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docs:techref:netifd

netifd (Network Interface Daemon) – Technical Reference

What is netifd?

netifd is an RPC-capable daemon written in C for better access to kernel APIs with the ability to listen on netlink events. Netifd has replaced the old OpenWrt-network configuration scripts, the actual scripts that configured the network, e.g.

  • /lib/network/*.sh,
  • /sbin/ifup
  • some scripts in /etc/hotplug.d.)

netifd is intended to stay compatible with the existing format of /etc/config/network, the only exceptions being rare special cases like aliases or the overlay variables in /var/state (though even most of those can be easily emulated).

Help with the development of netifd

  1. test what has been ported
  2. review of the code
  3. help porting more of our protocol handler scripts (so far, static, ppp, pppoe, pppoa and dhcp are supported)

Why do we want netifd?

One thing that netifd does much better then old OpenWrt-network configuration scripts is handling configuration changes. With netfid, when the file /etc/config/network changes, you no longer have to restart all interfaces. Simply run /etc/init.d/network reload. This will issue an ubus-call to netifd, telling it to figure out the difference between runtime state and the new config and apply only that. This works on a per-interface level, even with protocol handlers written as shell scripts.

It boils down to the fact that the current network and interface setup mechanisms (via network configuration scripts) are rather constrained and inflexible:

  • lack of statefulness
  • tendency for raceconditions
  • inability to properly nest protocols
  • limited featureset of the ash shell which will not allow for complex interface operations like e.g. calculating ULAs
  • you name it

Netifd will be able to manage even complex interface configurations with a mix of bonding, vlans, bridges, etc. and handle the dependencies between interfaces properly - and of course all that without adding unnecessary bloat. AFAIK there are no alternatives to netifd, e.g. connman seems to be centered around one specifific use case only: having a mobile device access the internet through multiple connections.

The following is a brief conversation from IRC regarding hints on how netifd is involved with wifi interface startup and variables used. It 'documents' my frustration with trying to add a new uci variable (utf8_ssid), and I don't think the answers contained should be lost:

[20:20:06] <jow> ldir: its complicated [20:20:29] <jow> ldir: upon start, netifd scans all wireless handlers in /lib/netifd/wireless/ [20:21:08] <jow> ldir: so for mac80211 that'd be /lib/netifd/wireless/mac80211.sh [20:22:33] <jow> ldir: the handler tells netifd about which options it recognized, for mac80211.sh this can be seen in drv_mac80211_init_device_config() (for config wifi-device) and drv_mac80211_init_iface_config() (for config wifi-iface) [20:27:26] <jow> ldir: netifd reads /etc/config/wireless, converts it into json and eventually passes it via various indirections back to the script [20:28:07] <jow> ldir: it will execute something like /lib/netifd/wireless/mac80211.sh mac80211 setup radio0 '{ lots of json encoded uci options }' [20:29:20] <jow> ldir: this invocation is catched by `init_wireless_driver “$@“` in /lib/netifd/wireless/mac80211.sh (declared in the shared /lib/netifd/netifd-wireless.sh) [20:31:03] <ldir> jow: thank you - I shall try to digest this. [20:31:38] <jow> ldir: init_wireless_driver() will parse the passed json into shell variables and dispatch back to one of the drv_*() functions in /lib/netifd/wireless/mac80211.sh [20:32:02] <jow> e.g. /lib/netifd/wireless/mac80211.sh mac80211 setup radio0 '{ lots of json encoded uci options }' will eventually call drv_mac80211_setup() [20:32:48] <jow> drv_mac80211_setup() will have access to all the uci config variables via the loaded jshn environment so you can accesss them using json_get_vars, json_select etc. [20:33:15] <jow> the radio we're operating on is passed as “$1” and will contain the uci wifi-device section name, e.g. “radio0” [20:35:11] <jow> from then on its “just” shell magic translating things back and forth, writing temporary hostapd config etc. and eventually instructing netifd to launch a hostapd process using wireless_add_process() [20:35:50] <jow> executive summary [20:36:03] <ldir> that's hell on a stick :-) [20:36:26] <ldir> btw the executive summary was 'it's complicated' ;-) [20:36:33] <jow> - register new config options in /lib/netifd/wireless/mac80211.sh using either drv_mac80211_init_device_config or drv_mac80211_init_iface_config - for utf8ssid you likely want drv_mac80211_init_iface_config [20:38:32] <jow> correction; register it in hostapd_common_add_bss_config() of /lib/netifd/hostapd.sh [20:39:07] <jow> - and process it in hostapd_set_bss_options() [20:39:12] <jow> thats it [20:39:19] <ldir> jow: in theory I've done that - I noticed mac80211.sh has a 'common' set options [20:39:36] <jow> you most likely need to restart netifd for it to become aware of the new option [20:39:50] <jow> du to the uci→blob→json→string→jshn call chain

docs/techref/netifd.txt · Last modified: 2018/11/14 15:41 by ldir