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net: fix build when libbpf is disabled, but libxdp is enabled

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The net/af-xdp.c code is enabled when the libxdp library is present,
however, it also has direct API calls to bpf_xdp_query_id &
bpf_xdp_detach which are provided by the libbpf library.

As a result if building with --disable-libbpf, but libxdp gets
auto-detected, we'll fail to link QEMU

  /usr/bin/ld: libcommon.a.p/net_af-xdp.c.o: undefined reference to symbol 'bpf_xdp_query_id@@LIBBPF_0.7.0'

There are two bugs here

 * Since we have direct libbpf API calls, when building
   net/af-xdp.c, we must tell meson that libbpf is a
   dependancy, so that we directly link to it, rather
   than relying on indirect linkage.

 * When must skip probing for libxdp at all, when libbpf
   is not found, raising an error if --enable-libxdp was
   given explicitly.

Fixes: cb039ef3d9e3112da01e1ecd9b136ac9809ef733
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2024-10-23 09:50:56 +01:00 committed by Jason Wang
parent cea8ac7854
commit 1f37280b37
2 changed files with 9 additions and 3 deletions
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10
meson.build
View File

@ -2164,8 +2164,14 @@ endif
# libxdp # libxdp
libxdp = not_found libxdp = not_found
if not get_option('af_xdp').auto() or have_system if not get_option('af_xdp').auto() or have_system
libxdp = dependency('libxdp', required: get_option('af_xdp'), if libbpf.found()
version: '>=1.4.0', method: 'pkg-config') libxdp = dependency('libxdp', required: get_option('af_xdp'),
version: '>=1.4.0', method: 'pkg-config')
else
if get_option('af_xdp').enabled()
error('libxdp requested, but libbpf is not available')
endif
endif
endif endif
# libdw # libdw

2
net/meson.build
View File

@ -39,7 +39,7 @@ if have_netmap
system_ss.add(files('netmap.c')) system_ss.add(files('netmap.c'))
endif endif
system_ss.add(when: libxdp, if_true: files('af-xdp.c')) system_ss.add(when: [libxdp, libbpf], if_true: files('af-xdp.c'))
if have_vhost_net_user if have_vhost_net_user
system_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('vhost-user.c'), if_false: files('vhost-user-stub.c')) system_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('vhost-user.c'), if_false: files('vhost-user-stub.c'))