Well, I don't know what you expected but it, yeah, sure, you can translate keikaku doori 計画通り as "all according to the plan," and, yes, indeed, keikaku 計画 means "plan" in Japanese. The word doori 通り, however, is a little more complicated to explain.
To begin with, the doori 通り is only pronounced doori 通り when it's a suffix like in keikaku doori 計画通り. Usually, doori 通り is toori 通り, not doori 通り, and that's important because toori 通り is just a conjugation of a verb, tooru 通る
Now, the tooru 通る verb means "to pass through." As in, ooku no hito ga tooru michi 多くの人が通る道, "the street which many people pass through." Something which can be passed through is a "way," also called toori 通り.
So toori 通り can be used for things you can walk through, like paths through the dark forest of evil and whatever, but also it has another meaning of "way," which is a thing you go through to reach certain destination. That can be interpreted as "according to" in certain situations. See the following examples:
- kono toori この通り！
The way I said!
- sono toori! その通り！
The way you said!
- iwareta toori 言われた通り
As I was told.
The way I was told.
- kotoba doori 言葉通り
As the words say. Literally.
The way the words said.
- omotta toori! 思った通り！
As I thought!
The way I thought!
- keikaku doori! 計画通り！
All according to the plan!
The way the plan said!
- subete wa ore no keikaku doori 全ては俺の計画通り
Everything was according to the plan!
Everything was the way my plan said.
So this is the explanation behind keikaku doori meaning "all according to the plan".