The DKMS config detects in-kernel o2ib support by checking for

rdma_cm.h, ib_cm.h and ib_verbs.h under ${kernel_source_dir}/include/rdma.

On Debian, the kernel headers are split into an arch-specific package

and a "-common" package, and the generic include/ tree (including

include/rdma) lives only in the latter, under

/usr/src/linux-headers-<version>-common. Since the arch-specific

directory has no include/rdma, can_o2ib_in_kernel stays "no" and the

in-kernel o2ib stack is never detected, so ko2iblnd is not built.

  modprobe: FATAL: Module ko2iblnd not found in directory

  /lib/modules/<kernel-version>

Search both ${kernel_source_dir} and

/usr/src/linux-headers-${kernelver%-*}-common for the RDMA headers,

and set can_o2ib_in_kernel=yes as soon as a directory contains all

three.