From e6eede725bbd395fb8b385aec4d0a32ce99e842c Mon Sep 17 00:00:00 2001
From: Phil Sutter <phil@nwl.cc>
Date: Mon, 21 Sep 2020 13:42:06 +0200
Subject: [PATCH] libxtables: Make sure extensions register in revision order

Insert extensions into pending lists in ordered fashion: Group by
extension name (and, for matches, family) and order groups by descending
revision number.

This allows to simplify the later full registration considerably. Since
that involves kernel compatibility checks, the extra cycles here pay off
eventually.

Signed-off-by: Phil Sutter <phil@nwl.cc>
(cherry picked from commit b3ac87038f4e45141831d9ab485a2f627daba3f1)
Signed-off-by: Phil Sutter <psutter@redhat.com>
---
 libxtables/xtables.c | 71 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 7 deletions(-)

diff --git a/libxtables/xtables.c b/libxtables/xtables.c
index 777c2b08e9896..13139d7f8ad62 100644
--- a/libxtables/xtables.c
+++ b/libxtables/xtables.c
@@ -902,8 +902,14 @@ static void xtables_check_options(const char *name, const struct option *opt)
 		}
 }
 
+static int xtables_match_prefer(const struct xtables_match *a,
+				const struct xtables_match *b);
+
 void xtables_register_match(struct xtables_match *me)
 {
+	struct xtables_match **pos;
+	bool seen_myself = false;
+
 	if (me->next) {
 		fprintf(stderr, "%s: match \"%s\" already registered\n",
 			xt_params->program_name, me->name);
@@ -955,10 +961,34 @@ void xtables_register_match(struct xtables_match *me)
 	if (me->extra_opts != NULL)
 		xtables_check_options(me->name, me->extra_opts);
 
-
-	/* place on linked list of matches pending full registration */
-	me->next = xtables_pending_matches;
-	xtables_pending_matches = me;
+	/* order into linked list of matches pending full registration */
+	for (pos = &xtables_pending_matches; *pos; pos = &(*pos)->next) {
+		/* group by name and family */
+		if (strcmp(me->name, (*pos)->name) ||
+		    me->family != (*pos)->family) {
+			if (seen_myself)
+				break; /* end of own group, append to it */
+			continue;
+		}
+		/* found own group */
+		seen_myself = true;
+		if (xtables_match_prefer(me, *pos) >= 0)
+			break; /* put preferred items first in group */
+	}
+	/* if own group was not found, prepend item */
+	if (!*pos && !seen_myself)
+		pos = &xtables_pending_matches;
+
+	me->next = *pos;
+	*pos = me;
+#ifdef DEBUG
+	printf("%s: inserted match %s (family %d, revision %d):\n",
+			__func__, me->name, me->family, me->revision);
+	for (pos = &xtables_pending_matches; *pos; pos = &(*pos)->next) {
+		printf("%s:\tmatch %s (family %d, revision %d)\n", __func__,
+		       (*pos)->name, (*pos)->family, (*pos)->revision);
+	}
+#endif
 }
 
 /**
@@ -1097,6 +1127,9 @@ void xtables_register_matches(struct xtables_match *match, unsigned int n)
 
 void xtables_register_target(struct xtables_target *me)
 {
+	struct xtables_target **pos;
+	bool seen_myself = false;
+
 	if (me->next) {
 		fprintf(stderr, "%s: target \"%s\" already registered\n",
 			xt_params->program_name, me->name);
@@ -1152,9 +1185,33 @@ void xtables_register_target(struct xtables_target *me)
 	if (me->family != afinfo->family && me->family != AF_UNSPEC)
 		return;
 
-	/* place on linked list of targets pending full registration */
-	me->next = xtables_pending_targets;
-	xtables_pending_targets = me;
+	/* order into linked list of targets pending full registration */
+	for (pos = &xtables_pending_targets; *pos; pos = &(*pos)->next) {
+		/* group by name */
+		if (!extension_cmp(me->name, (*pos)->name, (*pos)->family)) {
+			if (seen_myself)
+				break; /* end of own group, append to it */
+			continue;
+		}
+		/* found own group */
+		seen_myself = true;
+		if (xtables_target_prefer(me, *pos) >= 0)
+			break; /* put preferred items first in group */
+	}
+	/* if own group was not found, prepend item */
+	if (!*pos && !seen_myself)
+		pos = &xtables_pending_targets;
+
+	me->next = *pos;
+	*pos = me;
+#ifdef DEBUG
+	printf("%s: inserted target %s (family %d, revision %d):\n",
+			__func__, me->name, me->family, me->revision);
+	for (pos = &xtables_pending_targets; *pos; pos = &(*pos)->next) {
+		printf("%s:\ttarget %s (family %d, revision %d)\n", __func__,
+		       (*pos)->name, (*pos)->family, (*pos)->revision);
+	}
+#endif
 }
 
 static bool xtables_fully_register_pending_target(struct xtables_target *me)
-- 
2.28.0