IP_STATUS_FILE and routing improvements (#130)

- Obtains VPN public IP address from routing table
- Logs and writes VPN Public IP address to `/ip` as soon as VPN is up
- Obtain port forward, logs it and writes it as soon as VPN is up
- Routing fully refactored and tested
- Routing reads from `/proc/net/route`
- Routing mutates the routes using `ip route ...`

internal/params/system.go

@@ -2,6 +2,7 @@ package params
 
 import (
 	libparams "github.com/qdm12/golibs/params"
+	"github.com/qdm12/private-internet-access-docker/internal/models"
 )
 
 // GetUID obtains the user ID to use from the environment variable UID
@@ -18,3 +19,10 @@ func (p *paramsReader) GetGID() (gid int, err error) {
 func (p *paramsReader) GetTimezone() (timezone string, err error) {
 	return p.envParams.GetEnv("TZ")
 }
+
+// GetIPStatusFilepath obtains the IP status file path
+// from the environment variable IP_STATUS_FILE
+func (p *paramsReader) GetIPStatusFilepath() (filepath models.Filepath, err error) {
+	filepathStr, err := p.envParams.GetPath("IP_STATUS_FILE", libparams.Default("/ip"), libparams.CaseSensitiveValue())
+	return models.Filepath(filepathStr), err
+}