libxtables: change option precedence order to be intuitive

When using `-m mark --mark 2 -m connmark --mark 2`, the user currently
gets an error about the (libxt_mark) --mark option being used twice.
This is because libxt_connmark's option table does not override any
previous options. This patch changes this behavior, since the current
behavior does not allow connmark's option to be used at all, which is
illogical.

Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 28 insertions, 22 deletions

diff --git a/xtables.c b/xtables.c
index 47a0d9cb..7658038c 100644
--- a/xtables.c
+++ b/xtables.c
@@ -73,44 +73,50 @@ void basic_exit_err(enum xtables_exittype status, const char *msg, ...)
 	exit(status);
 }
 
-
-void xtables_free_opts(int reset_offset)
+void xtables_free_opts(int unused)
 {
-	if (xt_params->opts != xt_params->orig_opts) {
-		free(xt_params->opts);
-		xt_params->opts = xt_params->orig_opts;
-		if (reset_offset)
-			xt_params->option_offset = 0;
-	}
+	free(xt_params->opts);
 }
 
-struct option *xtables_merge_options(struct option *oldopts,
+struct option *xtables_merge_options(struct option *orig_opts,
+				     struct option *oldopts,
 				     const struct option *newopts,
 				     unsigned int *option_offset)
 {
-	unsigned int num_old, num_new, i;
-	struct option *merge;
+	unsigned int num_oold = 0, num_old = 0, num_new = 0, i;
+	struct option *merge, *mp;
 
 	if (newopts == NULL)
 		return oldopts;
 
-	for (num_old = 0; oldopts[num_old].name; num_old++) ;
+	for (num_oold = 0; orig_opts[num_oold].name; num_oold++) ;
+	if (oldopts != NULL)
+		for (num_old = 0; oldopts[num_old].name; num_old++) ;
 	for (num_new = 0; newopts[num_new].name; num_new++) ;
 
+	merge = malloc(sizeof(*mp) * (num_oold + num_old + num_new + 1));
+	if (merge == NULL)
+		return NULL;
+
+	/* Let the base options -[ADI...] have precedence over everything */
+	memcpy(merge, orig_opts, sizeof(*mp) * num_oold);
+	mp = merge + num_oold;
+
+	/* Second, the new options */
 	xt_params->option_offset += 256;
 	*option_offset = xt_params->option_offset;
+	memcpy(mp, newopts, sizeof(*mp) * num_new);
 
-	merge = malloc(sizeof(struct option) * (num_new + num_old + 1));
-	if (merge == NULL)
-		return NULL;
-	memcpy(merge, oldopts, num_old * sizeof(struct option));
-	xtables_free_opts(0);	/* Release any old options merged  */
-	for (i = 0; i < num_new; i++) {
-		merge[num_old + i] = newopts[i];
-		merge[num_old + i].val += *option_offset;
-	}
-	memset(merge + num_old + num_new, 0, sizeof(struct option));
+	for (i = 0; i < num_new; ++i, ++mp)
+		mp->val += *option_offset;
+
+	/* Third, the old options */
+	memcpy(mp, oldopts, sizeof(*mp) * num_old);
+	mp += num_old;
+	xtables_free_opts(0);
 
+	/* Clear trailing entry */
+	memset(mp, 0, sizeof(*mp));
 	return merge;
 }