Merge pull request #48319 from robmry/optional_fixed-cidr-v6 #679

Job	Run time
validate-dco / run	20s
build	2m 3s
test (dockerd, client, integration)	17m 6s
test (dockerd, cmd/buildctl, integration)	8m 7s
test (dockerd, solver, integration)	8m 20s
test (dockerd, frontend, integration)	8m 14s
test (dockerd, frontend/dockerfile, integration)	22m 21s
test (dockerd-containerd, client, integration)	20m 21s
test (dockerd-containerd, cmd/buildctl, integration)	8m 19s
test (dockerd-containerd, solver, integration)	8m 9s
test (dockerd-containerd, frontend, integration)	7m 59s
test (dockerd-containerd, frontend/dockerfile, integration)	24m 0s
	2h 15m 19s

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