add redis and ip assignment

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

net.go

@@ -0,0 +1,187 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/gomodule/redigo/redis"
+)
+
+const (
+	ipsKey = "gatekeeper/ips"
+)
+
+type subnetRange struct {
+	Start  net.IP
+	End    net.IP
+	Subnet *net.IPNet
+}
+
+func (s *Server) getIPs() (map[string]net.IP, error) {
+	c, err := s.getConn()
+	if err != nil {
+		return nil, err
+	}
+	defer c.Close()
+
+	values, err := redis.StringMap(c.Do("HGETALL", ipsKey))
+	if err != nil {
+		return nil, err
+	}
+
+	ips := make(map[string]net.IP, len(values))
+	for id, val := range values {
+		ip := net.ParseIP(string(val))
+		ips[id] = ip
+	}
+	return ips, nil
+}
+
+func (s *Server) getIP(id string) (net.IP, error) {
+	allIPs, err := s.getIPs()
+	if err != nil {
+		return nil, err
+	}
+
+	if ip, exists := allIPs[id]; exists {
+		return ip, nil
+	}
+	return nil, nil
+}
+
+func (s *Server) getOrAllocateIP(id, subnet string) (net.IP, *net.IPNet, error) {
+	r, err := s.parseSubnetRange(subnet)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	ip, err := s.getIP(id)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if ip != nil {
+		return ip, r.Subnet, nil
+	}
+
+	ip, err = s.allocateIP(id, r)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return ip, r.Subnet, nil
+}
+
+func (s *Server) allocateIP(id string, r *subnetRange) (net.IP, error) {
+	c, err := s.getConn()
+	if err != nil {
+		return nil, err
+	}
+	defer c.Close()
+
+	reservedIPs, err := s.getIPs()
+	if err != nil {
+		return nil, err
+	}
+
+	if ip, exists := reservedIPs[id]; exists {
+		return ip, nil
+	}
+
+	lookup := map[string]string{}
+	for id, ip := range reservedIPs {
+		lookup[ip.String()] = id
+	}
+	for ip := r.Start; !ip.Equal(r.End); s.nextIP(ip) {
+		// filter out network, gateway and broadcast
+		if !s.validIP(ip) {
+			continue
+		}
+		if _, exists := lookup[ip.String()]; exists {
+			// ip already reserved
+			continue
+		}
+
+		// save
+		if _, err := c.Do("HSET", ipsKey, id, ip.String()); err != nil {
+			return nil, err
+		}
+		return ip, nil
+	}
+
+	return nil, fmt.Errorf("no available IPs")
+}
+
+func (s *Server) releaseIP(id string) error {
+	c, err := s.getConn()
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+
+	ip, err := s.getIP(id)
+	if err != nil {
+		return err
+	}
+
+	if ip != nil {
+		if _, err := c.Do("HDEL", ipsKey, id); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *Server) nextIP(ip net.IP) {
+	for j := len(ip) - 1; j >= 0; j-- {
+		ip[j]++
+		if ip[j] > 0 {
+			break
+		}
+	}
+}
+
+func (s *Server) validIP(ip net.IP) bool {
+	v := ip[len(ip)-1]
+	switch v {
+	case 0, 1, 255:
+		return false
+	}
+	return true
+}
+
+// parseSubnetRange parses the subnet range
+// format can either be a subnet like 10.0.0.0/8 or range like 10.0.0.100-10.0.0.200/24
+func (s *Server) parseSubnetRange(subnet string) (*subnetRange, error) {
+	parts := strings.Split(subnet, "-")
+	if len(parts) == 1 {
+		ip, sub, err := net.ParseCIDR(parts[0])
+		if err != nil {
+			return nil, err
+		}
+
+		end := make(net.IP, len(ip))
+		copy(end, ip)
+		end[len(end)-1] = 254
+		return &subnetRange{
+			Start:  ip,
+			End:    end,
+			Subnet: sub,
+		}, nil
+	}
+	if len(parts) > 2 || !strings.Contains(subnet, "/") {
+		return nil, fmt.Errorf("invalid range specified; expect format 10.0.0.100-10.0.0.200/24")
+	}
+	start := net.ParseIP(parts[0])
+	end, sub, err := net.ParseCIDR(parts[1])
+	if err != nil {
+		return nil, err
+	}
+
+	return &subnetRange{
+		Start:  start,
+		End:    end,
+		Subnet: sub,
+	}, nil
+}