我试图在我的Ubuntu机器上安装mininet 2.3.0，我得到以下错误消息：

root@Mininet-PC:/home/mininet# mininet/util/install.sh -a
.
.
.
Cloning into 'openflow'...
fatal: unable to connect to github.com:
github.com[0: 140.82.121.4]: errno=Connection timed out

我试图ping到github.com140.82.121.4如上所示，我得到了0%的包丢失
当我尝试打开一个简单的拓扑时，我得到以下错误消息：

root@Mininet-PC:/home/mininet# mn
*** Creating network
*** Adding controller
*** Adding hosts:
h1 h2 
*** Adding switches:
Cannot find required executable ovs-vsctl.
Please make sure that Open vSwitch (openvswitch.org) is installed and available in your $PATH:
(/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin)

我尝试安装openvswitch-testcontroller，当我这样做时，我得到以下错误消息：

*** Adding controller
--------------------------------------------------------------------------------
Caught exception. Cleaning up...

Exception: Please shut down the controller which is running on port 6653:
Active Internet connections (servers and established)
tcp        0      0 0.0.0.0:6653            0.0.0.0:*               LISTEN      5982/ovs-testcontro 
--------------------------------------------------------------------------------
*** Removing excess controllers/ofprotocols/ofdatapaths/pings/noxes
killall controller ofprotocol ofdatapath ping nox_corelt-nox_core ovs-openflowd ovs-controllerovs-testcontroller udpbwtest mnexec ivs ryu-manager 2> /dev/null
killall -9 controller ofprotocol ofdatapath ping nox_corelt-nox_core ovs-openflowd ovs-controllerovs-testcontroller udpbwtest mnexec ivs ryu-manager 2> /dev/null
pkill -9 -f "sudo mnexec"
*** Removing junk from /tmp
rm -f /tmp/vconn* /tmp/vlogs* /tmp/*.out /tmp/*.log
*** Removing old X11 tunnels
*** Removing excess kernel datapaths
ps ax | egrep -o 'dp[0-9]+' | sed 's/dp/nl:/'
***  Removing OVS datapaths
ovs-vsctl --timeout=1 list-br
/bin/sh: 1: ovs-vsctl: not found
ovs-vsctl --timeout=1 list-br
/bin/sh: 1: ovs-vsctl: not found
*** Removing all links of the pattern foo-ethX
ip link show | egrep -o '([-_.[:alnum:]]+-eth[[:digit:]]+)'
ip link show
*** Killing stale mininet node processes
pkill -9 -f mininet:
*** Shutting down stale tunnels
pkill -9 -f Tunnel=Ethernet
pkill -9 -f .ssh/mn
rm -f ~/.ssh/mn/*
*** Cleanup complete.

我也试过apt-get update/apt-get upgrade还是没有运气。