启用 iptables 防火墙后无法连接到 SSH

Question

即使在防火墙上启用端口 22，我似乎也无法连接到我的 VPS。我尝试了多个 iptables 输入来尝试允许 SSH 工作。这是一个永久安装了 iptables 的 debian 9stretch 系统。下面是配置（命令形式）

    # Allow all loopback (lo) traffic and reject anything
# to localhost that does not originate from lo.
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT ! -i lo -s 127.0.0.0/8 -j REJECT
iptables -A OUTPUT -o lo -j ACCEPT

# Allow ping and ICMP error returns.
iptables -A INPUT -p icmp -m state --state NEW --icmp-type 8 -j ACCEPT
iptables -A INPUT -p icmp -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -p icmp -j ACCEPT

# Allow SSH.
iptables -A INPUT -i eth0 -p tcp -m state --state NEW,ESTABLISHED --dport 22 -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp -m state --state ESTABLISHED --sport 22 -j ACCEPT

# Allow UDP traffic on port 1194.
iptables -A INPUT -i eth0 -p udp -m state --state NEW,ESTABLISHED --dport 1194 -j ACCEPT
iptables -A OUTPUT -o eth0 -p udp -m state --state ESTABLISHED --sport 1194 -j ACCEPT

# Allow DNS resolution and limited HTTP/S on eth0.
# Necessary for updating the server and keeping time.
iptables -A INPUT -i eth0 -p udp -m state --state ESTABLISHED --sport 53 -j ACCEPT
iptables -A OUTPUT -o eth0 -p udp -m state --state NEW,ESTABLISHED --dport 53 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -m state --state ESTABLISHED --sport 80 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp -m state --state ESTABLISHED --sport 443 -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp -m state --state NEW,ESTABLISHED --dport 80 -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp -m state --state NEW,ESTABLISHED --dport 443 -j ACCEPT

# Allow traffic on the TUN interface.
iptables -A INPUT -i tuan0 -j ACCEPT
iptables -A OUTPUT -o tun0 -j ACCEPT

# then reject them.
iptables -A INPUT -j REJECT
iptables -A FORWARD -j REJECT
iptables -A OUTPUT -j REJECT

COMMIT