[PATCH nft] rule: ensure cache consistency

[Pablo Neira Ayuso <pablo@netfilter.org>]

Check for generation ID after the cache is populated. In case of
interference, release the inconsistent cache and retry.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/rule.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/rule.c b/src/rule.c
index 1e081c8fe862..cb5bd2162c02 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -244,8 +244,6 @@ static bool cache_is_updated(struct nft_cache *cache, uint16_t genid)
 
 int cache_update(struct nft_ctx *nft, enum cmd_ops cmd, struct list_head *msgs)
 {
-	uint16_t genid;
-	int ret;
 	struct netlink_ctx ctx = {
 		.list		= LIST_HEAD_INIT(ctx.list),
 		.nft		= nft,
@@ -253,7 +251,8 @@ int cache_update(struct nft_ctx *nft, enum cmd_ops cmd, struct list_head *msgs)
 		.nft		= nft,
 	};
 	struct nft_cache *cache = &nft->cache;
-
+	uint16_t genid, genid_stop;
+	int ret;
 replay:
 	ctx.seqnum = cache->seqnum++;
 	genid = mnl_genid_get(&ctx);
@@ -273,6 +272,13 @@ replay:
 		}
 		return -1;
 	}
+
+	genid_stop = mnl_genid_get(&ctx);
+	if (genid != genid_stop) {
+		cache_release(cache);
+		goto replay;
+	}
+
 	cache->genid = genid;
 	cache->cmd = cmd;
 	return 0;
-- 
2.11.0