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Stateful NAT with Open vSwitch
LinuxCon 2015, Seattle
Thomas Graf
Kernel & Open vSwitch Team
Noiro Networks (Cisco)
Agenda
● What is Open vSwitch
● Stateful NAT options for Open vSwitch
● Demo
● Q&A
Open vSwitch Connects
VM
Host
NIC
Container
Tunnel
Cloudy
Stuff
● Highly scaleable multi layer virtual switch for hypervisors
– Apache License (User Space), GPL (Kernel)
● Extensive flow table programming capabilities
– OpenFlow 1.0 – 1.5 (some partial)
– Vendor extensions
● Designed to manage overlay networks
– VXLAN (+ extensions), GRE, Geneve, LISP, STT, VLAN, ...
● Remote management protocol (OVSDB)
● Monitoring capabilities
Open vSwitch in a Nutshell
NAT Dependency:
Connection Tracking
● We are adding the ability to use the conntrack module from Linux
– Stateful tracking of flows
– Supports ALGs to punch holes for related “data” channels
● FTP, TFTP, SIP
● Implement a distributed firewall with enforcement at the edge
– Better performance
– Better visibility
● Introduce new OpenFlow extensions:
– Action to send to conntrack
– Match fields on state of connection
● Have prototype working. Expect to ship as part of OVS in next
release.
Netfilter Conntrack Integration
OVS Flow Table
Netfilter
Connection Tracker
CT
Table
Userspace Netlink API
Create & Update
CT entries
Connection State (conn_state=)
conntrack()
Recirculation
1
2
3
4
Zone 1
Connection Tracking Zones
OVS Flow Table
CT
Table
Zone 2
CT
Table
Netfilter
Connection Tracker
● Route packets through separate NAT network namespace
● Utilize Netfilter chains to perform NAT
● Pro: Working now
● Con: Requires linear Netfilter chain traversal
NAT with Open vSwitch
The Now
● Native OpenFlow NAT action
● Pro: Fast, clean & available to orchestration tools
● Con: Tricky to get right
The Future
Possible Future 1:
Native stateful NAT
OVS Flow Table
Netfilter
Connection Tracker CT
Table
Create & Update
CT entries
conntrack()
Recirculation
1
2
3
4
Netfilter
NAT
nat()
Possible Future 2:
Customizable NAT through eBPF
OVS Flow Table
Netfilter
Connection Tracker CT
Table
Create & Update
CT entries
conntrack()
Recirculation
1
2
3
4
BPF prog
performing NAT
bpf()
What is available now:
NAT with Netfilter
OVS Flow Table
Netfilter
Connection Tracker CT
Table
Create & Update
CT entries
conntrack()
Final L2/L3 decision
1
2
3
Namespace w/
-j SNAT / -j DNAT
output() to
internal port
5
4
Routing:
ip rule add iif nat-gw lookup 100
ip route add 1.1.1.1/32 dev nat-gw
ip route add default 
via 1.1.1.1 table 100
Demo
Q&A
Contact:
● E-Mail: tgraf@suug.ch
● Twitter: @tgraf__

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LinuxCon 2015 Stateful NAT with OVS

  • 1. Stateful NAT with Open vSwitch LinuxCon 2015, Seattle Thomas Graf Kernel & Open vSwitch Team Noiro Networks (Cisco)
  • 2. Agenda ● What is Open vSwitch ● Stateful NAT options for Open vSwitch ● Demo ● Q&A
  • 4. ● Highly scaleable multi layer virtual switch for hypervisors – Apache License (User Space), GPL (Kernel) ● Extensive flow table programming capabilities – OpenFlow 1.0 – 1.5 (some partial) – Vendor extensions ● Designed to manage overlay networks – VXLAN (+ extensions), GRE, Geneve, LISP, STT, VLAN, ... ● Remote management protocol (OVSDB) ● Monitoring capabilities Open vSwitch in a Nutshell
  • 5. NAT Dependency: Connection Tracking ● We are adding the ability to use the conntrack module from Linux – Stateful tracking of flows – Supports ALGs to punch holes for related “data” channels ● FTP, TFTP, SIP ● Implement a distributed firewall with enforcement at the edge – Better performance – Better visibility ● Introduce new OpenFlow extensions: – Action to send to conntrack – Match fields on state of connection ● Have prototype working. Expect to ship as part of OVS in next release.
  • 6. Netfilter Conntrack Integration OVS Flow Table Netfilter Connection Tracker CT Table Userspace Netlink API Create & Update CT entries Connection State (conn_state=) conntrack() Recirculation 1 2 3 4
  • 7. Zone 1 Connection Tracking Zones OVS Flow Table CT Table Zone 2 CT Table Netfilter Connection Tracker
  • 8. ● Route packets through separate NAT network namespace ● Utilize Netfilter chains to perform NAT ● Pro: Working now ● Con: Requires linear Netfilter chain traversal NAT with Open vSwitch The Now ● Native OpenFlow NAT action ● Pro: Fast, clean & available to orchestration tools ● Con: Tricky to get right The Future
  • 9. Possible Future 1: Native stateful NAT OVS Flow Table Netfilter Connection Tracker CT Table Create & Update CT entries conntrack() Recirculation 1 2 3 4 Netfilter NAT nat()
  • 10. Possible Future 2: Customizable NAT through eBPF OVS Flow Table Netfilter Connection Tracker CT Table Create & Update CT entries conntrack() Recirculation 1 2 3 4 BPF prog performing NAT bpf()
  • 11. What is available now: NAT with Netfilter OVS Flow Table Netfilter Connection Tracker CT Table Create & Update CT entries conntrack() Final L2/L3 decision 1 2 3 Namespace w/ -j SNAT / -j DNAT output() to internal port 5 4 Routing: ip rule add iif nat-gw lookup 100 ip route add 1.1.1.1/32 dev nat-gw ip route add default via 1.1.1.1 table 100
  • 12. Demo