( this is a good dhcp state diagram to follow along at home:
https://commons.wikimedia.org/wiki/File:DHCP_Client_State_Diagram_-_en.png )
On 2023-05-10 23:07 +10, David Diggles <da...@elven.com.au> wrote:
> I probably should have done numeric tcpdump output. Here's both again.
>
> tcpdump: WARNING: snaplen raised from 116 to 1500
> 22:36:40.276682 0.0.0.0.68 > 255.255.255.255.67: xid:0x74253f08 vend-rfc1048
> DHCP:REQUEST HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 RQ:202.63.67.36 [tos 0x10]
dhcpleased starts up and we have a lease file in /var/db/dhcpleased/, we
are in INIT-REBOOT and ask the dhcp server via broadcast if we can use
our previous IP address 202.63.67.36. We go to state REBOOTING.
> 22:36:40.327371 202.63.66.1.67 > 255.255.255.255.68: xid:0x74253f08
> flags:0x8000 Y:202.63.67.36 S:172.21.116.42 ether dc:9f:db:28:14:bf
> vend-rfc1048 DHCP:ACK SM:255.255.254.0 DG:202.63.66.1
> NS:119.40.106.35,119.40.106.36 NTP:125.253.59.254 LT:600 SID:202.63.66.1
> CID:1.220.159.219.40.20.191 [tos 0xc0]
dhcp server: yeah, that's fine (DHCP:ACK). Lifetime is 600 seconds. We
configure the interface and go into state BOUND.
some time passes
> 22:41:40.422661 202.63.67.36.56480 > 202.63.66.1.67: (request) xid:0xa180ce6b
> C:202.63.67.36 vend-rfc1048 DHCP:REQUEST HN:"sarah"
> CID:1.220.159.219.40.20.191 PR:SM+DG+NS+HN+DN+BR+119+121
Time T1 expires, we send a unicast DHCPREQUEST to the dhcpserver: is it
OK to hold on to our IP address? We go into state RENEWING.
> 22:41:40.434534 202.63.66.1.67 > 202.63.67.36.68: xid:0xa180ce6b
> C:202.63.67.36 S:172.21.116.42 vend-rfc1048 DHCP:NACK SID:202.63.66.1
> CID:1.220.159.219.40.20.191 [tos 0xc0]
dhcp server: Absolutely not! DHCP:NACK.
RFC 2131 has this:
If the client receives a DHCPNAK message, it cannot reuse its
remembered network address. It must instead request a new
address by restarting the configuration process, this time
using the (non-abbreviated) procedure described in section
3.1. This action also corresponds to the client moving to
the INIT state in the DHCP state diagram.
There is not a lot of wiggle room, we MUST remove our address. We go to
state INIT.
> 22:41:40.442012 0.0.0.0.68 > 255.255.255.255.67: xid:0x6a13ec33 vend-rfc1048
> DHCP:DISCOVER HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 [tos 0x10]
dhcpleased, broadcast: could I please have a lease? go to state SELECTING
> 22:41:41.532272 0.0.0.0.68 > 255.255.255.255.67: xid:0x6a13ec33 vend-rfc1048
> DHCP:DISCOVER HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 [tos 0x10]
dhcpleased, broadcast: could I please have a lease? pretty please? with
sugar on top? stay in state SELECTING
> 22:41:41.653804 202.63.66.1.67 > 255.255.255.255.68: xid:0x6a13ec33
> flags:0x8000 Y:202.63.67.36 S:172.21.116.42 ether dc:9f:db:28:14:bf
> vend-rfc1048 DHCP:OFFER SM:255.255.254.0 DG:202.63.66.1
> NS:119.40.106.35,119.40.106.36 NTP:125.253.59.254 LT:600 SID:202.63.66.1
> CID:1.220.159.219.40.20.191 [tos 0xc0]
server: ok fine, do you like this one?
> 22:41:41.658881 0.0.0.0.68 > 255.255.255.255.67: xid:0xdafa3da4 vend-rfc1048
> DHCP:REQUEST HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 RQ:202.63.67.36 SID:202.63.66.1 [tos 0x10]
dhcpleased: looks, good, is it ok if I use this one? go to state REQUESTING
> 22:41:42.414218 202.63.66.1.67 > 255.255.255.255.68: xid:0xdafa3da4
> flags:0x8000 Y:202.63.67.36 S:172.21.116.42 ether dc:9f:db:28:14:bf
> vend-rfc1048 DHCP:ACK SM:255.255.254.0 DG:202.63.66.1
> NS:119.40.106.35,119.40.106.36 NTP:125.253.59.254 LT:600 SID:202.63.66.1
> CID:1.220.159.219.40.20.191 [tos 0xc0]
dhcp server: yes, that's fine.
dhcpleased: configure address, go to state BOUND.
This process repeats every 5 minutes.
To me it looks like the server just NACKS all unicast requests. As far
as I remember our broadcast DHCPREQUESTs are exactly the same as our
unicast DHCPREQUESTs, so it's not the contents of the packet.
You were saying this works with other implementations? I would be
interested in seeing a tcpdump for those.
> 22:46:42.512451 202.63.67.36.63976 > 202.63.66.1.67: (request) xid:0x953f83f1
> C:202.63.67.36 vend-rfc1048 DHCP:REQUEST HN:"sarah"
> CID:1.220.159.219.40.20.191 PR:SM+DG+NS+HN+DN+BR+119+121
> 22:46:42.525222 202.63.66.1.67 > 202.63.67.36.68: xid:0x953f83f1
> C:202.63.67.36 S:172.21.116.42 vend-rfc1048 DHCP:NACK SID:202.63.66.1
> CID:1.220.159.219.40.20.191 [tos 0xc0]
> 22:46:42.531574 0.0.0.0.68 > 255.255.255.255.67: xid:0x66009a6e vend-rfc1048
> DHCP:DISCOVER HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 [tos 0x10]
> 22:46:43.622162 0.0.0.0.68 > 255.255.255.255.67: xid:0x66009a6e vend-rfc1048
> DHCP:DISCOVER HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 [tos 0x10]
> 22:46:43.762685 202.63.66.1.67 > 255.255.255.255.68: xid:0x66009a6e
> flags:0x8000 Y:202.63.67.36 S:172.21.116.42 ether dc:9f:db:28:14:bf
> vend-rfc1048 DHCP:OFFER SM:255.255.254.0 DG:202.63.66.1
> NS:119.40.106.35,119.40.106.36 NTP:125.253.59.254 LT:600
> SID:202.63.66.1 CID:1.220.159.219.40.20.191 [tos 0xc0]
> 22:46:43.768051 0.0.0.0.68 > 255.255.255.255.67: xid:0xfe3d764f
> vend-rfc1048 DHCP:REQUEST HN:"sarah" CID:1.220.159.219.40.20.191
> PR:SM+DG+NS+HN+DN+BR+119+121 RQ:202.63.67.36 SID:202.63.66.1 [tos
> 0x10]
> 22:46:44.526556 202.63.66.1.67 > 255.255.255.255.68: xid:0xfe3d764f
> flags:0x8000 Y:202.63.67.36 S:172.21.116.42 ether dc:9f:db:28:14:bf
> vend-rfc1048 DHCP:ACK SM:255.255.254.0 DG:202.63.66.1
> NS:119.40.106.35,119.40.106.36 NTP:125.253.59.254 LT:600
> SID:202.63.66.1 CID:1.220.159.219.40.20.191 [tos 0xc0]
>
> state_transition[cnmac2] Down -> Rebooting, timo: 1
> DHCPREQUEST on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: ff:ff:ff:ff:ff:ff
> parse_dhcp: 202.63.66.1:67 -> 255.255.255.255:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0x74253f08
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x8000
> dhcp_hdr ciaddr: 0.0.0.0
> dhcp_hdr yiaddr: 202.63.67.36
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPACK
> DHO_SUBNET_MASK: 255.255.254.0
> DHO_ROUTER: 202.63.66.1
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.35 (1/2)
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.36 (2/2)
> DHO_42, len: 4
> DHO_DHCP_LEASE_TIME 600s
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPACK on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> ff:ff:ff:ff:ff:ff/255.255.255.255
> adding 202.63.67.36 to cnmac2 (lease from 202.63.66.1)
> adding nameservers 119.40.106.35 119.40.106.36 (lease from 202.63.66.1 on
> cnmac2)
> state_transition[cnmac2] Rebooting -> Bound, timo: 300
> configure_interface cnmac2
> iface_timeout[3]: Bound
> state_transition[cnmac2] Bound -> Renewing, timo: 112
> DHCPREQUEST on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: dc:9f:db:28:14:bf
> parse_dhcp: 202.63.66.1:67 -> 202.63.67.36:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0xa180ce6b
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x0
> dhcp_hdr ciaddr: 202.63.67.36
> dhcp_hdr yiaddr: 0.0.0.0
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPNAK
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPNAK on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> dc:9f:db:28:14:bf/202.63.67.36
> deleting nameservers 119.40.106.35 119.40.106.36 (lease from 202.63.66.1 on
> cnmac2)
> deleting 202.63.67.36 from cnmac2 (lease from 202.63.66.1)
> state_transition[cnmac2] Renewing -> Init, timo: 1
> DHCPDISCOVER on cnmac2
> deconfigure_interface cnmac2
> iface_timeout[3]: Init
> state_transition[cnmac2] Init -> Init, timo: 2
> DHCPDISCOVER on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: ff:ff:ff:ff:ff:ff
> parse_dhcp: 202.63.66.1:67 -> 255.255.255.255:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0x6a13ec33
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x8000
> dhcp_hdr ciaddr: 0.0.0.0
> dhcp_hdr yiaddr: 202.63.67.36
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPOFFER
> DHO_SUBNET_MASK: 255.255.254.0
> DHO_ROUTER: 202.63.66.1
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.35 (1/2)
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.36 (2/2)
> DHO_42, len: 4
> DHO_DHCP_LEASE_TIME 600s
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPOFFER on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> ff:ff:ff:ff:ff:ff/255.255.255.255
> state_transition[cnmac2] Init -> Requesting, timo: 1
> DHCPREQUEST on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: ff:ff:ff:ff:ff:ff
> parse_dhcp: 202.63.66.1:67 -> 255.255.255.255:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0xdafa3da4
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x8000
> dhcp_hdr ciaddr: 0.0.0.0
> dhcp_hdr yiaddr: 202.63.67.36
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPACK
> DHO_SUBNET_MASK: 255.255.254.0
> DHO_ROUTER: 202.63.66.1
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.35 (1/2)
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.36 (2/2)
> DHO_42, len: 4
> DHO_DHCP_LEASE_TIME 600s
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPACK on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> ff:ff:ff:ff:ff:ff/255.255.255.255
> adding 202.63.67.36 to cnmac2 (lease from 202.63.66.1)
> adding nameservers 119.40.106.35 119.40.106.36 (lease from 202.63.66.1 on
> cnmac2)
> state_transition[cnmac2] Requesting -> Bound, timo: 300
> configure_interface cnmac2
> iface_timeout[3]: Bound
> state_transition[cnmac2] Bound -> Renewing, timo: 112
> DHCPREQUEST on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: dc:9f:db:28:14:bf
> parse_dhcp: 202.63.66.1:67 -> 202.63.67.36:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0x953f83f1
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x0
> dhcp_hdr ciaddr: 202.63.67.36
> dhcp_hdr yiaddr: 0.0.0.0
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPNAK
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPNAK on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> dc:9f:db:28:14:bf/202.63.67.36
> deleting nameservers 119.40.106.35 119.40.106.36 (lease from 202.63.66.1 on
> cnmac2)
> deleting 202.63.67.36 from cnmac2 (lease from 202.63.66.1)
> state_transition[cnmac2] Renewing -> Init, timo: 1
> DHCPDISCOVER on cnmac2
> deconfigure_interface cnmac2
> iface_timeout[3]: Init
> state_transition[cnmac2] Init -> Init, timo: 2
> DHCPDISCOVER on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: ff:ff:ff:ff:ff:ff
> parse_dhcp: 202.63.66.1:67 -> 255.255.255.255:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0x66009a6e
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x8000
> dhcp_hdr ciaddr: 0.0.0.0
> dhcp_hdr yiaddr: 202.63.67.36
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPOFFER
> DHO_SUBNET_MASK: 255.255.254.0
> DHO_ROUTER: 202.63.66.1
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.35 (1/2)
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.36 (2/2)
> DHO_42, len: 4
> DHO_DHCP_LEASE_TIME 600s
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPOFFER on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> ff:ff:ff:ff:ff:ff/255.255.255.255
> state_transition[cnmac2] Init -> Requesting, timo: 1
> DHCPREQUEST on cnmac2
> parse_dhcp, from: 0e:a2:00:04:00:03, to: ff:ff:ff:ff:ff:ff
> parse_dhcp: 202.63.66.1:67 -> 255.255.255.255:68
> dhcp_hdr op: Boot Reply (2)
> dhcp_hdr htype: Ethernet (1)
> dhcp_hdr hlen: 6
> dhcp_hdr hops: 0
> dhcp_hdr xid: 0xfe3d764f
> dhcp_hdr secs: 0
> dhcp_hdr flags: 0x8000
> dhcp_hdr ciaddr: 0.0.0.0
> dhcp_hdr yiaddr: 202.63.67.36
> dhcp_hdr siaddr: 172.21.116.42
> dhcp_hdr giaddr: 0.0.0.0
> dhcp_hdr chaddr: dc:9f:db:28:14:bf (00000000000000000000)
> DHO_DHCP_MESSAGE_TYPE: DHCPACK
> DHO_SUBNET_MASK: 255.255.254.0
> DHO_ROUTER: 202.63.66.1
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.35 (1/2)
> DHO_DOMAIN_NAME_SERVERS: 119.40.106.36 (2/2)
> DHO_42, len: 4
> DHO_DHCP_LEASE_TIME 600s
> DHO_DHCP_SERVER_IDENTIFIER: 202.63.66.1
> DHO_END
> DHCPACK on cnmac2 from 0e:a2:00:04:00:03/202.63.66.1 to
> ff:ff:ff:ff:ff:ff/255.255.255.255
> adding 202.63.67.36 to cnmac2 (lease from 202.63.66.1)
> adding nameservers 119.40.106.35 119.40.106.36 (lease from 202.63.66.1 on
> cnmac2)
> state_transition[cnmac2] Requesting -> Bound, timo: 300
> configure_interface cnmac2
>
--
In my defence, I have been left unsupervised.
