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Date:      Thu, 30 May 2024 02:54:01 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 263288] IPv6 system not responding to Neighbor Solicitation
Message-ID:  <bug-263288-7501-Dql9TCSLCU@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-263288-7501@https.bugs.freebsd.org/bugzilla/>
References:  <bug-263288-7501@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D263288

--- Comment #21 from Robert Blayzor <rblayzor@inoc.net> ---
I have run into this issue now a few times. I have seen hosts try to ping my
IPv6 hosts from off network and they just hang. Upon investigation I have f=
ound
that the host is hung up on ignoring NS messages from the router, even thou=
gh
on the host we have NDP entries for both the link local and the global IP
address. ie:

# ndp -an | grep lagg1 | grep 00:09:0f
2607:f058:xx::1                      00:09:0f:09:00:01  lagg1 23h34m17s S R
fe80::209:fff:fe09:1%lagg1           00:09:0f:09:00:01  lagg1 23h33m53s S R



PCAP shows NS messages from the router, but there is zero response, the host
just ignores them. No firewall enabled at all....

I can ping from other hosts on the same subnet, that seems to work.

The kicker is, if I ping6 FROM the host to the router it takes about 5 seco=
nds
(give or take) and then you're able to ping the gateway again. Once this
happens, packets from remote are able to ping and traffic flows again.

If I stop sending traffic and let things sit for about a minute, the process
repeats again. NDP sol messages from the router are ignored again and remain
broken until I ping the router from the host again.

If I keep a continuous ping from a host off link, it will never fail. This
seems to be some type of NDP timeout/cache issue.

I have tried setting: net.inet6.icmp6.nd6_onlink_ns_rfc4861=3D1. but that d=
oes
not seem to solve the problem.

I am currently seeing this on 13.1-RELEASE-p9 which is on a TrueNAS host. W=
hile
I realize 13.3 is current, TrueNAS seems to lag a little behind. I do have
other TrueNAS hosts running this version that don't seem to experience this
issue. (at least I've not reliably reproduced it on other machines)

I have tried just rebooting the host, but I CAN reliably reproduce this iss=
ue.

I have no other ND issues from the router to other hosts on this network. I
have confirmed the host *is* receiving the NS messages; it just never repli=
es..

--=20
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