Docker实践(4)—network namespace与veth pair

浏览数：46 / 时间：2015年06月09日

network namespace

创建network namespace

# ip netns add blue

# ip netns list

blue

添加网口到namespace

先创建veth

# ip link add veth0 type veth peer name veth1

在当前namespace可以看到veth0和veth1

# ip link list

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:b2:cf:72 brd ff:ff:ff:ff:ff:ff

3: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000

link/ether ae:0d:00:e1:11:38 brd ff:ff:ff:ff:ff:ff

4: veth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000

link/ether 42:e7:50:d4:bb:c5 brd ff:ff:ff:ff:ff:ff

将veth1加到namespace “blue”

# ip link set veth1 netns blue

此时，当前namepapce只能看到veth0。

通过如下命令可以查看blue namespace的网口

# ip netns exec blue ip link list

配置network namespace的网口

通过ip netns exec可以配置namespace的网口

# ip netns exec blue ifconfig veth1 172.17.42.2/16 up

network namespace的网口与物理网卡的通信

通过bridge来实现。参见veth pair一节。

主要参考

[0]Introducing Linux Network Namespaces

veth pair

veth pair是用于不同network namespace间进行通信的方式，veth pair将一个network namespace数据发往另一个network namespace的veth。如下：

# add the namespaces

ip netns add ns1

ip netns add ns2

# create the veth pair

ip link add tap1 type veth peer name tap2

# move the interfaces to the namespaces

ip link set tap1 netns ns1

ip link set tap2 netns ns2

# bring up the links

ip netns exec ns1 ip link set dev tap1 up

ip netns exec ns2 ip link set dev tap2 up

如果多个network namespace需要进行通信，则需要借助bridge：

# add the namespaces

ip netns add ns1

ip netns add ns2

# create the switch

BRIDGE=br-test

brctl addbr $BRIDGE

brctl stp $BRIDGE off

ip link set dev $BRIDGE up

#### PORT 1

# create a port pair

ip link add tap1 type veth peer name br-tap1

# attach one side to linuxbridge

brctl addif br-test br-tap1

# attach the other side to namespace

ip link set tap1 netns ns1

# set the ports to up

ip netns exec ns1 ip link set dev tap1 up

ip link set dev br-tap1 up

#### PORT 2

# create a port pair

ip link add tap2 type veth peer name br-tap2

# attach one side to linuxbridge

brctl addif br-test br-tap2

# attach the other side to namespace

ip link set tap2 netns ns2

# set the ports to up

ip netns exec ns2 ip link set dev tap2 up

ip link set dev br-tap2 up

内核实现

veth的实现与loopback interface类似，比较简单：

//drivers/net/veth.c

static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)

{

       struct net_device *rcv = NULL;

       struct veth_priv *priv, *rcv_priv;

 

       priv = netdev_priv(dev);

       rcv = priv->peer;

       rcv_priv = netdev_priv(rcv);

 

       stats = this_cpu_ptr(priv->stats);

 

       length = skb->len;

   //转发给peer

       if (dev_forward_skb(rcv, skb) != NET_RX_SUCCESS)

              goto rx_drop;