netdev - Re: [BUG] net: gre: IPv6 link-local multicast is silently dropped (Regression)

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Message-ID: <aGUGBjVZZPBWcRlA@debian>
Date: Wed, 2 Jul 2025 12:12:22 +0200
From: Guillaume Nault <gnault@...hat.com>
To: Ido Schimmel <idosch@...sch.org>, Aiden Yang <ling@...dove.com>
Cc: netdev@...r.kernel.org, kuba@...nel.org, pabeni@...hat.com,
	davem@...emloft.net, MoeDove NOC <noc@...dove.com>
Subject: Re: [BUG] net: gre: IPv6 link-local multicast is silently dropped
 (Regression)

On Tue, Jul 01, 2025 at 01:13:22PM +0300, Ido Schimmel wrote:
> Makes sense. So you will submit it to net and extend gre_ipv6_lladdr.sh
> to test for the presence of a multicast route?

Yes. I'd just like to have a confirmation from Aiden first.

Aiden, can you confirm that the following patch fixes the issue on your
side?

---- >8 ----

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index ba2ec7c870cc..870a0bd6c2ba 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3525,11 +3525,9 @@ static void addrconf_gre_config(struct net_device *dev)
 
 	ASSERT_RTNL();
 
-	idev = ipv6_find_idev(dev);
-	if (IS_ERR(idev)) {
-		pr_debug("%s: add_dev failed\n", __func__);
+	idev = addrconf_add_dev(dev);
+	if (IS_ERR(idev))
 		return;
-	}
 
 	/* Generate the IPv6 link-local address using addrconf_addr_gen(),
 	 * unless we have an IPv4 GRE device not bound to an IP address and
@@ -3543,9 +3541,6 @@ static void addrconf_gre_config(struct net_device *dev)
 	}
 
 	add_v4_addrs(idev);
-
-	if (dev->flags & IFF_POINTOPOINT)
-		addrconf_add_mroute(dev);
 }
 #endif