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Thu, 8 Jan 2026 11:27:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id zdDNM5+UX2mKEAAAD6G6ig (envelope-from ); Thu, 08 Jan 2026 11:27:27 +0000 Message-ID: Date: Thu, 8 Jan 2026 12:27:23 +0100 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: Brian Haley , 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> <099019ee-05f4-457b-a82b-0fac55d8dd48@gmail.com> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: <099019ee-05f4-457b-a82b-0fac55d8dd48@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Score: -2.80 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com,vger.kernel.org]; TAGGED_RCPT(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCPT_COUNT_SEVEN(0.00)[9]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid,suse.de:email] X-Spam-Level: X-Spam-Flag: NO On 1/7/26 6:05 PM, Brian Haley wrote: > 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. > Yes, I think you are right. Thanks! Fernando. > -Brian >