Troubleshoot Screen Mirroring Issue on OpenWrt router

sturgman · January 3, 2025, 1:14am

Hello all,

I have a router with OpenWrt set up as described in this wiki page:
https://openwrt.org/docs/guide-user/network/wifi/wifiextenders/bridgedap

This has been working great. However, recently I had the need to start mirroring my phone's screen (Samsung) to my TV (LG). In my current setup, I have enabled the wifi network in my ISP provided access point and in my OpenWrt device with different ssids. I observe the following:

If I connect phone and TV to the ssid provided by the ISP's device, everything works fine.
If I connect the TV to the ISP's device and the phone to the OpenWrt ssid, everything works fine.
If I connect both devices to the OpenWrt device, screen mirroring doesn't work.

I am running OpenWrt 23.05.3. Any thoughts on why there is an issue when both devices connect to the OpenWrt access point? Anyone successfully doing screen mirroring via their OpenWrt enabled router?

psherman · January 3, 2025, 1:18am

Is the TV on wifi? Do you have wifi isolation enabled on the OpenWrt AP?

Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:

Remember to redact passwords, MAC addresses and any public IP addresses you may have:

ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall

sturgman · January 3, 2025, 2:44am

Here you go. I don't know what to actually redact but I think I was overcareful here. Note that I have disabled firewall, dnsmasq, and odhcpd.
ubus call...

root@OpenWrt:~# ubus call system board
{
        "kernel": "5.15.150",
        "hostname": "OpenWrt",
        "system": "MediaTek MT7621 ver:1 eco:3",
        "model": "Netgear R6700 v2",
        "board_name": "netgear,r6700-v2",
        "rootfs_type": "squashfs",
        "release": {
                "distribution": "OpenWrt",
                "version": "23.05.3",
                "revision": "r23809-234f1a2efa",
                "target": "ramips/mt7621",
                "description": "OpenWrt 23.05.3 r23809-234f1a2efa"
        }
}

network

config interface 'loopback'
        option device 'lo'
        option proto 'static'
        option ipaddr '127.0.0.1'
        option netmask '255.0.0.0'

config globals 'globals'
        option ula_prefix redacted
        option packet_steering '1'

config device
        option name 'br-lan'
        option type 'bridge'
        list ports 'lan1'
        list ports 'lan2'
        list ports 'lan3'
        list ports 'lan4'
        option igmp_snooping '1'

config interface 'lan'
        option igmp_snooping '1'
        option device 'br-lan'
        option proto 'static'
        option ipaddr '10.0.0.89'
        option netmask '255.255.255.0'
        option ip6assign '60'
        option gateway '10.0.0.1'
        option broadcast '10.0.0.255'
        list dns '10.0.0.1'

config interface 'wan'
        option device 'wan'
        option proto 'dhcp'
        option type 'bridge'

config interface 'wan6'
        option device 'wan'
        option proto 'dhcpv6'

wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option path redacted
        option channel '9'
        option band '2g'
        option htmode 'HT40'
        option country 'US'
        option cell_density '0'

config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid redacted
        option encryption 'psk2'
        option key redacted

config wifi-device 'radio1'
        option type 'mac80211'
        option path redacted
        option channel '104'
        option band '5g'
        option htmode 'VHT40'
        option country 'US'
        option cell_density '0'

config wifi-iface 'wifinet1'
        option device 'radio1'
        option mode 'ap'
        option ssid redacted
        option encryption 'psk2'
        option key redacted
        option network 'lan'

dhcp

config dnsmasq
        option domainneeded '1'
        option boguspriv '1'
        option filterwin2k '0'
        option localise_queries '1'
        option rebind_protection '1'
        option rebind_localhost '1'
        option local '/lan/'
        option domain 'lan'
        option expandhosts '1'
        option nonegcache '0'
        option cachesize '1000'
        option authoritative '1'
        option readethers '1'
        option leasefile '/tmp/dhcp.leases'
        option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto'
        option nonwildcard '1'
        option localservice '1'
        option ednspacket_max '1232'
        option filter_aaaa '0'
        option filter_a '0'

config dhcp 'lan'
        option interface 'lan'
        option start '100'
        option limit '150'
        option leasetime '12h'
        option dhcpv4 'server'
        option ignore '1'

config dhcp 'wan'
        option interface 'wan'
        option ignore '1'

config odhcpd 'odhcpd'
        option maindhcp '0'
        option leasefile '/tmp/hosts/odhcpd'
        option leasetrigger '/usr/sbin/odhcpd-update'
        option loglevel '4'

firewall

config defaults
        option syn_flood        1
        option input            REJECT
        option output           ACCEPT
        option forward          REJECT
# Uncomment this line to disable ipv6 rules
#       option disable_ipv6     1

config zone
        option name             lan
        list   network          'lan'
        option input            ACCEPT
        option output           ACCEPT
        option forward          ACCEPT

config zone
        option name             wan
        list   network          'wan'
        list   network          'wan6'
        option input            REJECT
        option output           ACCEPT
        option forward          REJECT
        option masq             1
        option mtu_fix          1

config forwarding
        option src              lan
        option dest             wan

# We need to accept udp packets on port 68,
# see https://dev.openwrt.org/ticket/4108
config rule
        option name             Allow-DHCP-Renew
        option src              wan
        option proto            udp
        option dest_port        68
        option target           ACCEPT
        option family           ipv4

# Allow IPv4 ping
config rule
        option name             Allow-Ping
        option src              wan
        option proto            icmp
        option icmp_type        echo-request
        option family           ipv4
        option target           ACCEPT

config rule
        option name             Allow-IGMP
        option src              wan
        option proto            igmp
        option family           ipv4
        option target           ACCEPT

# Allow DHCPv6 replies
# see https://github.com/openwrt/openwrt/issues/5066
config rule
        option name             Allow-DHCPv6
        option src              wan
        option proto            udp
        option dest_port        546
        option family           ipv6
        option target           ACCEPT

config rule
        option name             Allow-MLD
        option src              wan
        option proto            icmp
        option src_ip           redacted
        list icmp_type          '130/0'
        list icmp_type          '131/0'
        list icmp_type          '132/0'
        list icmp_type          '143/0'
        option family           ipv6
        option target           ACCEPT

# Allow essential incoming IPv6 ICMP traffic
config rule
        option name             Allow-ICMPv6-Input
        option src              wan
        option proto    icmp
        list icmp_type          echo-request
        list icmp_type          echo-reply
        list icmp_type          destination-unreachable
        list icmp_type          packet-too-big
        list icmp_type          time-exceeded
        list icmp_type          bad-header
        list icmp_type          unknown-header-type
        list icmp_type          router-solicitation
        list icmp_type          neighbour-solicitation
        list icmp_type          router-advertisement
        list icmp_type          neighbour-advertisement
        option limit            1000/sec
        option family           ipv6
        option target           ACCEPT

# Allow essential forwarded IPv6 ICMP traffic
config rule
        option name             Allow-ICMPv6-Forward
        option src              wan
        option dest             *
        option proto            icmp
        list icmp_type          echo-request
        list icmp_type          echo-reply
        list icmp_type          destination-unreachable
        list icmp_type          packet-too-big
        list icmp_type          time-exceeded
        list icmp_type          bad-header
        list icmp_type          unknown-header-type
        option limit            1000/sec
        option family           ipv6
        option target           ACCEPT

config rule
        option name             Allow-IPSec-ESP
        option src              wan
        option dest             lan
        option proto            esp
        option target           ACCEPT

config rule
        option name             Allow-ISAKMP
        option src              wan
        option dest             lan
        option dest_port        500
        option proto            udp
        option target           ACCEPT

psherman · January 3, 2025, 2:56am

Remove the igmp snooping from both of these:

sturgman:

config device
        option name 'br-lan'
        option type 'bridge'
        list ports 'lan1'
        list ports 'lan2'
        list ports 'lan3'
        list ports 'lan4'
        option igmp_snooping '1'

config interface 'lan'
        option igmp_snooping '1'
        option device 'br-lan'
        option proto 'static'
        option ipaddr '10.0.0.89'
        option netmask '255.255.255.0'

Reboot and test again.

sturgman · January 5, 2025, 12:32pm

This worked! Thank you. Could you spare a moment to explain? I thought I added at least one of those lines after I found the issue. In any case, thank you!

system · January 15, 2025, 12:33pm

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