// ciphersuites and the id requested by the peer.
func mutualCipherSuite(have []uint16, want uint16) *cipherSuite {
	for _, id := range have {
		if id == want {
			return cipherSuiteByID(id)
		}
	}
	return nil
}

func cipherSuiteByID(id uint16) *cipherSuite {
	for _, cipherSuite := range cipherSuites {
		if cipherSuite.id == id {
			return cipherSuite
		}
	}
	return nil
}