NetBSD Problem Report #60323

From df4nx@gmx.net  Fri Jun 12 07:36:37 2026
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Date: Fri, 12 Jun 2026 09:28:12 +0200 (CEST)
From: df4nx@gmx.net
Reply-To: sirius.a@gmx.net
To: gnats-bugs@NetBSD.org
Subject: IPv6 NDP issue since upgrade to 11.0_RC4
X-Send-Pr-Version: 3.95
X-From4GNATS: "df4nx@gmx.net via gnats" <gnats-admin@NetBSD.org>

>Number:         60323
>Category:       kern
>Synopsis:       Neighbor Discovery Protocol on 11.0_RC4
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jun 12 07:40:00 +0000 2026
>Last-Modified:  Thu Jun 18 12:30:02 +0000 2026
>Originator:     =09
>Release:        NetBSD 11.0_RC4
>Organization:
	home user
>Environment:
=09
=09
System: NetBSD at166.local 11.0_RC4 NetBSD 11.0_RC4 (GENERIC) #0: Tue May =
12 04:23:51 UTC 2026 mkrepro@mkrepro.NetBSD.org:/usr/src/sys/arch/amd64/co=
mpile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
	The host runs IPv6 with a static assigned IPv6 address. Trying
	to ping6 this address from a Linux host on the LAN failes.
	ping6 from a other NetBSD or OpenBSD host on the same LAN works.
	Ping6 and connect from the internet to the static IPv6 address
	works. `tcpdump icmp6` on the Linux host on the same LAN shows
	outgoing NDP Packets, but no incoming answer.
	The problem did not occur on NetBSD 10.1.
	For test purposes I have switched off NPF, but this did not fix
	the issue.
	It looks like a problem with the Neighbor Discovery Protocol on
	11.0_RC4.
	To double check I have two other hosts without static IPv6
	address. One 10.1, the other 11.0_RC4. The 10.1 host can be
	pinged, the 11.0_RC4 not. I used the dynnamic assigned IPv6
	address. None of these two systems run NPF.
	See also this blogpost:
	https://sirius-a.neocities.org/#v6issue
>How-To-Repeat:
	I used a installed Debian 13.5, a Debian live system (13.5 XFCE)
	and a Fedora Live 44-1.7 to test on the LAN.
	Ping6 and connect from the internet with:
	https://www.ipv6tech.ch/?pingv4v6
	https://www.ipv6tech.ch/?tcpportscan
	Tests with OpenBSD are done with the FuguIta live system:
	https://fuguita.org/
>Fix:
	Work around: Running the following command on the Linux host
	(Debian 13.5) works:
	ip -6 neigh replace XXXX:XXXX:XXXX:XXXX::1 lladdr yy:yy:yy:yy:yy:yy dev e=
no1
	with XXXX is my /64 prefix and yy is my MAC.

>Audit-Trail:
From: Marcin Gondek <drixter@e-utp.net>
To: "gnats-bugs@netbsd.org" <gnats-bugs@netbsd.org>,
	"kern-bug-people@netbsd.org" <kern-bug-people@netbsd.org>,
	"gnats-admin@netbsd.org" <gnats-admin@netbsd.org>, "netbsd-bugs@netbsd.org"
	<netbsd-bugs@netbsd.org>
Cc: 
Subject: RE: kern/60323: IPv6 NDP issue since upgrade to 11.0_RC4
Date: Fri, 12 Jun 2026 07:52:24 +0000

 Hi

 I'm not using any firewall on Linux or NetBSD, it's done by HW firewall.

 I don't see such case, just FYI.

 Linux: 2001:67c:21ec:1000::c/64
 NetBSD: 2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3/64

 Linux:

 inferno:~ # uname -a
 Linux inferno.e-utp.net 7.0.9-1-default #1 SMP PREEMPT_DYNAMIC Sun May 17 1=
 9:37:08 UTC 2026 (9b5964b) aarch64 aarch64 aarch64 GNU/Linux
 inferno:~ # ip -6 neigh show
 fe80::e223:ffff:fe9f:26f dev end0 lladdr e0:23:ff:9f:02:6f router REACHABLE
 2001:67c:21ec::53 dev end0 lladdr b4:96:91:29:ce:c8 STALE
 2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3 dev end0 lladdr b4:96:91:29:ce:c8 ST=
 ALE
 fe80::b696:91ff:fe29:cec8 dev end0 lladdr b4:96:91:29:ce:c8 STALE
 fe80::e223:ffff:fe9f:270 dev end0 FAILED
 inferno:~ # ping -c 4 devil.e-utp.net
 PING devil.e-utp.net (2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3) 56 data bytes
 64 bytes from devil.e-utp.net (2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3): icm=
 p_seq=3D1 ttl=3D64 time=3D0.190 ms
 64 bytes from devil.e-utp.net (2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3): icm=
 p_seq=3D2 ttl=3D64 time=3D0.233 ms
 64 bytes from devil.e-utp.net (2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3): icm=
 p_seq=3D3 ttl=3D64 time=3D0.261 ms
 64 bytes from devil.e-utp.net (2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3): icm=
 p_seq=3D4 ttl=3D64 time=3D0.241 ms

 --- devil.e-utp.net ping statistics ---
 4 packets transmitted, 4 received, 0% packet loss, time 3057ms
 rtt min/avg/max/mdev =3D 0.190/0.231/0.261/0.025 ms
 inferno:~ #

 NetBSD 11.0_RC4:
 [NetBSD-root@devil:~]$ uname -a
 NetBSD devil.e-utp.net 11.0_RC4 NetBSD 11.0_RC4 (DEVIL) #12: Mon May 25 20:=
 18:27 CEST 2026  root@devil.e-utp.net:/usr/obj/sys/arch/amd64/compile/DEVIL=
  amd64
 [NetBSD-root@devil:~]$ ping6 -c 4 inferno.e-utp.net
 PING6(56=3D40+8+8 bytes) 2001:67c:21ec:1000:6e4b:90ff:fea3:6ec3 --> 2001:67=
 c:21ec:1000::c
 16 bytes from 2001:67c:21ec:1000::c, icmp_seq=3D0 hlim=3D64 time=3D0.331 ms
 16 bytes from 2001:67c:21ec:1000::c, icmp_seq=3D1 hlim=3D64 time=3D0.261 ms
 16 bytes from 2001:67c:21ec:1000::c, icmp_seq=3D2 hlim=3D64 time=3D0.288 ms
 16 bytes from 2001:67c:21ec:1000::c, icmp_seq=3D3 hlim=3D64 time=3D0.278 ms

 --- inferno.e-utp.net ping6 statistics ---
 4 packets transmitted, 4 packets received, 0.0% packet loss
 round-trip min/avg/max/std-dev =3D 0.261/0.290/0.331/0.030 ms
 [NetBSD-root@devil:~]$ ndp -an
 Neighbor                                Linklayer Address  Netif Expire    =
 S Fl
 fe80::e65f:1ff:fe4b:ccf1%ixg0           e4:5f:01:4b:cc:f1   ixg0 20s       =
 R
 2001:67c:21ec:1000::c                   e4:5f:01:4b:cc:f1   ixg0 15s       =
 R
 fe80::e223:ffff:fe9f:26f%ixg0           e0:23:ff:9f:02:6f   ixg0 5s        =
 R R
 2001:67c:21ec:1000:219:e2ff:feec:41c0   e0:23:ff:9f:02:6f   ixg0 21s       =
 R R
 [NetBSD-root@devil:~]$

 Thanks,

 --
 Marcin Gondek / Drixter
 http://fido.e-utp.net/
 AS56662

 -----Original Message-----
 From: netbsd-bugs-owner@NetBSD.org <netbsd-bugs-owner@NetBSD.org> On Behalf=
  Of df4nx@gmx.net via gnats
 Sent: Friday, June 12, 2026 9:40 AM
 To: kern-bug-people@netbsd.org; gnats-admin@netbsd.org; netbsd-bugs@netbsd.=
 org
 Subject: kern/60323: IPv6 NDP issue since upgrade to 11.0_RC4

 >Number:         60323
 >Category:       kern
 >Synopsis:       Neighbor Discovery Protocol on 11.0_RC4
 >Confidential:   no
 >Severity:       non-critical
 >Priority:       low
 >Responsible:    kern-bug-people
 >State:          open
 >Class:          sw-bug
 >Submitter-Id:   net
 >Arrival-Date:   Fri Jun 12 07:40:00 +0000 2026
 >Originator:     =3D09
 >Release:        NetBSD 11.0_RC4
 >Organization:
 	home user
 >Environment:
 =3D09
 =3D09
 System: NetBSD at166.local 11.0_RC4 NetBSD 11.0_RC4 (GENERIC) #0: Tue May =
 =3D
 12 04:23:51 UTC 2026 mkrepro@mkrepro.NetBSD.org:/usr/src/sys/arch/amd64/co=
 =3D
 mpile/GENERIC amd64
 Architecture: x86_64
 Machine: amd64
 >Description:
 	The host runs IPv6 with a static assigned IPv6 address. Trying
 	to ping6 this address from a Linux host on the LAN failes.
 	ping6 from a other NetBSD or OpenBSD host on the same LAN works.
 	Ping6 and connect from the internet to the static IPv6 address
 	works. `tcpdump icmp6` on the Linux host on the same LAN shows
 	outgoing NDP Packets, but no incoming answer.
 	The problem did not occur on NetBSD 10.1.
 	For test purposes I have switched off NPF, but this did not fix
 	the issue.
 	It looks like a problem with the Neighbor Discovery Protocol on
 	11.0_RC4.
 	To double check I have two other hosts without static IPv6
 	address. One 10.1, the other 11.0_RC4. The 10.1 host can be
 	pinged, the 11.0_RC4 not. I used the dynnamic assigned IPv6
 	address. None of these two systems run NPF.
 	See also this blogpost:
 	https://sirius-a.neocities.org/#v6issue
 >How-To-Repeat:
 	I used a installed Debian 13.5, a Debian live system (13.5 XFCE)
 	and a Fedora Live 44-1.7 to test on the LAN.
 	Ping6 and connect from the internet with:
 	https://www.ipv6tech.ch/?pingv4v6
 	https://www.ipv6tech.ch/?tcpportscan
 	Tests with OpenBSD are done with the FuguIta live system:
 	https://fuguita.org/
 >Fix:
 	Work around: Running the following command on the Linux host
 	(Debian 13.5) works:
 	ip -6 neigh replace XXXX:XXXX:XXXX:XXXX::1 lladdr yy:yy:yy:yy:yy:yy dev e=
 =3D
 no1
 	with XXXX is my /64 prefix and yy is my MAC.

 >Unformatted:
  =3D09
  =3D09

From: Robert Swindells <rjs@fdy2.co.uk>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: kern/60323
Date: Fri, 12 Jun 2026 15:58:30 +0100

 The PR states that you are using a static assigned IPv6 address, are
 you running dhcpcd(8) on the NetBSD machine?

From: DF4NX <df4nx@gmx.net>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: kern/60323
Date: Fri, 12 Jun 2026 17:08:51 +0200

 Hi,

 yes, dhcpcd(8) is running. My rc.conf includes among others the=20
 following three lines:

 ip6mode=3D"autohost"
 dhcpcd=3DYES
 dhcpcd_flags=3D"-6"

 ifconfig includes this:

 inet6 sec.local prefixlen 64 alias

 and sec.local is defined in /etc/hosts

 Thank you for helping :-)
 ~ Dieter

 Am 12.06.26 um 17:00 schrieb Robert Swindells via gnats:
 > The following reply was made to PR kern/60323; it has been noted by GNAT=
 S.
 >=20
 > From: Robert Swindells <rjs@fdy2.co.uk>
 > To: gnats-bugs@NetBSD.org
 > Cc:
 > Subject: Re: kern/60323
 > Date: Fri, 12 Jun 2026 15:58:30 +0100
 >=20
 >   The PR states that you are using a static assigned IPv6 address, are
 >   you running dhcpcd(8) on the NetBSD machine?
 >  =20

From: DF4NX <df4nx@gmx.net>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: kern/60323: IPv6 NDP issue since upgrade to 11.0_RC4
Date: Thu, 18 Jun 2026 14:26:26 +0200

 Maybe kern/59596 is related to this problem.
 Changes were made in neighbor discovery.

 ~ Dieter

 Am 12.06.26 um 09:40 schrieb gnats-admin@netbsd.org:
 > Thank you very much for your problem report.
 > It has the internal identification `kern/60323'.
 > The individual assigned to look at your
 > report is: kern-bug-people.
 >=20
 >> Category:       kern
 >> Responsible:    kern-bug-people
 >> Synopsis:       Neighbor Discovery Protocol on 11.0_RC4
 >> Arrival-Date:   Fri Jun 12 07:40:00 +0000 2026
 >=20

>Unformatted:
 =09
 =09

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