Yonghong Song [off-list ref] writes:

On 3/19/20 6:13 AM, Toke Høiland-Jørgensen wrote:

quoted

From: Toke Høiland-Jørgensen <redacted>

While it is currently possible for userspace to specify that an existing
XDP program should not be replaced when attaching to an interface, there is
no mechanism to safely replace a specific XDP program with another.

This patch adds a new netlink attribute, IFLA_XDP_EXPECTED_FD, which can be
set along with IFLA_XDP_FD. If set, the kernel will check that the program
currently loaded on the interface matches the expected one, and fail the
operation if it does not. This corresponds to a 'cmpxchg' memory operation.

The patch set itself looks good to me. But previously there is a
discussion regarding a potential similar functionality through bpf_link.
I guess maintainers (Alexei and Daniel) need to weigh in as some
future vision is involved.

Right, sure. See my reply to Jakub for why I went ahead with this
anyway.

-Toke