src/wifi/medium.rs

// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use crate::wifi::frame::Frame;
use crate::wifi::hostapd::Hostapd;
use crate::wifi::hwsim_attr_set::HwsimAttrSet;
use anyhow::{anyhow, Context};
use bytes::Bytes;
use log::{debug, info, warn};
use netsim_packets::ieee80211::{DataSubType, Ieee80211, MacAddress};
use netsim_packets::mac80211_hwsim::{HwsimCmd, HwsimMsg, HwsimMsgHdr, NlMsgHdr};
use pdl_runtime::Packet;
use std::collections::HashMap;
use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
use std::sync::{Arc, RwLock};

const NLMSG_MIN_TYPE: u16 = 0x10;
const NL_AUTO_SEQ: u16 = 0;
const NL_AUTO_PORT: u32 = 0;
// Default values for mac80211_hwsim.
const RX_RATE: u32 = 0;
const SIGNAL: u32 = 4294967246; // -50
const NL_MSG_HDR_LEN: usize = 16;

pub struct Processor {
    pub hostapd: bool,
    pub network: bool,
    pub wmedium: bool,
    pub frame: Frame,
    pub plaintext_ieee80211: Option<Ieee80211>,
}

impl Processor {
    /// Returns the decrypted IEEE 802.11 frame if available.
    /// Otherwise, returns the original IEEE 80211 frame.
    pub fn get_ieee80211(&self) -> &Ieee80211 {
        self.plaintext_ieee80211.as_ref().unwrap_or(&self.frame.ieee80211)
    }

    /// Returns the decrypted IEEE 802.11 frame as bytes if available.
    /// Otherwise, returns the original IEEE 80211 frame as bytes.
    pub fn get_ieee80211_bytes(&self) -> Bytes {
        if let Some(ieee80211) = self.plaintext_ieee80211.as_ref() {
            ieee80211.encode_to_vec().unwrap().into()
        } else {
            self.frame.data.clone().into()
        }
    }
}

#[allow(dead_code)]
#[derive(Debug)]
pub enum HwsimCmdEnum {
    Unspec,
    Register,
    Frame(Box<Frame>),
    TxInfoFrame,
    NewRadio,
    DelRadio,
    GetRadio,
    AddMacAddr,
    DelMacAddr,
}

#[derive(Clone)]
struct Station {
    client_id: u32,
    // Ieee80211 source address
    addr: MacAddress,
    // Hwsim virtual address from HWSIM_ATTR_ADDR_TRANSMITTER
    // Used to create the HwsimMsg to stations.
    hwsim_addr: MacAddress,
    // Caches the frequency (HWSIM_ATTR_FREQ) from the latest HwsimMsg request.
    // This value is used to populate the HWSIM_ATTR_FREQ field in HwsimMsg response.
    freq: Arc<AtomicU32>,
}

impl Station {
    fn new(client_id: u32, addr: MacAddress, hwsim_addr: MacAddress) -> Self {
        Self { client_id, addr, hwsim_addr, freq: Arc::new(AtomicU32::new(0)) }
    }

    fn update_freq(&self, freq: u32) {
        self.freq.store(freq, Ordering::Relaxed);
    }
}

#[derive(Clone)]
pub struct Client {
    pub enabled: Arc<AtomicBool>,
    pub tx_count: Arc<AtomicU32>,
    pub rx_count: Arc<AtomicU32>,
}

impl Client {
    fn new() -> Self {
        Self {
            enabled: Arc::new(AtomicBool::new(true)),
            tx_count: Arc::new(AtomicU32::new(0)),
            rx_count: Arc::new(AtomicU32::new(0)),
        }
    }
}

pub struct Medium {
    callback: HwsimCmdCallback,
    // Ieee80211 source address
    stations: RwLock<HashMap<MacAddress, Arc<Station>>>,
    clients: RwLock<HashMap<u32, Client>>,
    // Simulate the re-transmission of frames sent to hostapd
    ap_simulation: bool,
    hostapd: Arc<Hostapd>,
}

type HwsimCmdCallback = fn(u32, &Bytes);
impl Medium {
    pub fn new(callback: HwsimCmdCallback, hostapd: Arc<Hostapd>) -> Medium {
        Self {
            callback,
            stations: RwLock::new(HashMap::new()),
            clients: RwLock::new(HashMap::new()),
            ap_simulation: true,
            hostapd,
        }
    }

    pub fn add(&self, client_id: u32) {
        let _ = self.clients.write().unwrap().entry(client_id).or_insert_with(|| {
            info!("Insert client {}", client_id);
            Client::new()
        });
    }

    pub fn remove(&self, client_id: u32) {
        self.stations.write().unwrap().retain(|_, s| s.client_id != client_id);
        self.clients.write().unwrap().remove(&client_id);
    }

    pub fn reset(&self, client_id: u32) {
        if let Some(client) = self.clients.read().unwrap().get(&client_id) {
            client.enabled.store(true, Ordering::Relaxed);
            client.tx_count.store(0, Ordering::Relaxed);
            client.rx_count.store(0, Ordering::Relaxed);
        }
    }

    pub fn get(&self, client_id: u32) -> Option<Client> {
        self.clients.read().unwrap().get(&client_id).map(|c| c.to_owned())
    }

    fn contains_client(&self, client_id: u32) -> bool {
        self.clients.read().unwrap().contains_key(&client_id)
    }

    fn stations(&self) -> impl Iterator<Item = Arc<Station>> {
        self.stations.read().unwrap().clone().into_values()
    }

    fn contains_station(&self, addr: &MacAddress) -> bool {
        self.stations.read().unwrap().contains_key(addr)
    }

    fn get_station(&self, addr: &MacAddress) -> anyhow::Result<Arc<Station>> {
        self.stations.read().unwrap().get(addr).context("get station").cloned()
    }

    fn upsert_station(&self, client_id: u32, frame: &Frame) -> anyhow::Result<()> {
        let src_addr = frame.ieee80211.get_source();
        let hwsim_addr = frame.transmitter.context("transmitter")?;
        self.stations.write().unwrap().entry(src_addr).or_insert_with(|| {
            info!(
                "Insert station with client id {}, hwsimaddr: {}, \
                Ieee80211 addr: {}",
                client_id, hwsim_addr, src_addr
            );
            Arc::new(Station::new(client_id, src_addr, hwsim_addr))
        });
        if !self.contains_client(client_id) {
            warn!("Client {} is missing", client_id);
            self.add(client_id);
        }
        Ok(())
    }

    pub fn ack_frame(&self, client_id: u32, frame: &Frame) {
        // Send Ack frame back to source
        self.ack_frame_internal(client_id, frame).unwrap_or_else(move |e| {
            // TODO: add this error to the netsim_session_stats
            warn!("error ack frame {e}");
        });
    }

    fn ack_frame_internal(&self, client_id: u32, frame: &Frame) -> anyhow::Result<()> {
        self.send_tx_info_frame(frame)?;
        self.incr_tx(client_id)?;
        Ok(())
    }

    /// Process commands from the kernel's mac80211_hwsim subsystem.
    ///
    /// This is the processing that will be implemented:
    ///
    /// * The source MacAddress in 802.11 frames is re-mapped to a globally
    ///   unique MacAddress because resumed Emulator AVDs appear with the
    ///   same address.
    ///
    /// * 802.11 frames sent between stations
    ///
    /// * 802.11 multicast frames are re-broadcast to connected stations.
    pub fn get_processor(&self, client_id: u32, packet: &Bytes) -> Option<Processor> {
        let frame = self
            .validate(client_id, packet)
            .map_err(|e| warn!("error validate for client {client_id}: {e}"))
            .ok()?;

        // Creates Stations on the fly when there is no config file.
        // WiFi Direct will use a randomized mac address for probing
        // new networks. This block associates the new mac with the station.
        self.upsert_station(client_id, &frame)
            .map_err(|e| warn!("error upsert station for client {client_id}: {e}"))
            .ok()?;

        let plaintext_ieee80211 = self.hostapd.try_decrypt(&frame.ieee80211);

        let mut processor = Processor {
            hostapd: false,
            network: false,
            wmedium: false,
            frame,
            plaintext_ieee80211,
        };

        let dest_addr = processor.frame.ieee80211.get_destination();

        processor.frame.attrs.freq.map(|freq| {
            self.get_station(&processor.frame.ieee80211.get_source())
                .map(|sta| sta.update_freq(freq))
                .map_err(|e| {
                    warn!("Failed to get station for client {client_id} to update freq: {e}")
                })
        });

        if self.contains_station(&dest_addr) {
            processor.wmedium = true;
            return Some(processor);
        }
        if dest_addr.is_multicast() {
            processor.wmedium = true;
        }

        let ieee80211: &Ieee80211 = processor.get_ieee80211();
        // If the BSSID is unicast and does not match the hostapd's BSSID, the packet is not handled by hostapd. Skip further checks.
        if let Some(bssid) = ieee80211.get_bssid() {
            if !bssid.is_multicast() && bssid != self.hostapd.get_bssid() {
                return Some(processor);
            }
        }
        // Data frames
        if ieee80211.is_data() {
            // EAPoL is used in Wi-Fi 4-way handshake.
            let is_eapol = ieee80211.is_eapol().unwrap_or_else(|e| {
                debug!("Failed to get ether type for is_eapol(): {}", e);
                false
            });
            if is_eapol {
                processor.hostapd = true;
            } else if ieee80211.is_to_ap() {
                // Don't forward Null Data frames to slirp because they are used to maintain an active connection and carry no user data.
                if ieee80211.stype() != DataSubType::Nodata.into() {
                    processor.network = true;
                }
            }
        } else {
            // Mgmt or Ctrl frames.
            // TODO: Refactor this check after verifying all packets sent to hostapd are of ToAP type.
            let addr1 = ieee80211.get_addr1();
            if addr1.is_multicast() || addr1.is_broadcast() || addr1 == self.hostapd.get_bssid() {
                processor.hostapd = true;
            }
        }
        Some(processor)
    }

    fn validate(&self, client_id: u32, packet: &Bytes) -> anyhow::Result<Frame> {
        let hwsim_msg = HwsimMsg::decode_full(packet)?;

        // The virtio handler only accepts HWSIM_CMD_FRAME, HWSIM_CMD_TX_INFO_FRAME and HWSIM_CMD_REPORT_PMSR
        // in https://source.corp.google.com/h/kernel/pub/scm/linux/kernel/git/torvalds/linux/+/master:drivers/net/wireless/virtual/mac80211_hwsim.c
        match hwsim_msg.hwsim_hdr.hwsim_cmd {
            HwsimCmd::Frame => {
                let frame = Frame::parse(&hwsim_msg)?;
                // Incoming frame must contain transmitter, flag, cookie, and tx_info fields.
                if frame.transmitter.is_none()
                    || frame.flags.is_none()
                    || frame.cookie.is_none()
                    || frame.tx_info.is_none()
                {
                    return Err(anyhow!("Missing Hwsim attributes for incoming packet"));
                }
                // Use as receiver for outgoing HwsimMsg.
                let hwsim_addr = frame.transmitter.context("transmitter")?;
                let flags = frame.flags.context("flags")?;
                let cookie = frame.cookie.context("cookie")?;
                debug!(
                    "Frame chip {}, transmitter {}, flags {}, cookie {}, ieee80211 {}",
                    client_id, hwsim_addr, flags, cookie, frame.ieee80211
                );
                Ok(frame)
            }
            _ => Err(anyhow!("Another command found {:?}", hwsim_msg)),
        }
    }

    /// Handle Wi-Fi Ieee802.3 frame from network.
    /// Convert to HwsimMsg and send to clients.
    pub fn process_ieee8023_response(&self, packet: &Bytes) {
        let result = Ieee80211::from_ieee8023(packet, self.hostapd.get_bssid())
            .and_then(|ieee80211| self.handle_ieee80211_response(ieee80211));

        if let Err(e) = result {
            warn!("{}", e);
        }
    }

    /// Handle Wi-Fi Ieee802.11 frame from network.
    /// Convert to HwsimMsg and send to clients.
    pub fn process_ieee80211_response(&self, packet: &Bytes) {
        let result = Ieee80211::decode_full(packet)
            .context("Ieee80211")
            .and_then(|ieee80211| self.handle_ieee80211_response(ieee80211));

        if let Err(e) = result {
            warn!("{}", e);
        }
    }

    /// Determine the client id based on destination and send to client.
    fn handle_ieee80211_response(&self, mut ieee80211: Ieee80211) -> anyhow::Result<()> {
        if let Some(encrypted_ieee80211) = self.hostapd.try_encrypt(&ieee80211) {
            ieee80211 = encrypted_ieee80211;
        }
        let dest_addr = ieee80211.get_destination();
        if let Ok(destination) = self.get_station(&dest_addr) {
            self.send_ieee80211_response(&ieee80211, &destination)?;
        } else if dest_addr.is_multicast() {
            for destination in self.stations() {
                self.send_ieee80211_response(&ieee80211, &destination)?;
            }
        } else {
            warn!("Send frame response to unknown destination: {}", dest_addr);
        }
        Ok(())
    }

    fn send_ieee80211_response(
        &self,
        ieee80211: &Ieee80211,
        destination: &Station,
    ) -> anyhow::Result<()> {
        let hwsim_msg = self.create_hwsim_msg_from_ieee80211(ieee80211, destination)?;
        (self.callback)(destination.client_id, &hwsim_msg.encode_to_vec()?.into());
        self.incr_rx(destination.client_id)?;
        Ok(())
    }

    fn create_hwsim_msg_from_ieee80211(
        &self,
        ieee80211: &Ieee80211,
        destination: &Station,
    ) -> anyhow::Result<HwsimMsg> {
        let attributes = self.create_hwsim_msg_attr(ieee80211, destination)?;
        let hwsim_hdr = HwsimMsgHdr { hwsim_cmd: HwsimCmd::Frame, hwsim_version: 0, reserved: 0 };
        let nlmsg_len = (NL_MSG_HDR_LEN + hwsim_hdr.encoded_len() + attributes.len()) as u32;
        let nl_hdr = NlMsgHdr {
            nlmsg_len,
            nlmsg_type: NLMSG_MIN_TYPE,
            nlmsg_flags: NL_AUTO_SEQ,
            nlmsg_seq: NL_AUTO_PORT,
            nlmsg_pid: 0,
        };
        Ok(HwsimMsg { nl_hdr, hwsim_hdr, attributes })
    }

    fn create_hwsim_msg_attr(
        &self,
        ieee80211: &Ieee80211,
        destination: &Station,
    ) -> anyhow::Result<Vec<u8>> {
        let mut builder = HwsimAttrSet::builder();
        // Attributes required by mac80211_hwsim.
        builder.receiver(&destination.hwsim_addr.to_vec());
        let frame_bytes = ieee80211.encode_to_vec()?;
        builder.frame(&frame_bytes);
        builder.rx_rate(RX_RATE);
        builder.signal(SIGNAL);
        builder.freq(destination.freq.load(Ordering::Relaxed));
        Ok(builder.build()?.attributes)
    }

    pub fn set_enabled(&self, client_id: u32, enabled: bool) {
        if let Some(client) = self.clients.read().unwrap().get(&client_id) {
            client.enabled.store(enabled, Ordering::Relaxed);
        }
    }

    fn enabled(&self, client_id: u32) -> anyhow::Result<bool> {
        Ok(self
            .clients
            .read()
            .unwrap()
            .get(&client_id)
            .context(format!("client {client_id} is missing"))?
            .enabled
            .load(Ordering::Relaxed))
    }

    /// Create tx info frame to station to ack HwsimMsg.
    fn send_tx_info_frame(&self, frame: &Frame) -> anyhow::Result<()> {
        let client_id = self.get_station(&frame.ieee80211.get_source())?.client_id;
        let hwsim_msg_tx_info = build_tx_info(&frame.hwsim_msg).unwrap().encode_to_vec()?;
        (self.callback)(client_id, &hwsim_msg_tx_info.into());
        Ok(())
    }

    fn incr_tx(&self, client_id: u32) -> anyhow::Result<()> {
        self.clients
            .read()
            .unwrap()
            .get(&client_id)
            .context("incr_tx")?
            .tx_count
            .fetch_add(1, Ordering::Relaxed);
        Ok(())
    }

    fn incr_rx(&self, client_id: u32) -> anyhow::Result<()> {
        self.clients
            .read()
            .unwrap()
            .get(&client_id)
            .context("incr_rx")?
            .rx_count
            .fetch_add(1, Ordering::Relaxed);
        Ok(())
    }

    // Send an 802.11 frame from a station to a station after wrapping in HwsimMsg.
    // The HwsimMsg is processed by mac80211_hwsim framework in the guest OS.
    //
    // Simulates transmission through hostapd.
    fn send_from_sta_frame(
        &self,
        frame: &Frame,
        ieee80211: &Ieee80211,
        source: &Station,
        destination: &Station,
    ) -> anyhow::Result<()> {
        if self.enabled(source.client_id)? && self.enabled(destination.client_id)? {
            if let Some(packet) = self.create_hwsim_msg(frame, ieee80211, &destination.hwsim_addr) {
                self.incr_rx(destination.client_id)?;
                (self.callback)(destination.client_id, &packet.encode_to_vec()?.into());
                log_hwsim_msg(frame, source.client_id, destination.client_id);
            }
        }
        Ok(())
    }

    // Broadcast an 802.11 frame to all stations.
    /// TODO: Compare with the implementations in mac80211_hwsim.c and wmediumd.c.
    fn broadcast_from_sta_frame(
        &self,
        frame: &Frame,
        ieee80211: &Ieee80211,
        source: &Station,
    ) -> anyhow::Result<()> {
        for destination in self.stations() {
            if source.addr != destination.addr {
                self.send_from_sta_frame(frame, ieee80211, source, &destination)?;
            }
        }
        Ok(())
    }
    /// Queues the frame for sending to medium.
    ///
    /// The `frame` contains an `ieee80211` field, but it might be encrypted. This function uses the provided `ieee80211` parameter directly, as it's expected to be decrypted if necessary.
    pub fn queue_frame(&self, frame: Frame, ieee80211: Ieee80211) {
        self.queue_frame_internal(frame, ieee80211).unwrap_or_else(move |e| {
            // TODO: add this error to the netsim_session_stats
            warn!("queue frame error {e}");
        });
    }

    fn queue_frame_internal(&self, frame: Frame, ieee80211: Ieee80211) -> anyhow::Result<()> {
        let source = self.get_station(&ieee80211.get_source())?;
        let dest_addr = ieee80211.get_destination();
        if self.contains_station(&dest_addr) {
            debug!("Frame deliver from {} to {}", source.addr, dest_addr);
            let destination = self.get_station(&dest_addr)?;
            self.send_from_sta_frame(&frame, &ieee80211, &source, &destination)?;
            return Ok(());
        } else if dest_addr.is_multicast() {
            debug!("Frame multicast {}", ieee80211);
            self.broadcast_from_sta_frame(&frame, &ieee80211, &source)?;
            return Ok(());
        }

        Err(anyhow!("Dropped packet {}", ieee80211))
    }

    // Simulate transmission through hostapd by rewriting frames with 802.11 ToDS
    // and hostapd_bssid to frames with FromDS set.
    fn create_hwsim_attr(
        &self,
        frame: &Frame,
        ieee80211: &Ieee80211,
        dest_hwsim_addr: &MacAddress,
    ) -> anyhow::Result<Vec<u8>> {
        // Encrypt Ieee80211 if needed
        let attrs = &frame.attrs;
        let mut ieee80211_response = match self.ap_simulation
            && ieee80211.is_to_ap()
            && ieee80211.get_bssid() == Some(self.hostapd.get_bssid())
        {
            true => ieee80211.into_from_ap()?.try_into()?,
            false => ieee80211.clone(),
        };
        if let Some(encrypted_ieee80211) = self.hostapd.try_encrypt(&ieee80211_response) {
            ieee80211_response = encrypted_ieee80211;
        }
        let frame = ieee80211_response.encode_to_vec()?;

        let mut builder = HwsimAttrSet::builder();

        // Attributes required by mac80211_hwsim.
        builder.receiver(&dest_hwsim_addr.to_vec());
        builder.frame(&frame);
        // Incoming HwsimMsg don't have rx_rate and signal.
        builder.rx_rate(attrs.rx_rate_idx.unwrap_or(RX_RATE));
        builder.signal(attrs.signal.unwrap_or(SIGNAL));

        attrs.flags.map(|v| builder.flags(v));
        attrs.freq.map(|v| builder.freq(v));
        attrs.tx_info.as_ref().map(|v| builder.tx_info(v));
        attrs.tx_info_flags.as_ref().map(|v| builder.tx_info_flags(v));

        Ok(builder.build()?.attributes)
    }

    // Simulates transmission through hostapd.
    fn create_hwsim_msg(
        &self,
        frame: &Frame,
        ieee80211: &Ieee80211,
        dest_hwsim_addr: &MacAddress,
    ) -> Option<HwsimMsg> {
        let hwsim_msg = &frame.hwsim_msg;
        assert_eq!(hwsim_msg.hwsim_hdr.hwsim_cmd, HwsimCmd::Frame);
        let attributes_result = self.create_hwsim_attr(frame, ieee80211, dest_hwsim_addr);
        let attributes = match attributes_result {
            Ok(attributes) => attributes,
            Err(e) => {
                warn!("Failed to create from_ap attributes. E: {}", e);
                return None;
            }
        };

        let nlmsg_len = hwsim_msg.nl_hdr.nlmsg_len + attributes.len() as u32
            - hwsim_msg.attributes.len() as u32;
        let new_hwsim_msg = HwsimMsg {
            nl_hdr: NlMsgHdr {
                nlmsg_len,
                nlmsg_type: NLMSG_MIN_TYPE,
                nlmsg_flags: hwsim_msg.nl_hdr.nlmsg_flags,
                nlmsg_seq: 0,
                nlmsg_pid: 0,
            },
            hwsim_hdr: hwsim_msg.hwsim_hdr.clone(),
            attributes,
        };
        Some(new_hwsim_msg)
    }
}

fn log_hwsim_msg(frame: &Frame, client_id: u32, dest_client_id: u32) {
    debug!(
        "Sent hwsim_msg from client {} to {}. flags {:?}, ieee80211 {}",
        client_id, dest_client_id, frame.flags, frame.ieee80211,
    );
}

/// Build TxInfoFrame HwsimMsg from CmdFrame HwsimMsg.
///
/// Reference to ackLocalFrame() in external/qemu/android-qemu2-glue/emulation/VirtioWifiForwarder.cpp
fn build_tx_info(hwsim_msg: &HwsimMsg) -> anyhow::Result<HwsimMsg> {
    let attrs = HwsimAttrSet::parse(&hwsim_msg.attributes).context("HwsimAttrSet").unwrap();

    let hwsim_hdr = &hwsim_msg.hwsim_hdr;
    let nl_hdr = &hwsim_msg.nl_hdr;
    let mut new_attr_builder = HwsimAttrSet::builder();
    const HWSIM_TX_STAT_ACK: u32 = 1 << 2;

    new_attr_builder
        .transmitter(&attrs.transmitter.context("transmitter")?.into())
        .flags(attrs.flags.context("flags")? | HWSIM_TX_STAT_ACK)
        .cookie(attrs.cookie.context("cookie")?)
        .signal(attrs.signal.unwrap_or(SIGNAL))
        .tx_info(attrs.tx_info.context("tx_info")?.as_slice());

    let new_attr = new_attr_builder.build().unwrap();
    let nlmsg_len =
        nl_hdr.nlmsg_len + new_attr.attributes.len() as u32 - attrs.attributes.len() as u32;
    let new_hwsim_msg = HwsimMsg {
        attributes: new_attr.attributes,
        hwsim_hdr: HwsimMsgHdr {
            hwsim_cmd: HwsimCmd::TxInfoFrame,
            hwsim_version: 0,
            reserved: hwsim_hdr.reserved,
        },
        nl_hdr: NlMsgHdr {
            nlmsg_len,
            nlmsg_type: NLMSG_MIN_TYPE,
            nlmsg_flags: nl_hdr.nlmsg_flags,
            nlmsg_seq: 0,
            nlmsg_pid: 0,
        },
    };
    Ok(new_hwsim_msg)
}

// It's used by radiotap.rs for packet capture.
pub fn parse_hwsim_cmd(packet: &[u8]) -> anyhow::Result<HwsimCmdEnum> {
    let hwsim_msg = HwsimMsg::decode_full(packet)?;
    match hwsim_msg.hwsim_hdr.hwsim_cmd {
        HwsimCmd::Frame => {
            let frame = Frame::parse(&hwsim_msg)?;
            Ok(HwsimCmdEnum::Frame(Box::new(frame)))
        }
        HwsimCmd::TxInfoFrame => Ok(HwsimCmdEnum::TxInfoFrame),
        _ => Err(anyhow!("Unknown HwsimMsg cmd={:?}", hwsim_msg.hwsim_hdr.hwsim_cmd)),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::wifi::hostapd;
    use netsim_packets::ieee80211::{parse_mac_address, FrameType, Ieee80211, Ieee80211ToAp};

    #[test]
    fn test_get_plaintext_ieee80211() {
        // Test Data (802.11 frame with LLC/SNAP)
        let bssid = parse_mac_address("0:0:0:0:0:0").unwrap();
        let source = parse_mac_address("1:1:1:1:1:1").unwrap();
        let destination = parse_mac_address("2:2:2:2:2:2").unwrap();
        let ieee80211: Ieee80211 = Ieee80211ToAp {
            duration_id: 0,
            ftype: FrameType::Data,
            more_data: 0,
            more_frags: 0,
            order: 0,
            pm: 0,
            protected: 0,
            retry: 0,
            stype: 0,
            version: 0,
            bssid,
            source,
            destination,
            seq_ctrl: 0,
            payload: Vec::new(),
        }
        .try_into()
        .unwrap();

        let packet: Vec<u8> = include!("test_packets/hwsim_cmd_frame_mdns.csv");
        let hwsim_msg = HwsimMsg::decode_full(&packet).unwrap();
        let frame1 = Frame::parse(&hwsim_msg).unwrap();
        let frame2 = Frame::parse(&hwsim_msg).unwrap();

        // Case 1: plaintext_ieee80211 is None
        let processor = Processor {
            hostapd: false,
            network: false,
            wmedium: false,
            frame: frame1,
            plaintext_ieee80211: None,
        };
        assert_eq!(processor.get_ieee80211(), &processor.frame.ieee80211);
        assert_eq!(processor.get_ieee80211_bytes(), Bytes::from(processor.frame.data.clone()));

        // Case 2: plaintext_ieee80211 has a value
        let processor = Processor {
            hostapd: false,
            network: false,
            wmedium: false,
            frame: frame2,
            plaintext_ieee80211: Some(ieee80211),
        };
        assert_eq!(processor.get_ieee80211(), processor.plaintext_ieee80211.as_ref().unwrap());
        assert_eq!(
            processor.get_ieee80211_bytes(),
            Bytes::from(processor.plaintext_ieee80211.as_ref().unwrap().encode_to_vec().unwrap())
        );
    }

    #[test]
    fn test_remove() {
        let test_client_id: u32 = 1234;
        let other_client_id: u32 = 5678;
        let addr: MacAddress = parse_mac_address("00:0b:85:71:20:00").unwrap();
        let other_addr: MacAddress = parse_mac_address("00:0b:85:71:20:01").unwrap();
        let hwsim_addr: MacAddress = parse_mac_address("00:0b:85:71:20:ce").unwrap();
        let other_hwsim_addr: MacAddress = parse_mac_address("00:0b:85:71:20:cf").unwrap();

        let hostapd_options = netsim_proto::config::HostapdOptions::new();
        let (tx, _rx) = std::sync::mpsc::channel();
        let hostapd = Arc::new(hostapd::hostapd_run(hostapd_options, tx).unwrap());

        // Create a test Medium object
        let callback: HwsimCmdCallback = |_, _| {};
        let medium = Medium {
            callback,
            stations: RwLock::new(HashMap::from([
                (
                    addr,
                    Arc::new(Station {
                        client_id: test_client_id,
                        addr,
                        hwsim_addr,
                        freq: Arc::new(AtomicU32::new(0)),
                    }),
                ),
                (
                    other_addr,
                    Arc::new(Station {
                        client_id: other_client_id,
                        addr: other_addr,
                        hwsim_addr: other_hwsim_addr,
                        freq: Arc::new(AtomicU32::new(0)),
                    }),
                ),
            ])),
            clients: RwLock::new(HashMap::from([
                (test_client_id, Client::new()),
                (other_client_id, Client::new()),
            ])),
            ap_simulation: true,
            hostapd,
        };

        medium.remove(test_client_id);

        assert!(!medium.contains_station(&addr));
        assert!(medium.contains_station(&other_addr));
        assert!(!medium.contains_client(test_client_id));
        assert!(medium.contains_client(other_client_id));
    }

    #[test]
    fn test_netlink_attr() {
        let packet: Vec<u8> = include!("test_packets/hwsim_cmd_frame.csv");
        assert!(parse_hwsim_cmd(&packet).is_ok());

        let tx_info_packet: Vec<u8> = include!("test_packets/hwsim_cmd_tx_info.csv");
        assert!(parse_hwsim_cmd(&tx_info_packet).is_ok());
    }

    #[test]
    fn test_netlink_attr_response_packet() {
        // Response packet may not contain transmitter, flags, tx_info, or cookie fields.
        let response_packet: Vec<u8> =
            include!("test_packets/hwsim_cmd_frame_response_no_transmitter_flags_tx_info.csv");
        assert!(parse_hwsim_cmd(&response_packet).is_ok());

        let response_packet2: Vec<u8> =
            include!("test_packets/hwsim_cmd_frame_response_no_cookie.csv");
        assert!(parse_hwsim_cmd(&response_packet2).is_ok());
    }

    #[test]
    fn test_is_mdns_packet() {
        let packet: Vec<u8> = include!("test_packets/hwsim_cmd_frame_mdns.csv");
        let hwsim_msg = HwsimMsg::decode_full(&packet).unwrap();
        let mdns_frame = Frame::parse(&hwsim_msg).unwrap();
        assert!(!mdns_frame.ieee80211.get_source().is_multicast());
        assert!(mdns_frame.ieee80211.get_destination().is_multicast());
    }

    #[test]
    fn test_build_tx_info_reconstruct() {
        let packet: Vec<u8> = include!("test_packets/hwsim_cmd_tx_info.csv");
        let hwsim_msg = HwsimMsg::decode_full(&packet).unwrap();
        assert_eq!(hwsim_msg.hwsim_hdr().hwsim_cmd, HwsimCmd::TxInfoFrame);

        let new_hwsim_msg = build_tx_info(&hwsim_msg).unwrap();
        assert_eq!(hwsim_msg, new_hwsim_msg);
    }

    #[test]
    fn test_build_tx_info() {
        let packet: Vec<u8> = include!("test_packets/hwsim_cmd_frame.csv");
        let hwsim_msg = HwsimMsg::decode_full(&packet).unwrap();
        let hwsim_msg_tx_info = build_tx_info(&hwsim_msg).unwrap();
        assert_eq!(hwsim_msg_tx_info.hwsim_hdr().hwsim_cmd, HwsimCmd::TxInfoFrame);
    }

    fn build_tx_info_and_compare(frame_bytes: &Bytes, tx_info_expected_bytes: &Bytes) {
        let frame = HwsimMsg::decode_full(frame_bytes).unwrap();
        let tx_info = build_tx_info(&frame).unwrap();

        let tx_info_expected = HwsimMsg::decode_full(tx_info_expected_bytes).unwrap();

        assert_eq!(tx_info.hwsim_hdr(), tx_info_expected.hwsim_hdr());
        assert_eq!(tx_info.nl_hdr(), tx_info_expected.nl_hdr());

        let attrs = HwsimAttrSet::parse(tx_info.attributes()).context("HwsimAttrSet").unwrap();
        let attrs_expected =
            HwsimAttrSet::parse(tx_info_expected.attributes()).context("HwsimAttrSet").unwrap();

        // NOTE: TX info is different and the counts are all zeros in the TX info packet generated by WifiService.
        // TODO: Confirm if the behavior is intended in WifiService.
        assert_eq!(attrs.transmitter, attrs_expected.transmitter);
        assert_eq!(attrs.flags, attrs_expected.flags);
        assert_eq!(attrs.cookie, attrs_expected.cookie);
        assert_eq!(attrs.signal, attrs_expected.signal);
    }

    #[test]
    fn test_build_tx_info_and_compare() {
        let frame_bytes = Bytes::from(include!("test_packets/hwsim_cmd_frame_request.csv"));
        let tx_info_expected_bytes =
            Bytes::from(include!("test_packets/hwsim_cmd_tx_info_response.csv"));
        build_tx_info_and_compare(&frame_bytes, &tx_info_expected_bytes);
    }

    #[test]
    fn test_build_tx_info_and_compare_mdns() {
        let frame_bytes = Bytes::from(include!("test_packets/hwsim_cmd_frame_request_mdns.csv"));
        let tx_info_expected_bytes =
            Bytes::from(include!("test_packets/hwsim_cmd_tx_info_response_mdns.csv"));
        build_tx_info_and_compare(&frame_bytes, &tx_info_expected_bytes);
    }
}