RFC PATCH: Issue 90 (Test Clarification)

Ryan Gahagan ryangahagan18 at gmail.com
Mon Dec 21 23:10:35 UTC 2020


We were able to get the testing environment running after some
trial-and-error. The issue was that the version of libtirpc was out of
date, causing an error in meson.build when the XDR dependency was being
read. By updating the libtirpc-dev package we were able to start building
locally. However, we did have some questions about our tests. For now we
wanted to focus specifically on the qemublocktest.c file.

We have the function virDomainDiskSourceNetworkParse in
src/conf/domain_conf.c where XML is parsed into virStorageSource data and
the function qemuBlockStorageSourceCreateGetStorageProps under
src/qemu/qemu_block.c where this data is converted into a JSON object. Our
understanding of the tests/qemublocktest.c file is that we provide an XML
string example via TEST_JSON_FORMAT_NET and that this string was parsed
into JSON then formatted back into XML to make sure the process produced
the same output as the input. One issue is that for some reason our user
and group strings (i.e. “<nfs user=’+1’ group=’+2’/>”) are not getting
parsed into integers. The nfs_uid and nfs_gid fields are never set and
therefore result in a 0 every time. We have code to fix this in a method
under qemuDomainPrepareStorageSourceBlockdev in the file
src/qemu/qemu_domain.c which looks up the user and group and stores the
values we expect, but this method isn’t getting called. Where in this
process have we missed something? Should we move the virGetUserID and
virGetGroupID method calls to somewhere else?
We were also curious about the methods which parse the JSON values back
into data. In our case, this is virStorageSourceParseBackingJSONNFS in
src/util/virstoragefile.c. This method tries to retrieve the user and group
integers from the NFS JSON object. However, when constructing the JSON
object in the getStorageProps method we don't actually add those values if
they're "default" values. In JSON terms this means that the integers are
undefined, but how does C interpret it? Does the retrieve method return 0
or simply fail?
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