pppoe in ubuntu 18.04

在18.04中，ubuntu引入了netplan，netplan只支持networkd和NetworkManager渲染，不直接支持pppoe的设置

• 方案一： 删除netplan，使用ifupdown + ppppoeconf，回归到Ubuntu 16.04之前的状态
• 方案二： networkd + networkd-dispatcher + ppp

1. Install networkd, networkd-dispatcher, pppoe

sudo apt install networkd networkd-dispatcher pppoe

We won’t install pppoeconf, because it depends on ifupdown

2. Configure netplan to use networkd as render

/etc/netplan/enp3s0.yaml
----------------------------------------------------------
network:
  version: 2
  renderer: networkd
  ethernets:
    enp4s0:
      dhcp4: yes
      dhcp6: yes

3. Configure pppoe

Edit to add username and interface /etc/ppp/peers/dsl-provider

/etc/ppp/peers/dsl-provider
--------------------------------------------------------
# lines in file you need to notice
user *****
pty "/usr/sbin/pppoe -I enp4s0 -T 80 -m 1452"
# replace the local route
defaultroute
replacedefaultroute

Edit to add password in /etc/ppp/pap-secrets and /etc/ppp/chap-secrets

/etc/ppp/pap-secrets, /etc/ppp/chap-secrets
--------------------------------------------------------
<username> * <password>

Now, you can pon dsl-provider to connect or poff dsl-provider to disconnect

4. 使用networkd-dispatcher实现开机启动和网络重启时自动连接

networkd-dispatcher能够在网络状态改变时执行相应的脚本

/etc/networkd-dispatcher/routable.d/00-ppp
--------------------------------------------------------
#!/bin/bash

# log file
readonly LOG_FILE="/home/fancy/log/pppoe.log"
mkdir -p $(dirname $LOG_FILE) && touch $LOG_FILE
chown fancy $LOG_FILE
exec 1>>$LOG_FILE
exec 2>&1

date +"%m/%d/%Y %H:%M:%S $IFACE $STATE"

# record enp4s0 ip address to server
[ $IFACE = "enp4s0" ] \
&& echo "post-enp4s0:" \
&& bash /home/fancy/scripts/01_route_in_tju.sh \
&& bash /home/fancy/scripts/00_record_ip_to_server.sh

# if event from enp4s0, and the ppp0 daemon not exists, then start pppoe connection
# note /var/run/ppp0.pid is not reliable
pid=`pgrep -f /usr/sbin/pppd`
[ $? -ne 0 ] && [ $IFACE = "enp4s0" ]  && echo "start pppoe"  && pon dsl-provider

# if ppp0 connected, do something
[ $IFACE = "ppp0" ] && echo "ppp0 connected"

make it executable

sudo chmod u+x /etc/networkd-dispatcher/routable.d/00-ppp