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FS#1457 - odhcpd annoucing dhcpv6 even when it's not enabled #7781

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openwrt-bot opened this issue Mar 26, 2018 · 7 comments
Closed

FS#1457 - odhcpd annoucing dhcpv6 even when it's not enabled #7781

openwrt-bot opened this issue Mar 26, 2018 · 7 comments
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@openwrt-bot
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brianjmurrell:

Supply the following if possible:

  • Device problem occurs on
    wndr4300

  • Software versions of OpenWrt/LEDE release, packages, etc.
    17.01.4, r3560-79f57e422d
    odhcpd - 2018-03-02-2da5850f-3

  • Steps to reproduce
    /etc/config/dhcp snippet:

    config dhcp 'lan'
    option interface 'lan'
    option dhcpv6 'disabled'
    option ra 'server'
    option ra_management '1'
    list dns 'fd31:aeb1:48df::2'

Notice that "option dhcpv6 'disabled'" yet neighbour discovery is still saying DHCPv6 is available:

$ sudo rdisc6 eth0
Soliciting ff02::2 (ff02::2) on eth0...

Hop limit : 64 ( 0x40)
Stateful address conf. : Yes
...

@openwrt-bot
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brianjmurrell:

How do we get this backported to current openwrt/lede?

@openwrt-bot
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dedeckeh:

This is already in current OpenWRT/Lede master as the hash points to 413652910234f44e11d6550abf6871621474b8cb (https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=package/network/services/odhcpd/Makefile;h=f78fb9485bd599a26e7a0d180a62c41b53e1853d;hb=HEAD#l17) which includes the relevant fix

@openwrt-bot
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brianjmurrell:

But master is not where updates to current (i.e. 17.01) OpenWRT/Lede come from is it? Isn't that [[https://github.com/openwrt/openwrt/tree/lede-17.01|lede-17.01]]?

@openwrt-bot
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brianjmurrell:

I created a [[https://github.com//pull/984|PR]] FWIW.

@openwrt-bot
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dedeckeh:

The patch was not backported to lede-17.01 branch as it was not seen as a critical show stopper for lede-17.01 neither was it requested to be backported.
I can backport the patch to lede-17.01 so it will be included in the 17.01.05 release which is in the pipeline

@openwrt-bot
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artturnip:

The behaviour reported in this issue should be the intended (and documented) behaviour of odhcpd. From the documentation [[https://openwrt.org/docs/techref/odhcpd|here]]:

ra_management integer 1 RA management mode
0: no M-Flag but A-Flag
1: both M and A
2: M but not A

option ra_management '1' will set both the M and the A flags in a RA. This will indicate to a client that both stateless and stateful (DHCPv6) configuration is available.

To prevent the router showing DHCPv6 as available (M flag), one should set option ra_management '0'

The fix to this issue results in the M flag not being able to be set whilst the DHCPv6 server is disabled. This prevents the use of DHCPv6 servers elsewhere on the network allowing for centralised IP allocation management -- a main use case for DHCPv6.

@openwrt-bot
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artturnip:

Issue reported is should be the behaviour of odhcpd when configured in this way. This is necessary to support DHCPv6 servers running elsewhere on the network.

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