Hi,
I have been trying to debug OVS kernel module with printk and stack_dump().
Although Wireshark detects the tap
interface (vnet0) receives ICMP packets I was never able to use printk or
dump_stack() to trace the execution
path. Ultimately I would like to track rx packets through all involved kernel
and user functions, same for tx packets.
It’s a Unubtu 14.04 system with OVS 2.4.0
allan@allan-i7A:~/openvswitch-2.4.0$ uname -a
Linux allan-i7A 3.19.0-25-generic #26~14.04.1-Ubuntu SMP Fri Jul 24
21:16:20 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
allan@allan-i7A:~/openvswitch-2.4.0$
I put printk() and dump_stack() in the following functions:
netdev_frame_hook() vport-netdev.c
netdev_port_receive() vport-netdev.c
ovs_vport_receive() vport.c
ovs_vport_send() vport.c
ovs_dp_process_packet datapath.c
the setup is very simple:
A VirtualBox VM pings an OVS bridge (br100) device via vnet0,
Bridge "br100"
Port "vnet0"
Interface "vnet0"
Port "br100"
Interface "br100"
type: internal
vnet0 is added like this:
$ sudo ovs-vsctl add-br br100
$ sudo ip tuntap add mode tap vnet0
$ sudo ip link set vnet0 up
$ sudo ovs-vsctl add-port br100 vnet0
Both "ovs-appctl dpctl/show –s" and “ifconfig” show br0 receives packets but
vnet0 doesn’t, the inconsistent part
is Wireshark show vnet0 receives packets.
sudo ovs-appctl dpctl/show -s
port 20: vnet0
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:5880 aborted:0 carrier:0
collisions:0
RX bytes:0 TX bytes:0
port 21: br100 (internal)
RX packets:143 errors:0 dropped:0 overruns:0 frame:0
TX packets:683 errors:0 dropped:29 aborted:0 carrier:0
collisions:0
RX bytes:16618 (16.2 KiB) TX bytes:121064 (118.2 KiB)
allan@allan-i7A:~/openvswitch-2.4.0$ ifconfig
br100 Link encap:Ethernet HWaddr 26:1a:55:0f:b6:47
inet addr:172.16.1.1 Bcast:172.16.1.255 Mask:255.255.255.0
inet6 addr: fe80::241a:55ff:fe0f:b647/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:561 errors:0 dropped:29 overruns:0 frame:0
TX packets:118 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:100861 (100.8 KB) TX bytes:14280 (14.2 KB)
vnet0 Link encap:Ethernet HWaddr 16:59:1e:05:f8:e4
inet6 addr: fe80::1459:1eff:fe05:f8e4/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:5758 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
dmesg shows the VM is attached to vnet0 as expected,
allan@allan-i7A:~/openvswitch-2.4.0$ dmesg
[22035.615107] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz),
(N/A, 4000 mBm), (N/A)
[23407.097108] vboxdrv: ffffffffc011b020 VMMR0.r0
[23407.195612] vboxdrv: ffffffffc0214020 VBoxDDR0.r0
[23407.196406] vboxdrv: ffffffffc0232020 VBoxDD2R0.r0
[23407.208611] VBoxNetFlt: attached to 'vnet0' / 16:59:1e:05:f8:e4
allan@allan-i7A:~/openvswitch-2.4.0$
The questions are:
1. Am I looking at the right codes for OVS receiving data path?
2. Any issues with using printk() and dumo_stack() this way? Or what should
I do?
3. Any instructions to ensure or check packets from VM are processed by the
kernel module will be appreciated
— Allan
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