OpenStackneutronfloatingips与iptables的配置

1. 简介neutron-l3-agent

OpenStack neutron-l3-agent 主要负责实现网络三层协议，为虚拟机完成SNAT,DNAT等地址的转换与伪装，提供安全弹性隔离的云网络环境，

下面详细叙述了OpenStack如何使用iptables链与规则完成复杂的neutron-l3-agent 的网络地址转换(NAT)功能，虚拟机floating ip与fixed ip绑定的工作原理。

2. iptables 简介

    ２.1 iptables 链拓扑结构

　 2.2 iptables 表结构

           Table filter: 

                Chain INPUT

                Chain FORWARD

                Chain OUTPUT

            filter 表用于一般的信息包过滤，它包含 INPUT 、 OUTPUT 和 FORWARD 链。

          Table nat:

                Chain PREROUTING

                Chain OUTPUT

                Chain POSTROUTING

           PREROUTING 链由指定信息包一到达防火墙就改变它们的规则所组成，而 POSTROUTING 链由指定正当信息包打算离开防火墙时改变它们的规则所组成。 

3. iptables command

# 添加一条规则到 INPUT 链的末尾，ACCEPT 来自源地址 10.9.1.141 的包

[root@xianghui-10-9-1-141 ~]# iptables -A INPUT -s 10.9.1.141  -j ACCEPT

#允许protocol为TCP 、 UDP 、 ICMP 的包通过

[root@xianghui-10-9-1-141 ~]# iptables -A INPUT -p TCP, UDP
# 从INPUT链中删除掉规则“Drop 到端口80的包”
[root@xianghui-10-9-1-141 ~]# iptables -D INPUT --dport 80 -j DROP
# 将 INPUT 链的缺省规则指定为 DROP 
[root@xianghui-10-9-1-141 ~]# iptables -P INPUT DROP

# 创建一个新链new-chain

[root@xianghui-10-9-1-141 ~]# iptables -N new-chain

# 删除Table filter 中的所有规则

[root@xianghui-10-9-1-141 ~]# iptables -F

# 列出INPUT链中的所有规则

[root@xianghui-10-9-1-141 ~]# iptables -L INPUT
# 删除链
[root@xianghui-10-9-1-141 ~]# iptables -X
4. 配置neutron-l3-agent 
[root@xianghui-10-9-1-141 ~]# neutron router-create router1
+--------------------------------------+---------+-----------------------+
| id                                   | name    | external_gateway_info |
+--------------------------------------+---------+-----------------------+
|c36b384e-b1f5-45e5-bb4f-c3ed32885142 | router1 | null |
+--------------------------------------+---------+-----------------------+
[root@xianghui-10-9-1-141 ~]# vi /etc/neutron/l3_agent.ini
interface_driver = neutron.agent.linux.interface.OVSInterfaceDriver
# OS is RHEL6.4, not support namespace
use_namespaces = False
# This is done by setting the specific router_id.
router_id = c36b384e-b1f5-45e5-bb4f-c3ed32885142
# Name of bridge used for external network traffic. This should be set to
# empty value for the linux bridge
external_network_bridge = br-eth1
[root@xianghui-10-9-1-141 ~]# service neutron-l3-agent restart

启用转发功能

[root@xianghui-10-9-1-141 ~]#  echo 1 > /proc/sys/net/ipv4/ip_forward

5. neutron 利用iptables 实现 NAT 原理

iptables 中neutron l3 agent自定义的链:
neutron-l3-agent-PREROUTING
neutron-l3-agent-OUTPUT

neutron-l3-agent-POSTROUTING

创建外部网络（分配floatingip）

[root@xianghui-10-9-1-141 ~]#  neutron net-create ext_net --router:external=True
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | True                                 |
| id                        | 2d72d81b-cf09-459e-87fb-a50fa0e8730a |
| name                      | ext_net                              |
| provider:network_type     | vlan                                 |
| provider:physical_network | physnet1                             |
| provider:segmentation_id  | 1000                                 |
| router:external           | True                                 |
| shared                    | False                                |
| status                    | ACTIVE                               |
| subnets                   | e1932e73-1e4b-4f87-9ebf-758a757e20ef |
| tenant_id                 | b21a96e16c3c438caab4a27a1f58a5b8     |
+---------------------------+--------------------------------------+
[root@oc2603148815 cfn]# subnet-create ext_net --allocation-pool start=192.168.12.10,end=192.168.12.50 --gateway 192.168.12.1 192.168.12.0/24 --enable_dhcp=False
+------------------+----------------------------------------------------+
| Field            | Value                                              |
+------------------+----------------------------------------------------+
| allocation_pools | {"start": "192.168.12.10", "end": "192.168.12.50"} |
| cidr             | 192.168.12.0/24                                    |
| dns_nameservers  |                                                    |
| enable_dhcp      | False                                              |
| gateway_ip       | 192.168.12.1                                       |
| host_routes      |                                                    |
| id               | e1932e73-1e4b-4f87-9ebf-758a757e20ef               |
| ip_version       | 4                                                  |
| name             |                                                    |
| network_id       | 2d72d81b-cf09-459e-87fb-a50fa0e8730a               |
| tenant_id        | b21a96e16c3c438caab4a27a1f58a5b8                   |
+------------------+----------------------------------------------------+
创建内部网络(分配fixedip)
[root@oc2603148815 cfn]# neutron net-create vlan-70 --provider:network_type vlan --provider:physical_network physnet1 --provider:segmentation_id 16
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | True                                 |
| id                        | 793a95b7-cf1f-4bde-b7b8-5a9a2e552fae |
| name                      | vlan-70                              |
| provider:network_type     | vlan                                 |
| provider:physical_network | physnet1                             |
| provider:segmentation_id  | 16                                   |
| router:external           | False                                |
| shared                    | False                                |
| status                    | ACTIVE                               |
| subnets                   | f542941d-5d53-45e4-85d0-944e030c2bcc |
| tenant_id                 | b21a96e16c3c438caab4a27a1f58a5b8     |
+---------------------------+--------------------------------------+
[root@oc2603148815 cfn]# neutron subnet-create vlan-70 70.0.0.0/24
+------------------+--------------------------------------------+
| Field            | Value                                      |
+------------------+--------------------------------------------+
| allocation_pools | {"start": "70.0.0.2", "end": "70.0.0.254"} |
| cidr             | 70.0.0.0/24                                |
| dns_nameservers  |                                            |
| enable_dhcp      | True                                       |
| gateway_ip       | 70.0.0.1                                   |
| host_routes      |                                            |
| id               | f542941d-5d53-45e4-85d0-944e030c2bcc       |
| ip_version       | 4                                          |
| name             |                                            |
| network_id       | 793a95b7-cf1f-4bde-b7b8-5a9a2e552fae       |
| tenant_id        | b21a96e16c3c438caab4a27a1f58a5b8           |
+------------------+--------------------------------------------+
[root@oc2603148815 cfn]# neutron net-list
+--------------------------------------+---------+------------------------------------------------------+
| id                                   | name    | subnets                                              |
+--------------------------------------+---------+------------------------------------------------------+
| 2d72d81b-cf09-459e-87fb-a50fa0e8730a | ext_net | e1932e73-1e4b-4f87-9ebf-758a757e20ef 192.168.12.0/24 |
| 793a95b7-cf1f-4bde-b7b8-5a9a2e552fae | vlan-70 | f542941d-5d53-45e4-85d0-944e030c2bcc 70.0.0.0/24     |
+--------------------------------------+---------+------------------------------------------------------+
绑定内外网到router1
# neutron router-gateway-set $ROUTER_ID $EXTERNAL_NETWORK_ID
[root@oc2603148815 cfn]# neutron router-gateway-set 06d85a01-fc42-4cde-a0f1-377f2f394a64 2d72d81b-cf09-459e-87fb-a50fa0e8730a
# neutron router-interface-add $ROUTER_ID $SUBNET_ID
[root@oc2603148815 cfn]# neutron router-interface-add 06d85a01-fc42-4cde-a0f1-377f2f394a64 f542941d-5d53-45e4-85d0-944e030c2bcc

经过上面的步骤后neutron-l3-agent会加入下列规则到iptables:

-A PREROUTING -j neutron-l3-agent-PREROUTING
-A POSTROUTING -j neutron-l3-agent-POSTROUTING
-A POSTROUTING -j neutron-postrouting-bottom
-A OUTPUT -j neutron-l3-agent-OUTPUT
-A neutron-l3-agent-snat -j neutron-l3-agent-float-snat
-A neutron-l3-agent-snat -s 70.0.0.0/24 -j SNAT --to-source 192.168.12.10
-A neutron-postrouting-bottom -j neutron-l3-agent-snat
创建floating ip(192.168.12.11)并绑定到vm的fixed ip(选择70.0.0.3):
[root@xianghui-10-9-1-141 ~]# neutron floatingip-create 2d72d81b-cf09-459e-87fb-a50fa0e8730a
Created a new floatingip:
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| fixed_ip_address    |                                      |
| floating_ip_address | 192.168.12.11                        |
| floating_network_id | 2d72d81b-cf09-459e-87fb-a50fa0e8730a |
| id                  | f8b48ab7-ea51-4f29-bc84-0ab179808dbb |
| port_id             |                                      |
| router_id           |                                      |
| tenant_id           | adc4e7a4effa44ffa3c6e48dd5a8555a     |
+---------------------+--------------------------------------+

找出想要被绑定的fixed ip 的port id

[root@xianghui-10-9-1-141 ~]# neutron port-list
+--------------------------------------+------+-------------------+--------------------------------------------------------------------------------------+
| id                                   | name | mac_address       | fixed_ips                                                                            |
+--------------------------------------+------+-------------------+--------------------------------------------------------------------------------------+
| 0d06055b-2f31-4d8e-b8da-e048d76a07cc |      | fa:16:3e:d7:f4:19 | {"subnet_id": "5c62752f-27ba-4d38-9702-2ca17ec2741d", "ip_address": "70.0.0.3"}      |
+--------------------------------------+------+-------------------+--------------------------------------------------------------------------------------+
[root@xianghui-10-9-1-141 ~]# neutron floatingip-associate f8b48ab7-ea51-4f29-bc84-0ab179808dbb0d06055b-2f31-4d8e-b8da-e048d76a07cc
Associated floatingip f8b48ab7-ea51-4f29-bc84-0ab179808dbb
[root@xianghui-10-9-1-141 ~]# neutron floatingip-list
+--------------------------------------+------------------+---------------------+--------------------------------------+
| id                                   | fixed_ip_address | floating_ip_address | port_id                              |
+--------------------------------------+------------------+---------------------+--------------------------------------+
| f8b48ab7-ea51-4f29-bc84-0ab179808dbb | 70.0.0.3         | 192.168.12.11       | b0797fe6-b799-41ea-86d0-9d9bfa0b2eb9 |
+--------------------------------------+------------------+---------------------+--------------------------------------+

经过前面步骤后，iptables会多出下面的规则， 所有目标ip是192.168.12.11的包都会被转发到ip 70.0.0.3的guest上

-A neutron-l3-agent-OUTPUT -d 192.168.12.11/32 -j DNAT --to-destination 70.0.0.3
-A neutron-l3-agent-PREROUTING -d 192.168.12.11/32 -j DNAT --to-destination 70.0.0.3
-A neutron-l3-agent-float-snat -s 70.0.0.3/32 -j SNAT --to-source 192.168.12.11
6. neutron floating ip 与 fixed ip 的转换
源地址转换(SNAT)
[root@xianghui-10-9-1-141 ~]#  iptables -t nat -Aneutron-l3-agent-float-snat -s 70.0.0.6/32-j SNAT --to-source 192.168.12.100
 目的地址转换(DNAT)
[root@xianghui-10-9-1-141 ~]#  iptables -t nat -Aneutron-l3-agent-PREROUTING -d 192.168.12.100/32-j DNAT --to-destination 70.0.0.6

测试：（从guest 70.0.0.11上ping 192.168.12.100, 结果被转发到70.0.0.6的guest上）

[root@xianghui-10-9-1-141 ~]#  ssh ec2-user@70.0.0.11
[ec2-user@wordpress-test-wikidatabase-jevfsmkbakch ~]$ ping 192.168.12.100
PING 192.168.12.100 (192.168.12.100) 56(84) bytes of data.
64 bytes from 70.0.0.6: icmp_req=1 ttl=64 time=3.09 ms
64 bytes from 70.0.0.6: icmp_req=2 ttl=64 time=0.281 ms
64 bytes from 70.0.0.6: icmp_req=3 ttl=64 time=0.151 ms
将规则neutron-l3-agent-float-snat加到POSTROUTING规则之后，从70.0.0.6发出的包被伪装成来自192.168.12.16，借此掩盖源地址
[root@xianghui-10-9-1-141 ~]#  iptables -t nat -A POSTROUTING -j neutron-l3-agent-float-snat
[ec2-user@wordpress-test-wikidatabase-jevfsmkbakch ~]$ ping 192.168.12.100
PING 192.168.12.100 (192.168.12.100) 56(84) bytes of data.
64 bytes from 192.168.12.100: icmp_req=1 ttl=63 time=2.47 ms
64 bytes from 192.168.12.100: icmp_req=2 ttl=63 time=0.199 ms
64 bytes from 192.168.12.100: icmp_req=3 ttl=63 time=0.251 ms
7. 实例分析（ALL-IN-ONE）

7.1 虚拟机的网络拓扑

7.2 虚拟机之间用floating ip ping通

# ping 192.168.12.100(70.0.0.6) from 70.0.0.11
# s:70.0.0.11 d:70.0.0.6
# prerouting -> forward -> postrouting
[root@xianghui-10-9-1-141 ~]#  iptables -A neutron-l3-agent-FORWARD -d 70.0.0.11/32 -j ACCEPT
[root@xianghui-10-9-1-141 ~]#  iptables -A neutron-l3-agent-FORWARD -d 70.0.0.6/32 -j ACCEPT
[root@xianghui-10-9-1-141 ~]#  iptables -t nat -A neutron-l3-agent-PREROUTING -d 192.168.12.100/32 -j DNAT --to-destination 70.0.0.6

7.3 虚拟机主机ping通虚拟机的floating ip

-A OUTPUT -j neutron-l3-agent-OUTPUT
[root@xianghui-10-9-1-141 ~]#  iptables -A neutron-l3-agent-OUTPUT -d 192.168.12.100/32 -j DNAT --to-destination 70.0.0.6