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 and clears 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).
Note that this change by itself only marginally improves 'iptables-nft
-F' performance for a ruleset with many chains because
nft_xt_builtin_init() still fetches all chains from kernel. A follow-up
patch takes care of that, finally establishing O(1) complexity.
Signed-off-by: Phil Sutter <phil@xxxxxx>
---
iptables/nft.c | 54 ++++++++++++++++++++++++++++++++++----------------
1 file changed, 37 insertions(+), 17 deletions(-)
diff --git a/iptables/nft.c b/iptables/nft.c
index 294cb306700d0..5eb129461dab2 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -836,7 +836,7 @@ int nft_init(struct nft_handle *h, const struct builtin_table *t)
return 0;
}
-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);
@@ -844,9 +844,25 @@ static int __flush_rule_cache(struct nftnl_rule *r, void *data)
return 0;
}
-static 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);
+}
+
+static 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)
@@ -1860,7 +1876,7 @@ __nft_rule_flush(struct nft_handle *h, const char *table,
struct obj_update *obj;
struct nftnl_rule *r;
- if (verbose)
+ if (verbose && chain)
fprintf(stdout, "Flushing chain `%s'\n", chain);
r = nftnl_rule_alloc();
@@ -1868,7 +1884,8 @@ __nft_rule_flush(struct nft_handle *h, const char *table,
return;
nftnl_rule_set_str(r, NFTNL_RULE_TABLE, table);
- nftnl_rule_set_str(r, NFTNL_RULE_CHAIN, chain);
+ if (chain)
+ nftnl_rule_set_str(r, NFTNL_RULE_CHAIN, chain);
obj = batch_rule_add(h, NFT_COMPAT_RULE_FLUSH, r);
if (!obj) {
@@ -1882,19 +1899,21 @@ __nft_rule_flush(struct nft_handle *h, const char *table,
int nft_rule_flush(struct nft_handle *h, const char *chain, const char *table,
bool verbose)
{
- int ret = 0;
- struct nftnl_chain_list *list;
struct nftnl_chain_list_iter *iter;
- struct nftnl_chain *c;
+ struct nftnl_chain_list *list;
+ struct nftnl_chain *c = NULL;
+ int ret = 0;
nft_xt_builtin_init(h, table);
nft_fn = nft_rule_flush;
- list = nft_chain_list_get(h, table, chain);
- if (list == NULL) {
- ret = 1;
- goto err;
+ if (chain || verbose) {
+ list = nft_chain_list_get(h, table, chain);
+ if (list == NULL) {
+ ret = 1;
+ goto err;
+ }
}
if (chain) {
@@ -1903,9 +1922,11 @@ int nft_rule_flush(struct nft_handle *h, const char *chain, const char *table,
errno = ENOENT;
return 0;
}
+ }
+ if (chain || !verbose) {
__nft_rule_flush(h, table, chain, verbose, false);
- flush_rule_cache(c);
+ flush_rule_cache(h, table, c);
return 1;
}
@@ -1917,11 +1938,10 @@ int nft_rule_flush(struct nft_handle *h, const char *chain, const char *table,
c = nftnl_chain_list_iter_next(iter);
while (c != NULL) {
- const char *chain_name =
- nftnl_chain_get_str(c, NFTNL_CHAIN_NAME);
+ chain = nftnl_chain_get_str(c, NFTNL_CHAIN_NAME);
- __nft_rule_flush(h, table, chain_name, verbose, false);
- flush_rule_cache(c);
+ __nft_rule_flush(h, table, chain, verbose, false);
+ flush_rule_cache(h, table, c);
c = nftnl_chain_list_iter_next(iter);
}
nftnl_chain_list_iter_destroy(iter);
--
2.23.0
