Chinaunix首页 | 论坛 | 博客
  • 博客访问: 2472039
  • 博文数量: 1576
  • 博客积分: 19423
  • 博客等级: 上将
  • 技术积分: 16112
  • 用 户 组: 普通用户
  • 注册时间: 2007-06-19 21:36
个人简介

专注专心

文章分类

全部博文(1576)

文章存档

2020年(10)

2018年(8)

2016年(6)

2015年(21)

2014年(32)

2013年(279)

2012年(516)

2011年(309)

2010年(260)

2009年(92)

2008年(15)

2007年(28)

我的朋友

分类: 云计算

2020-09-25 10:24:33

Linux-虚拟网络设备-veth pair

基本概念

  • Virtual Ethernet Cable
  • Bidirectional FIFO
  • Often used to cross namespaces

       Linux container 中用到一个叫做veth的东西,这是一种新的设备,专门为 container 所建。veth 从名字上来看是 Virtual ETHernet 的缩写,它的作用很简单,就是要把从一个 network namespace 发出的数据包转发到另一个 namespace。veth 设备是成对的,一个是 container 之中,另一个在 container 之外,即在真实机器上能看到的。
        VETH设备总是成对出现,送到一端请求发送的数据总是从另一端以请求接受的形式出现。创建并配置正确后,向其一端输入数据,VETH会改变数据的方向并将其送入内核网络子系统,完成数据的注入,而在另一端则能读到此数据。(Namespace,其中往veth设备上任意一端上RX到的数据,都会在另一端上以TX的方式发送出去)veth工作在L2数据链路层,veth-pair设备在转发数据包过程中并不串改数据包内容。


这里写图片描述



       显然,仅有veth-pair设备,容器是无法访问网络的。因为容器发出的数据包,实质上直接进入了veth1设备的协议栈里。如果容器需要访问网络,需要使用bridge等技术,将veth1接收到的数据包通过某种方式转发出去
链接:

VETH: Typically used when you are trying to connect two entities which would want to “get hold of” (for lack of better phrase) an interface to forward/receive frames. These entities could be containers/bridges/ovs-switch etc. Say you want to connect a docker/lxc container to OVS. You can create a veth pair and push the first interface to the docker/lxc (say, as a phys interface) and push the other interface to OVS. You cannot do this with TAP.

创建veth的命令如下:

ip link add name veth0 type veth0 peer name veth1 
		
  • 1
  • 2

veth设备特点

  • veth和其它的网络设备都一样,一端连接的是内核协议栈
  • veth设备是成对出现的,另一端两个设备彼此相连
  • 一个设备收到协议栈的数据发送请求后,会将数据发送到另一个设备上去

常用命令

创建network namespace

root@ubuntu:/home/sunld# ip netns add sunldnamespace01 root@ubuntu:/home/sunld# ip netns list sunldnamespace01 
		
  • 1
  • 2
  • 3
  • 4

创建veth

root@ubuntu:/home/sunld# ip link add sunldveth01 type veth peer name sunldveth02 root@ubuntu:/home/sunld# ip link list 
		
  • 1
  • 2
  • 3

显示信息如下:

1: lo:  mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0:  mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 link/ether 00:0c:29:2d:d4:23 brd ff:ff:ff:ff:ff:ff 20: sunldveth02:  mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether c6:bb:c0:d0:54:71 brd ff:ff:ff:ff:ff:ff 21: sunldveth01:  mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether da:a1:36:d1:3b:36 brd ff:ff:ff:ff:ff:ff
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8

添加网卡到namespace

root@ubuntu:/home/sunld# ip link set sunldveth01 netns sunldnamespace01 
		
  • 1
  • 2

查看当前namespace中的veth,只有sunldveth02

root@ubuntu:/home/sunld# ip link list 
		
  • 1
  • 2

显示信息如下

1: lo:  mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0:  mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 link/ether 00:0c:29:2d:d4:23 brd ff:ff:ff:ff:ff:ff 3: virbr0:  mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default link/ether ba:d9:d4:48:55:65 brd ff:ff:ff:ff:ff:ff 20: sunldveth02:  mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether c6:bb:c0:d0:54:71 brd ff:ff:ff:ff:ff:ff 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9

通过命令查看sunldnamespace01中的veth

root@ubuntu:/home/sunld# ip netns exec sunldnamespace01 ip link list
		
  • 1

显示信息如下

1: lo:  mtu 65536 qdisc noop state DOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 21: sunldveth01:  mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether da:a1:36:d1:3b:36 brd ff:ff:ff:ff:ff:ff 
		
  • 1
  • 2
  • 3
  • 4
  • 5

配置network namespace的网口

root@ubuntu:/home/sunld# ip netns exec sunldnamespace01 ifconfig sunldveth01 100.2.96.2/16 up root@ubuntu:/home/sunld# ip netns exec sunldnamespace01 ip addr list 
		
  • 1
  • 2
  • 3

显示信息如下

1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 21: sunldveth01: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000 link/ether da:a1:36:d1:3b:36 brd ff:ff:ff:ff:ff:ff
    inet 100.2.96.2/16 brd 100.2.255.255 scope global sunldveth01
       valid_lft forever preferred_lft forever 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7

开启空间脚本

#可以使用这条命令开启一个 ns0 的 shell  ip netns exec ns0 sh
		
  • 1
  • 2

示例

Veth pair



这里写图片描述


# add the namespaces root@ubuntu:/# ip netns add sunldns1 root@ubuntu:/# ip netns add sunldns2 # create the veth pair root@ubuntu:/# ip link add sunldtap1 type veth peer name sunldtap2 # move the interfaces to the namespaces root@ubuntu:/# ip link set sunldtap1 netns sunldns1 root@ubuntu:/# ip link set sunldtap2 netns sunldns2 # bring up the links root@ubuntu:/# ip netns exec sunldns1 ip link set dev sunldtap1 up root@ubuntu:/# ip netns exec sunldns2 ip link set dev sunldtap2 up 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13

Linuxbridge with two veth pairs



这里写图片描述


# 可以使用这条命令开启一个 ns0 的 shell ip netns exec ns0 sh # create the switch root@ubuntu:/# brctl addbr br-testsunld01 # 关闭 STP (生成树协议),因为只有拓扑结构很简单,用不到,关闭可以提升性能 root@ubuntu:/# brctl stp br-testsunld01 off root@ubuntu:/# ip link set dev br-testsunld01 up # 为网桥设置IP地址 ifconfig br-testsunld01 192.168.88.1/24 up # add the namespaces root@ubuntu:/# ip netns add sunldns1 root@ubuntu:/# ip netns add sunldns2 #### PORT 1 # create a port pair root@ubuntu:/# ip link add sunldtap1 type veth peer name br-sunldtap1 # attach one side to linuxbridge root@ubuntu:/# brctl addif br-testsunld01 br-sunldtap1 # attach the other side to namespace root@ubuntu:/# ip link set sunldtap1 netns sunldns1 # set the ports to up root@ubuntu:/# ip netns exec sunldns1 ip link set dev sunldtap1 up root@ubuntu:/# ip link set dev br-sunldtap1 up # set ip root@ubuntu:/# ip netns exec sunldns1 ifconfig sunldtap1 192.168.88.3/24 up # 最后别忘了设置一下路由 root@ubuntu:/home/sunld# ip netns exec sunldns1 ip route add default via 192.168.88.1 #### PORT 2 # create a port pair root@ubuntu:/# ip link add sunldtap2 type veth peer name br-sunldtap2 # attach one side to linuxbridge root@ubuntu:/# brctl addif br-testsunld01 br-sunldtap2 # attach the other side to namespace root@ubuntu:/# ip link set sunldtap2 netns sunldns2 # set the ports to up root@ubuntu:/# ip netns exec sunldns2 ip link set dev sunldtap2 up root@ubuntu:/# ip link set dev br-sunldtap2 up # set ip root@ubuntu:/# ip netns exec sunldns2 ifconfig sunldtap2 192.168.88.4/24 up 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40

openvswitch and two veth pairs



这里写图片描述


# add the namespaces root@ubuntu:/# ip netns add ovssunldns1 root@ubuntu:/# ip netns add ovssunldns2 # create the switch root@ubuntu:/# ovs-vsctl add-br sunld_ovs_test root@ubuntu:/# ip link set dev sunld_ovs_test up # #### PORT 1 # create a port pair root@ubuntu:/# ip link add sunldveth03 type veth peer name ovs-sunldveth03 # attach one side to ovs root@ubuntu:/# ovs-vsctl add-port sunld_ovs_test ovs-sunldveth03 # attach the other side to namespace root@ubuntu:/# ip link set sunldveth03 netns ovssunldns1 # set the ports to up root@ubuntu:/# ip link set dev ovs-sunldveth03 up root@ubuntu:/# ip netns exec ovssunldns1 ip link set dev sunldveth03 up # #### PORT 2 # create a port pair root@ubuntu:/# ip link add sunldveth04 type veth peer name ovs-sunldveth04 # attach one side to ovs root@ubuntu:/# ovs-vsctl add-port sunld_ovs_test ovs-sunldveth04 # attach the other side to namespace root@ubuntu:/# ip link set sunldveth04 netns ovssunldns2 # set the ports to up root@ubuntu:/# ip link set dev ovs-sunldveth04 up root@ubuntu:/# ip netns exec ovssunldns2 ip link set dev sunldveth04 up ####配置IP root@ubuntu:/# ifconfig sunld_ovs_test 192.168.89.1/24 up root@ubuntu:/# ip netns exec ovssunldns1 ifconfig sunldveth03 192.168.89.3/24 up root@ubuntu:/# ip netns exec ovssunldns2 ifconfig sunldveth04 192.168.89.4/24 up #
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34

bridge信息

Bridge sunld_ovs_test Port sunld_ovs_test
            Interface sunld_ovs_test type: internal Port "ovs-sunldveth03" Interface "ovs-sunldveth03" Port "ovs-sunldveth04" Interface "ovs-sunldveth04"
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8

openvswitch and two openvswitch ports



这里写图片描述


# add the namespaces root@ubuntu:/# ip netns add ovssunldns3 root@ubuntu:/# ip netns add ovssunldns4 # create the switch root@ubuntu:/# ovs-vsctl add-br sunld_ovs_test2 root@ubuntu:/# ip link set dev sunld_ovs_test2 up # #### PORT 1 # create an internal ovs port root@ubuntu:/# ovs-vsctl add-port sunld_ovs_test2 sunldveth05 -- set Interface sunldveth05 type=internal # attach it to namespace root@ubuntu:/# ip link set sunldveth05 netns ovssunldns3 # set the ports to up root@ubuntu:/# ip netns exec ovssunldns3 ip link set dev sunldveth05 up # #### PORT 2 # create an internal ovs port root@ubuntu:/# ovs-vsctl add-port sunld_ovs_test2 sunldveth06 -- set Interface sunldveth06 type=internal # attach it to namespace root@ubuntu:/# ip link set sunldveth06 netns ovssunldns4 # set the ports to up root@ubuntu:/# ip netns exec ovssunldns4 ip link set dev sunldveth06 up #配置IP root@ubuntu:/# ifconfig sunld_ovs_test2 192.168.90.1/24 up root@ubuntu:/# ip netns exec ovssunldns3 ifconfig sunldveth05 192.168.90.3/24 up root@ubuntu:/# ip netns exec ovssunldns4 ifconfig sunldveth06 192.168.90.4/24 up 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28

bridge信息

Bridge "sunld_ovs_test2" Port "sunldveth05" Interface "sunldveth05" type: internal Port "sunldveth06" Interface "sunldveth06" type: internal Port "sunld_ovs_test2" Interface "sunld_ovs_test2" type: internal 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11

内核代码

static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
{ struct veth_priv *priv = netdev_priv(dev); struct net_device *rcv; int length = skb->len;
    rcu_read_lock();
    rcv = rcu_dereference(priv->peer); if (unlikely(!rcv)) {
        kfree_skb(skb);
        goto drop;
    } //转发给peer if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) { struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);
        u64_stats_update_begin(&stats->syncp);
        stats->bytes += length;
        stats->packets++;
        u64_stats_update_end(&stats->syncp);
    } else { drop:
        atomic64_inc(&priv->dropped);
    }
    rcu_read_unlock(); return NETDEV_TX_OK;
} 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28

如何工作

      向veth pair 的一端输入数据,veth pair 转换请求发送报文为需要接收处理的报文,将其注入内核协议栈,在另一端能读到此数据。
通过简单的实例分析工作流程

部署图



这里写图片描述


创建veth

root@ubuntu:/home/sunld# ip link add sunld-veth0 type veth peer name sunld-veth1 root@ubuntu:/home/sunld# ip link set dev sunld-veth0 up root@ubuntu:/home/sunld# ip link set dev sunld-veth1 up
		
  • 1
  • 2
  • 3

配置sunld-veth0的ip

root@ubuntu:/home/sunld# ifconfig sunld-veth0 192.168.100.11/24 up
		
  • 1

测试连通性-sunld-veth1没配置IP

直接ping 192.168.100.1-不通

root@ubuntu:/home/sunld# ping -c 4 192.168.100.1  PING 192.168.100.1 (192.168.100.1) 56(84) bytes of data. From 192.168.100.11 icmp_seq=1 Destination Host Unreachable From 192.168.100.11 icmp_seq=2 Destination Host Unreachable From 192.168.100.11 icmp_seq=3 Destination Host Unreachable From 192.168.100.11 icmp_seq=4 Destination Host Unreachable --- 192.168.100.1 ping statistics --- 4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3016ms
pipe 3 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11

查看抓包数据

veth0

root@ubuntu:/home/sunld# tcpdump -n -i sunld-veth0 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on sunld-veth0, link-type EN10MB (Ethernet), capture size 262144 bytes 08:10:36.369731 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:10:37.366887 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:10:38.366174 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:10:39.385792 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:10:40.382525 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:10:41.382961 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 ^C 6 packets captured 6 packets received by filter 0 packets dropped by kernel 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14

veth1

root@ubuntu:/home/sunld# tcpdump -n -i sunld-veth1 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on sunld-veth1, link-type EN10MB (Ethernet), capture size 262144 bytes 08:11:28.469362 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:11:29.466553 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:11:30.467384 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:11:31.478582 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:11:32.479044 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 08:11:33.478274 ARP, Request who-has 192.168.100.1 tell 192.168.100.11, length 28 ^C 6 packets captured 6 packets received by filter 0 packets dropped by kernel
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13

分析

执行ping的过程:


这里写图片描述


测试连通性sunld-veth1配置了IP

sunld-veth1配置IP

root@ubuntu:/home/sunld# ifconfig sunld-veth1 192.168.100.1/24 up
		
  • 1

直接ping192.168.100.1


注意:对于非debian系统,这里有可能ping不通,主要是因为内核中的一些ARP相关配置导致sunld-veth1不返回ARP应答包,如ubuntu上就会出现这种情况,解决办法如下:

root@ubuntu:/home/sunld# echo 1 > /proc/sys/net/ipv4/conf/sunld-veth1/accept_local root@ubuntu:/home/sunld# echo 1 > /proc/sys/net/ipv4/conf/sunld-veth0/accept_local root@ubuntu:/home/sunld# echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter root@ubuntu:/home/sunld# echo 0 > /proc/sys/net/ipv4/conf/sunld-veth0/rp_filter root@ubuntu:/home/sunld# echo 0 > /proc/sys/net/ipv4/conf/sunld-veth1/rp_filter
		
  • 1
  • 2
  • 3
  • 4
  • 5

再ping 192.168.100.1成功(由于192.168.100.1是本地IP,所以默认会走lo设备,为了避免这种情况,这里使用ping命令带上了-I参数,指定数据包走指定设备

root@ubuntu:/home/sunld# ping -c 4 192.168.100.1 -I sunld-veth0 PING 192.168.100.1 (192.168.100.1) from 192.168.100.11 sunld-veth0: 56(84) bytes of data. 64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.095 ms 64 bytes from 192.168.100.1: icmp_seq=2 ttl=64 time=0.119 ms 64 bytes from 192.168.100.1: icmp_seq=3 ttl=64 time=0.110 ms 64 bytes from 192.168.100.1: icmp_seq=4 ttl=64 time=0.186 ms --- 192.168.100.1 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3010ms
rtt min/avg/max/mdev = 0.095/0.127/0.186/0.036 ms
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10

查看抓包数据

veth0

root@ubuntu:/home/sunld# tcpdump -n -i sunld-veth0 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on sunld-veth0, link-type EN10MB (Ethernet), capture size 262144 bytes 09:43:51.218158 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30903, seq 1, length 64 09:43:52.224143 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30903, seq 2, length 64 09:43:53.223929 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30903, seq 3, length 64 09:43:54.222923 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30903, seq 4, length 64 ^C 4 packets captured 4 packets received by filter 0 packets dropped by kernel 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12

veth1

root@ubuntu:/home/sunld# tcpdump -n -i sunld-veth1 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on sunld-veth1, link-type EN10MB (Ethernet), capture size 262144 bytes 09:44:36.825998 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30921, seq 1, length 64 09:44:37.827332 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30921, seq 2, length 64 09:44:38.826755 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30921, seq 3, length 64 09:44:39.826982 IP 192.168.100.11 > 192.168.100.1: ICMP echo request, id 30921, seq 4, length 64 ^C 4 packets captured 4 packets received by filter 0 packets dropped by kernel 
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12

lo

root@ubuntu:/home/sunld# tcpdump -n -i lo | grep 192.168.100 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes 09:46:02.147861 IP 192.168.100.1 > 192.168.100.11: ICMP echo reply, id 30959, seq 1, length 64 09:46:03.146847 IP 192.168.100.1 > 192.168.100.11: ICMP echo reply, id 30959, seq 2, length 64 09:46:04.146913 IP 192.168.100.1 > 192.168.100.11: ICMP echo reply, id 30959, seq 3, length 64 09:46:05.146204 IP 192.168.100.1 > 192.168.100.11: ICMP echo reply, id 30959, seq 4, length 64 ^C355 packets captured 722 packets received by filter 0 packets dropped by kernel
		
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10

分析



这里写图片描述


结论

         从上面的介绍中可以看出,从sunld-veth0设备出去的数据包,会转发到sunld-veth1上,如果目的地址是sunld-veth1的IP的话,就能被协议栈处理,否则连ARP那关都过不了,IP forward啥的都用不上,所以不借助其它虚拟设备的话,这样的数据包只能在本地协议栈里面打转转,没法走到eth0上去,即没法发送到外面的网络中去。比如ovs、linuxbridge。

用途

如上所述,常用于不同命名空间之间进行数据穿越。

其他

NETIF_F_NETNS_LOCAL

NETIF_F_NETNS_LOCAL是网络设备的一个特性,设置该特性的网络设备,不允许在不同network namespace间移动。这类设备也叫做本地设备(local devices)。
Loopback,VXLAN,PPP,bridge都是这类设备。可以通过以下命令查看:

root@ubuntu:/sys/dev# ethtool -k sunld_ovs_test | grep netns netns-local: off [fixed] 
		
  • 1
  • 2
  • 3
root@ubuntu:/sys/dev# ethtool --show-features sunld_ovs_test|grep netns netns-local: off [fixed] 
		
  • 1
  • 2
  • 3

如果对这类设备network namespace,会报下面的错误:

ip link set br0 netns ns1
RTNETLINK answers: Invalid argument 
		
  • 1
  • 2
  • 3

参考资料

Linux 上的基础网络设备详解

Introducing Linux Network Namespaces
Linux Switching – Interconnecting Namespaces


Linux网络设备工作原理

阅读(233) | 评论(0) | 转发(0) |
给主人留下些什么吧!~~