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[iptables] xtables-restore: Fix flushing referenced custom chains

Message ID 20180906142645.1869-1-phil@nwl.cc
State Changes Requested
Delegated to: Pablo Neira
Headers show
Series [iptables] xtables-restore: Fix flushing referenced custom chains | expand

Commit Message

Phil Sutter Sept. 6, 2018, 2:26 p.m. UTC
The logic to replicate 'iptables-restore --noflush' behaviour of
flushing custom chains if listed in the dump was broken for chains being
referenced. A minimal dump reproducing the issue is:

| *filter
| :foobar - [0:0]
| -I INPUT -j foobar
| -A foobar -j ACCEPT
| COMMIT

With --noflush, this can be restored just once in iptables-nft-restore.
Consecutive attempts return an error since xtables tries to delete the
referenced chain and recreate it instead of performing a real flush.

Fix this by really flushing the custom chain in 'chain_user_flush'
callback and calling 'chain_user_add' callback only if 'noflush' is not
set.

Fixes: df3d92bec6007 ("xtables-compat-restore: flush user-defined chains with -n")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 iptables/nft.c             | 10 ++--------
 iptables/xtables-restore.c |  3 ++-
 2 files changed, 4 insertions(+), 9 deletions(-)

Comments

Florian Westphal Sept. 10, 2018, 1:45 p.m. UTC | #1
Phil Sutter <phil@nwl.cc> wrote:
> The logic to replicate 'iptables-restore --noflush' behaviour of
> flushing custom chains if listed in the dump was broken for chains being
> referenced. A minimal dump reproducing the issue is:
 
Applied.
diff mbox series

Patch

diff --git a/iptables/nft.c b/iptables/nft.c
index 7123060b34ef5..77ad38bea5211 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -1491,7 +1491,6 @@  static int __nft_chain_user_flush(struct nftnl_chain *c, void *data)
 	struct nft_handle *h = d->handle;
 	const char *table = d->table;
 	const char *chain = d->chain;
-	int ret;
 
 	if (strcmp(table, table_name) != 0)
 		return 0;
@@ -1499,13 +1498,8 @@  static int __nft_chain_user_flush(struct nftnl_chain *c, void *data)
 	if (strcmp(chain, chain_name) != 0)
 		return 0;
 
-	if (!nftnl_chain_is_set(c, NFTNL_CHAIN_HOOKNUM)) {
-		ret = batch_chain_add(h, NFT_COMPAT_CHAIN_USER_FLUSH, c);
-		if (ret < 0)
-			return ret;
-
-		nftnl_chain_list_del(c);
-	}
+	if (!nftnl_chain_is_set(c, NFTNL_CHAIN_HOOKNUM))
+		__nft_rule_flush(h, table, chain);
 
 	return 0;
 }
diff --git a/iptables/xtables-restore.c b/iptables/xtables-restore.c
index 3274543677329..5e22e74bb190f 100644
--- a/iptables/xtables-restore.c
+++ b/iptables/xtables-restore.c
@@ -246,7 +246,8 @@  void xtables_restore_parse(struct nft_handle *h,
 				ret = 1;
 
 			} else {
-				if (cb->chain_user_add &&
+				if (noflush == 0 &&
+				    cb->chain_user_add &&
 				    cb->chain_user_add(h, chain,
 						       curtable->name) < 0) {
 					if (errno == EEXIST)