xtables: Review nft_init()

Move common code into nft_init(), such as:

* initial zeroing nft_handle fields
* family ops lookup and assignment to 'ops' field
* setting of 'family' field

This requires minor adjustments in xtables_restore_main() so extra field
initialization doesn't happen before nft_init() call.

As a side-effect, this fixes segfaulting xtables-monitor binary when
printing rules for trace event as in that code-path 'ops' field wasn't
initialized.

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

1 files changed, 2 insertions, 7 deletions

diff --git a/iptables/xtables-save.c b/iptables/xtables-save.c
index 1b6c363b..28f74902 100644
--- a/iptables/xtables-save.c
+++ b/iptables/xtables-save.c
@@ -137,10 +137,8 @@ xtables_save_main(int family, int argc, char *argv[],
 	struct do_output_data d = {
 		.format = FMT_NOCOUNTS,
 	};
+	struct nft_handle h;
 	bool dump = false;
-	struct nft_handle h = {
-		.family	= family,
-	};
 	FILE *file = NULL;
 	int ret, c;
 
@@ -233,16 +231,13 @@ xtables_save_main(int family, int argc, char *argv[],
 		return 1;
 	}
 
-	if (nft_init(&h, tables) < 0) {
+	if (nft_init(&h, family, tables) < 0) {
 		fprintf(stderr, "%s/%s Failed to initialize nft: %s\n",
 				xtables_globals.program_name,
 				xtables_globals.program_version,
 				strerror(errno));
 		exit(EXIT_FAILURE);
 	}
-	h.ops = nft_family_ops_lookup(h.family);
-	if (!h.ops)
-		xtables_error(PARAMETER_PROBLEM, "Unknown family");
 
 	ret = do_output(&h, tablename, &d);
 	nft_fini(&h);