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Re: [libvirt] [PATCH 10/10] network: internal API functions to manage assignment of physdev to guest



On 07/08/2011 04:23 PM, Eric Blake wrote:
On 07/05/2011 10:18 PM, Laine Stump wrote:
I realized that PATCH 10/10 would cause the build to fail if someone
did a build --with-qemu but --without-network. I'm squashing the
following into the original patch to remedy that.

I'm not really a fan of putting #if all over the place, but this is
similar to what's done with WITH_MACVTAP, so at least there's
precedence. (This is necessary because this new "backend API" to the
network driver isn't called via a pointer table filled in at runtime,
as is done with the public API).
Would it be any easier to instead guarantee that even when #if
WITH_NETWORK is false, those same symbols are available as no-ops to
allow compilation to proceed?


That would mean either defining the functions inside qemu, or creating a dummy network module replacement to be built when WITH_NETWORK is false. I like both of those options even less.


+#if WITH_NETWORK
              /* If appropriate, grab a physical device from the configured
               * network's pool of devices, or resolve bridge device name
               * to the one defined in the network definition.
               */
              if (networkAllocateActualDevice(net)<  0)
                 goto error;
-
+#endif
That is, make networkAllocateActualDevice() be a no-op that returns 0 if
there is no network support compiled in, and therefore nothing to allocate.


But where would that NOP function live? The natural place for a function called "networkSomething" is in a network driver, but there isn't one.


+++ b/tests/Makefile.am
@@ -319,8 +319,11 @@ endif

  if WITH_QEMU

-qemu_LDADDS = ../src/libvirt_driver_qemu.la \
-	../src/libvirt_driver_network.la
+qemu_LDADDS = ../src/libvirt_driver_qemu.la
+
+if WITH_NETWORK
+qemu_LDADDS += ../src/libvirt_driver_network.la
+endif
Then again, if you are compiling --without-network, you don't want to
link against a library that won't be built.  That would imply that any
no-op stubs would have to be provided by static inline functions in the
header in the no-network case.

Ah, you're doing this mail "On the Road" style (stream of consciousness with no going back to edit), so I'll respond that way too :-)

Actually, I like this idea - in bridge_driver.h, I can put the function declrations inside #if WITH_NETWORK, and have a #else clause that contains inlines that return success but do nothing (exactly what is needed). That way the code in qemu won't need #if.

I'll do it that way in the next version.


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