probe: discover live media control path

Cargo.lock

@@ -1652,7 +1652,7 @@ checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
 
 [[package]]
 name = "lesavka_client"
-version = "0.22.56"
+version = "0.22.57"
 dependencies = [
  "anyhow",
  "async-stream",
@@ -1686,7 +1686,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_common"
-version = "0.22.56"
+version = "0.22.57"
 dependencies = [
  "anyhow",
  "base64",
@@ -1698,7 +1698,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_server"
-version = "0.22.56"
+version = "0.22.57"
 dependencies = [
  "anyhow",
  "base64",

client/Cargo.toml

@@ -4,7 +4,7 @@ path                    = "src/main.rs"
 
 [package]
 name                    = "lesavka_client"
-version                 = "0.22.56"
+version                 = "0.22.57"
 edition                 = "2024"
 
 [dependencies]

common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name                    = "lesavka_common"
-version                 = "0.22.56"
+version                 = "0.22.57"
 edition                 = "2024"
 build                   = "build.rs"
 

scripts/manual/run_synthetic_rct_uvc_probe.py

@@ -61,8 +61,11 @@ def parse_args() -> argparse.Namespace:
     )
     parser.add_argument(
         "--media-control-path",
-        default=os.environ.get("LESAVKA_MEDIA_CONTROL", DEFAULT_MEDIA_CONTROL_PATH),
-        help=f"local live-media control file used with --pause-local-live-upstream (default: {DEFAULT_MEDIA_CONTROL_PATH})",
+        default=os.environ.get("LESAVKA_MEDIA_CONTROL", ""),
+        help=(
+            "local live-media control file used with --pause-local-live-upstream; "
+            f"default discovers LESAVKA_MEDIA_CONTROL from running Lesavka processes, then falls back to {DEFAULT_MEDIA_CONTROL_PATH}"
+        ),
     )
     parser.add_argument(
         "--capture-before-inject",
@@ -190,8 +193,59 @@ def media_control_with_camera(raw: str | None, enabled: bool) -> str:
     return " ".join(rendered) + "\n"
 
 
+def discover_media_control_paths() -> list[pathlib.Path]:
+    candidates: set[pathlib.Path] = set()
+    proc = pathlib.Path("/proc")
+    if not proc.exists():
+        return []
+    for entry in proc.iterdir():
+        if not entry.name.isdigit():
+            continue
+        try:
+            environ = (entry / "environ").read_bytes()
+            cmdline = (entry / "cmdline").read_bytes().replace(b"\0", b" ")
+        except (FileNotFoundError, PermissionError, ProcessLookupError, OSError):
+            continue
+        if b"lesavka" not in cmdline and b"LESAVKA_MEDIA_CONTROL=" not in environ:
+            continue
+        for token in environ.split(b"\0"):
+            if token.startswith(b"LESAVKA_MEDIA_CONTROL="):
+                raw_path = token.split(b"=", 1)[1].decode(errors="replace")
+                if raw_path:
+                    candidates.add(pathlib.Path(raw_path))
+    return sorted(
+        candidates,
+        key=lambda path: (
+            not path.exists(),
+            -path.stat().st_mtime if path.exists() else 0,
+            str(path),
+        ),
+    )
+
+
+def resolve_media_control_path(args: argparse.Namespace) -> pathlib.Path:
+    if args.media_control_path:
+        return pathlib.Path(args.media_control_path)
+    discovered = discover_media_control_paths()
+    if discovered:
+        if len(discovered) > 1:
+            print(
+                "multiple live Lesavka media control paths discovered; using "
+                f"{discovered[0]} candidates={[str(path) for path in discovered]}",
+                file=sys.stderr,
+            )
+        else:
+            print(f"discovered live Lesavka media control path {discovered[0]}", file=sys.stderr)
+        return discovered[0]
+    print(
+        f"no running Lesavka media control path discovered; falling back to {DEFAULT_MEDIA_CONTROL_PATH}",
+        file=sys.stderr,
+    )
+    return pathlib.Path(DEFAULT_MEDIA_CONTROL_PATH)
+
+
 def pause_local_live_upstream(args: argparse.Namespace) -> tuple[pathlib.Path, bytes | None]:
-    path = pathlib.Path(args.media_control_path)
+    path = resolve_media_control_path(args)
     original = path.read_bytes() if path.exists() else None
     raw = original.decode(errors="replace") if original is not None else None
     path.write_text(media_control_with_camera(raw, False))

server/Cargo.toml

@@ -16,7 +16,7 @@ bench                   = false
 
 [package]
 name                    = "lesavka_server"
-version                 = "0.22.56"
+version                 = "0.22.57"
 edition                 = "2024"
 autobins                = false
 

tests/manual/server/rct/synthetic_rct_uvc_probe_manual_contract.rs

@@ -98,6 +98,9 @@ fn synthetic_probe_keeps_bundled_network_ingress_and_rct_comparison_markers() {
         "paused local live camera upstream",
         "restored local live media control",
         "media_control_with_camera",
+        "discover_media_control_paths",
+        "resolve_media_control_path",
+        "discovered live Lesavka media control path",
         "max_lower_mae",
         "ffmpeg",
         "v4l2",