Obtain PIA v4 server information from API (#257)

- Obtain CN for port forwarding https verification
- Obtain for each server if they support port forwarding
- Obtain for each server their IP address for openvpn UDP and openvpn TCP (one for each)
- Updater program updated to use API
- Hardcoded values updated for PIA v3 and v4 servers
- Clearer separation between pia v3 and v4
- Fixes #250

internal/updater/piav4.go

@@ -0,0 +1,100 @@
+package updater
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"sort"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func (u *updater) updatePIA() (err error) {
+	const url = "https://serverlist.piaservers.net/vpninfo/servers/v4"
+	response, err := u.httpGet(url)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	b, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		return err
+	} else if response.StatusCode != http.StatusOK {
+		return fmt.Errorf("%s: %s", response.Status, strings.ReplaceAll(string(b), "\n", ""))
+	}
+
+	// remove key/signature at the bottom
+	i := bytes.IndexRune(b, '\n')
+	b = b[:i]
+
+	var data struct {
+		Regions []struct {
+			Name        string `json:"name"`
+			PortForward bool   `json:"port_forward"`
+			Servers     struct {
+				UDP []struct {
+					IP net.IP `json:"ip"`
+					CN string `json:"cn"`
+				} `json:"ovpnudp"`
+				TCP []struct {
+					IP net.IP `json:"ip"`
+					CN string `json:"cn"`
+				} `json:"ovpntcp"`
+			} `json:"servers"`
+		} `json:"regions"`
+	}
+	if err := json.Unmarshal(b, &data); err != nil {
+		return err
+	}
+	servers := make([]models.PIAServer, 0, len(data.Regions))
+	for _, region := range data.Regions {
+		server := models.PIAServer{
+			Region:      region.Name,
+			PortForward: region.PortForward,
+		}
+		for _, udpServer := range region.Servers.UDP {
+			if len(server.OpenvpnUDP.CN) > 0 && server.OpenvpnUDP.CN != udpServer.CN {
+				return fmt.Errorf("CN is different for UDP for region %q: %q and %q", region.Name, server.OpenvpnUDP.CN, udpServer.CN)
+			}
+			if udpServer.IP != nil {
+				server.OpenvpnUDP.IPs = append(server.OpenvpnUDP.IPs, udpServer.IP)
+			}
+		}
+		for _, tcpServer := range region.Servers.TCP {
+			if len(server.OpenvpnTCP.CN) > 0 && server.OpenvpnTCP.CN != tcpServer.CN {
+				return fmt.Errorf("CN is different for TCP for region %q: %q and %q", region.Name, server.OpenvpnTCP.CN, tcpServer.CN)
+			}
+			if tcpServer.IP != nil {
+				server.OpenvpnTCP.IPs = append(server.OpenvpnTCP.IPs, tcpServer.IP)
+			}
+		}
+		if server.OpenvpnTCP.CN != server.OpenvpnUDP.CN {
+			return fmt.Errorf("not the same: %q, %q", server.OpenvpnTCP.CN, server.OpenvpnUDP.CN)
+		}
+		servers = append(servers, server)
+	}
+	sort.Slice(servers, func(i, j int) bool {
+		return servers[i].Region < servers[j].Region
+	})
+	if u.options.Stdout {
+		u.println(stringifyPIAServers(servers))
+	}
+	u.servers.Pia.Timestamp = u.timeNow().Unix()
+	u.servers.Pia.Servers = servers
+	return nil
+}
+
+func stringifyPIAServers(servers []models.PIAServer) (s string) {
+	s = "func PIAServers() []models.PIAServer {\n"
+	s += "	return []models.PIAServer{\n"
+	for _, server := range servers {
+		s += "		" + server.String() + ",\n"
+	}
+	s += "	}\n"
+	s += "}"
+	return s
+}