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46 lines
1.4 KiB
Markdown
46 lines
1.4 KiB
Markdown
---
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layout: post
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title: "IPv6 and Netgraph Ethernet pseudo-interface"
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date: 2017-12-28 12:47:00 +0100
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comments: true
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categories:
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---
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On a NanoBSD firewall, I want to have a separate
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MAC address on one of the Ethernet interfaces to
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act as the outer endpoint for IPv6 traffic. This
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is achieved using a Netgraph eiface:
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```plain /etc/rc.local
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kldload ng_ether
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ngctl mkpeer sis0: bridge lower link0
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ngctl name sis0:lower sis0bridge
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ngctl connect sis0: sis0bridge: upper link1
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ngctl mkpeer sis0bridge: eiface link2 ether
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ngctl msg sis0: setpromisc 1
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ngctl msg sis0: setautosrc 0
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ifconfig ngeth0 link 06:00:00:00:00:06
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```
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Note that this does *not* include an ifconfig call to
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set the interface's IPv6 address: this is done by
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devd, which calls the boot scripts' ifconfig routine
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when the interface comes up. Thus I have the following
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line in /etc/rc.conf:
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```plain /etc/rc.conf
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ifconfig_ngeth0_ipv6="inet6 fe80::6/64"
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```
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If instead of this line I have an explicit ifconfig
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in `/etc/rc.local` then there is a race condition between
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rc.local and devd. If devd runs last, the boot scripts
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won't see any IPv6 address configured for the newly
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created interface in `/etc/rc.conf`, and they will set
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`ifdisabled` on it (blocking all IPv6 traffic, and marking
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the configured link local address as "tentative").
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If devd runs first, the problem is dormant, because setting
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the link local address clears `ifdisabled` as a side effect.
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