xt: Delay libxtables access until translation

There is no point in spending efforts setting up the xt match/target
when it is not printed afterwards. So just store the statement data from
libnftnl in struct xt_stmt and perform the extension lookup from
xt_stmt_xlate() instead.

This means some data structures are only temporarily allocated for the
sake of passing to libxtables callbacks, no need to drag them around.
Also no need to clone the looked up extension, it is needed only to call
the functions it provides.

While being at it, select numeric output in xt_xlate_*_params -
otherwise there will be reverse DNS lookups which should not happen by
default.

Signed-off-by: Phil Sutter <phil@nwl.cc>

2 files changed, 80 insertions, 121 deletions

diff --git a/include/statement.h b/include/statement.h
index 2a2d3001..8651fc78 100644
--- a/include/statement.h
+++ b/include/statement.h
@@ -264,12 +264,11 @@ struct xtables_target;
 struct xt_stmt {
 	const char			*name;
 	enum nft_xt_type		type;
+	uint32_t			rev;
+	uint32_t			family;
+	size_t				infolen;
+	void				*info;
 	uint32_t			proto;
-	union {
-		struct xtables_match	*match;
-		struct xtables_target	*target;
-	};
-	void				*entry;
 };
 
 extern struct stmt *xt_stmt_alloc(const struct location *loc);
diff --git a/src/xt.c b/src/xt.c
index a5417352..7880fa1b 100644
--- a/src/xt.c
+++ b/src/xt.c
@@ -28,51 +28,94 @@
 
 #ifdef HAVE_LIBXTABLES
 #include <xtables.h>
+
+static void *xt_entry_alloc(const struct xt_stmt *xt, uint32_t af);
 #endif
 
 void xt_stmt_xlate(const struct stmt *stmt, struct output_ctx *octx)
 {
 #ifdef HAVE_LIBXTABLES
 	struct xt_xlate *xl = xt_xlate_alloc(10240);
+	struct xtables_target *tg;
+	struct xt_entry_target *t;
+	struct xtables_match *mt;
+	struct xt_entry_match *m;
+	size_t size;
+	void *entry;
+
+	xtables_set_nfproto(stmt->xt.family);
+	entry = xt_entry_alloc(&stmt->xt, stmt->xt.family);
 
 	switch (stmt->xt.type) {
 	case NFT_XT_MATCH:
-		if (stmt->xt.match->xlate) {
+		mt = xtables_find_match(stmt->xt.name, XTF_TRY_LOAD, NULL);
+		if (!mt) {
+			fprintf(stderr, "XT match %s not found\n",
+				stmt->xt.name);
+			return;
+		}
+		size = XT_ALIGN(sizeof(*m)) + stmt->xt.infolen;
+
+		m = xzalloc(size);
+		memcpy(&m->data, stmt->xt.info, stmt->xt.infolen);
+
+		m->u.match_size = size;
+		m->u.user.revision = stmt->xt.rev;
+
+		if (mt->xlate) {
 			struct xt_xlate_mt_params params = {
-				.ip		= stmt->xt.entry,
-				.match		= stmt->xt.match->m,
-				.numeric        = 0,
+				.ip		= entry,
+				.match		= m,
+				.numeric        = 1,
 			};
 
-			stmt->xt.match->xlate(xl, &params);
+			mt->xlate(xl, &params);
 			nft_print(octx, "%s", xt_xlate_get(xl));
-		} else if (stmt->xt.match->print) {
+		} else if (mt->print) {
 			printf("#");
-			stmt->xt.match->print(&stmt->xt.entry,
-					      stmt->xt.match->m, 0);
+			mt->print(&entry, m, 0);
 		}
+		xfree(m);
 		break;
 	case NFT_XT_WATCHER:
 	case NFT_XT_TARGET:
-		if (stmt->xt.target->xlate) {
+		tg = xtables_find_target(stmt->xt.name, XTF_TRY_LOAD);
+		if (!tg) {
+			fprintf(stderr, "XT target %s not found\n",
+				stmt->xt.name);
+			return;
+		}
+		size = XT_ALIGN(sizeof(*t)) + stmt->xt.infolen;
+
+		t = xzalloc(size);
+		memcpy(&t->data, stmt->xt.info, stmt->xt.infolen);
+
+		t->u.target_size = size;
+		t->u.user.revision = stmt->xt.rev;
+
+		strcpy(t->u.user.name, tg->name);
+
+		if (tg->xlate) {
 			struct xt_xlate_tg_params params = {
-				.ip		= stmt->xt.entry,
-				.target		= stmt->xt.target->t,
-				.numeric        = 0,
+				.ip		= entry,
+				.target		= t,
+				.numeric        = 1,
 			};
 
-			stmt->xt.target->xlate(xl, &params);
+			tg->xlate(xl, &params);
 			nft_print(octx, "%s", xt_xlate_get(xl));
-		} else if (stmt->xt.target->print) {
+		} else if (tg->print) {
 			printf("#");
-			stmt->xt.target->print(NULL, stmt->xt.target->t, 0);
+			tg->print(NULL, t, 0);
 		}
+		xfree(t);
 		break;
 	default:
 		break;
 	}
 
 	xt_xlate_free(xl);
+	xfree(entry);
 #else
 	nft_print(octx, "# xt_%s", stmt->xt.name);
 #endif
@@ -80,33 +123,12 @@ void xt_stmt_xlate(const struct stmt *stmt, struct output_ctx *octx)
 
 void xt_stmt_destroy(struct stmt *stmt)
 {
-#ifdef HAVE_LIBXTABLES
-	switch (stmt->xt.type) {
-	case NFT_XT_MATCH:
-		if (!stmt->xt.match)
-			break;
-		if (stmt->xt.match->m)
-			xfree(stmt->xt.match->m);
-		xfree(stmt->xt.match);
-		break;
-	case NFT_XT_WATCHER:
-	case NFT_XT_TARGET:
-		if (!stmt->xt.target)
-			break;
-		if (stmt->xt.target->t)
-			xfree(stmt->xt.target->t);
-		xfree(stmt->xt.target);
-		break;
-	default:
-		break;
-	}
-#endif
-	xfree(stmt->xt.entry);
 	xfree(stmt->xt.name);
+	xfree(stmt->xt.info);
 }
 
 #ifdef HAVE_LIBXTABLES
-static void *xt_entry_alloc(struct xt_stmt *xt, uint32_t af)
+static void *xt_entry_alloc(const struct xt_stmt *xt, uint32_t af)
 {
 	union nft_entry {
 		struct ipt_entry ipt;
@@ -173,24 +195,6 @@ static uint32_t xt_proto(const struct proto_ctx *pctx)
 
 	return 0;
 }
-
-static struct xtables_target *xt_target_clone(struct xtables_target *t)
-{
-	struct xtables_target *clone;
-
-	clone = xzalloc(sizeof(struct xtables_target));
-	memcpy(clone, t, sizeof(struct xtables_target));
-	return clone;
-}
-
-static struct xtables_match *xt_match_clone(struct xtables_match *m)
-{
-	struct xtables_match *clone;
-
-	clone = xzalloc(sizeof(struct xtables_match));
-	memcpy(clone, m, sizeof(struct xtables_match));
-	return clone;
-}
 #endif
 
 /*
@@ -201,43 +205,22 @@ void netlink_parse_match(struct netlink_parse_ctx *ctx,
 			 const struct location *loc,
 			 const struct nftnl_expr *nle)
 {
-	struct stmt *stmt;
-	const char *name;
-#ifdef HAVE_LIBXTABLES
-	struct xtables_match *mt;
 	const char *mtinfo;
-	struct xt_entry_match *m;
+	struct stmt *stmt;
 	uint32_t mt_len;
 
-	xtables_set_nfproto(ctx->table->handle.family);
-
-	name = nftnl_expr_get_str(nle, NFTNL_EXPR_MT_NAME);
-
-	mt = xtables_find_match(name, XTF_TRY_LOAD, NULL);
-	if (!mt) {
-		fprintf(stderr, "XT match %s not found\n", name);
-		return;
-	}
 	mtinfo = nftnl_expr_get(nle, NFTNL_EXPR_MT_INFO, &mt_len);
 
-	m = xzalloc(sizeof(struct xt_entry_match) + mt_len);
-	memcpy(&m->data, mtinfo, mt_len);
-
-	m->u.match_size = mt_len + XT_ALIGN(sizeof(struct xt_entry_match));
-	m->u.user.revision = nftnl_expr_get_u32(nle, NFTNL_EXPR_MT_REV);
-
 	stmt = xt_stmt_alloc(loc);
-	stmt->xt.name = strdup(name);
+	stmt->xt.name = strdup(nftnl_expr_get_str(nle, NFTNL_EXPR_MT_NAME));
 	stmt->xt.type = NFT_XT_MATCH;
-	stmt->xt.match = xt_match_clone(mt);
-	stmt->xt.match->m = m;
-#else
-	name = nftnl_expr_get_str(nle, NFTNL_EXPR_MT_NAME);
+	stmt->xt.rev = nftnl_expr_get_u32(nle, NFTNL_EXPR_MT_REV);
+	stmt->xt.family = ctx->table->handle.family;
+
+	stmt->xt.infolen = mt_len;
+	stmt->xt.info = xmalloc(mt_len);
+	memcpy(stmt->xt.info, mtinfo, mt_len);
 
-	stmt = xt_stmt_alloc(loc);
-	stmt->xt.name = strdup(name);
-	stmt->xt.type = NFT_XT_MATCH;
-#endif
 	ctx->table->has_xt_stmts = true;
 	rule_stmt_append(ctx->rule, stmt);
 }
@@ -246,44 +229,22 @@ void netlink_parse_target(struct netlink_parse_ctx *ctx,
 			  const struct location *loc,
 			  const struct nftnl_expr *nle)
 {
-	struct stmt *stmt;
-	const char *name;
-#ifdef HAVE_LIBXTABLES
-	struct xtables_target *tg;
 	const void *tginfo;
-	struct xt_entry_target *t;
-	size_t size;
+	struct stmt *stmt;
 	uint32_t tg_len;
 
-	xtables_set_nfproto(ctx->table->handle.family);
-
-	name = nftnl_expr_get_str(nle, NFTNL_EXPR_TG_NAME);
-	tg = xtables_find_target(name, XTF_TRY_LOAD);
-	if (!tg) {
-		fprintf(stderr, "XT target %s not found\n", name);
-		return;
-	}
 	tginfo = nftnl_expr_get(nle, NFTNL_EXPR_TG_INFO, &tg_len);
 
-	size = XT_ALIGN(sizeof(struct xt_entry_target)) + tg_len;
-	t = xzalloc(size);
-	memcpy(&t->data, tginfo, tg_len);
-	t->u.target_size = size;
-	t->u.user.revision = nftnl_expr_get_u32(nle, NFTNL_EXPR_TG_REV);
-	strcpy(t->u.user.name, tg->name);
-
 	stmt = xt_stmt_alloc(loc);
-	stmt->xt.name = strdup(name);
+	stmt->xt.name = strdup(nftnl_expr_get_str(nle, NFTNL_EXPR_TG_NAME));
 	stmt->xt.type = NFT_XT_TARGET;
-	stmt->xt.target = xt_target_clone(tg);
-	stmt->xt.target->t = t;
-#else
-	name = nftnl_expr_get_str(nle, NFTNL_EXPR_TG_NAME);
+	stmt->xt.rev = nftnl_expr_get_u32(nle, NFTNL_EXPR_TG_REV);
+	stmt->xt.family = ctx->table->handle.family;
+
+	stmt->xt.infolen = tg_len;
+	stmt->xt.info = xmalloc(tg_len);
+	memcpy(stmt->xt.info, tginfo, tg_len);
 
-	stmt = xt_stmt_alloc(loc);
-	stmt->xt.name = strdup(name);
-	stmt->xt.type = NFT_XT_TARGET;
-#endif
 	ctx->table->has_xt_stmts = true;
 	rule_stmt_append(ctx->rule, stmt);
 }
@@ -311,7 +272,6 @@ void stmt_xt_postprocess(struct rule_pp_ctx *rctx, struct stmt *stmt,
 		stmt->xt.type = NFT_XT_WATCHER;
 
 	stmt->xt.proto = xt_proto(&rctx->pctx);
-	stmt->xt.entry = xt_entry_alloc(&stmt->xt, rctx->pctx.family);
 }
 
 static int nft_xt_compatible_revision(const char *name, uint8_t rev, int opt)