[Dnsmasq-discuss] Weird Routing/FW/dnsmasq problem

Dan Shechter DanS at GoNetworks.com
Sun Oct 30 21:35:12 GMT 2005


Hi,
This isn't really a dnsmasq problem, but a "routing" problem,
I'm mailing this here hoping that someone overcame this before...

I'm trying to get dnsmasq to respond with "DHCPNAK" commands while in
dhcp-authorative mode.

The "catch", so to speak, is that the clients are roaming in from
different
networks. And sometimes when they "come-in" to the dnsmasq managed
network, they generate packets which are local broadcast packets from
their old source ip address to 255.255.255.255.

For example, clients generate DHCP REQUEST packets from:
10.100.4.134 -> 255.255.255.255
while dnsmasq runs on a machine where the interface receiving the
broadcast packet is configured as "192.168.101.200".

I cannot seem to successfully make dnsmasq "respond" to these packets.
dnsmasq remains sleeping (verified with strace) while these DHCP REQUEST
packets are generated.

I've attached two ethereal dump files, one is a plain packet dump, one
is a
Detailed one:
The client try the same DHCP request 3 times (packets 418-420), and
gives up after 40 seconds, doing a DHCP DISCOVER (packet 421) with
source address "0.0.0.0" which succeeds.

Any help will be GREATLY appreciated!

----------
Dan Shechter <dans *at* gonetworks.com>


-------------- next part --------------
No.     Time        Source                Destination           Protocol Info
    418 5990.757624 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 418 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    419 5995.762079 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 419 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    420 6002.762150 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 420 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    421 6022.310948 0.0.0.0               255.255.255.255       DHCP     DHCP Discover - Transaction ID 0x8f93ada4

Frame 421 (344 bytes on wire, 344 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 0.0.0.0 (0.0.0.0), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    422 6025.061742 192.168.101.200       255.255.255.255       DHCP     DHCP Offer    - Transaction ID 0x8f93ada4

Frame 422 (344 bytes on wire, 344 bytes captured)
Ethernet II, Src: TyanComp_30:e9:cf (00:e0:81:30:e9:cf), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 192.168.101.200 (192.168.101.200), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootpc (68)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    423 6025.062147 0.0.0.0               255.255.255.255       DHCP     DHCP Request  - Transaction ID 0x8f93ada4

Frame 423 (368 bytes on wire, 368 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 0.0.0.0 (0.0.0.0), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol

No.     Time        Source                Destination           Protocol Info
    424 6025.066490 192.168.101.200       255.255.255.255       DHCP     DHCP ACK      - Transaction ID 0x8f93ada4

Frame 424 (379 bytes on wire, 379 bytes captured)
Ethernet II, Src: TyanComp_30:e9:cf (00:e0:81:30:e9:cf), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 192.168.101.200 (192.168.101.200), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootpc (68)
Bootstrap Protocol
-------------- next part --------------
No.     Time        Source                Destination           Protocol Info
    418 5990.757624 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 418 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: Dell_3c:85:80 (00:11:43:3c:85:80)
    Type: IP (0x0800)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0xbb259ff8
    Seconds elapsed: 0
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 10.100.4.134 (10.100.4.134)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Request
    Option 61: Client identifier
    Option 12: Host Name = "qa-05-dell-d505"
    Option 81: FQDN
    Option 60: Vendor class identifier = "MSFT 5.0"
    Option 55: Parameter Request List
    End Option

No.     Time        Source                Destination           Protocol Info
    419 5995.762079 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 419 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: Dell_3c:85:80 (00:11:43:3c:85:80)
    Type: IP (0x0800)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0xbb259ff8
    Seconds elapsed: 1280
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 10.100.4.134 (10.100.4.134)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Request
    Option 61: Client identifier
    Option 12: Host Name = "qa-05-dell-d505"
    Option 81: FQDN
    Option 60: Vendor class identifier = "MSFT 5.0"
    Option 55: Parameter Request List
    End Option

No.     Time        Source                Destination           Protocol Info
    420 6002.762150 10.100.4.134          255.255.255.255       DHCP     DHCP Request  - Transaction ID 0xbb259ff8

Frame 420 (356 bytes on wire, 356 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: Dell_3c:85:80 (00:11:43:3c:85:80)
    Type: IP (0x0800)
Internet Protocol, Src: 10.100.4.134 (10.100.4.134), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0xbb259ff8
    Seconds elapsed: 3072
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 10.100.4.134 (10.100.4.134)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Request
    Option 61: Client identifier
    Option 12: Host Name = "qa-05-dell-d505"
    Option 81: FQDN
    Option 60: Vendor class identifier = "MSFT 5.0"
    Option 55: Parameter Request List
    End Option

No.     Time        Source                Destination           Protocol Info
    421 6022.310948 0.0.0.0               255.255.255.255       DHCP     DHCP Discover - Transaction ID 0x8f93ada4

Frame 421 (344 bytes on wire, 344 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: Dell_3c:85:80 (00:11:43:3c:85:80)
    Type: IP (0x0800)
Internet Protocol, Src: 0.0.0.0 (0.0.0.0), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x8f93ada4
    Seconds elapsed: 0
    Bootp flags: 0x8000 (Broadcast)
    Client IP address: 0.0.0.0 (0.0.0.0)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Discover
    Option 116: DHCP Auto-Configuration (1 bytes)
    Option 61: Client identifier
    Option 50: Requested IP Address = 10.100.4.134
    Option 12: Host Name = "qa-05-dell-d505"
    Option 60: Vendor class identifier = "MSFT 5.0"
    Option 55: Parameter Request List
    End Option

No.     Time        Source                Destination           Protocol Info
    422 6025.061742 192.168.101.200       255.255.255.255       DHCP     DHCP Offer    - Transaction ID 0x8f93ada4

Frame 422 (344 bytes on wire, 344 bytes captured)
Ethernet II, Src: TyanComp_30:e9:cf (00:e0:81:30:e9:cf), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: TyanComp_30:e9:cf (00:e0:81:30:e9:cf)
    Type: IP (0x0800)
Internet Protocol, Src: 192.168.101.200 (192.168.101.200), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootpc (68)
Bootstrap Protocol
    Message type: Boot Reply (2)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x8f93ada4
    Seconds elapsed: 0
    Bootp flags: 0x8000 (Broadcast)
    Client IP address: 0.0.0.0 (0.0.0.0)
    Your (client) IP address: 192.168.101.66 (192.168.101.66)
    Next server IP address: 192.168.101.200 (192.168.101.200)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Offer
    Option 54: Server Identifier = 192.168.101.200
    Option 51: IP Address Lease Time = 2 minutes
    Option 58: Renewal Time Value = 1 minute
    Option 59: Rebinding Time Value = 1 minute, 45 seconds
    Option 1: Subnet Mask = 255.255.255.0
    Option 3: Router = 192.168.101.200
    Option 6: Domain Name Server = 192.168.101.200
    Option 15: Domain Name = "gonetworks.com"
    End Option

No.     Time        Source                Destination           Protocol Info
    423 6025.062147 0.0.0.0               255.255.255.255       DHCP     DHCP Request  - Transaction ID 0x8f93ada4

Frame 423 (368 bytes on wire, 368 bytes captured)
Ethernet II, Src: Dell_3c:85:80 (00:11:43:3c:85:80), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: Dell_3c:85:80 (00:11:43:3c:85:80)
    Type: IP (0x0800)
Internet Protocol, Src: 0.0.0.0 (0.0.0.0), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x8f93ada4
    Seconds elapsed: 0
    Bootp flags: 0x8000 (Broadcast)
    Client IP address: 0.0.0.0 (0.0.0.0)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP Request
    Option 61: Client identifier
    Option 50: Requested IP Address = 192.168.101.66
    Option 54: Server Identifier = 192.168.101.200
    Option 12: Host Name = "qa-05-dell-d505"
    Option 81: FQDN
    Option 60: Vendor class identifier = "MSFT 5.0"
    Option 55: Parameter Request List
    End Option

No.     Time        Source                Destination           Protocol Info
    424 6025.066490 192.168.101.200       255.255.255.255       DHCP     DHCP ACK      - Transaction ID 0x8f93ada4

Frame 424 (379 bytes on wire, 379 bytes captured)
Ethernet II, Src: TyanComp_30:e9:cf (00:e0:81:30:e9:cf), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: TyanComp_30:e9:cf (00:e0:81:30:e9:cf)
    Type: IP (0x0800)
Internet Protocol, Src: 192.168.101.200 (192.168.101.200), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootpc (68)
Bootstrap Protocol
    Message type: Boot Reply (2)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x8f93ada4
    Seconds elapsed: 0
    Bootp flags: 0x8000 (Broadcast)
    Client IP address: 0.0.0.0 (0.0.0.0)
    Your (client) IP address: 192.168.101.66 (192.168.101.66)
    Next server IP address: 192.168.101.200 (192.168.101.200)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: Dell_3c:85:80 (00:11:43:3c:85:80)
    Server host name not given
    Boot file name not given
    Magic cookie: (OK)
    Option 53: DHCP Message Type = DHCP ACK
    Option 54: Server Identifier = 192.168.101.200
    Option 51: IP Address Lease Time = 2 minutes
    Option 58: Renewal Time Value = 1 minute
    Option 59: Rebinding Time Value = 1 minute, 45 seconds
    Option 1: Subnet Mask = 255.255.255.0
    Option 3: Router = 192.168.101.200
    Option 6: Domain Name Server = 192.168.101.200
    Option 15: Domain Name = "gonetworks.com"
    Option 81: FQDN
    End Option


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