#networking#lab#k8s#namespace#ip#link

namespace.sh

// 创建bridge
create_bridge() {
    local nsname="$1"
    local ifname="$2"

    echo "Creating bridge ${nsname}/${ifname}"

    ip netns add ${nsname}
    ip netns exec ${nsname} ip link set lo up
    ip netns exec ${nsname} ip link add ${ifname} type bridge
    ip netns exec ${nsname} ip link set ${ifname} up
}
// 在不同的net namespace 来创建汇end 节点
// https://iximiuz.com/en/posts/networking-lab-ethernet-broadcast-domains/
create_end_host() {
    local host_nsname="$1"
    local peer1_ifname="$2a"
    local peer2_ifname="$2b"
    local bridge_nsname="$3"
    local bridge_ifname="$4"

    echo "Creating end host ${host_nsname} connected to ${bridge_nsname}/${bridge_ifname} bridge"

    # Create end host network namespace.
    ip netns add ${host_nsname}
    ip netns exec ${host_nsname} ip link set lo up

    # Create a veth pair connecting end host and bridge namespaces.
    ip link add ${peer1_ifname} netns ${host_nsname} type veth peer \
                ${peer2_ifname} netns ${bridge_nsname}
    ip netns exec ${host_nsname} ip link set ${peer1_ifname} up
    ip netns exec ${bridge_nsname} ip link set ${peer2_ifname} up

    # Attach peer2 interface to the bridge.
    ip netns exec ${bridge_nsname} ip link set ${peer2_ifname} master ${bridge_ifname}
}



// 用来给制定的mac地址来发送L2包
#!/usr/bin/env python3

# Usage: ethsend.py eth0 ff:ff:ff:ff:ff:ff 'Hello everybody!'
#        ethsend.py eth0 06:e5:f0:20:af:7a 'Hello 06:e5:f0:20:af:7a!'
#
# Note: CAP_NET_RAW capability is required to use SOCK_RAW

import fcntl
import socket
import struct
import sys

def send_frame(ifname, dstmac, eth_type, payload):
    # Open raw socket and bind it to network interface.
    s = socket.socket(socket.AF_PACKET, socket.SOCK_RAW)
    s.bind((ifname, 0))

    # Get source interface's MAC address.
    info = fcntl.ioctl(s.fileno(),
                       0x8927,
                       struct.pack('256s', bytes(ifname, 'utf-8')[:15]))
    srcmac = ':'.join('%02x' % b for b in info[18:24])

    # Build Ethernet frame
    payload_bytes = payload.encode('utf-8')
    assert len(payload_bytes) <= 1500  # Ethernet MTU

    frame = human_mac_to_bytes(dstmac) + \
            human_mac_to_bytes(srcmac) + \
            eth_type + \
            payload_bytes

    # Send Ethernet frame
    return s.send(frame)

def human_mac_to_bytes(addr):
    return bytes.fromhex(addr.replace(':', ''))

def main():
  ifname = sys.argv[1]
  dstmac = sys.argv[2]
  payload = sys.argv[3]
  ethtype = b'\x7A\x05'  # arbitrary, non-reserved
  send_frame(ifname, dstmac, ethtype, payload)

if __name__ == "__main__":
    main()

创建bridge设备

ip netns add ${nsname}
ip netns exec ${nsname} ip link set lo up
ip netns exec ${nsname} ip link add ${ifname} type bridge
ip netns exec ${nsname} ip link set ${ifname} up