Date: Sun, 10 Jul 2022 16:55:04 -0500
From: "W. Michael Petullo" <mike@flyn.org>
To: ~alpine/users@lists.alpinelinux.org
Subject: IPv6 firewall blocking router advertisements
Message-ID: <YstKuMf89j67CIfO@imp.flyn.org>
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I am trying to configure an Alpine host to use DHCPv6 to obtain an IPv6
address. I have performed this task before using OpenWrt and Fedora.

On Alpine, it appears that the IPv6 firewall (ip6tables) prevents router
advertisements from working. I use "dhclient -6 ..."

Although the host receives the correct IPv6 address, the host does not
update its routing table if the IPv6 firewall is active. There are two
strange clues related to this:

(1) The router advertisements do not work even with a permissive IPv6
firewall configuration (allow everything).

(2) The kernel does not seem to log any firewall rejections, i.e., the
"pkts" fields in the output from "ip6tables -v -L" contain all zeros.
Likewise, I do not see any IPv6 rejections in /var/log/...

Yet things work when I deactivate the firewall (/etc/init.d/ip6tables
stop) and restart networking. In this case, my host updates its routing
table.

I see ICMPv6 "router solicitation" messages in Wireshark when the IPv6
firewall is off, but they do not appear when it is on.

I have been troubleshooting this for a while. Does anyone have any ideas
about what might be causing this or what else I ought to look at?

-- 
Mike

:wq