[BUG] Xen build error - undefined reference to bpf_program__set_socket_filter

[Arthur Borsboom <arthurborsboom@xxxxxxxxx>]

Xen 4.16.1, 4.16.2 and 4.17.0-rc1 don't build anymore in Arch Linux.

I believe it is caused by the missing function bpf_program__set_socket_filter provided by libbpf.

This function has been deprecated in v0.8 and has been removed in v1.0.

Arch Linux uses libbpf v1.0.1 since October 2022.

A downgrade to libbpf v0.8.1 fixes the Xen build problem.

Source about the deprecation: https://libbpf-test.readthedocs.io/en/latest/api.html

Build error:

/bin/ld: libcommon.fa.p/ebpf_ebpf_rss.c.o: in function `ebpf_rss_load':

/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools/qemu-xen-build/../qemu-xen/ebpf/ebpf_rss.c:52: undefined reference to `bpf_program__set_socket_filter'

collect2: error: ld returned 1 exit status
...
...
ninja: build stopped: subcommand failed.
make: *** [Makefile:156: run-ninja] Error 1
make: Leaving directory '/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools/qemu-xen-build'
make[3]: *** [Makefile:212: subdir-all-qemu-xen-dir] Error 2
make[3]: Leaving directory '/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools'
make[2]: *** [/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools/../tools/Rules.mk:161: subdirs-install] Error 2
make[2]: Leaving directory '/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools'
make[1]: *** [Makefile:66: install] Error 2
make[1]: Leaving directory '/home/arthur/.cache/yay/xen/src/xen-4.16.1/tools'
make: *** [Makefile:140: install-tools] Error 2
==> ERROR: A failure occurred in build().
Aborting...

-> error making: xen