[PATCH 1/2 net-next v3] ipv6: use the right ifindex when replying to icmpv6 from localhost

[PATCH 1/2 net-next v3] ipv6: use the right ifindex when replying to icmpv6 from localhost

[Fernando Fernandez Mancera]

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 <fmancera@suse.de>
---
v2: no changes
v3: use ipv6_addr_loopback() as it is more efficient
---
 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 c72270582d9c..1a25ecb92695 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -966,7 +966,9 @@ 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_loopback(&fl6.daddr) ?
+			 skb->dev->ifindex :
+			 icmp6_iif(skb);
 	fl6.fl6_icmp_type = type;
 	fl6.flowi6_mark = mark;
 	fl6.flowi6_uid = sock_net_uid(net, NULL);
-- 
2.52.0

[PATCH 2/2 net-next v3] selftests: net: add ipv6 ping to local address from localhost

[Fernando Fernandez Mancera]

Test ipv6 pinging to local configured address and linklocal address from
localhost with -I ::1.

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v2: shellcheck fixes, added VRF based tests and simplified linklocal
address parsing
v3: extend existing test in fcnal-test.sh instead of creating a new one,
notice some shellcheck warnings but I prefer to follow the style of the
existing code. It can be fixed if it is a requirement.
---
 tools/testing/selftests/net/fcnal-test.sh | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/selftests/net/fcnal-test.sh b/tools/testing/selftests/net/fcnal-test.sh
index 844a580ae74e..890c3f8e51bb 100755
--- a/tools/testing/selftests/net/fcnal-test.sh
+++ b/tools/testing/selftests/net/fcnal-test.sh
@@ -2327,6 +2327,13 @@ ipv6_ping_novrf()
 		log_test_addr ${a} $? 2 "ping local, device bind"
 	done
 
+	for a in ${NSA_LO_IP6} ${NSA_LINKIP6}%${NSA_DEV} ${NSA_IP6}
+	do
+		log_start
+		run_cmd ${ping6} -c1 -w1 -I ::1 ${a}
+		log_test_addr ${a} $? 0 "ping local, from localhost"
+	done
+
 	#
 	# ip rule blocks address
 	#
-- 
2.52.0

Re: [PATCH 2/2 net-next v3] selftests: net: add ipv6 ping to local address from localhost

[David Ahern]

On 1/21/26 12:44 PM, Fernando Fernandez Mancera wrote:
> Test ipv6 pinging to local configured address and linklocal address from
> localhost with -I ::1.
> 
> Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
> ---
> v2: shellcheck fixes, added VRF based tests and simplified linklocal
> address parsing
> v3: extend existing test in fcnal-test.sh instead of creating a new one,
> notice some shellcheck warnings but I prefer to follow the style of the
> existing code. It can be fixed if it is a requirement.
> ---
>  tools/testing/selftests/net/fcnal-test.sh | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/fcnal-test.sh b/tools/testing/selftests/net/fcnal-test.sh
> index 844a580ae74e..890c3f8e51bb 100755
> --- a/tools/testing/selftests/net/fcnal-test.sh
> +++ b/tools/testing/selftests/net/fcnal-test.sh
> @@ -2327,6 +2327,13 @@ ipv6_ping_novrf()
>  		log_test_addr ${a} $? 2 "ping local, device bind"
>  	done
>  
> +	for a in ${NSA_LO_IP6} ${NSA_LINKIP6}%${NSA_DEV} ${NSA_IP6}
> +	do
> +		log_start
> +		run_cmd ${ping6} -c1 -w1 -I ::1 ${a}
> +		log_test_addr ${a} $? 0 "ping local, from localhost"
> +	done
> +
>  	#
>  	# ip rule blocks address
>  	#

Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH 1/2 net-next v3] ipv6: use the right ifindex when replying to icmpv6 from localhost

[David Ahern]

On 1/21/26 12:44 PM, 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 <fmancera@suse.de>
> ---
> v2: no changes
> v3: use ipv6_addr_loopback() as it is more efficient
> ---
>  net/ipv6/icmp.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 


Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH 1/2 net-next v3] ipv6: use the right ifindex when replying to icmpv6 from localhost

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 21 Jan 2026 20:44:08 +0100 you 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
> 
> [...]

Here is the summary with links:
  - [1/2,net-next,v3] ipv6: use the right ifindex when replying to icmpv6 from localhost
    https://git.kernel.org/netdev/net/c/03cbcdf93866
  - [2/2,net-next,v3] selftests: net: add ipv6 ping to local address from localhost
    https://git.kernel.org/netdev/net/c/1742272bd3fa

You are awesome, thank you!
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