Hi Stefan, >I have however no clue, why the number of bytes is only 32 in case of aarch64. This value is taken from the struct ifconf read via ioctl(SIOCGIFCONF). guix/build/syscalls.scm has: >(define ifreq-struct-size > ;; 'struct ifreq' begins with an array of IF_NAMESIZE bytes containing the > ;; interface name (nul-terminated), followed by a bunch of stuff. This is > ;; its size in bytes. > (if (= 8 (sizeof '*)) > 40 > 32)) I think that should rather be (sizeof* '*) instead of (sizeof '*). Ludo? Can you try printing (@@ (guix build syscalls) ifreq-struct-size) directly ? >To be precise this is all running in a virtual machine with virtio-net-pci. >Both kernel and qemu on the host are rather old. However, building for x86_64 >works just fine, so I think the host setup is unrelated. Is it qemu-user or qemu-system ? (Note: Empirically, on armhf, that struct is 32 Bytes big in C. And indeed the Linux kernel contains a compat struct ifreq32 in fs/compat_ioctl.c)