expr: call expr->ops->snprintf only if defined

The notrack expression comes with no ->ops->snprintf, so skip this from
nftnl_expr_snprintf() if not set.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/expr.c b/src/expr.c
index 2779b3c..8d5c562 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -281,6 +281,9 @@ int nftnl_expr_snprintf(char *buf, size_t size, const struct nftnl_expr *expr,
 	int ret;
 	unsigned int offset = 0, len = size;
 
+	if (!expr->ops->snprintf)
+		return 0;
+
 	ret = expr->ops->snprintf(buf+offset, len, type, flags, expr);
 	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);