loader: XDP attach type fallback logic#44209
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Signed-off-by: Dylan Reimerink <dylan.reimerink@isovalent.com>
Due to changes in newer kernels and the cilium/ebpf library, XDP programs will in future be loaded as ebpf.AttachXDP. However, older Cilium versions will have already created links with ebpf.AttachNone programs. The kernel does not allow us to change the program of a link if its attach type does not match. This means that we can only use the new XDP attach type when a link is newly created. This commit adds logic which detects errors on link update and attempts to load and attach with the other attach type instead. So when upgrading from an older version to a newer version, new links are created as XDP attach type, but existing links will remain using the AttachNone. On downgrade, all links will be created with AttachNone, and existing links will continue to use AttachXDP. Signed-off-by: Dylan Reimerink <dylan.reimerink@isovalent.com> Co-authored-by: Timo Beckers <timo@isovalent.com>
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Due to changes in newer kernels and the cilium/ebpf library, XDP programs will in future be loaded as ebpf.AttachXDP. However, older Cilium versions will have already created links with ebpf.AttachNone programs. The kernel does not allow us to change the program of a link if its attach type does not match.
This means that we can only use the new XDP attach type when a link is newly created. This commit adds logic which detects errors on link update and attempts to load and attach with the other attach type instead. So when upgrading from an older version to a newer version, new links are created as XDP attach type, but existing links will remain using the AttachNone. On downgrade, all links will be created with AttachNone, and existing links will continue to use AttachXDP.
Fixes: #44063