https://git.netfilter.org/nftables/commit/?id=93560d0117639c8685fc287128ab06dec9950fbd
https://github.com/firewalld/firewalld/issues/1366
https://lore.kernel.org/netfilter-devel/Zp7FqL_YK3p_dQ8B@egarver-mac/

From 93560d0117639c8685fc287128ab06dec9950fbd Mon Sep 17 00:00:00 2001
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Wed, 24 Jul 2024 09:38:33 +0200
Subject: Revert "cache: recycle existing cache with incremental updates"

This reverts commit e791dbe109b6dd891a63a4236df5dc29d7a4b863.

Eric Garver reported two issues:

- index with rule breaks, because NFT_CACHE_REFRESH is missing.
- simple set updates.

Moreover, the current process could populate the cache with objects for
listing commands (no generation ID is bumped), while another process
could update the ruleset. Leading to a inconsistent cache due to the
genid + 1 check.

This optimization needs more work and more tests for -i/--interactive,
revert it.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
--- a/src/cache.c
+++ b/src/cache.c
@@ -1184,21 +1184,9 @@ static bool nft_cache_needs_refresh(struct nft_cache *cache, unsigned int flags)
 	       (flags & NFT_CACHE_REFRESH);
 }
 
-static bool nft_cache_is_updated(struct nft_cache *cache, unsigned int flags,
-				 uint16_t genid)
+static bool nft_cache_is_updated(struct nft_cache *cache, uint16_t genid)
 {
-	if (!genid)
-		return false;
-
-	if (genid == cache->genid)
-		return true;
-
-	if (genid == cache->genid + 1) {
-		cache->genid++;
-		return true;
-	}
-
-	return false;
+	return genid && genid == cache->genid;
 }
 
 bool nft_cache_needs_update(struct nft_cache *cache)
@@ -1223,7 +1211,7 @@ replay:
 	genid = mnl_genid_get(&ctx);
 	if (!nft_cache_needs_refresh(cache, flags) &&
 	    nft_cache_is_complete(cache, flags) &&
-	    nft_cache_is_updated(cache, flags, genid))
+	    nft_cache_is_updated(cache, genid))
 		return 0;
 
 	if (cache->genid)
-- 
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