[Patch V2 0/4] unshare: fix signal forwarding to child processes

[Kiran Rangoon <kiranrangoon0@gmail.com>]

Changes in V2 (responding to feedback from karelzak):
- Made signal forwarding opt-in via new --forward-signals flag
- Preserves default behavior (signals blocked) for backward compatibility
- Addresses concerns from PR #1087 about "impatient parent" problem

This adds --forward-signals to enable graceful shutdown of child processes
during system reboot. Since util-linux 2.36, unshare blocks SIGTERM/SIGINT
to prevent premature parent exit, but this prevents children from receiving
shutdown signals for cleanup.

The new flag installs signal handlers instead of blocking, forwards signals
to the child, and properly handles EINTR in waitpid(). Includes tests for
basic forwarding and --kill-child compatibility.


Kiran Rangoon (4):
  unshare: add --forward-signals option to argument parser
  unshare: implement signal forwarding when --forward-signals is used
  unshare: document --forward-signals in man page
  tests: add tests for unshare --forward-signals

 sys-utils/unshare.1.adoc                      | 13 ++++
 sys-utils/unshare.c                           | 67 +++++++++++++++++--
 tests/expected/unshare/forward-signals        |  1 +
 .../unshare/forward-signals-kill-child        |  1 +
 tests/ts/unshare/forward-signals              | 55 +++++++++++++++
 tests/ts/unshare/forward-signals-kill-child   | 56 ++++++++++++++++
 6 files changed, 186 insertions(+), 7 deletions(-)
 create mode 100644 tests/expected/unshare/forward-signals
 create mode 100644 tests/expected/unshare/forward-signals-kill-child
 create mode 100755 tests/ts/unshare/forward-signals
 create mode 100755 tests/ts/unshare/forward-signals-kill-child

-- 
2.47.3