netfilter: nfnetlink_hook: missing chain family

The family is relevant for pseudo-families like NFPROTO_INET
otherwise the user needs to rely on the hook function name to
differentiate it from NFPROTO_IPV4 and NFPROTO_IPV6 names.

Add nfnl_hook_chain_desc_attributes instead of using the existing
NFTA_CHAIN_* attributes, since these do not provide a family number.

Fixes: e2cf17d3 ("netfilter: add new hook nfnl subsystem")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nfnetlink_hook.h

@@ -43,6 +43,15 @@ enum nfnl_hook_chain_info_attributes {
 };
 #define NFNLA_HOOK_INFO_MAX (__NFNLA_HOOK_INFO_MAX - 1)
 
+enum nfnl_hook_chain_desc_attributes {
+	NFNLA_CHAIN_UNSPEC,
+	NFNLA_CHAIN_TABLE,
+	NFNLA_CHAIN_FAMILY,
+	NFNLA_CHAIN_NAME,
+	__NFNLA_CHAIN_MAX,
+};
+#define NFNLA_CHAIN_MAX (__NFNLA_CHAIN_MAX - 1)
+
 /**
  * enum nfnl_hook_chaintype - chain type
  *

net/netfilter/nfnetlink_hook.c

@@ -89,11 +89,15 @@ static int nfnl_hook_put_nft_chain_info(struct sk_buff *nlskb,
 	if (!nest2)
 		goto cancel_nest;
 
-	ret = nla_put_string(nlskb, NFTA_CHAIN_TABLE, chain->table->name);
+	ret = nla_put_string(nlskb, NFNLA_CHAIN_TABLE, chain->table->name);
 	if (ret)
 		goto cancel_nest;
 
-	ret = nla_put_string(nlskb, NFTA_CHAIN_NAME, chain->name);
+	ret = nla_put_string(nlskb, NFNLA_CHAIN_NAME, chain->name);
+	if (ret)
+		goto cancel_nest;
+
+	ret = nla_put_u8(nlskb, NFNLA_CHAIN_FAMILY, chain->table->family);
 	if (ret)
 		goto cancel_nest;