Network scripts

netifd can (probably) bring up a wired, static ip configuration without shell scripts. For everything else (PPPoE or 3G) it needs protocol handlers implemented as sets of shell functions.

Each protocol handler is a shell script in /lib/netifd/proto/. It is run (or maybe sourced) when netifd daemon starts. Changes made to the scripts do not take effect until netifd restarts. The name of the file usually matches option proto in /etc/config/network.

To be able to access the network functions, the script needs to include the necessary shell scripts at the beginning:

#!/bin/sh
 
[ -n "$INCLUDE_ONLY" ] || {
	. /lib/functions.sh
	. ../netifd-proto.sh
	init_proto "$@"
}

Current working directory is /lib/netifd/proto/ when the handler is sourced.

At the end of the script a handler should register itself by calling add_protocol protocolname.

A handler should at least define 2 shell functions: proto_protocolname_init_config and proto_protocolname_setup.

The main purpose of this function is to let netifd know which parameters does this protocol have. These parameters then can be stored in /etc/config/network.

proto_protocolname_init_config() {
	proto_config_add_string "stringparam"
	proto_config_add_int "intparam"
	proto_config_add_boolean "boolparam"
	...
}

The setup procedure implements the actual protocol specifc configuration logic and interface bringup.

When called, one or two parameters are passed:

1. Config, the UCI section name suitable for config_get calls
2. Interface name (only if no_device=0)

proto_protocolname_setup() {
	local config="$1"
	# set up the interface
}

This function must be implemented by any protocol backend.

There's usually no need to call ifconfig iface up at the end of this function. If no_device=0, netifd won't even try to start our profile until the device is already up. It waits for operstate=up and carrier=1, then starts the profile.

If no_device=1, netifd will bring it up, when it receives a notification from us:

proto_protocolname_setup () {
	...
	proto_init_update "$iface" 1
	proto_send_update "$config"
	...
}

However, this only works once. If someone called ifconfig iface down, netifd won't try to bring it up again (at least in BB), so just in case you may put the “up” command in the function.

Protocols that need special shutdown handling, for example to kill associated daemons, may implement a stop procedure. This procedure is called when an interface is brought down before the associated UCI state is cleared.

The function is called when we do ifdown profile or when no_device=0 and netifd detects link connectivity loss.

When called, two parameters are passed:

1. Config, the UCI section name suitable for config_get calls
2. iface, the network device

proto_protocolname_teardown() {
	local config="$1"
	local iface="$2"
	# tear down the interface
}

This function is optional.

By default, only interfaces present in /proc/net/dev, like eth0, are brought up on boot. Protocols which use virtual interfaces must set two variables at the beginning of init_config.

proto_protocolname_init_config() {
	no_device=1
	available=1
	...
}

• STDERR in protos is redirected to the syslog. echo “message” > 2>&1 can be used to print.
• As set -x also prints to STDERR, it can be used to trace which commands are called inside the proto. However this is very spammy.
• There is a pending patch: https://patchwork.ozlabs.org/project/openwrt/patch/20201229233319.164640-1-me@irrelefant.net/.

Flags can be added to a proto handler in proto_protoname_init_config, by setting their value to 1. The information about all loaded protocols can be obtained by calling ubus call network get_proto_handlers.

If errors for interfaces occur, the json object in ifstatus interfacename or in ubus call network.interface dump have an attribute “error”. If there are no errors, this attribute is not existing.

Custom error codes can be thrown from the proto scripts aswell. This is done via proto_notify_error “$config” MY_CUSTOM_ERROR_ID.

init_proto $proto $cmd $interface $data $ifname

This function takes all all arguments from the proto.sh file, interprets them and then defines the implementation of add_protocol().

If $cmd = “dump” then add_protocol() will do the following:

• A json output dump of the results of proto_protocolname_init_config will be printed.
• Other parameters than $cmd will be ignored.

If $cmd ∈ {“setup”, “teardown”, “renew”} add_protocol() will do the following:

• If $proto ≠ protoname nothing will be done.
• $data is loaded via json_load
• proto_protoname_... $interface $ifname will be called.

Otherwise the script will fail with something like:

• add_protocol: not found

The following functions are defined in /lib/netifd/netifd-proto.sh.

• add_protocol
• init_proto
• proto_config_add_boolean
• proto_config_add_int
• proto_config_add_string

Note: some of these function exit immediately. These functions are dispatched to ubus and arrive here

• proto_block_restart $interface
• proto_init_update $ifname $up [$external]
• proto_kill_command $interface [$signal]
• proto_notify_error $interface $str1 [$str2] [$str3] ...
• proto_run_command

We can start a daemon that maintains the connection asynchronously by calling proto_run_command “$config” custom_script. Netifd remembers its pid. It can be killed manually by calling proto_kill_command “$config”. Netifd can automatically kill it, when the profile stopped.

* proto_add_host_dependency

It seems to avoid race conditions in protos. We can register the following type of dependencies by calling:

• proto_add_host_dependency “$config” “$host” “$ifname”
• proto_add_host_dependency “$config” \'\' “$ifname” (only wait for an iface)
• (maybe more?)

Only if $iface is up, the corresponding $config will be loaded. So we need another proto to be completed, we can use this here.

From some observations I think it looks like technically the $config is initially loaded, then the proto_add_host_dependency is called inside the proto handler and then the $config is removed again until $iface is available, up, ... or so. However, currently I do not know where to find the source code, so this is only a vague idea of what happens.

• proto_send_update $interface
• proto_set_available $interface $state

• json_add_string
• json_dump
• json_init
• json_get_var
• json_get_vars

Network functions rely on runtime configuration and can return unexpected result if you are using MWAN or VPN. Replace automatic WAN detection with explicit interface definition if necessary.

# Runtime configuration
NET_IF="lan"
. /lib/functions/network.sh
network_flush_cache
network_get_ipaddr NET_ADDR "${NET_IF}"
network_get_ipaddr6 NET_ADDR6 "${NET_IF}"
echo "${NET_ADDR}"
echo "${NET_ADDR6}"

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_find_wan6 NET_IF6
echo "${NET_IF}"
echo "${NET_IF6}"

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_find_wan6 NET_IF6
network_get_physdev NET_L2D "${NET_IF}"
network_get_physdev NET_L2D6 "${NET_IF6}"
echo "${NET_L2D}"
echo "${NET_L2D6}"

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_find_wan6 NET_IF6
network_get_device NET_L3D "${NET_IF}"
network_get_device NET_L3D6 "${NET_IF6}"
echo "${NET_L3D}"
echo "${NET_L3D6}"
 
# Persistent configuration
uci get network.wan.device
uci get network.wan6.device

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_find_wan6 NET_IF6
network_get_ipaddr NET_ADDR "${NET_IF}"
network_get_ipaddr6 NET_ADDR6 "${NET_IF6}"
echo "${NET_ADDR}"
echo "${NET_ADDR6}"
 
# Persistent static configuration
uci get network.wan.ipaddr
uci get network.wan6.ip6addr

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_find_wan6 NET_IF6
network_get_gateway NET_GW "${NET_IF}"
network_get_gateway6 NET_GW6 "${NET_IF6}"
echo "${NET_GW}"
echo "${NET_GW6}"
 
# Persistent static configuration
uci get network.wan.gateway
uci get network.wan6.ip6gw

# Runtime configuration
. /lib/functions/network.sh
network_flush_cache
network_find_wan6 NET_IF6
network_get_prefix6 NET_PFX6 "${NET_IF6}"
echo "${NET_PFX6}"
 
# Persistent static configuration
uci get network.wan6.ip6prefix

# Runtime configuration
ubus call network.interface dump \
| jsonfilter -e "$['interface'][*]['inactive']
['route'][*]['target'='0.0.0.0','mask'='0','nexthop']"