chapter3_1.json

{
    "Nodes": {
        "helloworld":{}
    }
}

chapter3_2.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0": {
                    "ipv4_address": "192.0.2.1/24"
                }
            }
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0": {
                    "ipv4_address": "192.0.2.2/24"
                }
            }
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["ns2", "ns2-veth0"]]
    ]
}

chapter3_4.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0":{
                    "ipv4_address": "192.0.2.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"192.0.2.254"
                }
            ]
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0":{
                    "ipv4_address": "198.51.100.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"198.51.100.254"
                }
            ]
        },
        "router":{
            "interfaces": {
                "gw-veth0":{
                    "ipv4_address": "192.0.2.254/24"
                },
                "gw-veth1":{
                    "ipv4_address": "198.51.100.254/24"
                }
            }
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["router", "gw-veth0"]],
        [["ns2", "ns2-veth0"], ["router", "gw-veth1"]]
    ]
}

chapter3_5.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0":{
                    "ipv4_address": "192.0.2.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"192.0.2.254"
                }
            ]
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0":{
                    "ipv4_address": "198.51.100.1/24"
                }
            },            
            "routes":[
                {
                    "dst":"default",
                    "via":"198.51.100.254"
                }
            ]
        },
        "router1":{
            "interfaces": {
                "gw1-veth0":{
                    "ipv4_address": "192.0.2.254/24"
                },
                "gw1-veth1":{
                    "ipv4_address": "203.0.113.1/24"
                }                
            },
            "routes":[
                {
                    "dst":"198.51.100.0/24",
                    "via":"203.0.113.2"
                }
            ],
            "ipv4_forward": true
        },
        "router2":{
            "interfaces": {
                "gw2-veth0":{
                    "ipv4_address": "203.0.113.2/24"
                },
                "gw2-veth1":{
                    "ipv4_address": "198.51.100.254/24"
                }                
            },
            "routes":[
                {
                    "dst":"192.0.2.0/24",
                    "via":"203.0.113.1"
                }
            ],
            "ipv4_forward": true
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["router1", "gw1-veth0"]],
        [["router1", "gw1-veth1"], ["router2", "gw2-veth0"]],
        [["router2", "gw2-veth1"], ["ns2", "ns2-veth0"]]
    ]
}

chapter4_2.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0": {
                    "ipv4_address": "192.0.2.1/24",
                    "mac_address": "00:00:5E:00:53:01"
                }
            }
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0": {
                    "ipv4_address": "192.0.2.2/24",
                    "mac_address": "00:00:5E:00:53:02"
                }
            }
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["ns2", "ns2-veth0"]]
    ]
}

chapter4_4.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0": {
                    "mac_address": "00:00:5E:00:53:11",
                    "ipv4_address": "192.0.2.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"192.0.2.254"
                }
            ]
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0": {
                    "mac_address": "00:00:5E:00:53:22",
                    "ipv4_address": "198.51.100.1/24"
                }
            },
            "routes":[              
                {
                    "dst":"default",
                    "via":"198.51.100.254"
                }
            ]
        },
        "gw":{
            "interfaces": {
                "gw-veth0": {
                    "mac_address": "00:00:5E:00:53:12",
                    "ipv4_address": "192.0.2.254/24"
                },
                "gw-veth1": {
                    "mac_address": "00:00:5E:00:53:21",
                    "ipv4_address": "198.51.100.254/24"
                }
            },
            "ipv4_forward": true
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["gw", "gw-veth0"]],
        [["ns2", "ns2-veth0"], ["gw", "gw-veth1"]]
    ]
}

chapter4_5.json

{
    "Nodes": {
        "ns1":{
            "interfaces": {
                "ns1-veth0": {
                    "ipv4_address": "192.0.2.1/24",
                    "mac_address": "00:00:5E:00:53:01"
                }
            }
        },
        "ns2":{
            "interfaces": {
                "ns2-veth0": {
                    "ipv4_address": "192.0.2.2/24",
                    "mac_address": "00:00:5E:00:53:02"
                }
            }
        },
        "ns3":{
            "interfaces": {
                "ns3-veth0": {
                    "ipv4_address": "192.0.2.3/24",
                    "mac_address": "00:00:5E:00:53:03"
                }
            }
        },
        "br0":{
            "node_type": "Bridge",
            "interfaces": {
                "ns1-br0": {},
                "ns2-br0": {},
                "ns3-br0": {}
            }
        }
    },
    "Links": [
        [["ns1", "ns1-veth0"], ["br0", "ns1-br0"]],
        [["ns2", "ns2-veth0"], ["br0", "ns2-br0"]],
        [["ns3", "ns3-veth0"], ["br0", "ns3-br0"]]
    ]
}

chapter6_3.json

{
    "Nodes": {
        "server":{
            "interfaces": {
                "s-veth0": {
                    "ipv4_address": "192.0.2.254/24"
                }
            }
        },
        "client":{
            "interfaces": {
                "c-veth0": {
                }
            }
        }
    },
    "Links": [
        [["server", "s-veth0"], ["client", "c-veth0"]]
    ]
}

chapter7_1.json

{
    "Nodes": {
        "lan":{
            "interfaces":{
                "lan-veth0": {
                    "node_name": "lan",
                    "ipv4_address": "192.0.2.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"192.0.2.254"
                }
            ]
        },
        "router":{
            "interfaces": {
                "gw-veth0": {
                    "node_name": "router",
                    "ipv4_address": "192.0.2.254/24"
                },
                "gw-veth1": {
                    "node_name": "router",
                    "ipv4_address": "203.0.113.254/24"
                }
            }
        },
        "wan": {
            "interfaces": {
                "wan-veth0": {
                    "node_name": "wan",
                    "ipv4_address": "203.0.113.1/24"
                }
            },
            "routes":[
                {
                    "dst":"default",
                    "via":"203.0.113.254"
                }
            ]
        }
    },
    "Links": [
        [["lan", "lan-veth0"], ["router", "gw-veth0"]],
        [["router", "gw-veth1"], ["wan", "wan-veth0"]]
    ]
}

netns.py

import json
import subprocess as sp
import sys


def _run_command(cmd):
    print(' '.join(cmd))
    sp.run(cmd)


class Node(object):
    def __init__(self, name: str, interfaces={}, routes=[], ipv4_forward=True, **_):
        super(Node, self).__init__()
        self.name = name
        self.routes = routes
        self.interfaces = {k: NetInterface(k, self, **v)
                           for k, v in interfaces.items()}
        self.ipv4_forward = ipv4_forward

    def create_command(self):
        cmd = ['sudo', 'ip', 'netns', 'add', self.name]
        _run_command(cmd)
        if self.ipv4_forward:
            cmd = ['sudo', 'ip', 'netns', 'exec',
                   self.name, 'sysctl', 'net.ipv4.ip_forward=1']
            _run_command(cmd)

    def remove_command(self):
        cmd = ['sudo', 'ip', 'netns', 'delete', self.name]
        _run_command(cmd)

    def add_interface(self, if_name: str):
        cmd = ['sudo', 'ip', 'link', 'set', if_name, 'netns', self.name]
        _run_command(cmd)

        cmd = ['sudo', 'ip', 'netns', 'exec', self.name,
               'ip', 'link', 'set', if_name, 'up']
        _run_command(cmd)

    def set_route(self):
        for r in self.routes:
            dst = r['dst']
            via = r['via']
            cmd = ['sudo', 'ip', 'netns', 'exec',
                   self.name, 'ip', 'route', 'add', dst, 'via', via]
            _run_command(cmd)


class Bridge(object):
    def __init__(self, name: str, interfaces={}, **_):
        super(Bridge, self).__init__()
        self.name = name
        self.interfaces = {k: NetInterface(k, self, **v)
                           for k, v in interfaces.items()}

    def create_command(self):
        cmd = ['sudo', 'ip', 'link', 'add', 'dev', self.name, 'type', 'bridge']
        _run_command(cmd)
        cmd = ['sudo', 'ip', 'link', 'set', self.name, 'up']
        _run_command(cmd)

    def remove_command(self):
        cmd = ['sudo', 'ip', 'link', 'delete', self.name]
        _run_command(cmd)

    def add_interface(self, if_name: str):
        cmd = ['sudo', 'ip', 'link', 'set', if_name, 'master', self.name]
        _run_command(cmd)
        cmd = ['sudo', 'ip', 'link', 'set', if_name, 'up']
        _run_command(cmd)

    def set_route(self):
        pass


def create_node(name: str, node_type: str = "Node", **kargs):
    cls = getattr(sys.modules[__name__], node_type)
    return cls(name, **kargs)


class NetInterface(object):
    def __init__(self, name: str, node, ipv4_address: str = None, mac_address: str = None, **_):
        super(NetInterface, self).__init__()
        self.name = name
        self.node = node
        self.ipv4_address = ipv4_address
        self.mac_address = mac_address

    def create_command(self):
        self.node.add_interface(self.name)
        if self.ipv4_address:
            cmd = ['sudo', 'ip', 'netns', 'exec', self.node.name, 'ip',
                   'address', 'add', self.ipv4_address, 'dev', self.name]
            _run_command(cmd)
        if self.mac_address:
            cmd = ['sudo', 'ip', 'netns', 'exec', self.node.name,
                   'ip', 'link', 'set', 'dev', self.name, 'address', self.mac_address]
            _run_command(cmd)


class Link(object):
    def __init__(self, if0: NetInterface, if1: NetInterface):
        super(Link, self).__init__()
        self.if0 = if0
        self.if1 = if1

    def create_command(self):
        cmd = ['sudo', 'ip', 'link', 'add', self.if0.name,
               'type', 'veth', 'peer', 'name', self.if1.name]
        _run_command(cmd)

        self.if0.create_command()
        self.if1.create_command()


def create_network(j):
    nodes = {}

    def _get_node(name: str, **kwargs):
        if name in nodes:
            return nodes[name]

        node = create_node(name, **kwargs)
        node.create_command()
        nodes[name] = node
        return node

    nodes = {}
    for k, v in j['Nodes'].items():
        nodes[k] = _get_node(k, **v)

    if 'Links' in j:
        for if0, if1 in j['Links']:
            node_name0, if_name0 = if0
            node_name1, if_name1 = if1

            node0 = _get_node(node_name0)
            node1 = _get_node(node_name1)
            if0 = node0.interfaces[if_name0]
            if1 = node1.interfaces[if_name1]
            l = Link(if0, if1)
            l.create_command()
        for n in nodes.values():
            n.set_route()


def clean_network(j):
    for k, v in j['Nodes'].items():
        node = create_node(k, **v)
        node.remove_command()


def print_usage(prog_name):
    print(prog_name, ': json start|stop')
    exit(0)


if len(sys.argv) < 3:
    print_usage(sys.argv[0])

with open(sys.argv[1], "r") as f:
    j = json.load(f)
    if sys.argv[2] == 'start':
        create_network(j)
    elif sys.argv[2] == 'stop':
        clean_network(j)
    else:
        print_usage(sys.argv[0])