Openwrt
Recommended Router
Current:
high traffic: x86 PC
low traffic: ARM / MIPS with the following:
* uboot bootloader * doesn't require multiple hoops to install (i.e. no 'two different' serial speeds on the same UART. moron ubiquiti...) * promotes FOSS and is ok with LEDE/openwrt
Compiling
See developers guide - build system usage.
Also pay attention to this note:
Using official build config Compile OpenWrt in a way that it gets the same packages as the default official image: For example if you are flashing for the archer_c7 you can locate on its wiki page the factory firmware URL https://downloads.openwrt.org/releases/21.02.1/targets/ath79/generic/openwrt-21.02.1-ath79-generic-tplink_archer-c7-v2-squashfs-factory.bin 'ath79' tells you the Target, 'generic' tells you the Subtarget while 'archer-c7-v2' tells you the Target profile for the very specific device. Download the config by removing everything up to the subtarget 'generic' and adding 'config.buildinfo': # OpenWrt 19.07 and later wget https://downloads.openwrt.org/releases/21.02.1/targets/ath79/generic/config.buildinfo -O .config # OpenWrt 18.06 and before wget https://downloads.openwrt.org/releases/18.06.0/targets/ramips/mt7621/config.seed -O .config When using this configuration the correct defaults will be already selected for the Target and Subtarget but not for the Target profile so you will have to tailor it for the specific device if you want to build only that one.
Double check you have the right tag.
Tips
include /etc/firewall.user
This was changed, with the move to nft. The syntax for this has a few more options. Note that it now expects nft syntax.
Contents of /etc/config/firewall
Be aware of the traps with the move to nft (see port forwarding section below), compared to iptables.
open port
Contents of /etc/config/firewall
port forwarding
Port forwarding is one step:
- redirect port from outside to internal (prerouting chain, before input)
Contents of /etc/config/firewall
Note: Proto can be 'tcp' OR 'tcpudp' OR 'udp'. If you have multiple src allows, make multiple. See: https://forum.openwrt.org/t/port-forward-for-two-source-addresses/24067/2 Note that this is handled in nft, in the prerouting chain, before the input table, so you can't just add an input table src block. This is a potential trap, because services like SSH which are on the firewall, you can put blocks in the input chain - and they will work. However, any redirects must be handled separately. Ipsets can not be used with redirect and fw4 according to the wiki, 2/2/23.
Trap from iptables fw4 to nft fw4
Beware with NFT. The behavior is different. Review the following:
#redirects here show up in dstnat_wan
config redirect
option name 'computer2'
option src 'wan'
option proto 'tcp'
option src_ip '<allowediphere>'
option src_dport '222'
option dest_port '222'
option dest_ip '10.0.0.233'
option target 'DNAT'
option dest 'lan'
config redirect
option name 'laptop'
option src 'wan'
option proto 'tcp'
option src_dport '224'
option dest_port '224'
option dest_ip '10.0.0.139'
option target 'DNAT'
option dest 'lan'
chain dstnat_wan {
ip saddr <yourhomeiphere> tcp dport 222 counter packets 1 bytes 60 dnat ip to 10.0.0.233:222
meta nfproto ipv4 udp dport 224 counter packets 2 bytes 352 dnat ip to 10.0.0.139:224
}
adding a nft block or allow in /etc/firewall.user such as:
nft insert rule inet fw4 input tcp dport 224 counter reject
and an equivalent src ip allow in the input table will NOT work. it used to in iptables, but nft has different behavior. The dstnat_wan chain/table is the one to look at. When in doubt, always run a test on the ports from two ips.
Know that you can use nft allows/blocks in the /etc/firewall.user script for the input table, however they are primarily for services on the router (although snat for wireguard can be put there). Although you could probably put rules in the dstnat_wan table/chain instead of input (though it's not as graceful as iptables was).
Is this a good idea? I would expect inputs go in the inputs, and not in inputs AND dstnat_wan.
reserved ip / static lease
Contents of /etc/config/dhcp
ref: https://openwrt.org/docs/guide-user/base-system/dhcp_configuration#static_leases
I tried to add this to the wiki, but someone (https://openwrt.org/docs/guide-user/base-system/dhcp_configuration?rev=1596434574) decided to replace my simple solution with a scriptable yet obfuscated one that requires uci commands. So instead, it will remain here. EDIT: I added it back. See how long that lasts...
route
This can be useful if you want to bypass a VPN.
Contents of /etc/config/network
openvpn
opkg install openvpn-openssl
Contents of /etc/config/openvpn
And your .ovpn in /etc/openvpn/.
dhcp options: ntp server
https://forum.openwrt.org/t/dhcpv6-ntp-server-not-working/157498/8
You can also forward requests for the ntp server on the router to a different client on the lan via nft/iptables.
aliases
Put in /etc/profile. e.g.
export TERM=xterm alias vpnme= 'openvpn --config /etc/openvpn/myconfigfile.ovpn & ./script.sh &'
mwan3
Mwan3 can be tricky. The wiki lacks a quick start*. The following files get edited:
/etc/config/network /etc/config/mwan3 /etc/config/firewall
Tips Page: Mwan3_On_Openwrt
If you add a new WAN interface, (e.g. wanb or wan2) you must add wanb to the existing wan firewall zone for outgoing comms. How this is handled differs from 17 to 19.*2
Balanced policies can have issues with connections jumping from one wan to another.
* the current mwan3 page is a lengthy multi-page behemoth (which has grown over time) that expects no less of you than to understand all functional and architectural details of how the failover works. It's a lot for someone that just wants to setup backup internet. But mwan3 can and does work.
- 2 ctrl-f for firewall comes up with half a dozen mentions of firewall masking (something done automatically) and one easily missable note, for GUI setup only, about adding the new wan2 to the firewall zone. An absolutely required step.
Trap: Again on balanced connections. Balanced internet doesn't necessarily work properly with mwan3, as connections can hop between interfaces which means an existing session will jump to a different interface and be half in one and half in the other. I learned to not use balanced, and just use the priority options, i.e. use wan1 only, and wan2 if wan1 goes offline, but DON'T try to use both at once. It didn't work right for me. There may be simpler solutions than mwan3. See for example https://github.com/GTANAdam/openwrt-wan-failover-script One thing is certain, mwan3 is complex. It has lots of features (good) but it may be more than what you need, if you only need failover.
Again, see Tips Page: Mwan3_On_Openwrt I think I've been bitten by the firewall part multiple times. Ugh.
iptables vs fw3
In the firewall:
iptables -L
will list current rules, but the iptables rule generator is fw3.
fw3 print
Will display iptables commands that make up the firewall. fw3 script is described in firewall pages on official wiki. Please review that. 22 now uses nft.
nft list tables
less with / search
The stock 'less' command does not include '/' search.
opkg install less
To get forward slash search https://dev.archive.openwrt.org/ticket/7132
remove poweroff command
cd /sbin/ rm ./poweroff
Now to power off, you must type
busybox poweroff
This will keep you from accidentally shutting down a router.
misc
start wifi
wifi up wifi status
transfer files using nc / scp on lean embedded devices
Logging
display (RAM based) logs (note that this is not in /var/log/messages...)
logread
https://openwrt.org/docs/guide-user/perf_and_log/start e.g. https://openwrt.org/docs/guide-user/perf_and_log/statistic.custom and https://openwrt.org/docs/guide-user/perf_and_log/log.messages
Blink LEDs
If you poke around the Linux Kernel you will come across core Netfilter configuration. It's not in an obvious place, but in 5.4 here:
Location: │ │ -> Networking support (NET [=y]) │ │ -> Networking options │ │ -> Network packet filtering framework (Netfilter) (NETFILTER [=y]) │ │ -> Core Netfilter Configuration │ │ -> Netfilter Xtables support (required for ip_tables) (NETFILTER_XTABLES [=y])
Why am I poking around xtables support? Wireguard needs it for <5.6. But, in this page, you will find some familiar sights: REDIRECT,MASQUERADE,DROP,LOG, etc... All parameters for iptables. Here you will learn what the difference between REDIRECT and MASQUERADE is (one is input, one is output)(which is interesting, because it might be a thing people commonly get wrong, on online tips for using iptables, or if you don't know which does what, you won't know what to look for). Forget about that, there's one named LED. Hey that sounds interesting. That means I can control a LED from the firewall?
Does this work with Openwrt? No idea, but from here I went to the official owrt docs
https://openwrt.org/docs/guide-user/base-system/led_configuration
And you may already know the leds are there, but here's how to configure them. Some of them require modules. e.g.
The LED flashes with link status and/or send and receive activity on the configured interface. If not installed already, install it with: opkg install kmod-ledtrig-netdev
will enable netdev, which will enable led activity on any NIC. so it requires that module and some configuration... e.g.
#:/sys/devices/platform/leds/leds/:green:wan# ls brightness device_name link rx trigger uevent device interval max_brightness subsystem tx #:/sys/devices/platform/leds/leds/:green:wan# cat * 0 cat: read error: Is a directory eth0.2 50 0 255 1 cat: read error: Is a directory none switch0 timer default-on [netdev] phy0rx phy0tx phy0assoc phy0radio phy0tpt 0 OF_NAME=wan OF_FULLNAME=/leds/wan OF_COMPATIBLE_N=0
I had to set rx or tx to 1 (only 1 of them). and also needed to set device_name (not device like docs say) to eth0.2
Just set a ping, then tweak the knobs; should start blinking.
"But what if I want to blink more LEDs from userspace?" See Arduino for ulisp.
Periodic Reboot
One of my routers had DHCP fail after 60 days. It's not common, but a good idea might be a periodic reboot. This is taken from the owrt site.
- Reboot at 4:30am every day
- Note: To avoid infinite reboot loop, wait 70 seconds
- and touch a file in /etc so clock will be set
- properly to 4:31 on reboot before cron starts.
30 4 * * * sleep 70 && touch /etc/banner && reboot
NOTE: I've never had issues with reboot, but above looks like a good idea.
Run Script on Boot / etc hotplug.d
You can use rc.local, however sometimes you need more control.
It's also possible to put scripts in /etc/hotplug.d that run after certain events. (e.g. [1])
Here are two examples.
1) Run an iptables firewall command only after DNS is active.
#!/bin/sh logger -t hotplug "Starting firewall_DNS.sh" [ "$ACTION" == "ifup" ] && [ "$INTERFACE" == "wan" ] && /etc/firewall_DNS.sh /etc/hotplug.d/iface/99-iptables_dns_lookup
2) Assign a shell script to a button.
#logger "the button was ${BUTTON} and the action was ${ACTION}"
logger -t netiface "reset network button pressed"
[ "$BUTTON" == "BTN_0" ] && [ "$ACTION" == "pressed" ] && /etc/restart_net.sh
[ "$BUTTON" == "BTN_0" ] && [ "$ACTION" == "released" ] && /etc/restart_net.sh
/etc/hotplug.d/buttons/buttons
This latter one should be tested to remove the redundant command, but I didn't use it in practice. It's left unfinished as a reference.
Packages are Located in Multiple Places
This is something that confused me as a user (not a developer) of owrt. The packages are in different places. There are the kernel modules, and some programs, then there may be a different path for the application programs. Pay attention to where opkg searches in /etc/opkg/ e.g.
src/gz openwrt_core https://downloads.openwrt.org/releases/####/targets/processor/generic/packages src/gz openwrt_packages https://downloads.openwrt.org/releases/####/packages/maybe different processor/packages
Always test with RAM only images
Test firmware images without writing them to flash by using ramdisk images.
In make menuconfig select Target Images and then you can select the ramdisk option.
This will create an image with kernel + initramfs, that will have initramfs in the name. The resulting image can be loaded in the device through the bootloader's tftp function and should boot to a prompt without relying on flash/filesystem support. This way, if you brick something, it's only on the RAM, and you can reboot the device.
MTD Partitions data
You can run lsblk, but it won't show the descriptions for the mtd partitions. That is in /proc/mtd. See:
root@OpenWrt:/etc/config# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 149.1G 0 disk └─sda1 8:1 0 149G 0 part mtdblock0 31:0 0 256K 1 disk mtdblock1 31:1 0 31.3M 0 disk mtdblock2 31:2 0 3M 0 disk mtdblock3 31:3 0 28.3M 0 disk /rom mtdblock4 31:4 0 23.4M 0 disk /overlay mtdblock5 31:5 0 256K 1 disk mtdblock6 31:6 0 128K 1 disk mtdblock7 31:7 0 128K 1 disk root@OpenWrt:/etc/config# cat /proc/mtd dev: size erasesize name mtd0: 00040000 00020000 "Boatlooter" mtd1: 01f40000 00020000 "firmware" mtd2: 00300000 00020000 "kernel" mtd3: 01c40000 00020000 "rootfs" mtd4: 01760000 00020000 "rootfs_data" mtd5: 00040000 00020000 "rgdb" mtd6: 00020000 00020000 "nvram" mtd7: 00020000 00020000 "LangPack" root@OpenWrt:/etc/config#
Programs to install upon start
less (less is included, but this package contains the / search), tcpdump, nano-plus (includes nanorc functionality for emacs like ctrl-b, ctrl-f), htop. for nano-plus put in /etc/nanorc:
bind ^B back all bind ^f forward all
opkg update && opkg install less tcpdump nano-plus htop
various links i found interesting
- https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm - speed test, and traffic shaping to speed up a 'slow' network. protip: use x86 instead of arm if openwrt is slow.
- https://openwrt.org/docs/guide-user/services/nas/netatalk_configuration - apple time machine backup server
- https://openwrt.org/docs/guide-user/network/wan/multiwan/mwan3 - failover for wan. i have used this before, and it worked well.
- https://openwrt.org/tag/faq - FAQs
- https://openwrt.org/docs/techref/flash.layout - Partitions on
HDDflash. And overlay fs.
- https://openwrt.org/docs/techref/start - Technical Reference. Has some informative dives into various aspects of low power routers. As an example see this link on flash: https://openwrt.org/docs/techref/flash IME, flash is built in obsolescence. usb drives, sd cards, and onboard flash tend to last much less than advertised. not recommended. SD and SSDs are a trap. from this: even 'reading' flash can cause bad blocks. that's right, even reading. therefore flash is guaranteed to fail. tech companies love it.
- https://forum.openwrt.org/t/favor-to-do-custom-build-for-anyone-w-dev-toolchain/138275 Appears to be a basic device add to the owrt tree, copying existing code.
- http://web.archive.org/web/20211017192705/https://sagacioussuricata.com/posts/meraki-mr33/ Showing how to flash to nand from owrt running in ram, i think.
- web.archive.org/web/https://cybergibbons.com/hardware-hacking/recovering-firmware-through-u-boot/
- https://forum.openwrt.org/t/x86-booting-two-instances-of-openwrt/106282 have a backup owrt partition on x86 (possibly useful for upgrades)
- https://forum.openwrt.org/t/howto-speech-recongnition/149477 speech recognition / AI
- https://forum.openwrt.org/t/openwrtai-with-internet-radio-and-local-media/149818 speech recognition / AI
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