I found the answer to this, posting it for others' benefit. The configuration
is as follows, but the parameters vary depending on the mode in which the GRE
needs to work on UML/Ubuntu:
1. Boot-up UML with GRE enabled
./vmlinux ubd0=guest3,uml-ext2-img con0=null con=fd:0,fd:1 umid=guest3 mem=32m
eth0=tapng,,tap1 eth1=gre,,10.0.0.1,10.0.0.2,0x0,0x0,0x9 cgroup_disable=memory
init=/etc/preinit
2. Configure a 'Ethernet over GRE' tunnel on Ubuntu
#sudo ip link add gt0 type gretap remote <IP> local <IP> [csum] [seq]
#sudo ip addr add 10.20.30.70/24 dev gt0
#sudo ip link set gt0 up
With everything in between them working, the systems will now be able to talk
over GRE.
________________________________
From: madhusudan r <madhu...@yahoo.com>
To: "user-mode-linux-user@lists.sourceforge.net"
<user-mode-linux-user@lists.sourceforge.net>
Sent: Friday, 28 June 2013 12:12 PM
Subject: [uml-user] Configuring GRE tunnel between Ubuntu and UML
Hi,
I'm trying to setup a GRE tunnel between an Ubuntu system and a UML (running on
a different system). This is how the systems were configured:
1. UML
Boot arguments: ./vmlinux ubd0=guest3,uml-ext2-img con0=null con=fd:0,fd:1
umid=guest3 mem=32m eth0=tapng,,tap1 eth1=gre,,10.0.0.1,10.0.0.2,9
cgroup_disable=memory init=/etc/preinit
root@OpenWrt:/# ifconfig
eth0 Link encap:Ethernet HWaddr 5A:86:C4:0D:19:F5
UP BROADCAST RUNNING MULTICAST MTU:1500
Metric:1
RX packets:43 errors:0 dropped:22 overruns:0 frame:0
TX packets:777 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2321 (2.2 KiB) TX bytes:312354 (305.0 KiB)
Interrupt:5
eth1 Link encap:Ethernet HWaddr 76:5A:7B:B7:D9:F6
inet addr:192.168.252.1 Bcast:192.168.252.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:611 errors:0 dropped:611 overruns:0
frame:0
TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:42518 (41.5 KiB) TX bytes:402 (402.0 B)
Interrupt:5
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
2. Ubuntu
This is the entry I added to /etc/network/interfaces:
auto gre1
iface gre1 inet static
address
192.168.252.110
netmask 255.255.255.252
pre-up iptunnel add gre1 mode gre local 10.0.0.1 remote 10.0.0.2 ttl 255
up ifconfig gre1 multicast
pointtopoint 192.168.252.1
post-down iptunnel del gre1
ubuntu# ifconfig
eth0 Link encap:Ethernet HWaddr 78:e7:d1:c6:23:71
inet addr:10.0.0.1 Bcast:10.78.49.255
Mask:255.255.255.0
inet6 addr: fe80::7ae7:d1ff:fec6:2371/64 Scope:Link
inet6 addr: 2001:220:abcd::20/64 Scope:Global
inet6 addr: 2001:220:abcd:70::26/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3331 errors:0 dropped:284 overruns:0 frame:0
TX packets:543 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1200307 (1.2 MB) TX bytes:114051 (114.0 KB)
Interrupt:17
gre1 Link encap:UNSPEC HWaddr
0A-4E-31-4B-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:192.168.252.110 P-t-P:192.168.252.110 Mask:255.255.255.252
inet6 addr: fe80::5efe:a4e:314b/64 Scope:Link
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1476 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:168 (168.0 B)
The ubuntu box is able to ping the IP 192.168.252.1, but strangely I don't see
packets going out to 10.0.0.2. Also, the UML is not able to ping
192.168.252.110.
Is this configuration correct or is there something missing?
Thanks!
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