Tugnsten Fabric-MPLS-三层转发

http://www.opencontrail.org/a-journey-of-a-packet-within-opencontrail/

vm1 and vm2不在同一网段，走各自默认路由。

We can start by the interfaces (ItfReq) introspect page to find the TAP interface corresponding to VM1：http://:8085/agent.xml

vif --list=>vrf(查看unindex)

rt --dump vrf_id=>

Vrouter inet4 routing table 0/1/unicast
Flags: L=Label Valid, P=Proxy ARP, T=Trap ARP, F=Flood ARP
 
Destination          PPL        Flags        Label         Nexthop    Stitched MAC(Index)
 
...
192.168.0.3/32         32           LP         16             19        -
...

找到目的ip为192.168.0.3的条目:

We see that the packet will be encapsulated in a MPLS packet. The MPLS label will be 16, as shown in the label column.

下一跳为19

$ nh --get 19
Id:19         Type:Tunnel    Fmly: AF_INET  Flags:Valid, MPLSoGRE,   Rid:0  Ref_cnt:2 Vrf:0
             Oif:0 Len:14 Flags Valid, MPLSoGRE,  Data:fa 16 3e 4b f6 05 fa 16 3e 68 f9 e8 08 00
             Vrf:0  Sip:10.43.91.10  Dip:10.43.91.12

debug查看报文是否发给对端：

sudo tcpdump -n -i eth0 dst 10.43.91.12

12:13:16.908957 IP 10.43.91.10 > 10.43.91.12: GREv0, 
length 92: MPLS (label 16, exp 0, [S], ttl 63) 
IP 10.0.0.3 > 192.168.0.3: ICMP echo request, id 5889, seq 43, length 64

另一端，the vRouter on the second compute node will receive the encapsulated packet. According to the MPLS Label, it does a lookup on a MPLS Label/NextHop as we can see on its introspect.

查看MLPS lable=16的mplsResp

As we can see here the NextHop field for the Label 16 is the TAP interface of our second VM. On the datapath side we can check the same informations. Checking the MPLS Label/NextHop table :

$ mpls --get 16
MPLS Input Label Map
 
  Label    NextHop
-------------------
     16        14

nh --get 14
Id:14         Type:Encap     Fmly: AF_INET  Flags:Valid, Policy,   Rid:0  Ref_cnt:4 Vrf:1
             EncapFmly:0806 Oif:3 Len:14 Data:02 8a 39 ff 98 d3 00 00 5e 00 01 00 08 00O

Oif:3

$ vif --get 3
Vrouter Interface Table
 
Flags: P=Policy, X=Cross Connect, S=Service Chain, Mr=Receive Mirror
      Mt=Transmit Mirror, Tc=Transmit Checksum Offload, L3=Layer 3, L2=Layer 2
      D=DHCP, Vp=Vhost Physical, Pr=Promiscuous, Vnt=Native Vlan Tagged
      Mnp=No MAC Proxy, Dpdk=DPDK PMD Interface, Rfl=Receive Filtering Offload, Mon=Interface is Monitored
      Uuf=Unknown Unicast Flood
 
vif0/3      OS: tap8a39ff98-d3
           Type:Virtual HWaddr:00:00:5e:00:01:00 IPaddr:0
           Vrf:1 Flags:PL3L2 MTU:9160 Ref:6
           RX packets:2957  bytes:293636 errors:0
           TX packets:3085  bytes:297115 errors:0

完毕