esp_wifi_80211_tx does not allow sending on a specific channel (IDFGH-1785)

[seppestas]

Environment

• Development Kit: none
• Module or chip used: ESP32-S0WD
• IDF version (run git describe --tags to find it): v3.1.3
• Build System: Make
• Compiler version (run xtensa-esp32-elf-gcc --version to find it):
  // (crosstool-NG crosstool-ng-1.22.0-80-g6c4433a) 5.2.0
• Operating System: macOS
• Power Supply: external 5V / Battery

Problem Description

When using the esp_wifi_80211_tx function to send arbitrary WiFi frames with the WiFi interface configure in STA mode it is not possible to change the WiFi channel on which the frame is sent. I have tried to change the channel using the esp_wifi_set_config with interface set to WIFI_IF_AP and conf->sta.channel to different channels (tested with channel 6 and 11) and I have tried the esp_wifi_set_channel function, but neither work to change the channel on which esp_wifi_80211_tx sends the frames.

This issue is similar to #3210, but here @ingframin talks about sending "beacons", presumably management frames sent from a device set up as an access point. I'm trying to send non-QoS data frames (WDS Frames).

Expected Behavior

esp_wifi_80211_tx should be able to send frames on an arbitrary WiFi channel. Either by using the channel configured with esp_wifi_set_config or using a different, documented method.

Actual Behavior

esp_wifi_80211_tx always sends frames on channel 1.

Steps to repropduce

1. Configure the WiFi interface in STA mode
2. Set the STA interface channel to a channel different than 1 using esp_wifi_set_config
3. Create a non-QoS data frame
4. Send the data frame using the esp_wifi_80211_tx function

Code to reproduce this issue

uint8_t frame_buffer[200];

// First 4 bytes bytes of the frame. The rest of the frame might be Cisco proprietary and thus fall under NDA.
frame_buffer[0] = 0x08; // Version (B0-1): 00 (802.11), Type (B2-3): 10 (Data) Subtype: 0000 (Data) _ 0000100 = 0x08
frame_buffer[1] = 0x03; // To DS: 1 From DS: 1 More Fragments: 0 Retry: 0, Power Management: 0 More Data: 0, Protected Frame_buffer: 0, +HTC Order: 0

// 2-3 Duration - The Duration field must be set to all zeros.
frame_buffer[2] = 0x00;
frame_buffer[3] = 0x00;

// 4-9 Destination address - Multicast address (1)
// 16-21 BSSID - Unused (3), set to 0.0.0.0
// 24-29 Source address - Unused (4), set to 0.0.0.0

void app_main(void) {
    // ...
    // init stuf
    wifi_config_t ap_config = {
        .sta = {
            .channel = 6,
        }
    };

    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &ap_config));
    ESP_ERROR_CHECK(esp_wifi_start());
    ESP_ERROR_CHECK(esp_wifi_set_ps(WIFI_PS_NONE));

    // Note: actual size is calculated
    free80211_send(frame_buffer, sizeof(frame_buffer), false);
}

[Alvin1Zhang]

@seppestas Thanks for reporting this. We will take a look at. Thanks.

[seppestas]

It looks like my use-case is not that secret, or at least there seems to be some information publicly available here: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Mobility/WiFiLBS-DG/wifich6.html

Since my implementation is based on a partner level document I'm afraid I can't share my code publicly, but this should give some more indication about the use-case and the sort of frames I'm trying to send.

It also showcases the need of being able to send frames on different channels.

[negativekelvin]

Have you tried esp_wifi_set_channel in WiFi null mode with/without promiscuous rx enabled?

[seppestas]

Hi @negativekelvin

I now tried putting the WiFi interface in promiscuous mode, however when sending the frame I get the same result as when trying to send the frame in AP mode: esp_wifi_80211_tx returns an error code.

However, I found that putting the channel in promiscuous mode, setting the channel using and then switching to station mode seems to work. I will do some more testing and report any workaround I find if it works.

I also changed the way I use the esp_wifi_set_channel. before I used WIFI_SECOND_CHAN_BELOW, now I use WIFI_SECOND_CHAN_NONE. It might be this caused it to work.

[HarveyRong-Esp]

Hi @seppestas Has the problem been solved? If not, I will deal with it in time.

[Alvin1Zhang]

@seppestas Thanks for reporting. Would you please help share if any updates for the issue? Has your issue been resolved? Thanks.

[seppestas]

@Alvin1Zhang yes, I got this working eventually but had to use a workaround I believe. I’ll have a look to see if I can find back the code, but I’m afraid I now work for a different company.

I’ll close this issue for now.

[HarveyRong-Esp]

Hi @seppestas,
Like #4002 , what is your specific version number? E.g. commit ID
I used the latest v3.1 and did not reproduce the issue.

[liuzfesp]

This issue has been fixed, now you can call `esp_wifi_set_channel()' to configure the channel number.

• master - 36c726d
• v4.1 - 4d10eb2
• v3.3 - c9e7a04

The fix will be back-ported to v3.1/v3.2/v4.0 soon.