merged with fixes

internal/transport/metadata.go

@@ -0,0 +1,28 @@
+// Package transport holds neutral transport metadata shared across the
+// protocol/edge boundary and the RPC business layer. It must not import any
+// business package (internal/rpc, internal/app, ...), so that mtprotoedge can
+// produce transport facts without depending on the RPC implementation.
+package transport
+
+import "context"
+
+type ctxKey int
+
+const (
+	clientIPKey ctxKey = iota
+)
+
+// WithClientIP records the client remote IP as neutral transport metadata.
+// An empty ip is ignored.
+func WithClientIP(ctx context.Context, ip string) context.Context {
+	if ip == "" {
+		return ctx
+	}
+	return context.WithValue(ctx, clientIPKey, ip)
+}
+
+// ClientIPFrom returns the client remote IP carried in ctx, if set.
+func ClientIPFrom(ctx context.Context) (string, bool) {
+	v, ok := ctx.Value(clientIPKey).(string)
+	return v, ok && v != ""
+}

internal/transport/metadata_test.go

@@ -0,0 +1,27 @@
+package transport
+
+import (
+	"context"
+	"testing"
+)
+
+func TestWithClientIPRoundTrip(t *testing.T) {
+	ctx := WithClientIP(context.Background(), "203.0.113.7")
+	ip, ok := ClientIPFrom(ctx)
+	if !ok || ip != "203.0.113.7" {
+		t.Fatalf("round-trip mismatch: got %q ok=%v", ip, ok)
+	}
+}
+
+func TestWithClientIPEmptyIgnored(t *testing.T) {
+	ctx := WithClientIP(context.Background(), "")
+	if _, ok := ClientIPFrom(ctx); ok {
+		t.Fatalf("empty ip must not be stored")
+	}
+}
+
+func TestClientIPFromNotSet(t *testing.T) {
+	if _, ok := ClientIPFrom(context.Background()); ok {
+		t.Fatalf("no ip set, ok must be false")
+	}
+}