add node group support for chain

chain.go

@@ -12,28 +12,51 @@ var (
 
 // Chain is a proxy chain that holds a list of proxy nodes.
 type Chain struct {
-	nodes []Node
+	nodeGroups []*NodeGroup
 }
 
-// NewChain creates a proxy chain with proxy nodes nodes.
+// NewChain creates a proxy chain with a list of proxy nodes.
 func NewChain(nodes ...Node) *Chain {
-	return &Chain{
-		nodes: nodes,
+	chain := &Chain{}
+	for _, node := range nodes {
+		chain.nodeGroups = append(chain.nodeGroups, NewNodeGroup(node))
 	}
+	return chain
 }
 
 // Nodes returns the proxy nodes that the chain holds.
-func (c *Chain) Nodes() []Node {
-	return c.nodes
+// If a node is a node group, the first node in the group will be returned.
+func (c *Chain) Nodes() (nodes []Node) {
+	for _, group := range c.nodeGroups {
+		if ns := group.Nodes(); len(ns) > 0 {
+			nodes = append(nodes, ns[0])
+		}
+	}
+	return
+}
+
+// NodeGroups returns the list of node group.
+func (c *Chain) NodeGroups() []*NodeGroup {
+	return c.nodeGroups
 }
 
 // LastNode returns the last node of the node list.
 // If the chain is empty, an empty node is returns.
+// If the last node is a node group, the first node in the group will be returned.
 func (c *Chain) LastNode() Node {
 	if c.IsEmpty() {
 		return Node{}
 	}
-	return c.nodes[len(c.nodes)-1]
+	last := c.nodeGroups[len(c.nodeGroups)-1]
+	return last.nodes[0]
+}
+
+// LastNodeGroup returns the last group of the group list.
+func (c *Chain) LastNodeGroup() *NodeGroup {
+	if c.IsEmpty() {
+		return nil
+	}
+	return c.nodeGroups[len(c.nodeGroups)-1]
 }
 
 // AddNode appends the node(s) to the chain.
@@ -41,13 +64,25 @@ func (c *Chain) AddNode(nodes ...Node) {
 	if c == nil {
 		return
 	}
-	c.nodes = append(c.nodes, nodes...)
+	for _, node := range nodes {
+		c.nodeGroups = append(c.nodeGroups, NewNodeGroup(node))
+	}
+}
+
+// AddNodeGroup appends the group(s) to the chain.
+func (c *Chain) AddNodeGroup(groups ...*NodeGroup) {
+	if c == nil {
+		return
+	}
+	for _, group := range groups {
+		c.nodeGroups = append(c.nodeGroups, group)
+	}
 }
 
 // IsEmpty checks if the chain is empty.
-// An empty chain means that there is no proxy node in the chain.
+// An empty chain means that there is no proxy node or node group in the chain.
 func (c *Chain) IsEmpty() bool {
-	return c == nil || len(c.nodes) == 0
+	return c == nil || len(c.nodeGroups) == 0
 }
 
 // Dial connects to the target address addr through the chain.
@@ -57,12 +92,12 @@ func (c *Chain) Dial(addr string) (net.Conn, error) {
 		return net.Dial("tcp", addr)
 	}
 
-	conn, err := c.Conn()
+	conn, nodes, err := c.getConn()
 	if err != nil {
 		return nil, err
 	}
 
-	cc, err := c.LastNode().Client.Connect(conn, addr)
+	cc, err := nodes[len(nodes)-1].Client.Connect(conn, addr)
 	if err != nil {
 		conn.Close()
 		return nil, err
@@ -72,39 +107,68 @@ func (c *Chain) Dial(addr string) (net.Conn, error) {
 
 // Conn obtains a handshaked connection to the last node of the chain.
 // If the chain is empty, it returns an ErrEmptyChain error.
-func (c *Chain) Conn() (net.Conn, error) {
+func (c *Chain) Conn() (conn net.Conn, err error) {
+	conn, _, err = c.getConn()
+	return
+}
+
+func (c *Chain) getConn() (conn net.Conn, nodes []Node, err error) {
 	if c.IsEmpty() {
-		return nil, ErrEmptyChain
+		err = ErrEmptyChain
+		return
 	}
-
-	nodes := c.nodes
-	conn, err := nodes[0].Client.Dial(nodes[0].Addr, nodes[0].DialOptions...)
+	groups := c.nodeGroups
+	selector := groups[0].Selector
+	if selector == nil {
+		selector = &defaultSelector{}
+	}
+	node, err := selector.Select(groups[0].Nodes(), groups[0].Options...)
 	if err != nil {
-		return nil, err
+		return
 	}
+	nodes = append(nodes, node)
 
-	conn, err = nodes[0].Client.Handshake(conn, nodes[0].HandshakeOptions...)
+	cn, err := node.Client.Dial(node.Addr, node.DialOptions...)
 	if err != nil {
-		return nil, err
+		return
 	}
 
-	for i, node := range nodes {
-		if i == len(nodes)-1 {
+	cn, err = node.Client.Handshake(cn, node.HandshakeOptions...)
+	if err != nil {
+		return
+	}
+
+	preNode := node
+	for i := range groups {
+		if i == len(groups)-1 {
 			break
 		}
+		selector = groups[i+1].Selector
+		if selector == nil {
+			selector = &defaultSelector{}
+		}
+		node, err = selector.Select(groups[i+1].Nodes(), groups[i+1].Options...)
+		if err != nil {
+			cn.Close()
+			return
+		}
+		nodes = append(nodes, node)
 
-		next := nodes[i+1]
-		cc, err := node.Client.Connect(conn, next.Addr)
+		var cc net.Conn
+		cc, err = preNode.Client.Connect(cn, node.Addr)
 		if err != nil {
-			conn.Close()
-			return nil, err
+			cn.Close()
+			return
 		}
-		cc, err = next.Client.Handshake(cc, next.HandshakeOptions...)
+		cc, err = node.Client.Handshake(cc, node.HandshakeOptions...)
 		if err != nil {
-			conn.Close()
-			return nil, err
+			cn.Close()
+			return
 		}
-		conn = cc
+		cn = cc
+		preNode = node
 	}
-	return conn, nil
+
+	conn = cn
+	return
 }

node.go

@@ -13,9 +13,9 @@ type Node struct {
 	Remote           string // remote address, used by tcp/udp port forwarding
 	User             *url.Userinfo
 	Values           url.Values
-	Client           *Client
 	DialOptions      []DialOption
 	HandshakeOptions []HandshakeOption
+	Client           *Client
 }
 
 // ParseNode parses the node info.
@@ -75,3 +75,33 @@ func ParseNode(s string) (node Node, err error) {
 
 	return
 }
+
+// NodeGroup is a group of nodes.
+type NodeGroup struct {
+	nodes    []Node
+	Options  []SelectOption
+	Selector Selector
+}
+
+// NewNodeGroup creates a node group
+func NewNodeGroup(nodes ...Node) *NodeGroup {
+	return &NodeGroup{
+		nodes: nodes,
+	}
+}
+
+// AddNode adds node or node list into group
+func (ng *NodeGroup) AddNode(node ...Node) {
+	if ng == nil {
+		return
+	}
+	ng.nodes = append(ng.nodes, node...)
+}
+
+// Nodes returns node list in the group
+func (ng *NodeGroup) Nodes() []Node {
+	if ng == nil {
+		return nil
+	}
+	return ng.nodes
+}

selector.go

@@ -0,0 +1,73 @@
+package gost
+
+import "errors"
+
+var (
+	// ErrNoneAvailable indicates there is no node available
+	ErrNoneAvailable = errors.New("none available")
+)
+
+// SelectOption used when making a select call
+type SelectOption func(*SelectOptions)
+
+// Selector as a mechanism to pick nodes and mark their status.
+type Selector interface {
+	Select(nodes []Node, opts ...SelectOption) (Node, error)
+	// Mark(node Node)
+	String() string
+}
+
+type defaultSelector struct {
+}
+
+func (s *defaultSelector) Select(nodes []Node, opts ...SelectOption) (Node, error) {
+	sopts := SelectOptions{
+		Strategy: defaultStrategy,
+	}
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	for _, filter := range sopts.Filters {
+		nodes = filter(nodes)
+	}
+	if len(nodes) == 0 {
+		return Node{}, ErrNoneAvailable
+	}
+	return sopts.Strategy(nodes), nil
+}
+
+func (s *defaultSelector) String() string {
+	return "default"
+}
+
+// Filter is used to filter a node during the selection process
+type Filter func([]Node) []Node
+
+// Strategy is a selection strategy e.g random, round robin
+type Strategy func([]Node) Node
+
+func defaultStrategy(nodes []Node) Node {
+	return nodes[0]
+}
+
+// SelectOptions is the options for node selection
+type SelectOptions struct {
+	Filters  []Filter
+	Strategy Strategy
+}
+
+// WithFilter adds a filter function to the list of filters
+// used during the Select call.
+func WithFilter(f ...Filter) SelectOption {
+	return func(o *SelectOptions) {
+		o.Filters = append(o.Filters, f...)
+	}
+}
+
+// WithStrategy sets the selector strategy
+func WithStrategy(s Strategy) SelectOption {
+	return func(o *SelectOptions) {
+		o.Strategy = s
+	}
+}