[solved] Bridging wired and wireless networks with a Raspi

[christoph_peter_s]

Dear fellow Gentooers,

I want to provide internet access to a little wired network segment by connecting a Raspi running Gentoo to an existing WLAN. While I already have learned to handle my daily tasks of administering these little boxes, I have a bit clueless, when it comes to the very details of networking. It all begins with the fact, that I am not sure, which where the correct terms for the networking scenario, I am wishing to install.

I see two fundamental approaches:

- first I could use different IP-ranges within the WLAN and the wired LAN. This would mean, that the raspi would act like a router. The wired LAN IP of the raspi would be the default gateway within the wired LAN (basically in one room of the apartment, where I only have limited WLAN access, which I can overcome by using a really big antenna on the WLAN stick attached to the raspi). And on the boxes attached to the WLAN the IP address assigned to the raspi's WLAN stick would be the target of the routes to the wired LAN, which is behind the raspi when seen from the WLAN.

- the second solution would be using the same IP range within the WLAN and within the wired LAN. But depending on the capability of the WLAN base station (it is a relatively new FritzBox) this might require additional measures, as e.g. there might be troubles with ARP.

So my first question is: what are the keywords I should search for in order to find useful information, that helps me to understand the implication of the described networking situation. And maybe some of You have advice on which of these directions I should follow first.


The second part of my question is more down to earth... I have troubles to connect the raspi to the WLAN - which inevitably is the very first task I have to do. I have bought a TP-Link TL-WN722N rev. 2 WLAN stick, which is based on a Realtek chipset. That stick is served by the r8188eu driver, which should be provided by the Raspi-foundations mainline kernel (which I use, currently 4.19.71-v7+). I have read the Gentoo documentation on WLAN in general, on wpa_supplicant, and on WLAN on the AMD64 architecture (which answers some questions, but I still lack the understanding of the big thing...).

So reading through the docu I have installed these packages: sys-kernel/linux-firmware, net-wireless/wpa_supplicant, net-wireless/wireless-tools, net-wireless/iw. Most likely more than I need - it was desperation, that made me doing so.

The stick shows up like expected:

[NeddySeagoon]

christoph_peter_s,

It will be easier to make work if you use the Pi as a router.

Bridging is setting up a logical interface composed of zero or more physical interfaces.
In many cases Wifi cannot be bridged.
The real interfaces are brought up without configuring them then the br0 logical interface is configured in the normal way.

From my bare metal KVM host
# eth interfaces for firewall
# we don't want them getting IP addresses
# as they are being donated to bridges

[christoph_peter_s]

Hi Neddy,

Thank You for Your support.
So basically You tell me, not to worry for the missing IP on wlan0 - but go and define a bridge.
And then follow https://wiki.gentoo.org/wiki/Home_router - and configure LAN and "Connect another LAN"...

That sounds indeed as a pretty elegant approach.

Best regards
Peter

[NeddySeagoon]

christoph_peter_s,

Not exactly. Do not use a bridge. Its not supported by most Wifi systems.
If you want to try it, I pointed the way

Set up a home router on the Pi instead. That process is known to work.
All the bits are known to work on arm.

A cascade of routers works. The entire interned depends on that.

This is my routing table now. lo is removed for simplicity.

[christoph_peter_s]

Hi Neddy,

OK, I have read through the Home Router guide - and as I understand it now, I have to set up iptables, just replacing WAN with WLAN - and set the rules in a way, that all the necessary packets are forwarded, right?

But the issue, on how to get an IP address to wlan0 remains to be solved...

Best regards
Peter

[NeddySeagoon]

christoph_peter_s,

wlan0 will have a static IP address.
The Pi will run a dhcp server to give out network settings to other hosts on your WiFi network.
The wlan0 static IP address will be the default route for your WiFi hosts.

The Pi will run Network Address Translation (NAT) for you WiFi hosts.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[christoph_peter_s]

Hi Neddy,

I fixed two errors. First in /etc/conf.d/wpa_supplicant there must not be a -M option.
And I removed the routes_SsId123 line in /etc/conf.d/net.
So now rc-service wpa_supplicant does work just like the debug call from the command line.
But - and I really can't see why, at least not tonight - I don't got any IP address assigned to wlan0.

Best regards
Peter

[crocket]

What does it take to bridge a WLAN with a LAN or another WLAN?

Are manufacturers trying to extract more money by turning wireless bridge into various proprietary technologies?

[christoph_peter_s]

As far as I understood, there is some sort of a shortcoming in the IEEE specifications, that originally assumed, that there was only one user behind each logged in WLAN client, which is apparently not the case, if You use a switch behind a WLAN client. Neddy therefore requested me, to use different IP ranges in the different net segments, i.e. my device should act like a router (switching one network level higher than a normal switch). In that case, on MAC level (i.e. below IP) the routers WLAN entry port is the destination of all the IP packets headed for the net segment behind that router.

Once again: as far as I know there has been some work to overcome that restriction, but that is not covered by the rigid specifications of IEEE (or it is in some late extensions, which are not commonly used), so that different manufactures did come up with different solutions - or no solution at all. So one can not assume, that using WLAN to attach a network segment was working at all...

Best regards
Peter

PS: sorry, this is a quite naive explanation. I did not understand it better than that...

[christoph_peter_s]

After triple checking everything in the morning, I am still clueless.
wlan0 doesn't get an IP, albeit the WLAN connection seems to be OK.

[christoph_peter_s]

To check the issue, I have bought another Wifi stick (they cost next to nothing...), a Edimax EW-7612UAn v2. It uses another Realtek chipset...

[NeddySeagoon]

christoph_peter_s,

Wifi dongles can operate in three modes.

Host mode, which everyone is used to in their laptops
Access Point mode, where the interface operates an a WiFi Access Point and controls all the other connected hosts.
Monitor mode, where the dongle just listens.

Not all dongles can do all modes. They all do host mode, as that's the common mode of operation.

You need your wifi interface to operate in Access Point mode as you want the Pi to be a WiFi Access Point.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[christoph_peter_s]

[NeddySeagoon]

christoph_peter_s,

I misunderstood. You need host mode as you say.

You configure your WiFi in the normal way with wpa_supplicant an /etc/conf.d/net.

[christoph_peter_s]

There is a wee bit of progress...

First of all, I had no dhcp daemon running (the raspi did use fixed IPs ever since the first install).
So I did install net-misc/dhcpcd and add it to runlevel default...

The situation is a bit tricky, as one of my Wifi dongles seems to use a buggy driver. Whenever I restart wpa_supplicant, the dongle does no longer accept a request for restart. So it took a lot of reboots to investigate the issue... Anyway that does't hurt too much and for the time being I switched back to the better working dongle.

Furthermore I did remove the duplicates of the wpa_supplicant options. Some were in /etc/conf.d/net in "wpa_supplicant_wlan0=..." lines, others in /etc/conf.d/wpa_supplicant, here in "wpa_supplicant_args=..." lines. So my current config looks like that:

[christoph_peter_s]

OK, I have found a solution. It's not a nice one, but it works...

I configure the wlan0 IP to dhcp and run the dhcpcd daemon. But inside /etc/dhcpcd.conf I added:

[christoph_peter_s]

It wasn't that easy... due to that Wifi limitation, that it only allows point-to-point connections.
So I have implemented this solution:

Once the Wifi connection is there, I start an tunnel on the remote host using