netdev - [PATCH RFC nf-next 5/9] netfilter: reduce allowed hook count to 32

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Date:   Thu, 14 Oct 2021 14:10:42 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netfilter-devel@...r.kernel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, me@...que.spb.ru,
        Florian Westphal <fw@...len.de>
Subject: [PATCH RFC nf-next 5/9] netfilter: reduce allowed hook count to 32

1k is huge and will mean we'd need to support tailcalls in the
nf_hook bpf converter.

We need about 5 insns per hook at this time, ignoring prologue/epilogue.

32 should be fine, typically even extreme cases need about 8 hooks per
hook location.

Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 3fd268afc13e..f4359179eba9 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -42,7 +42,7 @@ EXPORT_SYMBOL(nf_hooks_needed);
 static DEFINE_MUTEX(nf_hook_mutex);
 
 /* max hooks per family/hooknum */
-#define MAX_HOOK_COUNT		1024
+#define MAX_HOOK_COUNT		32
 
 #define nf_entry_dereference(e) \
 	rcu_dereference_protected(e, lockdep_is_held(&nf_hook_mutex))
-- 
2.32.0