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([2601:18f:901:12c::100d]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c37f51cdcesm405934685a.26.2026.01.07.09.05.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Jan 2026 09:05:16 -0800 (PST) Message-ID: <099019ee-05f4-457b-a82b-0fac55d8dd48@gmail.com> Date: Wed, 7 Jan 2026 12:05:15 -0500 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2 net-next v2] ipv6: use the right ifindex when replying to icmpv6 from localhost To: Fernando Fernandez Mancera , netdev@vger.kernel.org Cc: davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, shuah@kernel.org, linux-kselftest@vger.kernel.org References: <20260107153841.5030-1-fmancera@suse.de> Content-Language: en-US From: Brian Haley In-Reply-To: <20260107153841.5030-1-fmancera@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Fernando, On 1/7/26 10:38 AM, Fernando Fernandez Mancera wrote: > When replying to a ICMPv6 echo request that comes from localhost address > the right output ifindex is 1 (lo) and not rt6i_idev dev index. Use the > skb device ifindex instead. This fixes pinging to a local address from > localhost source address. > > $ ping6 -I ::1 2001:1:1::2 -c 3 > PING 2001:1:1::2 (2001:1:1::2) from ::1 : 56 data bytes > 64 bytes from 2001:1:1::2: icmp_seq=1 ttl=64 time=0.037 ms > 64 bytes from 2001:1:1::2: icmp_seq=2 ttl=64 time=0.069 ms > 64 bytes from 2001:1:1::2: icmp_seq=3 ttl=64 time=0.122 ms > > 2001:1:1::2 ping statistics > 3 packets transmitted, 3 received, 0% packet loss, time 2032ms > rtt min/avg/max/mdev = 0.037/0.076/0.122/0.035 ms > > Fixes: 1b70d792cf67 ("ipv6: Use rt6i_idev index for echo replies to a local address") > Signed-off-by: Fernando Fernandez Mancera > --- > v2: no changes > --- > net/ipv6/icmp.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c > index 5d2f90babaa5..5de254043133 100644 > --- a/net/ipv6/icmp.c > +++ b/net/ipv6/icmp.c > @@ -965,7 +965,9 @@ static enum skb_drop_reason icmpv6_echo_reply(struct sk_buff *skb) > fl6.daddr = ipv6_hdr(skb)->saddr; > if (saddr) > fl6.saddr = *saddr; > - fl6.flowi6_oif = icmp6_iif(skb); > + fl6.flowi6_oif = ipv6_addr_type(&fl6.daddr) & IPV6_ADDR_LOOPBACK ? > + skb->dev->ifindex : > + icmp6_iif(skb); > fl6.fl6_icmp_type = type; > fl6.flowi6_mark = mark; > fl6.flowi6_uid = sock_net_uid(net, NULL); Using ipv6_addr_loopback(&fl6.daddr) might be more efficient as it does a direct comparison of the address. -Brian