add pkgs from core

hosts/hosts.go

@@ -0,0 +1,127 @@
+package hosts
+
+import (
+	"net"
+	"strings"
+	"sync"
+
+	"github.com/go-gost/core/logger"
+)
+
+type hostMapping struct {
+	IPs      []net.IP
+	Hostname string
+}
+
+// Hosts is a static table lookup for hostnames.
+// For each host a single line should be present with the following information:
+// IP_address canonical_hostname [aliases...]
+// Fields of the entry are separated by any number of blanks and/or tab characters.
+// Text from a "#" character until the end of the line is a comment, and is ignored.
+type Hosts struct {
+	mappings sync.Map
+	Logger   logger.Logger
+}
+
+func NewHosts() *Hosts {
+	return &Hosts{}
+}
+
+// Map maps ip to hostname or aliases.
+func (h *Hosts) Map(ip net.IP, hostname string, aliases ...string) {
+	if hostname == "" {
+		return
+	}
+
+	v, _ := h.mappings.Load(hostname)
+	m, _ := v.(*hostMapping)
+	if m == nil {
+		m = &hostMapping{
+			IPs:      []net.IP{ip},
+			Hostname: hostname,
+		}
+	} else {
+		m.IPs = append(m.IPs, ip)
+	}
+	h.mappings.Store(hostname, m)
+
+	for _, alias := range aliases {
+		// indirect mapping from alias to hostname
+		if alias != "" {
+			h.mappings.Store(alias, &hostMapping{
+				Hostname: hostname,
+			})
+		}
+	}
+}
+
+// Lookup searches the IP address corresponds to the given network and host from the host table.
+// The network should be 'ip', 'ip4' or 'ip6', default network is 'ip'.
+// the host should be a hostname (example.org) or a hostname with dot prefix (.example.org).
+func (h *Hosts) Lookup(network, host string) (ips []net.IP, ok bool) {
+	m := h.lookup(host)
+	if m == nil {
+		m = h.lookup("." + host)
+	}
+	if m == nil {
+		s := host
+		for {
+			if index := strings.IndexByte(s, '.'); index > 0 {
+				m = h.lookup(s[index:])
+				s = s[index+1:]
+				if m == nil {
+					continue
+				}
+			}
+			break
+		}
+	}
+
+	if m == nil {
+		return
+	}
+
+	// hostname alias
+	if !strings.HasPrefix(m.Hostname, ".") && host != m.Hostname {
+		m = h.lookup(m.Hostname)
+		if m == nil {
+			return
+		}
+	}
+
+	switch network {
+	case "ip4":
+		for _, ip := range m.IPs {
+			if ip = ip.To4(); ip != nil {
+				ips = append(ips, ip)
+			}
+		}
+	case "ip6":
+		for _, ip := range m.IPs {
+			if ip.To4() == nil {
+				ips = append(ips, ip)
+			}
+		}
+	default:
+		ips = m.IPs
+	}
+
+	if len(ips) > 0 {
+		h.Logger.Debugf("host mapper: %s -> %s", host, ips)
+	}
+
+	return
+}
+
+func (h *Hosts) lookup(host string) *hostMapping {
+	if h == nil || host == "" {
+		return nil
+	}
+
+	v, ok := h.mappings.Load(host)
+	if !ok {
+		return nil
+	}
+	m, _ := v.(*hostMapping)
+	return m
+}