TUN-4063: Cleanup dependencies between packages.

- Move packages the provide generic functionality (such as config) from `cmd` subtree to top level.
- Remove all dependencies on `cmd` subtree from top level packages.
- Consolidate all code dealing with token generation and transfer to a single cohesive package.

config/model.go

@@ -0,0 +1,113 @@
+package config
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/cloudflare/cloudflared/tunneldns"
+)
+
+// Forwarder represents a client side listener to forward traffic to the edge
+type Forwarder struct {
+	URL           string `json:"url"`
+	Listener      string `json:"listener"`
+	TokenClientID string `json:"service_token_id" yaml:"serviceTokenID"`
+	TokenSecret   string `json:"secret_token_id" yaml:"serviceTokenSecret"`
+	Destination   string `json:"destination"`
+}
+
+// Tunnel represents a tunnel that should be started
+type Tunnel struct {
+	URL          string `json:"url"`
+	Origin       string `json:"origin"`
+	ProtocolType string `json:"type"`
+}
+
+// DNSResolver represents a client side DNS resolver
+type DNSResolver struct {
+	Enabled                bool     `json:"enabled"`
+	Address                string   `json:"address,omitempty"`
+	Port                   uint16   `json:"port,omitempty"`
+	Upstreams              []string `json:"upstreams,omitempty"`
+	Bootstraps             []string `json:"bootstraps,omitempty"`
+	MaxUpstreamConnections int      `json:"max_upstream_connections,omitempty"`
+}
+
+// Root is the base options to configure the service
+type Root struct {
+	LogDirectory string      `json:"log_directory" yaml:"logDirectory,omitempty"`
+	LogLevel     string      `json:"log_level" yaml:"logLevel,omitempty"`
+	Forwarders   []Forwarder `json:"forwarders,omitempty" yaml:"forwarders,omitempty"`
+	Tunnels      []Tunnel    `json:"tunnels,omitempty" yaml:"tunnels,omitempty"`
+	Resolver     DNSResolver `json:"resolver,omitempty" yaml:"resolver,omitempty"`
+}
+
+// Hash returns the computed values to see if the forwarder values change
+func (f *Forwarder) Hash() string {
+	h := md5.New()
+	io.WriteString(h, f.URL)
+	io.WriteString(h, f.Listener)
+	io.WriteString(h, f.TokenClientID)
+	io.WriteString(h, f.TokenSecret)
+	io.WriteString(h, f.Destination)
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
+// Hash returns the computed values to see if the forwarder values change
+func (r *DNSResolver) Hash() string {
+	h := md5.New()
+	io.WriteString(h, r.Address)
+	io.WriteString(h, strings.Join(r.Bootstraps, ","))
+	io.WriteString(h, strings.Join(r.Upstreams, ","))
+	io.WriteString(h, fmt.Sprintf("%d", r.Port))
+	io.WriteString(h, fmt.Sprintf("%d", r.MaxUpstreamConnections))
+	io.WriteString(h, fmt.Sprintf("%v", r.Enabled))
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
+// EnabledOrDefault returns the enabled property
+func (r *DNSResolver) EnabledOrDefault() bool {
+	return r.Enabled
+}
+
+// AddressOrDefault returns the address or returns the default if empty
+func (r *DNSResolver) AddressOrDefault() string {
+	if r.Address != "" {
+		return r.Address
+	}
+	return "localhost"
+}
+
+// PortOrDefault return the port or returns the default if 0
+func (r *DNSResolver) PortOrDefault() uint16 {
+	if r.Port > 0 {
+		return r.Port
+	}
+	return 53
+}
+
+// UpstreamsOrDefault returns the upstreams or returns the default if empty
+func (r *DNSResolver) UpstreamsOrDefault() []string {
+	if len(r.Upstreams) > 0 {
+		return r.Upstreams
+	}
+	return []string{"https://1.1.1.1/dns-query", "https://1.0.0.1/dns-query"}
+}
+
+// BootstrapsOrDefault returns the bootstraps or returns the default if empty
+func (r *DNSResolver) BootstrapsOrDefault() []string {
+	if len(r.Bootstraps) > 0 {
+		return r.Bootstraps
+	}
+	return []string{"https://162.159.36.1/dns-query", "https://162.159.46.1/dns-query", "https://[2606:4700:4700::1111]/dns-query", "https://[2606:4700:4700::1001]/dns-query"}
+}
+
+// MaxUpstreamConnectionsOrDefault return the max upstream connections or returns the default if negative
+func (r *DNSResolver) MaxUpstreamConnectionsOrDefault() int {
+	if r.MaxUpstreamConnections >= 0 {
+		return r.MaxUpstreamConnections
+	}
+	return tunneldns.MaxUpstreamConnsDefault
+}