Please find the latest version of these slides at:

https://code.google.com/p/ganeti/wiki/LISA2013

• Why gnt-network?
  • MAC + IP + link + mode = enough?
  • challenges
  • gnt-network support
• snf-network + nfdhcpd
• Hands on gnt-network

NIC configuration

• DHCP: Subnet? IPv6?
• mode=bridged. brctl addif only? firewall?
• All NICs same MAC prefix. Why?

Management

• Which VMs are on the same collision domain?
• A VM wants an IP. Which one is available?
• One router broke down. Renumber VMs now! How?

• easy way to assign IPs to instances
  • If resources are shared in multiple clusters, allocation must be done externally
• provide a way to configure each NIC differently
• find a way to hide underlying infrastructure
• better networking overview

masterd: config.data integrity

• abstract network infrastructure: network + netparams per nodegroup
• IP uniqueness inside network: IP pool management
  • bitarray, TemporaryReservationmanager, Locking
• encapsulate network information in NIC opjects: RPC

external scripts and hooks: ping vm1.ganeti.example.com

• use exported environment provided by noded
• brctl, iptables, ebtables, ip rule, etc.
• update external dhcp/DNS server entries
• let VM act unaware of the "situation" (dhclient, etc.)

• gnt-network alone is nothing more than a nice config.data
• snf-network: node level scripts and hooks
• nfdhcpd: node level DHCP server based on NFQUEUE

• overrides Ganeti default scripts (kvm-ifup, vif-ganeti)
• looks for specific tag types in NIC's network
• applies corresponding rules
• created nfdhcpd binding files
• provides hook to update DNS entries

• listens on specific NFQEUE
• updates its leases db
  • inotify on specific directory for binding files
• mangles DHCP requests and replies based on it's db
• responds to RS and NS for IPv6 auto-configuration

Create and connect a new network

gnt-network add --network 192.168.1.0/24 --gateway 192.168.1.1 --tags nfdhcpd net1
gnt-network connect net1 bridged prv0

Create an instance inside this network

gnt-instance add --net 0:ip=pool,network=net1 ... inst1
gnt-instance info inst1
gnt-network info net1

Use snf-network and nfdhcdpd

apt-get install snf-network nfdhcdpd
iptables -t mangle -A PREROUTING -i prv+ -p udp -m udp --dport 67 \
   -j NFQUEUE --queue-num 42
ip addr add 192.168.1.1/24 dev prv0

Test connectivity

gnt-instance reboot inst1
ping 192.168.1.2

• snf-network: http://code.grnet.gr/git/snf-network
• nfdhcpd: http://code.grnet.gr/git/snf-nfdhcpd