[Dnsmasq-discuss] Making dnsmasq make OFFER faster than virtualbox NAT DHCP

[Sebastian Tarach]

Hello,

I'm trying to make *dnsmasq* work on my Debian Virtualbox guest but I keep
getting reply from my VBox host DHCP first.

I have configured bridge ( br0 ) using openvswitch:

$ ovs-vsctl show
> cbda5c6b-c9ba-4fb4-8143-a1f0683e1e96
>     Manager "ptcp:6640"
>     Bridge "br0"
>         Port "eth0"
>             Interface "eth0"
>         Port "vport1"
>             Interface "vport1"
>         Port "br0"
>             Interface "br0"
>                 type: internal
>     ovs_version: "2.4.0"


And have *dnsmasq* running on *br0*
I have also removed configuration from *eth0*
*ifconfig eth0 0 *and set default gateway to b*r0*
*route add default gateway 192.168.1.129*

> $ route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> 0.0.0.0         192.168.1.129   0.0.0.0         UG    0      0        0 br0
> 172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0
> docker0
> 192.168.1.128   0.0.0.0         255.255.255.128 U     0      0        0 br0
> 192.168.56.0    0.0.0.0         255.255.255.0   U     0      0        0
> eth1


But when I'm running *nmap --script broadcast-dhcp-discover -e br0*
the tdpdump process show response/OFFER from VBox DHCP comes first.

*tcpdump -i br0 -nev udp port 68*

> tcpdump: listening on br0, link-type EN10MB (Ethernet), capture size
> 262144 bytes
> 01:29:51.031925 08:00:27:b6:c1:90 > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 355: (tos 0x0, ttl 64, id 23681, offset 0, flags [DF],
> proto UDP (17), length 341)
>     192.168.1.129.68 > 255.255.255.255.67: BOOTP/DHCP, Request from
> de:ad:c0:de:ca:fe, length 313, xid 0x514a3f0c, Flags [Broadcast]
>           Client-Ethernet-Address de:ad:c0:de:ca:fe
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Discover
>             Parameter-Request Option 55, length 61:
>               Subnet-Mask, Time-Zone, Default-Gateway, Time-Server
>               IEN-Name-Server, Domain-Name-Server, LOG, CS
>               LPR-Server, IM, RL, Hostname
>               BS, DP, Domain-Name, SS
>               RP, EP, IPF, SRT
>               PF, RSZ, TTL, MTU-Timeout
>               MTU-Table, MTU, LSN, BR
>               MD, MS, Router-Discovery, RSA
>               Static-Route, UT, AT, IE
>               TT, KI, KG, YD
>               YS, NTP, Vendor-Option, Netbios-Name-Server
>               WDD, Netbios-Node, Netbios-Scope, XFS
>               XDM, Requested-IP, Lease-Time, OO
>               DHCP-Message, Server-ID, Parameter-Request, MSG
>               MSZ, RN, RB, Vendor-Class
>               Client-ID
>             Lease-Time Option 51, length 4: 1
> 01:29:51.034866 52:54:00:12:35:02 > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 590: (tos 0x10, ttl 64, id 1, offset 0, flags [none],
> proto UDP (17), length 576)
>     10.0.2.2.67 > 255.255.255.255.68: BOOTP/DHCP, Reply, length 548, xid
> 0x514a3f0c, Flags [Broadcast]
>           Your-IP 10.0.2.15
>           Server-IP 10.0.2.4
>           Client-Ethernet-Address de:ad:c0:de:ca:fe
>           file "debian8.pxe"
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Offer
>             Subnet-Mask Option 1, length 4: 255.255.255.0
>             Default-Gateway Option 3, length 4: 10.0.2.2
>             Domain-Name-Server Option 6, length 8: 192.168.1.1,192.168.1.1
>             Domain-Name Option 15, length 4: "home"
>             Lease-Time Option 51, length 4: 86400
>             Server-ID Option 54, length 4: 10.0.2.2
> 01:29:54.031972 08:00:27:b6:c1:90 > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 347: (tos 0xc0, ttl 64, id 24077, offset 0, flags [none],
> proto UDP (17), length 333)
>     192.168.1.129.67 > 255.255.255.255.68: BOOTP/DHCP, Reply, length 305,
> xid 0x514a3f0c, Flags [Broadcast]
>           Your-IP 192.168.1.176
>           Server-IP 192.168.1.129
>           Client-Ethernet-Address de:ad:c0:de:ca:fe
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Offer
>             Server-ID Option 54, length 4: 192.168.1.129
>             Lease-Time Option 51, length 4: 120
>             RN Option 58, length 4: 60
>             RB Option 59, length 4: 105
>             Subnet-Mask Option 1, length 4: 255.255.255.128
>             BR Option 28, length 4: 192.168.1.255
>             Domain-Name-Server Option 6, length 4: 192.168.1.129
>             Domain-Name Option 15, length 11: "mydomain.io"
>             Default-Gateway Option 3, length 4: 192.168.1.129


What did I do wrong?
~Thanks

My dnsmasq.conf file:

> interface=br0
> domain-needed
> bogus-priv
> no-resolv
> local=/mydomain.io/
> no-poll
> no-hosts
> domain=mydomain.io
> dhcp-range=192.168.1.129,192.168.1.254,255.255.255.128,192.168.1.255,12h
> dhcp-option=3,192.168.1.129
> log-queries
> log-dhcp
> dhcp-authoritative
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