Re: [Autotest] [KVM-AUTOTEST PATCH] KVM test: make use of tcpdump optional

[Michael Goldish <mgoldish@redhat.com>]

On 05/17/2010 04:35 PM, Lucas Meneghel Rodrigues wrote:
> On Mon, 2010-05-17 at 16:29 +0300, Michael Goldish wrote:
>> To disable tcpdump, set 'run_tcpdump = no' in a config file.
>> If 'run_tcpdump' isn't set at all, it defaults to 'yes'.
>>
>> (Currently TAP mode cannot be used without tcpdump.)
> 
> Maybe we can just tie tcpdump execution to tap mode - if running on tap
> mode, enable tcpdump, else, disable it. I'd rather prefer this
> approach. 

Checking for nic_mode == 'tap' is incorrect IMO, because nic_mode is a
VM parameter, not a global parameter.
There can be several VMs, some with nic_mode == 'user' and some with
nic_mode == 'tap', e.g.

nic_mode = user         # default value for all VMs
nic_mode_vm2 = tap      # specific to vm2 (overrides nic_mode)

so if we went by nic_mode, we wouldn't run tcpdump, which is required by
vm2.

Also, a test is free to start its own VMs.  Consider this (somewhat
unlikely) scenario: nic_mode=user, so vm1 uses user mode, and the test
clones it, changes the clone's mode to tap, and starts the clone.  If we
went by nic_mode, we wouldn't start tcpdump even though the clone needs it.

>> Signed-off-by: Michael Goldish <mgoldish@redhat.com>
>> ---
>>  client/tests/kvm/kvm_preprocessing.py  |    2 +-
>>  client/tests/kvm/tests_base.cfg.sample |    1 +
>>  2 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/client/tests/kvm/kvm_preprocessing.py b/client/tests/kvm/kvm_preprocessing.py
>> index 50db65c..e11207a 100644
>> --- a/client/tests/kvm/kvm_preprocessing.py
>> +++ b/client/tests/kvm/kvm_preprocessing.py
>> @@ -196,7 +196,7 @@ def preprocess(test, params, env):
>>      if "tcpdump" in env and not env["tcpdump"].is_alive():
>>          env["tcpdump"].close()
>>          del env["tcpdump"]
>> -    if "tcpdump" not in env:
>> +    if "tcpdump" not in env and params.get("run_tcpdump", "yes") == "yes":
>>          command = "/usr/sbin/tcpdump -npvi any 'dst port 68'"
>>          logging.debug("Starting tcpdump (%s)...", command)
>>          env["tcpdump"] = kvm_subprocess.kvm_tail(
>> diff --git a/client/tests/kvm/tests_base.cfg.sample b/client/tests/kvm/tests_base.cfg.sample
>> index c9dfd0b..1276267 100644
>> --- a/client/tests/kvm/tests_base.cfg.sample
>> +++ b/client/tests/kvm/tests_base.cfg.sample
>> @@ -46,6 +46,7 @@ nic_mode = user
>>  #nic_mode = tap
>>  nic_script = scripts/qemu-ifup
>>  address_index = 0
>> +run_tcpdump = yes
>>  
>>  # Misc
>>  run_kvm_stat = yes
> 
> 
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