server: detect graphical sessions under systemd --user compositors - #558
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TheSkyentist wants to merge 3 commits into
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server: detect graphical sessions under systemd --user compositors#558TheSkyentist wants to merge 3 commits into
TheSkyentist wants to merge 3 commits into
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Add two fallbacks to SessionType detection, used only when logind can't place the peer in a session at all: reading the peer's own /proc/<pid>/environ for WAYLAND_DISPLAY/DISPLAY, and, since that is commonly blocked by Yama's ptrace_scope, falling back further to the systemd --user manager's own exported environment, which compositors following this integration model populate on startup and which is readable over D-Bus without needing ptrace access.
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Extract the WAYLAND_DISPLAY/DISPLAY lookup shared by from_environ and from_systemd_user_environment into from_display_vars, add unit tests for it, drop the unneeded allocation, and make both helpers private since only detect() is used externally.
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Fixes #557
Fix
SessionType::detectnow falls back pastlogind, in order:/proc/<pid>/environ, since compositors exportWAYLAND_DISPLAY/DISPLAYto the clients they spawn. This is often blocked by Yama'sptrace_scope(default 1 on many distros), since the daemon is never an ancestor of its D-Bus peers.--usermanager's own exported environment, which compositors following this integration model populate on startup (e.g. viadbus-update-activation-environment) and which isreadable live over D-Bus with noptrace_scoperestriction. This is coarser, since it is session-wide rather than peer-specific, so it is only used oncelogindgives no answer at all for the peer.Each step is only consulted if the previous one could not place the peer in a session at all, so a definite non-graphical answer from
logind(e.g. a real tty/SSH login) is still trusted as-is.Testing
Reproduced and confirmed fixed on Arch Linux with niri run as a systemd
--userservice andlyas greeter. Added unit tests forfrom_environ.cargo test,cargo clippy --all-targetsclean.