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Astaar
Asked: 2014-09-24 00:41:41 +0800 CST

DNS 查找不再起作用 - 管理上禁止

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我遇到了一个奇怪的问题，我的服务器现在拒绝进行 DNS 查找（使用绑定）。我使用 CentOS 机器作为 OpenVPN 网关并向客户端提供 DNS 服务。一个月以来，一切都按预期正常工作，而今天 DNS 服务不再工作。没有对配置进行任何更改...

这是 named.conf 文件：

options {
        # Hide bind version
        version "Not shown";
        # Listen only on localhost and VPN gateway IPv4
        listen-on port 53 { 127.0.0.1; 10.44.3.1; };
        listen-on-v6 port 53 { ::1; };

        # Forward requests to Google public DNS
        forwarders { 8.8.8.8; 8.8.4.4; };
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { localhost; crypto; };
        allow-recursion { localhost; crypto; };
        recursion yes;

        dnssec-enable no;
        dnssec-validation no;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";
};

acl crypto{
        10.44.3.0/29; // SSL VPN
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

注意 ACL ：服务器必须只为来自 10.44.3.0/29 子网的客户端（10.44.3.1-10.44.3.6 IP 范围，.1 是网关）提供服务。现在，当我让客户端建立 VPN 隧道，然后监控 DNS 解析时，我可以看出它由于 ICMP 错误消息而被拒绝：

    [root@vps50300 ~]# tcpdump -i tun0 host 10.44.3.6
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    listening on tun0, link-type RAW (Raw IP), capture size 65535 bytes
    10:10:16.735977 IP 10.44.3.6.61219 > 10.44.3.1.domain: 1+ PTR? 1.3.44.10.in-addr.arpa. (40)
    10:10:16.736038 IP 10.44.3.1 > 10.44.3.6: ICMP host 10.44.3.1 unreachable - admin prohibited, length 76
    10:10:18.736269 IP 10.44.3.6.61220 > 10.44.3.1.domain: 2+ A? www.google.com. (32)
    10:10:18.736330 IP 10.44.3.1 > 10.44.3.6: ICMP host 10.44.3.1 unreachable - admin prohibited, length 68
    10:10:20.737701 IP 10.44.3.6.61221 > 10.44.3.1.domain: 3+ AAAA? www.google.com. (32)
    10:10:20.737758 IP 10.44.3.1 > 10.44.3.6: ICMP host 10.44.3.1 unreachable - admin prohibited, length 68
    10:10:22.738068 IP 10.44.3.6.61222 > 10.44.3.1.domain: 4+ A? www.google.com. (32)
    10:10:22.738154 IP 10.44.3.1 > 10.44.3.6: ICMP host 10.44.3.1 unreachable - admin prohibited, length 68
    10:10:24.737910 IP 10.44.3.6.61223 > 10.44.3.1.domain: 5+ AAAA? www.google.com. (32)
    10:10:24.737965 IP 10.44.3.1 > 10.44.3.6: ICMP host 10.44.3.1 unreachable - admin prohibited, length 68

最后但并非最不重要的一点是，我认为我的 iptable 看起来是正确的（来自 10.44.3.0/29 的所有流量都被接受并转发）：

[root@vps50300 ~]# iptables -L -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
1897K  320M ACCEPT     all  --  any    any     anywhere             anywhere            state RELATED,ESTABLISHED 
 229K   14M ACCEPT     icmp --  any    any     anywhere             anywhere            
10957  820K ACCEPT     all  --  lo     any     anywhere             anywhere            
 7128  421K ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:http state NEW 
 7166  425K ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:https state NEW 
14457  819K ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:ssh state NEW 
   59  2636 ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:ftp state NEW 
    0     0 ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:45632 state NEW 
    0     0 ACCEPT     tcp  --  venet0 any     anywhere             anywhere            tcp dpt:45633 state NEW 
   16  1120 ACCEPT     udp  --  venet0 any     anywhere             anywhere            udp dpt:openvpn state NEW 
47288 3095K REJECT     all  --  any    any     anywhere             anywhere            reject-with icmp-host-prohibited 

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
4062K 3220M ACCEPT     all  --  any    any     anywhere             anywhere            state RELATED,ESTABLISHED 
43961 2562K ACCEPT     all  --  any    any     10.44.3.0/29         anywhere            
    0     0 REJECT     all  --  any    any     anywhere             anywhere            reject-with icmp-host-prohibited 

Chain OUTPUT (policy ACCEPT 3107K packets, 3306M bytes)
 pkts bytes target     prot opt in     out     source               destination

但是自从我收到 ICMP 管理员禁止消息后，我似乎仍然违反了其中一条规则？

我不确定如何解决这个问题，任何建议将不胜感激。

bind

1 个回答

  1. Best Answer

    没有允许 DNS 流量到您的主机的规则规则（只有当源和目标都不是这台机器时，数据包才会由 FORWARD 链处理。如果 DNS 服务在这些规则来自的服务器上运行，您必须查看 INPUT 链）。

    尝试添加：iptables -i tun0 -I INPUT 8 -p udp --dsport 53 -j ACCEPT。

    • 0

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