使能Ubuntu的IPv6转发功能

root@yanhc-Aspire-4738G:/home/yanhc# cat /proc/sys/net/ipv4/ip_forward
0
root@yanhc-Aspire-4738G:/home/yanhc# cat /proc/sys/net/ipv6/ip_forward
cat: /proc/sys/net/ipv6/ip_forward: 没有那个文件或目录
root@yanhc-Aspire-4738G:/home/yanhc# cat /proc/sys/net/ipv6/conf/all/forwarding
0
root@yanhc-Aspire-4738G:/home/yanhc# sysctl -w net.ipv6.conf.all.forwarding=1
net.ipv6.conf.all.forwarding = 1
root@yanhc-Aspire-4738G:/home/yanhc# cat /proc/sys/net/ipv6/conf/all/forwarding
1