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Using IPv6 Segment Routing

IPMininet enables you to use the Linux implementation of IPv6 Segment Routing (SRv6).

Using this part of IPMininet requires a recent version of the linux kernel (see https://segment-routing.org/index.php/Implementation/Installation) for more details.

Note that all the abstractions presented here have to be used once the network is setup. We leverage the following method to do it:

ipmininet.iptopo.IPTopo.post_build

Activation

By default, routers and hosts will drop packets with IPv6 Segment Routing Header. You can enable IPv6 Segment Routing on a per-node basis with the following function.

ipmininet.srv6.enable_srv6

Here is an example of topology where IPv6 Segment Routing is enabled on all hosts and routers:

srv6activate

from ipmininet.iptopo import IPTopo from ipmininet.srv6 import enable_srv6

class MyTopology(IPTopo):

def build(self, args,*kwargs):

r1 = self.addRouter("r1") r2 = self.addRouter("r2") h1 = self.addHost("h1") h2 = self.addHost("h2")

self.addLink(r1, r2) self.addLink(r1, h1) self.addLink(r2, h2)

super().build(args,*kwargs)

def post_build(self, net):
for n in net.hosts + net.routers:

enable_srv6(n)

super().post_build(net)

Using any of the following SRv6 abstractions also enables SRv6 on all hosts and routers.

Insertion and encapsulation

The following abstraction enables you to insert or encapsulate SRH in your packets based on the destination.

ipmininet.srv6.SRv6Encap.__init__

srv6encapsulation

from ipmininet.iptopo import IPTopo from ipmininet.srv6 import SRv6Encap

class MyTopology(IPTopo):

def build(self, args,*kwargs):

r1 = self.addRouter("r1") r2 = self.addRouter("r2") h1 = self.addHost("h1") h2 = self.addHost("h2")

self.addLink(r1, r2) self.addLink(r1, h1) self.addLink(r2, h2)

super().build(args,*kwargs)

def post_build(self, net):

# No need to enable SRv6 because the call to the abstraction # triggers it

# This adds an SRH encapsulation route on h1 for packets to h2 SRv6Encap(net=net, node="h1", to="h2", # You can specify the intermediate point with any # of the host, its name, an interface or the address # itself through=[net["r1"], "r1", net["r1"].intf("lo"), net["r1"].intf("lo").ip6], # Either insertion (INLINE) or encapsulation (ENCAP) mode=SRv6Encap.INLINE) super().post_build(net)

Advanced configuration

The advanced processing of SRv6-enabled packets detailed in https://segment-routing.org/index.php/Implementation/AdvancedConf is also supported by IPMininet with the following abstractions:

ipmininet.srv6.SRv6EndFunction.__init__

ipmininet.srv6.SRv6EndXFunction.__init__

ipmininet.srv6.SRv6EndTFunction.__init__

ipmininet.srv6.SRv6EndDX2Function.__init__

ipmininet.srv6.SRv6EndDX6Function.__init__

ipmininet.srv6.SRv6EndDX4Function.__init__

ipmininet.srv6.SRv6EndDT6Function.__init__

ipmininet.srv6.SRv6EndB6Function.__init__

ipmininet.srv6.SRv6EndB6EncapsFunction.__init__

They are used in the same way as SRv6Encap in the previous section. You can instantiate any of these classes to make add the corresponding route to your network.

However, these special routes are supposed to be in a separate tables, called a Local SID table so that we can split plain routing and SRH management. To create this new table in a router, you can instantiate the following class:

ipmininet.srv6.LocalSIDTable.__init__

This LocalSIDTable instance can then be used to instantiate the previous classes to insert the routes in this table instead of the default one.

srv6functions

from ipmininet.iptopo import IPTopo from ipmininet.srv6 import SRv6Encap, SRv6EndFunction, LocalSIDTable

class MyTopology(IPTopo):

def build(self, args,*kwargs):

r1 = self.addRouter("r1") r2 = self.addRouter("r2", lo_addresses="2042:2:2::1/64") h1 = self.addHost("h1") h2 = self.addHost("h2")

self.addLink(r1, r2) self.addLink(r1, h1) self.addLink(r2, h2)

super().build(args,*kwargs)

def post_build(self, net):

# No need to enable SRv6 because the call to the abstraction # triggers it

# This adds an SRH encapsulation route on h1 for packets to h2 SRv6Encap(net=net, node="h1", to="h2", # You can specify the intermediate point with any # of the host, its name, an interface or the address # itself through=[net["r1"], "r1", net["r1"].intf("lo"), net["r1"].intf("lo").ip6, "2042:2:2::200"], # Either insertion (INLINE) or encapsulation (ENCAP) mode=SRv6Encap.INLINE)

# Creates a LocalSIDTable table handling all traffic for # 2042:2:2::/64 (except 2042:2:2::1 which is the loopback address) sid_table = LocalSIDTable(net["r2"], matching=["2042:2:2::/64"])

# Receiving a packet on r2 with "2042:2:2::200" as active segment # will trigger the function 'End' which is regular SRH processing SRv6EndFunction(net=net, node="r2", to="2042:2:2::200", table=sid_table)

super().post_build(net)

from ipmininet.clean import cleanup cleanup(level='warning')

try:

MyTopology

except NameError:

MyTopology = None

if MyTopology is not None:

from ipmininet.ipnet import IPNet net = IPNet(topo=MyTopology()) net.start()

try:

net

except NameError:

net = None

if net is not None:

net.stop()