What's the Story of the Edomites?

In 2 Samuel chapter 8, David killed a bunch of Edomites in the Valley of Salt. In verse 17 that Hadad fled to Egypt. He's of royal stock, but they don't get him. So he runs off and he goes with some other Edomites when he was just a little. They go to Peron, which is kind of a way station between where the Edomites lived in Egypt. And they came to Egypt, to Pharaoh, King of Egypt, who gave him a house.