core: add ability to define arbitrary bind mounts for services

This adds two new settings BindPaths= and BindReadOnlyPaths=. They allow
defining arbitrary bind mounts specific to particular services. This is
particularly useful for services with RootDirectory= set as this permits making
specific bits of the host directory available to chrooted services.

The two new settings follow the concepts nspawn already possess in --bind= and
--bind-ro=, as well as the .nspawn settings Bind= and BindReadOnly= (and these
latter options should probably be renamed to BindPaths= and BindReadOnlyPaths=
too).

Fixes: #3439

1 files changed, 2 insertions, 0 deletions

diff --git a/src/core/execute.h b/src/core/execute.h
index 951c8f4da3..84ab4339cf 100644
--- a/src/core/execute.h
+++ b/src/core/execute.h
@@ -161,6 +161,8 @@ struct ExecContext {
 
         char **read_write_paths, **read_only_paths, **inaccessible_paths;
         unsigned long mount_flags;
+        BindMount *bind_mounts;
+        unsigned n_bind_mounts;
 
         uint64_t capability_bounding_set;
         uint64_t capability_ambient_set;