[PATCH nft] src: netlink: fix crash when ops doesn't support udata

[Florian Westphal <fw@strlen.de>]

Whenever a new version adds udata support to an expression, then old
versions of nft will crash when trying to list such a ruleset generated
by a more recent version of nftables.

Fix this by falling back to 'type' format.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/netlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/netlink.c b/src/netlink.c
index 25ee3419772b..5825a68d03bc 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -913,7 +913,7 @@ static struct expr *set_make_key(const struct nftnl_udata *attr)
 
 	etype = nftnl_udata_get_u32(ud[NFTNL_UDATA_SET_TYPEOF_EXPR]);
 	ops = expr_ops_by_type_u32(etype);
-	if (!ops)
+	if (!ops || !ops->parse_udata)
 		return NULL;
 
 	expr = ops->parse_udata(ud[NFTNL_UDATA_SET_TYPEOF_DATA]);
-- 
2.49.0