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[Haojie Jia <jiahaojie201@xxxxxxxxxxxxx>]

Public bug reported:

why can't turn dhcp discovery and request message into unicast ?

As we know, The DHCP operation begins with clients broadcasting a
request, then DHCP server send a DHCP offer message to the client. In
response to the DHCP offer,the client replies with a DHCP request to
request the offered address. DHCP Discovery message and DHCP request
message are both broadcast. In some scenarios, we want to broadcast
messages as little as possible, Why can't turn DHCP discovery and
request message into unicast before the broadcast outflow from host?
Maybe we add some flow entries in OVS bridge to modify mac_address of
DHCP broadcast, the premise is L2 agent to be able to get mac_address of
dhcp port. I add some flow entries for br-eth1 bridge which modify
broadcast into unicast, it works, and vm successfully request IP
addresses automatically.

[root@compute1 ~]# ovs-ofctl dump-flows br-eth1    #####this is my flow
entries, mac_address of dhcp port is fa:16:3e:c0:4e:ea#####

NXST_FLOW reply (xid=0x4):

cookie=0x0, duration=263106.173s, table=0, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=9,ip,in_port=2,dl_dst=ff:ff:ff:ff:ff:ff,nw_src=0.0.0.0,nw_dst=255.255.255.255
actions=resubmit(,26)

cookie=0x0, duration=263106.155s, table=26, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=2,dl_vlan=13,dl_src=fa:16:3e:5f:2f:7b
actions=mod_vlan_vid:333,mod_dl_dst:fa:16:3e:c0:4e:ea,NORMAL

cookie=0x0, duration=263107.295s, table=26, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534, priority=0 actions=drop

I also develop some codes for neutron which can get mac_address of
dhcp_port and add flow entries for ovs bridge.

** Affects: neutron
     Importance: Wishlist
         Status: Opinion

** Changed in: hybrid-cloud
   Importance: Undecided => High

** Project changed: hybrid-cloud => neutron

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https://bugs.launchpad.net/bugs/1584568

Title:
  why can't turn dhcp discovery and request message into unicast ?

Status in neutron:
  Opinion

Bug description:
  why can't turn dhcp discovery and request message into unicast ?

  As we know, The DHCP operation begins with clients broadcasting a
  request, then DHCP server send a DHCP offer message to the client. In
  response to the DHCP offer,the client replies with a DHCP request to
  request the offered address. DHCP Discovery message and DHCP request
  message are both broadcast. In some scenarios, we want to broadcast
  messages as little as possible, Why can't turn DHCP discovery and
  request message into unicast before the broadcast outflow from host?
  Maybe we add some flow entries in OVS bridge to modify mac_address of
  DHCP broadcast, the premise is L2 agent to be able to get mac_address
  of dhcp port. I add some flow entries for br-eth1 bridge which modify
  broadcast into unicast, it works, and vm successfully request IP
  addresses automatically.

  [root@compute1 ~]# ovs-ofctl dump-flows br-eth1    #####this is my
  flow entries, mac_address of dhcp port is fa:16:3e:c0:4e:ea#####

  NXST_FLOW reply (xid=0x4):

  cookie=0x0, duration=263106.173s, table=0, n_packets=0, n_bytes=0,
  idle_age=65534, hard_age=65534,
  priority=9,ip,in_port=2,dl_dst=ff:ff:ff:ff:ff:ff,nw_src=0.0.0.0,nw_dst=255.255.255.255
  actions=resubmit(,26)

  cookie=0x0, duration=263106.155s, table=26, n_packets=0, n_bytes=0,
  idle_age=65534, hard_age=65534,
  priority=2,dl_vlan=13,dl_src=fa:16:3e:5f:2f:7b
  actions=mod_vlan_vid:333,mod_dl_dst:fa:16:3e:c0:4e:ea,NORMAL

  cookie=0x0, duration=263107.295s, table=26, n_packets=0, n_bytes=0,
  idle_age=65534, hard_age=65534, priority=0 actions=drop

  I also develop some codes for neutron which can get mac_address of
  dhcp_port and add flow entries for ovs bridge.

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