Topic: Fails to forward ARP with hostapd using multiple virtual interfaces
I'm using trunk r20254, WNDR3700 router (ath9k on 2.4 GHz and 5 GHz) with wpad-mini...but I think my test case should apply to even a standard single-band router. Testing this doesn't require anything other than an OpenWrt router.
I previously reported a problem when trying to use some wireless speakers via AirTunes across the 5 GHz interface of my router. After pulling out much hair, I finally found the source of the problem, and it applies to . It actually relates to the usage of hostapd in a multi-VIF configuration when WPA2-PSK is enabled. If I have only one VIF in use, or if I have multiple VIFs but the connection is unencrypted, everything works fine. (In my referenced AirTunes post, I had multiple VIFs on 5 GHz and only a single VIF on 2.4 GHz, so I originally thought that the problem was 5G-related, but that turns out not to be the case.)
Would someone else be willing to try this test to confirm this issue too? If so, I will go ahead and file a bug.
TEST SEQUENCE (WORKING):
- Router is configured as 192.168.1.1.
- Set up your wireless interface to use WPA2-PSK, and enable only one virtual interface on the radio (in AP mode). This interface should be bridged to your wired Ethernet ports as usual.
- SSH into the router and try to continuously ping a nonexistent IP address on the local subnet (eg. 192.168.1.123).
- Using a client computer connected to the router wirelessly, run tcpdump with an arp filter (eg. "tcpdump -i <wlan_device> arp") on the wireless interface.
- If you see ARP who-has requests for 192.168.1.123 coming into the wireless interface at a periodic interval, everything works.
TEST SEQUENCE (BROKEN):
- Do everything as above, except set up two VIFs on the *same* radio (both also in AP mode). Ensure that WPA2-PSK is used on both.
- Now connect the client to each wireless interface in turn, listening for the same ARP requests from your ping.
- If you see ARP requests on only one (or neither) of the interfaces, something is presumably broken.
Note that the presence of multiple interfaces seems to be a problem even when all of the multiple VIFs are assigned to different local networks! (In other words, even when only one WLAN is assigned to the br-lan network that should be receiving the corresponding ARP traffic, the mere presence of additional VIFs attached to OTHER different LAN segments causes it to break.)
I'd really appreciate it if someone could help confirm this for me. If it works for you (or not), please state your platform, wireless chipset and build version.