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Wed, 09 Jul 2025 07:15:25 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHHJ9guzGEu6LsDd3s8dzvUQCpYjaNvz1LiX+hCFrH/tfoZaINYGrF+3wLoBFP8RviUuzjVig== X-Received: by 2002:a05:6000:2313:b0:3a4:fbd9:58e6 with SMTP id ffacd0b85a97d-3b5e4530f28mr2348225f8f.50.1752070525032; Wed, 09 Jul 2025 07:15:25 -0700 (PDT) Received: from debian ([2001:4649:f075:0:a45e:6b9:73fc:f9aa]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454d5050794sm24762395e9.13.2025.07.09.07.15.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jul 2025 07:15:24 -0700 (PDT) Date: Wed, 9 Jul 2025 16:15:21 +0200 From: Guillaume Nault To: Gary Guo Cc: davem@davemloft.net, idosch@idosch.org, kuba@kernel.org, ling@moedove.com, netdev@vger.kernel.org, noc@moedove.com, pabeni@redhat.com, Gary Guo Subject: Re: [BUG] net: gre: IPv6 link-local multicast is silently dropped (Regression) Message-ID: References: <20250706154030.3010068-1-gary@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250706154030.3010068-1-gary@kernel.org> On Sun, Jul 06, 2025 at 04:40:30PM +0100, Gary Guo wrote: > On Wed, 2 Jul 2025 12:12:22 +0200, Guillaume Nault wrote: > > Aiden, can you confirm that the following patch fixes the issue on your > > side? > > Not Aiden, but I get hit with the same regression after updating kernel on my > router from v6.12.28 to v6.12.35 today. Symptom for me is bird complaining > about "Socket error: Network is unreachable", and strace shows that it's sending > packets to ff02::1:6 and get hit with ENETUNREACH. > > I can confirm that applying this patch on top of v6.12.35 fixes the issue for me. > I also took a look of the code, not a net expert, but this approach does look > like a proper fix to me. Thanks Gary, it's good to have such feedback. I'm going to formally send the patch soon. > Reviewed-by: Gary Guo > Tested-by: Gary Guo > > > > > ---- >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 >