[client] Implement environment variable handling for Android (#4440)

Some features can only be manipulated via environment variables. With this PR, environment variables can be managed from Android.

Author: pappz

client/android/client.go

@@ -4,6 +4,7 @@ package android
 
 import (
 	"context"
+	"os"
 	"slices"
 	"sync"
 
@@ -83,7 +84,8 @@ func NewClient(cfgFile string, androidSDKVersion int, deviceName string, uiVersi
 }
 
 // Run start the internal client. It is a blocker function
-func (c *Client) Run(urlOpener URLOpener, dns *DNSList, dnsReadyListener DnsReadyListener) error {
+func (c *Client) Run(urlOpener URLOpener, dns *DNSList, dnsReadyListener DnsReadyListener, envList *EnvList) error {
+	exportEnvList(envList)
 	cfg, err := profilemanager.UpdateOrCreateConfig(profilemanager.ConfigInput{
 		ConfigPath: c.cfgFile,
 	})
@@ -118,7 +120,8 @@ func (c *Client) Run(urlOpener URLOpener, dns *DNSList, dnsReadyListener DnsRead
 
 // RunWithoutLogin we apply this type of run function when the backed has been started without UI (i.e. after reboot).
 // In this case make no sense handle registration steps.
-func (c *Client) RunWithoutLogin(dns *DNSList, dnsReadyListener DnsReadyListener) error {
+func (c *Client) RunWithoutLogin(dns *DNSList, dnsReadyListener DnsReadyListener, envList *EnvList) error {
+	exportEnvList(envList)
 	cfg, err := profilemanager.UpdateOrCreateConfig(profilemanager.ConfigInput{
 		ConfigPath: c.cfgFile,
 	})
@@ -249,3 +252,14 @@ func (c *Client) SetConnectionListener(listener ConnectionListener) {
 func (c *Client) RemoveConnectionListener() {
 	c.recorder.RemoveConnectionListener()
 }
+
+func exportEnvList(list *EnvList) {
+	if list == nil {
+		return
+	}
+	for k, v := range list.AllItems() {
+		if err := os.Setenv(k, v); err != nil {
+			log.Errorf("could not set env variable %s: %v", k, err)
+		}
+	}
+}

client/android/env_list.go

@@ -0,0 +1,32 @@
+package android
+
+import "github.com/netbirdio/netbird/client/internal/peer"
+
+var (
+	// EnvKeyNBForceRelay Exported for Android java client
+	EnvKeyNBForceRelay = peer.EnvKeyNBForceRelay
+)
+
+// EnvList wraps a Go map for export to Java
+type EnvList struct {
+	data map[string]string
+}
+
+// NewEnvList creates a new EnvList
+func NewEnvList() *EnvList {
+	return &EnvList{data: make(map[string]string)}
+}
+
+// Put adds a key-value pair
+func (el *EnvList) Put(key, value string) {
+	el.data[key] = value
+}
+
+// Get retrieves a value by key
+func (el *EnvList) Get(key string) string {
+	return el.data[key]
+}
+
+func (el *EnvList) AllItems() map[string]string {
+	return el.data
+}

client/internal/peer/conn.go

@@ -6,7 +6,6 @@ import (
 	"math/rand"
 	"net"
 	"net/netip"
-	"os"
 	"runtime"
 	"sync"
 	"time"
@@ -174,7 +173,7 @@ func (conn *Conn) Open(engineCtx context.Context) error {
 	conn.handshaker = NewHandshaker(conn.Log, conn.config, conn.signaler, conn.workerICE, conn.workerRelay)
 
 	conn.handshaker.AddOnNewOfferListener(conn.workerRelay.OnNewOffer)
-	if os.Getenv("NB_FORCE_RELAY") != "true" {
+	if !isForceRelayed() {
 		conn.handshaker.AddOnNewOfferListener(conn.workerICE.OnNewOffer)
 	}
 

client/internal/peer/env.go

@@ -0,0 +1,14 @@
+package peer
+
+import (
+	"os"
+	"strings"
+)
+
+const (
+	EnvKeyNBForceRelay = "NB_FORCE_RELAY"
+)
+
+func isForceRelayed() bool {
+	return strings.EqualFold(os.Getenv(EnvKeyNBForceRelay), "true")
+}