I have set /proc/sys/net/ipv4/ip_forward=1 and have ensured that this is
set to 1 for all the participating ports.
I send the packet with the OVS bridge's MAC address. This means that when
the GRE header is popped off, the packet's dest MAC is the same as that of
the OVS bridge. I now expect the linux kernel to kick in. I however dont
see the packet getting forwarded. Can somebody guide me on what else i can
look at?
>From the logs you can see that the packet after GRE decap comes with the
MAC address of the OVS bridge.
root@akabra:/proc/sys/net/ipv4/conf# tcpdump -xx -ni OFSWITCH not port 22
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on OFSWITCH, link-type EN10MB (Ethernet), capture size 65535 bytes
11:52:48.980347 IP 52.27.111.115 > 172.31.1.48: GREv0, key=0x258, length
106: IP 8.8.8.1 > 202.83.17.191: ICMP echo request, id 23162, seq 476,
length 64
0x0000: 0645 1ad2 1ced 0628 ae10 f98a 0800 4500
0x0010: 007e 9f8d 4000 352f 54e6 341b 6f73 ac1f
0x0020: 0130 2000 6558 0000 0258 0645 1ad2 1ced
0x0030: 5e21 e8f3 446a 0800 4500 0054 bf46 4000
0x0040: 4001 8f47 0808 0801 ca53 11bf 0800 bb3f
0x0050: 5a7a 01dc 96ec a855 0000 0000 d854 0a00
0x0060: 0000 0000 1011 1213 1415 1617 1819 1a1b
0x0070: 1c1d 1e1f 2021 2223 2425 2627 2829 2a2b
0x0080: 2c2d 2e2f 3031 3233 3435 3637
11:52:48.980347 IP 8.8.8.1 > 202.83.17.191: ICMP echo request, id 23162,
seq 476, length 64
0x0000: 0645 1ad2 1ced 5e21 e8f3 446a 0800 4500
0x0010: 0054 bf46 4000 4001 8f47 0808 0801 ca53
0x0020: 11bf 0800 bb3f 5a7a 01dc 96ec a855 0000
0x0030: 0000 d854 0a00 0000 0000 1011 1213 1415
0x0040: 1617 1819 1a1b 1c1d 1e1f 2021 2223 2425
0x0050: 2627 2829 2a2b 2c2d 2e2f 3031 3233 3435
0x0060: 3637
root@akabra:/proc/sys/net/ipv4/conf# ovs-ofctl show OFSWITCH
OFPT_FEATURES_REPLY (xid=0x2): dpid:000006451ad21ced
n_tables:254, n_buffers:256
capabilities: FLOW_STATS TABLE_STATS PORT_STATS QUEUE_STATS ARP_MATCH_IP
actions: OUTPUT SET_VLAN_VID SET_VLAN_PCP STRIP_VLAN SET_DL_SRC SET_DL_DST
SET_NW_SRC SET_NW_DST SET_NW_TOS SET_TP_SRC SET_TP_DST ENQUEUE
1(eth0): addr:06:45:1a:d2:1c:ed
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
3(gre0): addr:da:67:8f:b2:c1:34
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
LOCAL(OFSWITCH): addr:06:45:1a:d2:1c:ed
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (xid=0x4): frags=normal miss_send_len=0
Thanks, Abhishek
On Thu, Jul 16, 2015 at 2:57 PM, Abhishek Verma <[email protected]>
wrote:
> Hi,
>
> I am using a GRE tunnel to connect two VMs, VM-A and VM-B. VM-B is
> connected to other networks as well.
>
> I want the packets terminating at the GRE tunnel on VM-B, to do an L3
> lookup, and to get forwarded based on the result of the L3 lookup.
>
> To do this, i changed the destination MAC at the ingress (on VM-A) to
> match the MAC address of one of the ports on VM-B. This way when the
> packets emerge from the GRE tunnel, they already have a dest MAC that
> matches one of its port MACs. I assumed that because of this the kernel
> will automatically do an L3 lookup and will forward the packet out to the
> right place. However, this isnt happening, and am wondering why.
>
> I see that i am able to ping the interface if it resides on VM-B. I can
> however, not get the VM-B to L3 route that packet out. I want the packet to
> be looked up in the L3 kernel table and get forwarded out. Is there
> anything that i am missing here.
>
> My configs:
>
> *The packet arrives on a GRE tunnel (port 4) and i hence add a rule which
> says that anything arriving on port 4, should undergo normal (L2 and L3)
> processing. However, since the dest MAC matches one of the port's MACs, i
> expect the packet to undergo L3 processing.*
>
> root@:/home/ubuntu# ovs-ofctl show OFSWITCH
> OFPT_FEATURES_REPLY (xid=0x2): dpid:000006451ad21ced
> n_tables:254, n_buffers:256
> capabilities: FLOW_STATS TABLE_STATS PORT_STATS QUEUE_STATS ARP_MATCH_IP
> actions: OUTPUT SET_VLAN_VID SET_VLAN_PCP STRIP_VLAN SET_DL_SRC SET_DL_DST
> SET_NW_SRC SET_NW_DST SET_NW_TOS SET_TP_SRC SET_TP_DST ENQUEUE
> 1(eth0): addr:06:45:1a:d2:1c:ed
> config: 0
> state: 0
> speed: 0 Mbps now, 0 Mbps max
> 4(gre0): addr:06:48:6f:be:b0:f5
> config: 0
> state: 0
> speed: 0 Mbps now, 0 Mbps max
> LOCAL(OFSWITCH): addr:06:45:1a:d2:1c:ed
> config: 0
> state: 0
> speed: 0 Mbps now, 0 Mbps max
> OFPT_GET_CONFIG_REPLY (xid=0x4): frags=normal miss_send_len=0
> root@:/home/ubuntu#
>
> root@:/home/ubuntu# ovs-ofctl dump-flows OFSWITCH
> NXST_FLOW reply (xid=0x4):
> cookie=0x0, duration=147000.263s, table=0, n_packets=196105,
> n_bytes=117995996, idle_age=0, hard_age=65534, priority=0 actions=NORMAL
> cookie=0x0, duration=1185.832s, table=0, n_packets=62, n_bytes=6076,
> idle_age=971, priority=501,in_port=4 actions=NORMAL
>
>
> Thanks, Abhishek
>
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