From: Stas Sergeev stsp2@yandex.ru Date: Sat, 16 Nov 2024 13:11:20 +0300
Currently SCM_PIDFD cmsg cannot be sent via unix socket (returns -EINVAL) and SO_PASSPIDFD doesn't support flags. The created pidfd always has flags set to 0.
This patch implements SCM_PIDFD cmsg in AF_UNIX socket, which can be used to send flags to SO_PASSPIDFD-enabled recipient.
Self-test is added for the propagation of PIDFD_NONBLOCK flag.
This is mainly needed for the future extensions, like eg this one: https://lore.kernel.org/lkml/8288a08e-448b-43c2-82dc-59f87d0d9072@yandex.ru/... where it was suggested to try solving the supplementary groups problem with pidfd.
Changes in v3: specify target tree in patch subject
It seems you missed other feedback, especially __scm_recv_common() needs a small change.
net-next is closed during the merge window for v6.13-rc1, so please post v4 after Dec 2nd. https://lore.kernel.org/netdev/20241118071654.695bb1a2@kernel.org/