lunaryorn c4a2c7362e journald: send large journal payloads through memfd (#1744) ...

See #1698: Properly write large payloads to journal.

I'd appreciate a very careful review; this cmsg stuff is nasty, and
while it's well documented in `cmsg(3)` I had to fiddle a bit because
the corresponding functions in libc aren't const and thus don't permit a
direct allocation of the buffer as most `cmsg` C code around does.

Closes #1698

## Motivation

Linux limits the maximum amount of data permitted for a single Unix
datagram; sending large payloads directly will fail.

## Solution

Follow systemd.io/JOURNAL_NATIVE_PROTOCOL/ and check for `EMSGSIZE` from
`send()`; in this case write the payload to a memfd, seal it, and pass
it on to journald via a corresponding SCM_RIGHTS control message.

Per discussion in #1698 this adds no dependency on `nix`, and instead
implements fd forwarding directly with some bits of unsafe `libc` code.

2021-12-19 16:23:54 -08:00

..

journal.rs

journald: send large journal payloads through memfd (#1744)

2021-12-19 16:23:54 -08:00