--- name: "if_rtwn" section: "4" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["freebsd"] url: "https://new.carta.tech/if_rtwn" --- # if\_rtwn(4) Realtek IEEE 802.11n/ac wireless network driver ## NAME **rtwn** – Realtek IEEE 802.11n/ac wireless network driver ## SYNOPSIS **options RTWN\_DEBUG** **options RTWN\_WITHOUT\_UCODE** To compile this driver into the kernel, place the following lines in your kernel configuration file: **device rtwn** **device rtwnfw** **device rtwn\_usb** **device rtwn\_pci** **device wlan** **device firmware** Alternatively, to load the driver as a module at boot time, place following lines in [loader.conf(5)](/loader.conf/5.md): ``` if_rtwn_pci_load="YES" if_rtwn_usb_load="YES" ``` ## DESCRIPTION The **rtwn** driver provides support for 802.11n/ac wireless network PHYs supplied by [rtwn\_pci(4)](/rtwn_pci/4.md) and [rtwn\_usb(4)](/rtwn_usb/4.md). The **rtwn** driver supports **station**, **adhoc**, **hostap** and **monitor** mode operation. There are no limitations for number of **monitor** mode virtual interfaces; in addition to any other virtual interface one **station** interface can be added (Note: RTL8821AU supports two non-monitor mode interfaces at the same time). All chips have hardware support for WEP, AES-CCM and TKIP encryption. The **rtwn** driver can be configured at runtime with [ifconfig(8)](/ifconfig/8.md). ## HARDWARE The **rtwn** driver supports USB and PCI devices with the following chipsets: - Realtek 802.11n wireless 8188e (RTL8188E) - Realtek 802.11n wireless 8192c (RTL8192C) - Realtek 802.11n wireless 8192e (RTL8192E) - Realtek 802.11n wireless 8723b (RTL8723B) - Realtek 802.11ac wireless 8812a (RTL8812A) - Realtek 802.11ac wireless 8821a (RTL8821A) For specific devices, see [rtwn\_pci(4)](/rtwn_pci/4.md) and [rtwn\_usb(4)](/rtwn_usb/4.md). ## FILES - */usr/share/doc/legal/realtek.LICENSE* **rtwn** firmware license The driver (if not compiled with **options** **RTWN\_WITHOUT\_UCODE**) may use following firmware files, which are loaded when an interface is brought up: - */boot/kernel/rtwn-rtl8188eefw.ko* - */boot/kernel/rtwn-rtl8188eufw.ko* - */boot/kernel/rtwn-rtl8192cfwE\_B.ko* - */boot/kernel/rtwn-rtl8192cfwE.ko* - */boot/kernel/rtwn-rtl8192cfwT.ko* - */boot/kernel/rtwn-rtl8192cfwU.ko* - */boot/kernel/rtwn-rtl8192eufw.ko* - */boot/kernel/rtwn-rtl8723bufw.ko* - */boot/kernel/rtwn-rtl8812aufw.ko* - */boot/kernel/rtwn-rtl8821aufw.ko* ## EXAMPLES Join an existing BSS network (i.e., connect to an access point): ``` ifconfig wlan create wlandev rtwn0 inet 192.0.2.20/24 ``` Join a specific BSS network with network name *my\_net*: ``` ifconfig wlan create wlandev rtwn0 ssid my_net up ``` Join a specific BSS network with 64-bit WEP encryption: ``` ifconfig wlan create wlandev rtwn0 ssid my_net \ wepmode on wepkey 0x1234567890 weptxkey 1 up ``` Create an IBSS network with 128-bit WEP encryption on the channel 4: ``` ifconfig wlan create wlandev rtwn0 wlanmode adhoc ssid my_net \ wepmode on wepkey 0x01020304050607080910111213 weptxkey 1 \ channel 4 ``` Join/create an 802.11b IBSS network with network name *my\_net*: ``` ifconfig wlan0 create wlandev rtwn0 wlanmode adhoc ifconfig wlan0 inet 192.0.2.20/24 ssid my_net mode 11b ``` Create a host-based access point: ``` ifconfig wlan0 create wlandev rtwn0 wlanmode hostap ifconfig wlan0 inet 192.0.2.20/24 ssid my_ap ``` ## LOADER TUNABLES Tunables can be set at the [loader(8)](/loader/8.md) prompt before booting the kernel or stored in [loader.conf(5)](/loader.conf/5.md). - *dev.rtwn.%d.hwcrypto* This tunable controls how key slots are assigned: 0 - disable h/w crypto support. Features that require access to frame contents (e.g., TCP/UDP/IP Rx checksum validation) will not work; 1 - use h/w crypto support for pairwise keys only; 2 - use h/w crypto support for all keys; may not work for multi-vap configurations. By default it is set to 1. - *dev.rtwn.%d.ratectl* This tunable switches between rate control implementations: 0 - no rate control; 1 - driver sends 'tx complete' reports to net80211; algorithm is controlled via net80211; 2 - firmware-based rate control. By default it is set to 1; however driver may choose another algorithm in case if it is not implemented Currently selected algorithm is reported via *dev.rtwn.%d.ratectl\_selected* read-only OID. - *dev.rtwn.%d.rx\_buf\_size* (USB only) Controls size of temporary Rx buffer; smaller buffer size may increase number of interrupts. ## DIAGNOSTICS - rtwn%d: could not read efuse byte at address 0x%x - rtwn%d: %s: cannot read rom, error %d There was an error while reading ROM; device attach will be aborted. This should not happen. - rtwn%d: failed loadfirmware of file %s For some reason, the driver was unable to read the microcode file from the filesystem. The file might be missing or corrupted. The driver will disable firmware-dependent features. - rtwn%d: wrong firmware size (%zu) - rtwn%d: %s: failed to upload firmware %s (error %d) - rtwn%d: timeout waiting for firmware readiness Firmware upload failed; the file might be corrupted. The driver will disable firmware-dependent features. This should not happen. - rtwn%d: device timeout A frame dispatched to the hardware for transmission did not complete in time. The driver will reset the hardware. This should not happen. ## SEE ALSO [intro(4)](/intro/4.md), [netintro(4)](/netintro/4.md), [rtwn\_pci(4)](/rtwn_pci/4.md), [rtwn\_usb(4)](/rtwn_usb/4.md), [rtwnfw(4)](/rtwnfw/4.md), [wlan(4)](/wlan/4.md), [wlan\_amrr(4)](/wlan_amrr/4.md), [wlan\_ccmp(4)](/wlan_ccmp/4.md), [wlan\_tkip(4)](/wlan_tkip/4.md), [wlan\_wep(4)](/wlan_wep/4.md), [wlan\_xauth(4)](/wlan_xauth/4.md), [networking(7)](/networking/7.md), [hostapd(8)](/hostapd/8.md), [ifconfig(8)](/ifconfig/8.md), [wpa\_supplicant(8)](/wpa_supplicant/8.md) ## HISTORY The **urtwn** driver first appeared in OpenBSD 4.9 and FreeBSD 10.0; the **rtwn** driver first appeared in OpenBSD 5.8 and FreeBSD 11.0. ## AUTHORS The **rtwn** driver was initially written by Stefan Sperling ⟨*stsp@openbsd.org*⟩ and ported by Kevin Lo ⟨*kevlo@FreeBSD.org*⟩. It was based on the **urtwn** driver written by Damien Bergamini ⟨*damien.bergamini@free.fr*⟩. ## BUGS The **rtwn** driver currently does not implement firmware-based rate control. The RTL8723BU seems to depend on some firmware commands for antenna setup. Hence, it does not work without firmware.