[iptables PATCH] extensions: libipt_icmp: Fix translation of type 'any'

[iptables PATCH] extensions: libipt_icmp: Fix translation of type 'any'

[Phil Sutter]

By itself, '-m icmp --icmp-type any' is a noop, it matches any icmp
types. Yet nft_ipv4_xlate() does not emit an 'ip protocol' match if
there's an extension with same name present in the rule. Luckily, legacy
iptables demands icmp match to be prepended by '-p icmp', so we can
assume this is present and just emit the 'ip protocol' match from icmp
xlate callback.

Fixes: aa158ca0fda65 ("extensions: libipt_icmp: Add translation to nft")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 extensions/libipt_icmp.c      | 5 +++++
 extensions/libipt_icmp.txlate | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/extensions/libipt_icmp.c b/extensions/libipt_icmp.c
index e76257c54708c..e5e236613f39f 100644
--- a/extensions/libipt_icmp.c
+++ b/extensions/libipt_icmp.c
@@ -256,6 +256,11 @@ static int icmp_xlate(struct xt_xlate *xl,
 		if (!type_xlate_print(xl, info->type, info->code[0],
 				      info->code[1]))
 			return 0;
+	} else {
+		/* '-m icmp --icmp-type any' is a noop by itself,
+		 * but it eats a (mandatory) previous '-p icmp' so
+		 * emit it here */
+		xt_xlate_add(xl, "ip protocol icmp");
 	}
 	return 1;
 }
diff --git a/extensions/libipt_icmp.txlate b/extensions/libipt_icmp.txlate
index 434f8cc4eb1ae..a2aec8e26df75 100644
--- a/extensions/libipt_icmp.txlate
+++ b/extensions/libipt_icmp.txlate
@@ -6,3 +6,6 @@ nft add rule ip filter INPUT icmp type destination-unreachable counter accept
 
 iptables-translate -t filter -A INPUT -m icmp ! --icmp-type 3 -j ACCEPT
 nft add rule ip filter INPUT icmp type != destination-unreachable counter accept
+
+iptables-translate -t filter -A INPUT -m icmp --icmp-type any -j ACCEPT
+nft add rule ip filter INPUT ip protocol icmp counter accept
-- 
2.28.0

Re: [iptables PATCH] extensions: libipt_icmp: Fix translation of type 'any'

[Florian Westphal]

Phil Sutter <phil@nwl.cc> wrote:
> By itself, '-m icmp --icmp-type any' is a noop, it matches any icmp
> types. Yet nft_ipv4_xlate() does not emit an 'ip protocol' match if
> there's an extension with same name present in the rule. Luckily, legacy
> iptables demands icmp match to be prepended by '-p icmp', so we can
> assume this is present and just emit the 'ip protocol' match from icmp
> xlate callback.

Reviewed-by: Florian Westphal <fw@strlen.de>