ip-masq-agent 是一个用来管理 IP 伪装的扩展，即管理节点中 IP 网段的 SNAT 规则。

ip-masq-agent 配置 iptables 规则，以便将流量发送到集群节点之外的目标时处理 IP 伪装。默认情况下，RFC 1918 定一个的三个私有 IP 范围是非伪装网段，即 10.0.0.0/8、172.16.0.0/12 和 192.168.0.0/16。另外，链接本地地址（169.254.0.0/16）也被视为非伪装网段。

ip-masq-agent - 图1

部署方法

首先，标记要运行 ip-masq-agent 的 Node

  1. kubectl label nodes my-node beta.kubernetes.io/masq-agent-ds-ready=true

然后部署 ip-masq-agent：

  1. kubectl create -f https://raw.githubusercontent.com/kubernetes-incubator/ip-masq-agent/master/ip-masq-agent.yaml

部署好，查看 iptables 规则，可以发现

  1. iptables -t nat -L IP-MASQ-AGENT
  2. RETURN     all  --  anywhere             169.254.0.0/16       /* ip-masq-agent: cluster-local traffic should not be subject to MASQUERADE */ ADDRTYPE match dst-type !LOCAL
  3. RETURN     all  --  anywhere             10.0.0.0/8           /* ip-masq-agent: cluster-local traffic should not be subject to MASQUERADE */ ADDRTYPE match dst-type !LOCAL
  4. RETURN     all  --  anywhere             172.16.0.0/12        /* ip-masq-agent: cluster-local traffic should not be subject to MASQUERADE */ ADDRTYPE match dst-type !LOCAL
  5. RETURN     all  --  anywhere             192.168.0.0/16       /* ip-masq-agent: cluster-local traffic should not be subject to MASQUERADE */ ADDRTYPE match dst-type !LOCAL
  6. MASQUERADE  all  --  anywhere             anywhere             /* ip-masq-agent: outbound traffic should be subject to MASQUERADE (this match must come after cluster-local CIDR matches) */ ADDRTYPE match dst-type !LOCAL

使用方法

自定义 SNAT 网段的方法：

  1. cat >config <<EOF
  2. nonMasqueradeCIDRs:
  3.   - 10.0.0.0/8
  4. resyncInterval: 60s
  5. EOF
  7. kubectl create configmap ip-masq-agent --from-file=config --namespace=kube-system

这样，查看 iptables 规则可以发现

  1. $ iptables -t nat -L IP-MASQ-AGENT
  2. Chain IP-MASQ-AGENT (1 references)
  3. target     prot opt source               destination         
  4. RETURN     all  --  anywhere             169.254.0.0/16       /* ip-masq-agent: cluster-local traffic should not be subject to MASQUERADE */ ADDRTYPE match dst-type !LOCAL
  5. RETURN     all  --  anywhere             10.0.0.0/8           /* ip-masq-agent: cluster-local
  6. MASQUERADE  all  --  anywhere             anywhere             /* ip-masq-agent: outbound traffic should be subject to MASQUERADE (this match must come after cluster-local CIDR matches) */ ADDRTYPE match dst-type !LOCAL