On 17.03.2014 20:31, Brian Rak wrote:
I've been trying to use domain.setInterfaceParameters, and I'm finding
it's throwing the mysterious error:
libvirt.libvirtError: argument unsupported: parameter '' not supported
Enabling debug mode in libvirt reveals this:
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8001 : dom=0x7f2ecc0009b0, (VM:
name=SRVID8736, uuid=5121c1d6-19aa-4494-b6a7-09af270f24da),
device=vnet0, params=0x7f2ecc0011f0, nparams=6, flags=0
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)0
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)64000
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)10
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)64000
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)0
2014-03-17 18:41:33.780+0000: 16927: debug :
virDomainSetInterfaceParameters:8002 : params[""]=(uint)0
(irreverent lines trimmed)
Which ultimately led me to setPyVirTypedParameter lines 200-202. These
don't seem to work properly. I added some debugging:
strncpy(temp->field, keystr, sizeof(*temp->field) - 1);
temp->field[sizeof(*temp->field) - 1] = '\0';
DEBUG("current key name in: %s, out: %s field size: %i\n",
keystr, temp->field, sizeof(*temp->field) - 1);
temp->type = params[i].type;
which was displaying:
current key name in: outbound.peak, out: field size: 0
current key name in: inbound.peak, out: field size: 0
current key name in: inbound.burst, out: field size: 0
current key name in: inbound.average, out: field size: 0
current key name in: outbound.average, out: field size: 0
current key name in: outbound.burst, out: field size: 0
I am not good enough in C to determine what exactly the correct fix is
here. It seems like nothing that used this function could have ever
worked. My trivial patch was:
--- a/python27-libvirt/libvirt-python-1.2.2/libvirt-override.c
+++ b/python27-libvirt/libvirt-python-1.2.2/libvirt-override.c
@@ -197,8 +197,8 @@ setPyVirTypedParameter(PyObject *info,
goto cleanup;
}
- strncpy(temp->field, keystr, sizeof(*temp->field) - 1);
- temp->field[sizeof(*temp->field) - 1] = '\0';
+ strncpy(temp->field, keystr, VIR_TYPED_PARAM_FIELD_LENGTH - 1);
+ temp->field[VIR_TYPED_PARAM_FIELD_LENGTH - 1] = '\0';
temp->type = params[i].type;
VIR_FREE(keystr);
Yes, you're right. The problem is temp->field is a fixed-size array, so
dereferencing *temp->field addresses the first item which is size of 1B.
So we effectively copy nothing. The fix is either to discard the
dereference or use the constant. I suggest going with the latter as it's
more obvious. Moreover, there's no need for terminating the string: the
@temp is always within freshly allocated zero that is initially filled
with zeros. And I've noticed a memleak too.
I've proposed patch:
https://www.redhat.com/archives/libvir-list/2014-March/msg01055.html
Michal
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