dhcpcd-discuss

Hi,

I am trying to debug an issue I have with DHCPv6 IA_PD on my ISP's 
network. I'm using dhcpcd-7.0.0-rc3 with the following configuration:

hostname
duid
persistent
option rapid_commit
option domain_name_servers, domain_name, domain_search, host_name
option classless_static_routes
option ntp_servers
option interface_mtu
require dhcp_server_identifier
slaac private
nohook wpa_supplicant
nohook resolv.conf, ntp.conf, yp.conf, hostname, lookup-hostname, timezone, wpa_supplicant
denyinterfaces eth0 eth0.2 eth0.55 eth0.666 br0 br55 wlan* tap* veth*
noipv4
noipv6
noipv6rs
noipv4ll
interface eth0.777
    ipv4
    ipv6
    ipv6rs
    ia_na 1
    ia_pd 2/::/48 br0/0/64

Initial Solicit-Advertise-Request-Reply seems to work fine, and in the 
Reply packet I am getting:

DHCPv6
    Message type: Reply (7)
    Identity Association for Non-temporary Address
        Option: Identity Association for Non-temporary Address (3)
        Length: 66
        IAID: 00000001
        T1: 1200
        T2: 1800
        IA Address
            Option: IA Address (5)
            Length: 24
            IPv6 address: 2a02:168:<redacted1>
    (...)
    Identity Association for Prefix Delegation
        Option: Identity Association for Prefix Delegation (25)
        IAID: 00000002
        T1: 1200
        T2: 1800
        IA Prefix
            Option: IA Prefix (26)
            Length: 25
            Preferred lifetime: 3600
            Valid lifetime: 86400
            Prefix length: 48
            Prefix address: 2a02:168:<redacted2>
        Status code
            Option: Status code (13)
            Length: 32
            Status Code: Success (0)
            Status Message: Assigned fixed in-pool prefix.

Within the same reply I'm also receiving Server-unicast (12) option:

    Server unicast
        Option: Server unicast (12)
        Length: 16
        IPv6 address: 2001:1620:<redacted3>

So far so good. After 20 minutes (as per T1) my dhcpcd sends Renew 
packets, which don't get any reply from my ISP side.
And that's what makes me wonder - source address in those Renews is my 
link-local address:

initial Reply:
 12 20:48:17.353653 fe80::224:14ff:feef:72ff -> fe80::baae:edff:fe76:98d6 
DHCPv6 346 Reply XID: 0xfedcba IAA: 2a02:168:<redacted1> CID: 012345...

subsequent Renews:
 13 21:08:17.360399 fe80::baae:edff:fe76:98d6 -> 2001:1620:<redacted3> 
DHCPv6 288 Renew XID: 0xabcdef CID: 012345... IAA: 2a02:168:<redacted1>
 14 21:08:26.492686 fe80::baae:edff:fe76:98d6 -> 2001:1620:<redacted3> 
DHCPv6 288 Renew XID: 0xabcdef CID: 012345... IAA: 2a02:168:<redacted1>
 15 21:08:43.910163 fe80::baae:edff:fe76:98d6 -> 2001:1620:<redacted3> 
DHCPv6 288 Renew XID: 0xabcdef CID: 012345... IAA: 2a02:168:<redacted1>
 16 21:09:18.636170 fe80::baae:edff:fe76:98d6 -> 2001:1620:<redacted3> 
DHCPv6 288 Renew XID: 0xabcdef CID: 012345... IAA: 2a02:168:<redacted1>
 17 21:10:26.345222 fe80::baae:edff:fe76:98d6 -> 2001:1620:<redacted3> 
DHCPv6 288 Renew XID: 0xabcdef CID: 012345... IAA: 2a02:168:<redacted1>

All those Renews are for both IA_NA and IA_PD (with T1=T2=0).

I'm quite surprised to see a link-local used as source here, when there is 
a global-scope unicast address assigned to that interface already. But I 
might be misinterpreting RFC3315 section 16:

   When a client sends a DHCP message directly to a server using unicast
   (after receiving the Server Unicast option from that server), the
   source address in the header of the IP datagram MUST be an address
   assigned to the interface for which the client is interested in
   obtaining configuration and which is suitable for use by the server
   in responding to the client.

And although RFC3633 section 8 says

   Delegated prefixes are not associated with a particular interface in
   the same way as addresses are for address assignment, and the rules
   described in section 16, "Client Source Address and Interface
   Selection" of RFC 3315 do not apply.

it also says

   When a requesting router sends a DHCP message directly to a
   delegating router using unicast (after receiving the Server Unicast
   option from that delegating router), the source address SHOULD be an
   address from the upstream interface and which is suitable for use by
   the delegating router in responding to the requesting router.


Can somebody more clueful than me clarify this? :)


Cheers,
 Jakub 'shasta' Jankowski


--
Jakub Jankowski|shasta@xxxxxxxxxxx|http://toxcorp.com/
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