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, 61 insertions, 10 deletions

diff --git a/src/libnftables.c b/src/libnftables.c
index e76f32ef..bd71ae9e 100644
--- a/src/libnftables.c
+++ b/src/libnftables.c
@@ -395,6 +395,18 @@ void nft_ctx_set_dry_run(struct nft_ctx *ctx, bool dry)
 	ctx->check = dry;
 }
 
+EXPORT_SYMBOL(nft_ctx_get_optimize);
+uint32_t nft_ctx_get_optimize(struct nft_ctx *ctx)
+{
+	return ctx->optimize_flags;
+}
+
+EXPORT_SYMBOL(nft_ctx_set_optimize);
+void nft_ctx_set_optimize(struct nft_ctx *ctx, uint32_t flags)
+{
+	ctx->optimize_flags = flags;
+}
+
 EXPORT_SYMBOL(nft_ctx_output_get_flags);
 unsigned int nft_ctx_output_get_flags(struct nft_ctx *ctx)
 {
@@ -626,8 +638,7 @@ retry:
 	return rc;
 }
 
-EXPORT_SYMBOL(nft_run_cmd_from_filename);
-int nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
+static int __nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
 {
 	struct cmd *cmd, *next;
 	int rc, parser_rc;
@@ -638,13 +649,6 @@ int nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
 	if (rc < 0)
 		goto err;
 
-	if (!strcmp(filename, "-"))
-		filename = "/dev/stdin";
-
-	if (!strcmp(filename, "/dev/stdin") &&
-	    !nft_output_json(&nft->output))
-		nft->stdin_buf = stdin_to_buffer();
-
 	rc = -EINVAL;
 	if (nft_output_json(&nft->output))
 		rc = nft_parse_json_filename(nft, filename, &msgs, &cmds);
@@ -653,6 +657,9 @@ int nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
 
 	parser_rc = rc;
 
+	if (nft->optimize_flags)
+		nft_optimize(nft, &cmds);
+
 	rc = nft_evaluate(nft, &msgs, &cmds);
 	if (rc < 0)
 		goto err;
@@ -694,7 +701,51 @@ err:
 	if (rc)
 		nft_cache_release(&nft->cache);
 
+	return rc;
+}
+
+static int nft_run_optimized_file(struct nft_ctx *nft, const char *filename)
+{
+	uint32_t optimize_flags;
+	bool check;
+	int ret;
+
+	check = nft->check;
+	nft->check = true;
+	optimize_flags = nft->optimize_flags;
+	nft->optimize_flags = 0;
+
+	/* First check the original ruleset loads fine as is. */
+	ret = __nft_run_cmd_from_filename(nft, filename);
+	if (ret < 0)
+		return ret;
+
+	nft->check = check;
+	nft->optimize_flags = optimize_flags;
+
+	return __nft_run_cmd_from_filename(nft, filename);
+}
+
+EXPORT_SYMBOL(nft_run_cmd_from_filename);
+int nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
+{
+	int ret;
+
+	if (!strcmp(filename, "-"))
+		filename = "/dev/stdin";
+
+	if (!strcmp(filename, "/dev/stdin") &&
+	    !nft_output_json(&nft->output))
+		nft->stdin_buf = stdin_to_buffer();
+
+	if (nft->optimize_flags) {
+		ret = nft_run_optimized_file(nft, filename);
+		xfree(nft->stdin_buf);
+		return ret;
+	}
+
+	ret = __nft_run_cmd_from_filename(nft, filename);
 	xfree(nft->stdin_buf);
 
-	return rc;
+	return ret;
 }