Packets in Open vSwitch flow through two main components - the vswitchd daemon in userspace which configures connections to controllers, and the datapath module in the kernel which performs packet forwarding based on flows. The datapath first receives packets from a NIC or VM's virtual NIC. It either follows instructions from vswitchd on how to handle the packet, or passes it to vswitchd if no instructions exist. Vswitchd then determines how to handle the packet and passes it back with actions for the datapath to cache and apply to similar future packets.

1. OpenvSwitch Code Flow
Packet flowin openvswitch
VISHAL KAPOOR

2. Openvswitch 2.7.2 implementation Vishal Kapoor
 Architecture of Open vSwitch
Two Main components –
vswitchdinuserspace for configurationandconnectiontocontroller.
datapathin Kernel space forpacketforwardingbasedonflow
The datapath module inthe kernel receivesthe packetsfirst,fromaphysical NICora VM’svirtual
NIC.Eitherovs-vswitchdhas instructedthe datapathhow tohandle packetsof thistype,or ithas
not. In the formercase,the datapathmodule simplyfollowsthe instructions,calledactions,givenby
ovs-vswitchd,whichlistphysical portsortunnelsonwhichtotransmitthe packet.Actionsmayalso
specifypacketmodifications,packetsampling,orinstructionstodropthe packet.In the othercase,
where the datapathhas notbeentoldwhatto do withthe packet,itdeliversittoovs-vswitchd.In
userspace,ovs-vswitchddetermineshow the packetshouldbe handled, andthen itpassesthe
packetback to the datapath withthe desiredhandling.Usually,ovs-vswitchdalsotellsthe datapath
to cache the actions,forhandlingsimilarfuture packets.

3. Openvswitch 2.7.2 implementation Vishal Kapoor
ovs_vport_receive
ovs_vport_receive
ovs_dp_process_packet
ovs_vport_receive
ovs_flow_tbl_lookup_stats
ovs_vport_receive
ovs_dp_upcall
!flow
ovs_execute_actions
flow_lookup()
ovs_vport_receive
masked_flow_lookup()
ovs_vport_receive
flow
queue_userspace_packet
do_execute_actions
Various operations based on
action attribute
push_mpls pop_mpls push_vlan pop_vlan
do_output ovs_vport_send
send(skb)
netdev_frame_hook
ovs_vport_receive
netdev_port_receive
ovs_vport_receive