f72848021d
Currently a higher priority client can remove a lower priority client's filter with equal match-expression. This might happen if (a) the higher priority client has a double-free bug, or (b) another client with sufficient priority replaced and then removed an equal filter, allowing the low priority client to insert an equal filter. In neither case does it actually make sense to carry out the removal; we should say the filter doesn't exist, as the filter currently present is not the one that the high-priority client is referring to. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>