config.go

/*
 * VC5 load balancer. Copyright (C) 2021-present David Coles
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package vc5

import (
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"net/netip"
	"os"
	"regexp"
	"strconv"
	//"time"

	"github.com/davidcoles/bgp"
	"github.com/davidcoles/cue"
	"github.com/davidcoles/cue/mon"
)

//go:embed static/*
var STATIC embed.FS

type Priority = priority
type Protocol = protocol

const (
	TCP = 0x06
	UDP = 0x11
)

type Real struct {
	Checks   []mon.Check `json:"checks,omitempty"`
	Disabled bool        `json:"disabled,omitempty"`
	Weight   uint8       `json:"weight,omitempty"`
}

// Describes a Layer 4 service
type ServiceDefinition struct {
	// The service name - should be a short identifier, suitable for using as a Prometheus label value
	Name string `json:"name,omitempty"`

	// A short description of the service
	Description string `json:"description,omitempty"`

	// critical, high, medium or low (default is critical)
	Priority priority `json:"priority"`

	// The minimum number of real servers which need to be healthy to consider this service viable
	Need uint8 `json:"need,omitempty"`

	// Backend servers and corresponding health checks
	Destinations map[Destination]Real `json:"reals,omitempty"`

	// If set to true, the backend selection algorithm will not include layer 4 port numbers
	Sticky bool `json:"sticky,omitempty"`

	Scheduler string `json:"scheduler"`
	Persist   uint32 `json:"persist"`         // used in IPVS version
	Reset     bool   `json:"reset,omitempty"` // used in IPVS version

	TunnelType            string `json:"tunnel-type,omitempty"`
	TunnelPort            uint16 `json:"tunnel-port,omitempty"`
	TunnelEncapNoChecksum bool   `json:"tunnel-no-checksum,omitempty"`
}

type services map[Service]ServiceDefinition

// Load balancer configuration
type Config struct {
	Services services                  `json:"services,omitempty"`
	VLANs    map[uint16]netip.Prefix   `json:"vlans,omitempty"`  // VLAN ID to subnet mappings
	VLANs6   map[uint16]netip.Prefix   `json:"vlans6,omitempty"` // VLAN ID to subnet mappings
	BGP      map[string]bgp.Parameters `json:"bgp,omitempty"`    // BGP peers
	Logging  Logging_                  `json:"logging,omitempty"`
}

func (c *Config) Prefixes() map[uint16]netip.Prefix {
	return c.VLANs
}

func (c *Config) Prefixes6() map[uint16]netip.Prefix {
	return c.VLANs6
}

func (c *Config) LoggingConfig() Logging {
	return c.Logging.Logging()
}

func (c *Config) Bgp(asn uint16, mp bool) map[string]bgp.Parameters {
	if asn > 0 {
		return map[string]bgp.Parameters{"127.0.0.1": bgp.Parameters{ASNumber: asn, HoldTime: 4, Multiprotocol: mp}}
	}

	return c.BGP
}

func (c *Config) Priorities() map[netip.Addr]priority {

	priorities := map[netip.Addr]priority{}

	for k, v := range c.Services {
		p, ok := priorities[k.Address]

		if !ok {
			p = LOW
			priorities[k.Address] = p
		}

		if v.Priority < p {
			priorities[k.Address] = v.Priority
		}
	}

	return priorities
}

// Reads the load-balancer configuration from a JSON file. Returns a
// pointer to the Config object on success, and sets the error to
// non-nil on failure.
func Load(file string) (*Config, error) {

	f, err := os.Open(file)

	if err != nil {
		return nil, err
	}

	defer f.Close()

	b, err := ioutil.ReadAll(f)

	if err != nil {
		return nil, err
	}

	var config Config

	err = json.Unmarshal(b, &(config))

	if err != nil {
		return nil, err
	}

	return &config, nil
}

type Prefix net.IPNet

func (p *Prefix) String() string {
	return (*net.IPNet)(p).String()
}

func (p *Prefix) Contains(i netip.Addr) bool {
	var ip net.IP
	if i.Is4() {
		t := i.As4()
		ip = t[:]
	} else if i.Is6() {
		t := i.As16()
		ip = t[:]
	}

	return (*net.IPNet)(p).Contains(ip)
}

func (p *Prefix) UnmarshalJSON(data []byte) error {

	l := len(data)

	if l < 3 || data[0] != '"' || data[l-1] != '"' {
		return errors.New("CIDR address should be a string: " + string(data))
	}

	cidr := string(data[1 : l-1])

	//ip, ipnet, err := net.ParseCIDR(cidr)
	_, ipnet, err := net.ParseCIDR(cidr)

	if err != nil {
		return err
	}

	//if ip.String() != ipnet.IP.String() {
	//return errors.New("CIDR address contains host portion: " + cidr)
	//}

	*p = Prefix(*ipnet)

	return nil
}

func (c *Config) Parse() []cue.Service {

	var services []cue.Service

	for ipp, svc := range c.Services {

		service := cue.Service{
			Address:   ipp.Address,
			Port:      ipp.Port,
			Protocol:  uint8(ipp.Protocol),
			Required:  svc.Need,
			Scheduler: svc.Scheduler,
			Persist:   svc.Persist,
			Sticky:    svc.Sticky,
			Reset:     svc.Reset,
		}

		for ap, dst := range svc.Destinations {

			destination := cue.Destination{
				Address:  ap.Address,
				Port:     ap.Port,
				Weight:   dst.Weight,
				Disabled: dst.Disabled,
				Checks:   append([]mon.Check{}, dst.Checks...),
			}

			service.Destinations = append(service.Destinations, destination)

		}

		services = append(services, service)
	}

	return services
}

type protocol uint8

func (p protocol) MarshalText() ([]byte, error) {
	switch p {
	case TCP:
		return []byte("tcp"), nil
	case UDP:
		return []byte("udp"), nil
	}
	return nil, errors.New("Invalid protocol")
}

func (p protocol) string() string {
	switch p {
	case TCP:
		return "tcp"
	case UDP:
		return "udp"
	}
	return fmt.Sprintf("%d", p)
}

func (p protocol) String() string {
	switch p {
	case TCP:
		return "tcp"
	case UDP:
		return "udp"
	}
	return fmt.Sprintf("%d", p)
}

type priority uint8

const CRITICAL = 0
const HIGH = 1
const MEDIUM = 2
const LOW = 3

func (p *priority) UnmarshalText(data []byte) error {

	text := string(data)

	switch text {
	case "critical":
		*p = CRITICAL
	case "high":
		*p = HIGH
	case "medium":
		*p = MEDIUM
	case "low":
		*p = LOW
	default:
		return errors.New("Invalid prority")
	}
	return nil
}

func (p priority) MarshalText() ([]byte, error) {
	switch p {
	case CRITICAL:
		return []byte("critcal"), nil
	case HIGH:
		return []byte("high"), nil
	case MEDIUM:
		return []byte("medium"), nil
	case LOW:
		return []byte("low"), nil
	}
	return nil, errors.New("Invalid prority")
}

type Service struct {
	Address  netip.Addr
	Port     uint16
	Protocol Protocol
}

func (s Service) String() string {
	return fmt.Sprintf("%s:%d:%s", s.Address, s.Port, s.Protocol)
}

func (t Service) MarshalText() ([]byte, error) {
	return []byte(fmt.Sprintf("%s:%d:%s", t.Address, t.Port, t.Protocol)), nil
}

func (t *Service) UnmarshalText(data []byte) error {

	text := string(data)

	//re := regexp.MustCompile(`^(\d+\.\d+\.\d+\.\d+):(\d+):(tcp|udp)$`)
	re := regexp.MustCompile(`^([0-9-a-f:\.]+):(\d+):(tcp|udp)$`)

	m := re.FindStringSubmatch(text)

	if len(m) != 4 {
		return errors.New("Badly formed ip:port:protocol - " + text)
	}

	ip, err := netip.ParseAddr(m[1])

	if err != nil {
		return err
	}

	t.Address = ip

	port, err := strconv.Atoi(m[2])
	if err != nil {
		return err
	}

	if port < 0 || port > 65535 {
		return errors.New("Badly formed ip:port:protocol, port out of rance 0-65535 - " + text)
	}

	t.Port = uint16(port)

	switch m[3] {
	case "tcp":
		t.Protocol = TCP
	case "udp":
		t.Protocol = UDP
	default:
		return errors.New("Badly formed ip:port:protocol, tcp/udp - " + text)
	}

	return nil
}

type Destination struct {
	Address netip.Addr
	Port    uint16
}

func (d Destination) String() string {
	return fmt.Sprintf("%s:%d", d.Address, d.Port)
}

func (i Destination) MarshalText() ([]byte, error) {
	return []byte(fmt.Sprintf("%s:%d", i.Address, i.Port)), nil
}

func (i *Destination) UnmarshalText(data []byte) error {

	//re := regexp.MustCompile(`^(\d+\.\d+\.\d+\.\d+)(|:(\d+))$`)
	re := regexp.MustCompile(`^([0-9-a-f:\.]+?)(|:(\d+))$`)

	m := re.FindStringSubmatch(string(data))

	if len(m) != 4 {
		return errors.New("Badly formed ip:port")
	}

	ip, err := netip.ParseAddr(m[1])

	if err != nil {
		return err
	}

	i.Address = ip

	if m[3] != "" {

		port, err := strconv.Atoi(m[3])
		if err != nil {
			return err
		}

		if port < 0 || port > 65535 {
			return errors.New("Badly formed ip:port")
		}

		i.Port = uint16(port)
	}

	return nil
}