull request, I know it's very late but this time I think it's worth a
bit of rush.
The following patchset contains Netfilter/nf_tables updates for net-next, more
specifically concatenation support and dynamic stateful expression
instantiation.
This also comes with a couple of small patches. One to fix the ebtables.h
userspace header and another to get rid of an obsolete example file in tree
that describes a nf_tables expression.
This time, I decided to paste the original descriptions. This will result in a
rather large commit description, but I think these bytes to keep.
Patrick McHardy says:
====================
netfilter: nf_tables: concatenation support
The following patches add support for concatenations, which allow multi
dimensional exact matches in O(1).
The basic idea is to split the data registers, currently consisting of
4 registers of 16 bytes each, into smaller units, 16 registers of 4
bytes each, and making sure each register store always leaves the
full 32 bit in a well defined state, meaning smaller stores will
zero the remaining bits.
Based on that, we can load multiple adjacent registers with different
values, thereby building a concatenated bigger value, and use that
value for set lookups.
Sets are changed to use variable sized extensions for their key and
data values, removing the fixed limit of 16 bytes while saving memory
if less space is needed.
As a side effect, these patches will allow some nice optimizations in
the future, like using jhash2 in nft_hash, removing the masking in
nft_cmp_fast, optimized data comparison using 32 bit word size etc.
These are not done so far however.
The patches are split up as follows:
* the first five patches add length validation to register loads and
stores to make sure we stay within bounds and prepare the validation
functions for the new addressing mode
* the next patches prepare for changing to 32 bit addressing by
introducing a struct nft_regs, which holds the verdict register as
well as the data registers. The verdict members are moved to a new
struct nft_verdict to allow to pull struct nft_data out of the stack.
* the next patches contain preparatory conversions of expressions and
sets to use 32 bit addressing
* the next patch introduces so far unused register conversion helpers
for parsing and dumping register numbers over netlink
* following is the real conversion to 32 bit addressing, consisting of
replacing struct nft_data in struct nft_regs by an array of u32s and
actually translating and validating the new register numbers.
* the final two patches add support for variable sized data items and
variable sized keys / data in set elements
The patches have been verified to work correctly with nft binaries using
both old and new addressing.
====================
Patrick McHardy says:
====================
netfilter: nf_tables: dynamic stateful expression instantiation
The following patches are the grand finale of my nf_tables set work,
using all the building blocks put in place by the previous patches
to support something like iptables hashlimit, but a lot more powerful.
Sets are extended to allow attaching expressions to set elements.
The dynset expression dynamically instantiates these expressions
based on a template when creating new set elements and evaluates
them for all new or updated set members.
In combination with concatenations this effectively creates state
tables for arbitrary combinations of keys, using the existing
expression types to maintain that state. Regular set GC takes care
of purging expired states.
We currently support two different stateful expressions, counter
and limit. Using limit as a template we can express the functionality
of hashlimit, but completely unrestricted in the combination of keys.
Using counter we can perform accounting for arbitrary flows.
The following examples from patch 5/5 show some possibilities.
Userspace syntax is still WIP, especially the listing of state
tables will most likely be seperated from normal set listings
and use a more structured format:
1. Limit the rate of new SSH connections per host, similar to iptables
hashlimit:
flow ip saddr timeout 60s \
limit 10/second \
accept
2. Account network traffic between each set of /24 networks:
flow ip saddr & 255.255.255.0 . ip daddr & 255.255.255.0 \
counter
3. Account traffic to each host per user:
flow skuid . ip daddr \
counter
4. Account traffic for each combination of source address and TCP flags:
flow ip saddr . tcp flags \
counter
The resulting set content after a Xmas-scan look like this:
{
192.168.122.1 . fin | psh | urg : counter packets 1001 bytes 40040,
192.168.122.1 . ack : counter packets 74 bytes 3848,
192.168.122.1 . psh | ack : counter packets 35 bytes 3144
}
In the future the "expressions attached to elements" will be extended
to also support user created non-stateful expressions to allow to
efficiently select beween a set of parameter sets, f.i. a set of log
statements with different prefixes based on the interface, which currently
require one rule each. This will most likely have to wait until the next
kernel version though.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
