core/overreach: impl set/get runtime's internal env

Author: ignoramous

intra/core/overreach.go

@@ -7,16 +7,12 @@
 package core
 
 import (
+	"os"
 	"runtime/debug"
 	"syscall"
 	_ "unsafe" // for go:linkname
 )
 
-// RuntimeEnviron returns the Go runtime's cached environment slice.
-func RuntimeEnviron() []string {
-	return syscall.Environ()
-}
-
 // github.com/golang/go/issues/69868
 // Unfortunately, Android apps have AT_SECURE set
 // (read bytes in /proc/self/auxv on non-rooted Androids).
@@ -60,6 +56,46 @@ func RuntimeFinishDebugVarsSetup() {
 	runtime_finishDebugVarsSetup()
 }
 
+// RuntimeEnviron returns the Go runtime's cached environment vars.
+// github.com/golang/go/blob/e2fef50def98/src/runtime/runtime1.go#L98
+func RuntimeEnviron() []string {
+	return runtime_environ()
+}
+
+// SetRuntimeEnviron sets / adds a key-value pair in the Go runtime's
+// cached environment vars.
+func SetRuntimeEnviron(key, val string) (found bool, err error) {
+	envs := runtime_environ()
+	kv := key + "="
+	for i, e := range envs {
+		if len(e) >= len(kv) && e[:len(kv)] == kv {
+			envs[i] = kv + val
+			found = true
+			break
+		}
+	}
+	if !found {
+		envs = append(envs, kv+val)
+	}
+	return found, os.Setenv(key, val)
+}
+
+// GetRuntimeEnviron gets a value from the Go runtime's cached
+// environment vars.
+func GetRuntimeEnviron(key string) (val string, found bool) {
+	envs := runtime_environ()
+	kv := key + "="
+	for _, e := range envs {
+		if len(e) >= len(kv) && e[:len(kv)] == kv {
+			return e[len(kv):], true
+		}
+	}
+	return
+}
+
+//go:linkname runtime_environ runtime.environ
+func runtime_environ() []string
+
 //go:linkname runtime_finishDebugVarsSetup runtime.finishDebugVarsSetup
 func runtime_finishDebugVarsSetup()
 

intra/tun2socks.go

@@ -120,15 +120,15 @@ func LogLevel(gologLevel, consolelogLevel int32) {
 	// github.com/golang/go/blob/fed3b0a298/src/runtime/runtime1.go#L586
 	// gomobile builds a c-shared gojnilib:
 	// github.com/golang/mobile/blob/2553ed8ce2/cmd/gomobile/bind_androidapp.go#L393
-	prevtraceback := os.Getenv("GOTRACEBACK")
+	prevtraceback, _ := core.GetRuntimeEnviron("GOTRACEBACK")
 	if settings.Debug {
-		os.Setenv("GOTRACEBACK", sys.s())
+		core.SetRuntimeEnviron("GOTRACEBACK", sys.s())
 		debug.SetTraceback(sys.s())
 	} else {
-		os.Setenv("GOTRACEBACK", usr.s())
+		core.SetRuntimeEnviron("GOTRACEBACK", usr.s())
 		debug.SetTraceback(usr.s())
 	}
-	curtraceback := os.Getenv("GOTRACEBACK")
+	curtraceback, _ := core.GetRuntimeEnviron("GOTRACEBACK")
 	core.RuntimeFinishDebugVarsSetup()
 	gotracelevel, gotraceall, gotracecrash := core.RuntimeGotraceback()