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2dd86bbe5a
VMware uses a mix of percent-, pipe- and base64-encoding in different combinations in different places. Add a testcase for this.
114 lines
5.0 KiB
Plaintext
114 lines
5.0 KiB
Plaintext
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Some links to relevant documentation
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====================================
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VI/vSphere API:
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http://www.vmware.com/support/developer/vc-sdk/visdk25pubs/ReferenceGuide/
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http://www.vmware.com/support/developer/vc-sdk/visdk400pubs/ReferenceGuide/
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http://www.vmware.com/support/developer/vc-sdk/visdk41pubs/ApiReference/
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VMX config:
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http://www.sanbarrow.com/vmx.html
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CPUID:
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http://www.sandpile.org/ia32/cpuid.htm
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Memory model:
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http://www.vmware.com/pdf/esx3_memory.pdf
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http://www.vmware.com/pdf/usenix_resource_mgmt.pdf
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Virtual serial port (network backed):
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http://www.vmware.com/support/developer/vc-sdk/visdk41pubs/ApiReference/vim.vm.device.VirtualSerialPort.URIBackingInfo.html
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http://www.vmware.com/support/developer/vc-sdk/visdk41pubs/vsp41_usingproxy_virtual_serial_ports.pdf
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Automatic question handling
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===========================
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What is a question in the ESX context?
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--------------------------------------
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The VI API contains methods that start tasks, for example PowerOnVM_Task(). Such
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tasks may be blocked by questions if the ESX host detects an issue with the
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virtual machine that requires user interaction.
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An example: If a virtual machine has a serial port that is realized via a file,
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the ESX host will ask a question on power-on of this virtual machine whether
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new content should be appended to this file or the file should be replaced.
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Until this question is answered the power-on task is blocked and the virtual
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machine won't get powered on.
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The ESX driver cannot prompt the user to answer a question, libvirt doesn't
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have an API for something like this. The VI API provides the AnswerVM() method
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to programmatically answer such questions. A question comes together with a list
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of possible answers. One of this answers is marked as the default one. For all
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questions I've seen so far the default answer is always a non-destructive one.
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There are two options how to handle a question that is blocking a task: either
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answer it automatically or report it as error and try to cancel the blocked
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task.
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The auto_answer query parameter defines how the driver should handle questions.
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Possible values are 0 for the report-error-and-try-to-cancel option and 1 for
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the automatic-answer option.
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How is automatic question handling implemented?
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-----------------------------------------------
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Before any new task is started the driver checks if there is a pending task
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blocked by a question. If automatic question handling is disabled the driver
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reports an error that includes the question and returns from the driver
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function. If automatic question handling is enabled the driver answers the
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question with the default answer and returns from the driver function.
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In both cases the actual desired task is not started. If the question was not
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answered the blocked task is still blocked and because task can't be executed
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in parallel in general it's of no use to start yet another task. If the
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question was answered the blocked task may already perform the desired action
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and one must wait for its completion, so it's of no use to start yet another
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task.
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If there is no question blocking a task or another pending task that had not
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finished yet the driver starts the desired task and waits for its completion.
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While polling for status updates of the task it also checks for question that
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may have been triggered by the current task and handles them according to the
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value of the auto_answer query parameter. If automatic question handling is
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enabled the driver answers the question with the default answer and continues
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polling for status updates. If automatic question handling is disabled the
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driver reports an error that includes the question, tries to cancel the blocked
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task and returns from the driver function.
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It tries to cancel the blocked task, but this may not be possible, because
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there are task like the power-on task that is marked as non-cancelable. So the
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driver may leave blocked tasks behind if automatic question handling is
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disabled.
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Different escaping schemes used in different places
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===================================================
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A domain name in the vSphere API has [%/\] escaped as %XX (percent-encoding),
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where XX is the ASCII code of the escaped char in hex.
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A domainName entry in a VMX config file is percent-encoded and has [|"] escaped
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as |XX (pipe-encoding).
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A annotation entry in a VMX config file is pipe-encoded.
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A datastore item name has the special Windows path characters ["*<>:|?]
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replaced by underscores (_). The result is escaped using percent-encoding and
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base64-encoding. This isn't a bijective encoding. Therefore, escaped datastore
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item names cannot be unescaped completely.
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For base64-encoding sequences of chars that don't match [a-zA-Z0-9'(),. _-]
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are replaced by their base64 form (the padding is omitted). An encoded sequence
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begins with a plus (+), ends with a minus (-) and can contain a plus (+). The
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minus (-) is omitted if the string ends in a base64-encoded sequence. VMware
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uses the comma (,) instead of the slash (/) in the base64 alphabet to avoid
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conflicts with the slash as path separator.
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