nft: Optimize flushing all chains of a table

Leverage nftables' support for flushing all chains of a table by
omitting NFTNL_RULE_CHAIN attribute in NFT_MSG_DELRULE payload.

The only caveat is with verbose output, as that still requires to have a
list of (existing) chains to iterate over. Apart from that, implementing
this shortcut is pretty straightforward: Don't retrieve a chain list and
just call __nft_rule_flush() directly which doesn't set above attribute
if chain name pointer is NULL.

A bigger deal is keeping rule cache consistent: Instead of just clearing
rule list for each flushed chain, flush_rule_cache() is updated to
iterate over all cached chains of the given table, clearing their rule
lists if not called for a specific chain.

While being at it, sort local variable declarations in nft_rule_flush()
from longest to shortest and drop the loop-local 'chain_name' variable
(but instead use 'chain' function parameter which is not used at that
point).

Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 19 insertions, 3 deletions

diff --git a/iptables/nft-cache.c b/iptables/nft-cache.c
index 64dcda57..c55970d0 100644
--- a/iptables/nft-cache.c
+++ b/iptables/nft-cache.c
@@ -384,7 +384,7 @@ static void __nft_flush_cache(struct nft_handle *h)
 	}
 }
 
-static int __flush_rule_cache(struct nftnl_rule *r, void *data)
+static int ____flush_rule_cache(struct nftnl_rule *r, void *data)
 {
 	nftnl_rule_list_del(r);
 	nftnl_rule_free(r);
@@ -392,9 +392,25 @@ static int __flush_rule_cache(struct nftnl_rule *r, void *data)
 	return 0;
 }
 
-void flush_rule_cache(struct nftnl_chain *c)
+static int __flush_rule_cache(struct nftnl_chain *c, void *data)
 {
-	nftnl_rule_foreach(c, __flush_rule_cache, NULL);
+	return nftnl_rule_foreach(c, ____flush_rule_cache, NULL);
+}
+
+int flush_rule_cache(struct nft_handle *h, const char *table,
+		     struct nftnl_chain *c)
+{
+	const struct builtin_table *t;
+
+	if (c)
+		return __flush_rule_cache(c, NULL);
+
+	t = nft_table_builtin_find(h, table);
+	if (!t || !h->cache->table[t->type].chains)
+		return 0;
+
+	return nftnl_chain_list_foreach(h->cache->table[t->type].chains,
+					__flush_rule_cache, NULL);
 }
 
 static int __flush_chain_cache(struct nftnl_chain *c, void *data)