VXLAN如何實現(xiàn)同網(wǎng)段跨節(jié)點通信

VXLAN是一種封裝協(xié)議，將二層數(shù)據(jù)包封裝在三層數(shù)據(jù)包中。出現(xiàn)主要為了解決vlan id不足問題。


vxlan報文

為了測試vxlan來實現(xiàn)跨節(jié)點間同子網(wǎng)通信，利用netns搭建如下網(wǎng)絡環(huán)境，拓撲如下，設置命令見文末

+-----------------+                           +-----------------+
|node-1           |                           |node-2           |
| +---------+     |                           | +---------+     |
| |   br0   |     |                           | |   br0   |     |
| +---------+     |                           | +---------+     |
| |         |     |                           | |         |     |
| br0       |     |                           | br0       |     |
|4e:69:85:99:e0:04|                           |e6:39:1c:37:20:a2|
|192.168.101.2/24 |                           |192.168.101.3/24 |
|           |     |                           |           |     |
|         vxlan0  |                           |         vxlan0  |
|4e:69:85:99:e0:04|                           |e6:39:1c:37:20:a2|
|                 |          +-----+          |                 |
|node1-eth -------|----------| sw0 |----------|-------node-2-eth|
|ae:93:c0:59:9e:a0|          +-----+          |4e:8b:ee:bd:58:b5|
|192.168.1.2/24   |                           |192.168.1.3/24   |
+-----------------+                           +-----------------+

node-1和node-2分別有一個192.168.101.0/24的ip，vxlan如何實現(xiàn)這兩個節(jié)點該網(wǎng)段的互通？
node-1，2上br0網(wǎng)橋的br0口上都配置192.168.101.0網(wǎng)段ip，并且添加一個vxlan0的tun設備，vxlan0配置remote和local及vni id。
當node-1中ping 192.168.101.3時：

  1. 查本地路由表，匹配后走br0，所以sip=192.168.101.2 dip=192.168.101.3 smac=[MAC node-1 br0] dmac=[MAC node-2 br0]

    ?  ~ ip netns exec node-1 ip r | grep 192.168.101.0
192.168.101.0/24 dev br0 proto kernel scope link src 192.168.101.2

  2. 數(shù)據(jù)包到br0后，br0是個switch，查fdb(forward database)決定數(shù)據(jù)包發(fā)給vxlan0的port

    ?  ~ ip netns exec node-1 bridge fdb | grep e6:39:1c:37:20:a2
e6:39:1c:37:20:a2 dev vxlan0 master br0
e6:39:1c:37:20:a2 dev vxlan0 dst 192.168.1.3 self

  3. 二層數(shù)據(jù)包到vxlan口后根據(jù)vxlan的配置，設置vxlan頭，udp頭，和ip頭

    ?  ~ ip netns exec node-1 ip -d l show vxlan0
3: vxlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 4e:69:85:99:e0:04 brd ff:ff:ff:ff:ff:ff promiscuity 1 minmtu 68 maxmtu 65535
    vxlan id 1111 remote 192.168.1.3 local 192.168.1.2 dev node1-eth srcport 0 0 dstport 4789 ttl auto ageing 300 udpcsum noudp6zerocsumtx noudp6zerocsumrx
    bridge_slave state forwarding priority 32 cost 2 hairpin off guard off root_block off fastleave off learning on flood on port_id 0x8001 port_no 0x1 designated_port 32769 designated_cost 0 designated_bridge 8000.4e:69:85:99:e0:4 designated_root 8000.4e:69:85:99:e0:4 hold_timer    0.00 message_age_timer    0.00 forward_delay_timer    0.00 topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off mcast_router 1 mcast_fast_leave off mcast_flood on mcast_to_unicast off neigh_suppress off group_fwd_mask 0 group_fwd_mask_str 0x0 vlan_tunnel off isolated off addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535

  4. 封裝后的三層數(shù)據(jù)包再通過查路由表后，將數(shù)據(jù)包封裝以太網(wǎng)頭部后從node1-eth口發(fā)出

    ?  ~ ip netns exec node-1 ip r | grep 192.168.1.0
192.168.1.0/24 dev node1-eth proto kernel scope link src 192.168.1.2

在node-2抓包如下:

?  ~ ip netns exec node-2 tcpdump -i any -nnev
tcpdump: data link type LINUX_SLL2
tcpdump: listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
14:33:49.402662 node2-eth In  ifindex 10 ae:93:c0:59:9e:a0 ethertype IPv4 (0x0800), length 154: (tos 0x0, ttl 64, id 10391, offset 0, flags [none], proto UDP (17), length 134)
    192.168.1.2.45186 > 192.168.1.3.4789: VXLAN, flags [I] (0x08), vni 1111
4e:69:85:99:e0:04 > e6:39:1c:37:20:a2, ethertype IPv4 (0x0800), length 98: (tos 0x0, ttl 64, id 6168, offset 0, flags [DF], proto ICMP (1), length 84)
    192.168.101.2 > 192.168.101.3: ICMP echo request, id 64021, seq 1, length 64
14:33:49.402662 vxlan0 In  ifindex 3 4e:69:85:99:e0:04 ethertype IPv4 (0x0800), length 104: (tos 0x0, ttl 64, id 6168, offset 0, flags [DF], proto ICMP (1), length 84)
    192.168.101.2 > 192.168.101.3: ICMP echo request, id 64021, seq 1, length 64
14:33:49.402662 br0   In  ifindex 2 4e:69:85:99:e0:04 ethertype IPv4 (0x0800), length 104: (tos 0x0, ttl 64, id 6168, offset 0, flags [DF], proto ICMP (1), length 84)
    192.168.101.2 > 192.168.101.3: ICMP echo request, id 64021, seq 1, length 64
14:33:49.402678 br0   Out ifindex 2 e6:39:1c:37:20:a2 ethertype IPv4 (0x0800), length 104: (tos 0x0, ttl 64, id 26146, offset 0, flags [none], proto ICMP (1), length 84)
    192.168.101.3 > 192.168.101.2: ICMP echo reply, id 64021, seq 1, length 64
14:33:49.402679 vxlan0 Out ifindex 3 e6:39:1c:37:20:a2 ethertype IPv4 (0x0800), length 104: (tos 0x0, ttl 64, id 26146, offset 0, flags [none], proto ICMP (1), length 84)
    192.168.101.3 > 192.168.101.2: ICMP echo reply, id 64021, seq 1, length 64
14:33:49.402680 node2-eth Out ifindex 10 4e:8b:ee:bd:58:b5 ethertype IPv4 (0x0800), length 154: (tos 0x0, ttl 64, id 2944, offset 0, flags [none], proto UDP (17), length 134)
    192.168.1.3.45186 > 192.168.1.2.4789: VXLAN, flags [I] (0x08), vni 1111
e6:39:1c:37:20:a2 > 4e:69:85:99:e0:04, ethertype IPv4 (0x0800), length 98: (tos 0x0, ttl 64, id 26146, offset 0, flags [none], proto ICMP (1), length 84)
    192.168.101.3 > 192.168.101.2: ICMP echo reply, id 64021, seq 1, length 64

6 packets captured
6 packets received by filter
0 packets dropped by kernel

參考文檔
rfc7348 (ietf.org)
附錄
環(huán)境設置腳本

brctl addbr sw0
ip l set sw0 up
ip netns add node-1
ip netns add node-2
ip l add node1-eth type veth peer node1-tap
ip l add node2-eth type veth peer node2-tap
ip l set node1-eth netns node-1
ip l set node2-eth netns node-2
brctl addif sw0 node1-tap
brctl addif sw0 node2-tap
ip l set node1-tap up
ip l set node2-tap up
ip netns exec node-1 ip l set lo up
ip netns exec node-2 ip l set lo up
ip netns exec node-1 ip l set node1-eth up
ip netns exec node-2 ip l set node2-eth up
ip netns exec node-1 ip a add 192.168.1.2/24 dev node1-eth
ip netns exec node-2 ip a add 192.168.1.3/24 dev node2-eth
ip netns exec node-1 brctl addbr br0
ip netns exec node-2 brctl addbr br0
ip netns exec node-1 ip l set br0 up
ip netns exec node-2 ip l set br0 up
ip netns exec node-1 ip a add 192.168.101.2/24 dev br0
ip netns exec node-2 ip a add 192.168.101.3/24 dev br0
# 設置單播點對點的vxlan（如果設置多播使用命令 ip l add vxlan0 type vxlan id 1111 dstport 4789 group 239.1.1.1 dev node1-eth）
ip netns exec node-1 ip l add vxlan0 type vxlan id 1111 dstport 4789 remote 192.168.1.3 local 192.168.1.2 dev node1-eth
ip netns exec node-2 ip l add vxlan0 type vxlan id 1111 dstport 4789 remote 192.168.1.2 local 192.168.1.3 dev node2-eth
ip netns exec node-1 ip l set vxlan0 up
ip netns exec node-2 ip l set vxlan0 up
ip netns exec node-1 brctl addif br0 vxlan0
ip netns exec node-2 brctl addif br0 vxlan0
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