[ipxe-devel] Boot fails if advertised IPv6 prefix isn't on-link

[Hannes Reinecke]

On 11/13/2015 11:00 AM, Tore Anderson wrote:
> Hello,
> 
> I've found that iPXE fails to operate correctly if the advertised IPv6
> prefix isn't on-link, that is, if the Prefix Information Option (PIO)
> in the ICMPv6 Router Advertisement (RA) doesn't have the L flag set, it
> simply doesn't fails to boot correctly.
> 
> If SLAAC is being used (A flag set in PIO), then it will fail with a
> "Connection timed out" error message. However no actual packets
> indicating an attempt to contact the upstream source (in my case,
> http://boot.ipxe.org/demo/boot.php) are seen on the wire, not even a DNS
> query for "boot.ipxe.org").
> 
> If DHCPv6 is being used (A flag unset in PIO and M flag set in RA), it
> will get stuck in a loop where it repeats the DHCPv6 Request six times
> (getting a Reply every time) before failing with "Error 0x040ee119".
> 
> If I change the RAs so the L flag is set, then everything starts
> working just fine (in both the SLAAC and DHCPv6 cases).
> 
> This suggests that iPXE assigns some incorrect meaning to the L flag.
> The only thing the L flag signals is whether or not destinations in the
> advertised prefix (2a02:c0:300:103::/64 in my case) should be reached
> directly (using IPv6 Neighbour Solicitations) or if those destinations
> must be reached via the default router. However neither boot.ipxe.org
> nor the advertised DNS server (google-public-dns-a.google.com) is found
> within that prefix, so the on- or off-link state of the prefix shouldn't
> have made no difference to the boot-up process.
> 
> For your reference I've uploaded PCAPs of the four boot attempts
> described above to http://filebin.net/wiklwkspjg .
> 
Ah. That would explain some IPv6 failures I've encountered during my
iSCSI testing. Lemme check ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
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