Support manual bitrate mask control

Add support for setting cfg80211_bitrate_mask via set_bitrate_mask().
This enables users to manually specify legacy bitrates using the iw,
which influences the simulated transmission latency.

The packet latency logic has been updated to reflect real-world behavior
by making delay inversely proportional to the configured bitrate.
When a valid bitrate mask is applied, the delay is calculated as:

(datalen * 8 * 1000) / bitrate_kbps

If no valid bitrate is set, fallback to default delay is used.

This change improves fidelity of wireless emulation by making packet
timing sensitive to user configuration and network rate conditions.

Author: horseface1110

vwifi.c

@@ -1,6 +1,7 @@
 #include <linux/etherdevice.h>
 #include <linux/hashtable.h>
 #include <linux/hrtimer.h>
+#include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/random.h>
@@ -35,6 +36,12 @@ MODULE_DESCRIPTION("virtual cfg80211 driver");
 
 #define SCAN_TIMEOUT_MS 100 /*< millisecond */
 
+#define VWIFI_ALL_RATES_2GHZ 0x0FFF
+#define VWIFI_ALL_RATES_5GHZ 0x0FF0  // bit 4~11 set
+
+static const struct ieee80211_rate vwifi_supported_rates[];
+static const int vwifi_supported_rates_count = 12;
+
 /* Note: vwifi_cipher_suites is an array of int defining which cipher suites
  * are supported. A pointer to this array and the number of entries is passed
  * on to upper layers.
@@ -88,6 +95,7 @@ struct vwifi_vif {
     struct wireless_dev wdev;
     struct net_device *ndev;
     struct net_device_stats stats;
+    struct cfg80211_bitrate_mask bitrate_mask;
 
     size_t ssid_len;
     /* Currently connected BSS id */
@@ -206,6 +214,10 @@ static int station = 2;
 module_param(station, int, 0444);
 MODULE_PARM_DESC(station, "Number of virtual interfaces running in STA mode.");
 
+static int ap = 0;
+module_param(ap, int, 0444);
+MODULE_PARM_DESC(ap, "number of AP mode interfaces to create");
+
 /* Global context */
 static struct vwifi_context *vwifi = NULL;
 
@@ -548,6 +560,46 @@ static void inform_bss(struct vwifi_vif *vif)
     }
 }
 
+static int vwifi_set_bitrate_mask(struct wiphy *wiphy,
+                                  struct net_device *dev,
+                                  unsigned int link_id,
+                                  const u8 *peer,
+                                  const struct cfg80211_bitrate_mask *mask)
+{
+    struct vwifi_vif *vif = netdev_priv(dev);
+
+    if (!(dev->flags & IFF_UP) || !netif_running(dev)) {
+        return -ENETDOWN;
+    }
+
+    bool has_valid_rate = false;
+
+    for (int band = 0; band < NUM_NL80211_BANDS; band++) {
+        u32 user_mask = mask->control[band].legacy;
+        u32 basic_mask = 0;
+
+        if (band == NL80211_BAND_2GHZ)
+            basic_mask = VWIFI_ALL_RATES_2GHZ;
+        else if (band == NL80211_BAND_5GHZ)
+            basic_mask = VWIFI_ALL_RATES_5GHZ;
+        else
+            continue;
+
+        if (user_mask & basic_mask) {
+            has_valid_rate = true;
+            break;
+        }
+    }
+
+    if (!has_valid_rate)
+        return -EINVAL;
+
+    memcpy(&vif->bitrate_mask, mask, sizeof(*mask));
+    pr_info("vwifi: bitrate mask saved. legacy 2.4GHz = 0x%x\n",
+            mask->control[NL80211_BAND_2GHZ].legacy);
+    return 0;
+}
+
 /* Helper function that prepares a structure with self-defined BSS information
  * and "informs" the kernel about the "new" Independent BSS.
  */
@@ -871,6 +923,26 @@ static int __vwifi_ndo_start_xmit(struct vwifi_vif *vif,
                 eth_hdr->h_source);
     }
 
+    int bitrate_kbps = 0;
+    const struct cfg80211_bitrate_mask *mask = &vif->bitrate_mask;
+
+    for (int band = 0; band < NUM_NL80211_BANDS; band++) {
+        u32 mask_val = mask->control[band].legacy;
+        if (mask_val) {
+            for (int i = 0; i < vwifi_supported_rates_count; i++) {
+                if (mask_val & (1 << i)) {
+                    bitrate_kbps = vwifi_supported_rates[i].bitrate * 100;
+                    break;
+                }
+            }
+            break;
+        }
+    }
+
+    if (bitrate_kbps > 0) {
+        int delay_us = (datalen * 8 * 1000) / bitrate_kbps;
+        udelay(delay_us);
+    }
     /* Directly send to rx_queue, simulate the rx interrupt */
     vwifi_rx(dest_vif->ndev);
 
@@ -1425,15 +1497,40 @@ static int vwifi_get_station(struct wiphy *wiphy,
      * https://semfionetworks.com/blog/mcs-table-updated-with-80211ax-data-rates/
      * IEEE 802.11n : https://zh.wikipedia.org/zh-tw/IEEE_802.11n
      */
-    sinfo->rxrate.flags |= RATE_INFO_FLAGS_MCS;
-    sinfo->rxrate.mcs = 31;
-    sinfo->rxrate.bw = RATE_INFO_BW_20;
-    sinfo->rxrate.n_bonded_ch = 1;
-
-    sinfo->txrate.flags |= RATE_INFO_FLAGS_MCS;
-    sinfo->txrate.mcs = 31;
-    sinfo->txrate.bw = RATE_INFO_BW_20;
-    sinfo->txrate.n_bonded_ch = 1;
+    const struct cfg80211_bitrate_mask *mask = &vif->bitrate_mask;
+    bool legacy_rate_set = false;
+
+    for (int band = 0; band < NUM_NL80211_BANDS; band++) {
+        u32 mask_val = mask->control[band].legacy;
+        if (mask_val) {
+            int bitrate = 0;
+            for (int i = 0; i < 32; i++) {
+                if (mask_val & (1 << i)) {
+                    bitrate = vwifi_supported_rates[i].bitrate;
+                    break;
+                }
+            }
+
+            if (bitrate > 0) {
+                sinfo->txrate.legacy = bitrate;
+                sinfo->rxrate.legacy = bitrate;
+                legacy_rate_set = true;
+                break;
+            }
+        }
+    }
+
+    if (!legacy_rate_set) {
+        sinfo->txrate.flags |= RATE_INFO_FLAGS_MCS;
+        sinfo->txrate.mcs = 31;
+        sinfo->txrate.bw = RATE_INFO_BW_20;
+        sinfo->txrate.n_bonded_ch = 1;
+
+        sinfo->rxrate.flags |= RATE_INFO_FLAGS_MCS;
+        sinfo->rxrate.mcs = 31;
+        sinfo->rxrate.bw = RATE_INFO_BW_20;
+        sinfo->rxrate.n_bonded_ch = 1;
+    }
     return 0;
 }
 
@@ -2170,6 +2267,7 @@ static struct cfg80211_ops vwifi_cfg_ops = {
     .get_tx_power = vwifi_get_tx_power,
     .join_ibss = vwifi_join_ibss,
     .leave_ibss = vwifi_leave_ibss,
+    .set_bitrate_mask = vwifi_set_bitrate_mask,
 };
 
 /* Macro for defining 2GHZ channel array */
@@ -3340,6 +3438,14 @@ static int __init vwifi_init(void)
             goto interface_add;
     }
 
+    for (int i = 0; i < ap; ++i) {
+        struct wiphy *wiphy = vwifi_cfg80211_add();
+        if (!wiphy)
+            goto cfg80211_add;
+        if (!vwifi_interface_add(wiphy, i))
+            goto interface_add;
+    }
+
     nl_sk = netlink_kernel_create(&init_net, NETLINK_USERSOCK, &nl_config);
     if (!nl_sk) {
         pr_info("Error creating netlink socket\n");