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Andreas Rammhold 55c09a884a nixos/modules/system/boot/networkd: enable socket activation 
Since cd1dedac67 systemd-networkd has it's
netlink socket created via a systemd.socket unit. One might think that
this doesn't make much sense since networkd is just going to create it's
own socket on startup anyway. The difference here is that we have
configuration-time control over things like socket buffer sizes vs
compile-time constants.

For larger setups where networkd has to create a lot of (virtual)
devices the default buffer size of currently 128MB is not enough.

A good example is a machine with >100 virtual interfaces (e.g.,
wireguard tunnels, VLANs, …) that all have to be brought up during
startup. The receive buffer size will spike due to all the generated
message from the new interfaces. Eventually some of the message will be
dropped since there is not enough (permitted) buffer space available.

By having networkd start through / with a netlink socket created by
systemd we can configure the `ReceiveBufferSize` parameter in the socket
options without recompiling networkd.

Since the actual memory requirements depend on hardware, timing, exact
configurations etc. it isn't currently possible to infer a good default
from within the NixOS module system. Administrators are advised to
monitor the logs of systemd-networkd for `rtnl: kernel receive buffer
overrun` spam and increase the memory as required.

Note: Increasing the ReceiveBufferSize doesn't allocate any memory.  It
just increases the upper bound on the kernel side. The memory allocation
depends on the amount of messages that are queued on the kernel side of
the netlink socket.
2020-06-16 00:41:41 +02:00
..
doc nixos/modules/system/boot/networkd: enable socket activation 2020-06-16 00:41:41 +02:00
lib Merge pull request #90261 from prusnak/installer-zstd-rm 2020-06-14 10:39:10 +08:00
maintainers
modules Merge pull request #90343 from flokli/hardware-u2f-remove 2020-06-15 17:53:47 +02:00
tests Merge pull request #89781 from mdlayher/mdl-corerad-settings 2020-06-14 16:48:54 +02:00
COPYING
default.nix
README treewide: use https for nixos.org and hydra.nixos.org 2020-05-03 22:14:21 -07:00
release-combined.nix nixos/release-combined: add systemd-networkd-ipv6-prefix-delegation test 2020-05-01 17:45:40 +02:00
release-small.nix
release.nix nixos/release.nix: closures.lapp: use enablePHP, fixes metrics job #86439 2020-05-01 10:07:04 +02:00

README 

*** NixOS ***

NixOS is a Linux distribution based on the purely functional package
management system Nix.  More information can be found at
https://nixos.org/nixos and in the manual in doc/manual.