設定 Linux 路由器以透過 OpenVPN 隧道轉送某些 LAN 主機的流量和 DNS？

2024-7-27 • tag-icon

設定 Linux 路由器以透過 OpenVPN 隧道轉送某些 LAN 主機的流量和 DNS？

我有一個 GNU/Linux 機器，我已將其設定為家庭網路的路由器。我有三個網路介面...

ppp0 是上游連接
lan 是本地網絡
NordVPN 是 VPN 隧道

我正在使用 nftables 作為防火牆，並且正在運行快取 DNS 伺服器 (dnsmasq)。來自 LAN 的 DNS 請求被攔截並傳送到路由器上的 DNS 伺服器。到目前為止一切都很好，但......

預設情況下 NordVPN 路由全部透過 VPN 隧道的上行流量，如果這樣配置它就可以工作，但我不想要這樣。我希望大部分互聯網流量都透過 ppp0 接口，而來自特定 LAN 主機的流量則透過 VPN 發送。使用 VPN 的主機的 DNS 請求應定向到 VPN 提供者的 DNS 伺服器而不是本機伺服器。

我讀過各種討論如何做類似（但不相同）事情的文章，但到目前為止我還無法使其發揮作用。我顯然至少做錯了一件事。據我了解，我應該能夠在防火牆中標記資料包，然後使用自訂路由表透過nordvpn 介面發送這些資料包。到目前為止我所擁有的如下......

我已將以下行新增至/etc/iproute2/rt_tables.

5     nordvpn

為了防止 openvpn 設定它自己的路由，我已將這些行新增到/etc/openvpn/client/nordvpn.conf.

route-noexec
script-security 2
route-up /etc/openvpn/client/mkroute.sh

我相信我需要停用nordvpn 介面上的反向路徑過濾才能正常運作？這是 openvpn 用來設定路由的腳本。

#!/bin/bash

TABLE="nordvpn"
MARK="0x5"

die() {
  echo "Error: $1"
  exit 1
}

[ $(id -u) -eq 0 ] || die "Not running as root"

ip route flush cache || echo "error 1"
ip route flush table "$TABLE" || echo "error 2"

ip route add 192.168.2.0/24 dev lan src 192.168.2.1 table "$TABLE" || echo "error 3"
ip route add $route_vpn_gateway dev lan src $ifconfig_local table "$TABLE" || echo "error 4"
ip route add default via $route_vpn_gateway dev "$dev" table "$TABLE" || echo "error 5"
ip rule delete fwmark "$MARK" || :
ip rule add fwmark "$MARK" lookup "$TABLE" || echo "error 6"
sysctl -w net.ipv4.conf.nordvpn.rp_filter=0 || echo "error 7"

最後，這是我的 nftables 腳本。

flush ruleset

define i_wan = ppp0
define i_nordvpn = nordvpn
define i_lan = lan

define p_dns = 53

define a4_nordvpn_dns_1 = 103.86.96.100
define m_nordvpn = 5

define h4_nimrod = 192.168.2.21

table ip ip4_firewall {

  set s_inet_nordvpn { type ipv4_addr; elements = { $h4_nimrod }; }

  chain c_here_to_wan { tcp flags syn tcp option maxseg size set rt mtu; accept; }
  chain c_here_to_nordvpn { tcp flags syn tcp option maxseg size set rt mtu; accept; }
  chain c_here_to_lan { accept; }
  chain c_wan_to_here { ip protocol icmp accept; drop; }
  chain c_wan_to_lan { ip protocol icmp accept; drop; }
  chain c_nordvpn_to_here { ip protocol icmp accept; drop; }
  chain c_nordvpn_to_lan { ip protocol icmp accept; drop; }
  chain c_lan_to_here { accept; }
  chain c_lan_to_wan { tcp flags syn tcp option maxseg size set rt mtu; accept; }
  chain c_lan_to_nordvpn { tcp flags syn tcp option maxseg size set rt mtu; accept; }

  chain preroute_nordvpn {
    udp dport $p_dns mark set $m_nordvpn dnat $a4_nordvpn_dns_1
    tcp dport $p_dns mark set $m_nordvpn dnat $a4_nordvpn_dns_1
    oif $i_wan mark set $m_nordvpn
  }

  chain prerouting { type nat hook prerouting priority -100
    ip saddr @s_inet_nordvpn goto preroute_nordvpn
    iif $i_lan oif $i_wan udp dport $p_dns redirect
    iif $i_lan oif $i_wan tcp dport $p_dns redirect
  }

  chain postrouting { type nat hook postrouting priority 100
    oif $i_nordvpn masquerade
    oif $i_wan snat <my public IP address>
  }

  chain input { type filter hook input priority 0; policy drop
    ct state established,related accept
    ct state invalid drop
    iif vmap {
      lo: accept,
      $i_wan : jump c_wan_to_here,
      $i_nordvpn : jump c_nordvpn_to_here,
      $i_lan : jump c_lan_to_here
    }
    log prefix "Unhandled input: " drop
  }

  chain output { type filter hook output priority 0; policy drop
    ct state established,related accept
    ct state invalid drop
    oif vmap {
      lo: accept,
      $i_wan : jump c_here_to_wan,
      $i_nordvpn : jump c_here_to_nordvpn,
      $i_lan : jump c_here_to_lan
    }
    log prefix "Unhandled output: " drop
  }

  chain forward { type filter hook forward priority 0; policy drop
    ct state established,related accept
    ct state invalid drop
    iif . oif vmap {
      $i_lan . $i_wan : jump c_lan_to_wan,
      $i_wan . $i_lan : jump c_wan_to_lan,
      $i_lan . $i_nordvpn : jump c_lan_to_nordvpn,
      $i_nordvpn . $i_lan : jump c_nordvpn_to_lan,
    }
    log prefix "Unhandled forward: " drop
  }
}

配置完成後，我有以下內容。

[root@cerberus ~]# ip rule ls
0:      from all lookup local
32765:  from all fwmark 0x65 lookup nordvpn
32766:  from all lookup main
32767:  from all lookup default
[root@cerberus ~]# ip route ls
default dev ppp0 scope link 
10.0.0.1 dev ppp0 proto kernel scope link src <my public IP address> 
10.8.0.0/24 dev nordvpn proto kernel scope link src 10.8.0.12 
192.168.2.0/24 dev lan proto kernel scope link src 192.168.2.1 
[root@cerberus ~]# ip route ls table nordvpn
default via 10.8.0.1 dev nordvpn 
10.8.0.1 dev lan scope link src 10.8.0.12 
192.168.2.0/24 dev lan scope link src 192.168.2.1 
[root@cerberus ~]# ip rule ls
0:      from all lookup local
32764:  from all fwmark 0x5 lookup nordvpn
32766:  from all lookup main
32767:  from all lookup default

當啟用指派給 VPN 的用戶端時，其 DNS 查找會失敗。請求似乎是透過 VPN 隧道發送的，但回覆到達輸入鏈而不是轉送鏈，並且不會到達客戶端。我哪裡錯了？

先感謝您的幫助:)

答案1

嘗試改變：

  chain preroute_nordvpn {
    udp dport $p_dns mark set $m_nordvpn dnat $a4_nordvpn_dns_1
    tcp dport $p_dns mark set $m_nordvpn dnat $a4_nordvpn_dns_1
    oif $i_wan mark set $m_nordvpn
  }

  chain prerouting { type nat hook prerouting priority -100
    ip saddr @s_inet_nordvpn goto preroute_nordvpn
    iif $i_lan oif $i_wan udp dport $p_dns redirect
    iif $i_lan oif $i_wan tcp dport $p_dns redirect
  }

到：

  chain fwmark { type filter hook prerouting priority -150
    ip saddr @s_inet_nordvpn mark set $m_nordvpn
  }

  chain lan_dns {
    ip saddr @s_inet_nordvpn dnat $a4_nordvpn_dns_1
    redirect
  }

  chain lan_dnat {
    udp dport $p_dns goto lan_dns
    tcp dport $p_dns goto lan_dns
  }

  chain prerouting { type nat hook prerouting priority -100
    iif $i_lan goto lan_dnat
  }

答案1

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