From 82ccfb488eeac5507471099b9b4e6d136cc06e3b Mon Sep 17 00:00:00 2001
From: Jacek Tomasiak <jacek.tomasiak@gmail.com>
Date: Mon, 19 Jun 2023 13:46:36 +0200
Subject: iptables: Fix handling of non-existent chains

Since 694612adf87 the "compatibility" check considers non-existent
chains as "incompatible". This broke some scripts which used calls
like `iptables -L CHAIN404` to test for chain existence and expect
"No chain/target/match by that name." in the output.

This patch changes the logic of `nft_is_table_compatible()` to
report non-existent chains as "compatible" which restores the old
behavior.

Fixes: 694612adf87 ("nft: Fix selective chain compatibility checks")
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1648
Signed-off-by: Jacek Tomasiak <jtomasiak@arista.com>
Signed-off-by: Jacek Tomasiak <jacek.tomasiak@gmail.com>
Signed-off-by: Phil Sutter <phil@nwl.cc>

Conflict: NA
Reference: https://git.netfilter.org/iptables/commit?id=82ccfb488eeac5507471099b9b4e6d136cc06e3b

---
 iptables/nft.c                                              | 2 +-
 iptables/tests/shell/testcases/iptables/0004-return-codes_0 | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/iptables/nft.c b/iptables/nft.c
index 1cb104e7..020553a4 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -3860,7 +3860,7 @@ bool nft_is_table_compatible(struct nft_handle *h,
 	if (chain) {
 		struct nft_chain *c = nft_chain_find(h, table, chain);
 
-		return c && !nft_is_chain_compatible(c, h);
+		return !c || !nft_is_chain_compatible(c, h);
 	}
 
 	return !nft_chain_foreach(h, table, nft_is_chain_compatible, h);
diff --git a/iptables/tests/shell/testcases/iptables/0004-return-codes_0 b/iptables/tests/shell/testcases/iptables/0004-return-codes_0
index 33c5f1f3..234f3040 100755
--- a/iptables/tests/shell/testcases/iptables/0004-return-codes_0
+++ b/iptables/tests/shell/testcases/iptables/0004-return-codes_0
@@ -58,6 +58,7 @@ cmd 1 "$ENOENT" -Z bar
 cmd 0 -E foo bar
 cmd 1 "$EEXIST_F" -E foo bar
 cmd 1 "$ENOENT" -E foo bar2
+cmd 1 "$ENOENT" -L foo
 cmd 0 -N foo2
 cmd 1 "$EEXIST_F" -E foo2 bar
 
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