p2p: allow NetPermissions::ClearFlag() only with PF_ISIMPLICIT

NetPermissions::ClearFlag() is currently only called in the codebase with
an `f` value of NetPermissionFlags::PF_ISIMPLICIT.

If that should change in the future, ClearFlag() should not be called
with `f` being a subflag of a multiflag, e.g. NetPermissionFlags::PF_RELAY
or NetPermissionFlags::PF_DOWNLOAD, as that would leave `flags` in an
invalid state corresponding to none of the existing NetPermissionFlags.

Therefore, allow only calling ClearFlag with the implicit flag for now.

Co-authored-by: Vasil Dimov <vd@FreeBSD.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/net_permissions.h b/src/net_permissions.h
index bba0ea1695..142b317bf6 100644
--- a/src/net_permissions.h
+++ b/src/net_permissions.h
@@ -51,8 +51,14 @@ public:
     {
         flags = static_cast<NetPermissionFlags>(flags | f);
     }
+    //! ClearFlag is only called with `f` == NetPermissionFlags::PF_ISIMPLICIT.
+    //! If that should change in the future, be aware that ClearFlag should not
+    //! be called with a subflag of a multiflag, e.g. NetPermissionFlags::PF_RELAY
+    //! or NetPermissionFlags::PF_DOWNLOAD, as that would leave `flags` in an
+    //! invalid state corresponding to none of the existing flags.
     static inline void ClearFlag(NetPermissionFlags& flags, NetPermissionFlags f)
     {
+        assert(f == NetPermissionFlags::PF_ISIMPLICIT);
         flags = static_cast<NetPermissionFlags>(flags & ~f);
     }
 };