src: add ruleset optimization infrastructure

This patch adds a new -o/--optimize option to enable ruleset
optimization.

You can combine this option with the dry run mode (--check) to review
the proposed ruleset updates without actually loading the ruleset, e.g.

 # nft -c -o -f ruleset.test
 Merging:
 ruleset.nft:16:3-37:           ip daddr 192.168.0.1 counter accept
 ruleset.nft:17:3-37:           ip daddr 192.168.0.2 counter accept
 ruleset.nft:18:3-37:           ip daddr 192.168.0.3 counter accept
 into:
        ip daddr { 192.168.0.1, 192.168.0.2, 192.168.0.3 } counter packets 0 bytes 0 accept

This infrastructure collects the common statements that are used in
rules, then it builds a matrix of rules vs. statements. Then, it looks
for common statements in consecutive rules which allows to merge rules.

This ruleset optimization always performs an implicit dry run to
validate that the original ruleset is correct. Then, on a second pass,
it performs the ruleset optimization and add the rules into the kernel
(unless --check has been specified by the user).

From libnftables perspective, there is a new API to enable
this feature:

  uint32_t nft_ctx_get_optimize(struct nft_ctx *ctx);
  void nft_ctx_set_optimize(struct nft_ctx *ctx, uint32_t flags);

This patch adds support for the first optimization: Collapse a linear
list of rules matching on a single selector into a set as exposed in the
example above.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/nft.txt b/doc/nft.txt
index e4ed9824..7240deaa 100644
--- a/doc/nft.txt
+++ b/doc/nft.txt
@@ -62,6 +62,11 @@ understanding of their meaning. You can get information about options by running
 *--check*::
 	Check commands validity without actually applying the changes.
 
+*-o*::
+*--optimize*::
+	Optimize your ruleset. You can combine this option with '-c' to inspect
+        the proposed optimizations.
+
 .Ruleset list output formatting that modify the output of the list ruleset command:
 
 *-a*::