WIP: feat(6lowpan_ble): Simplified esp_netif driver

.github/workflows/netif_6lowpan_ble__build.yml

@@ -0,0 +1,28 @@
+name: "6lowpan_ble: build-tests"
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types: [opened, synchronize, reopened, labeled]
+
+jobs:
+  build_6lowpan_ble:
+    if: contains(github.event.pull_request.labels.*.name, 'component::6lowpan_ble') || github.event_name == 'push'
+    name: Build
+    strategy:
+      matrix:
+        idf_ver: ["latest", "release-v5.2", "release-v5.3"]
+
+    runs-on: ubuntu-22.04
+    container: espressif/idf:${{ matrix.idf_ver }}
+    steps:
+      - name: Checkout esp-protocols
+        uses: actions/checkout@v4
+      - name: Build with IDF-${{ matrix.idf_ver }}
+        shell: bash
+        run: |
+          . ${IDF_PATH}/export.sh
+          pip install idf-component-manager idf-build-apps --upgrade
+          python ci/build_apps.py components/netif_6lowpan_ble/examples/ -m components/netif_6lowpan_ble/examples/.build-test-rules.yml -c

.pre-commit-config.yaml

@@ -62,7 +62,7 @@ repos:
     hooks:
       - id: commit message scopes
         name: "commit message must be scoped with: mdns, modem, websocket, asio, mqtt_cxx, console, common, eppp, wifi_remote, tls_cxx"
-        entry: '\A(?!(feat|fix|ci|bump|test|docs)\((mdns|modem|common|console|websocket|asio|mqtt_cxx|examples|eppp|wifi_remote|tls_cxx)\)\:)'
+        entry: '\A(?!(feat|fix|ci|bump|test|docs)\((mdns|modem|common|console|websocket|asio|mqtt_cxx|examples|eppp|wifi_remote|tls_cxx|6lowpan_ble)\)\:)'
         language: pygrep
         args: [--multiline]
         stages: [commit-msg]

components/netif_6lowpan_ble/CMakeLists.txt

@@ -0,0 +1,22 @@
+idf_component_register(
+  SRCS
+    src/debug_print_utils.c
+    src/lowpan6_ble.c
+    src/lowpan6_ble_netif.c
+  INCLUDE_DIRS
+    include
+  PRIV_INCLUDE_DIRS
+    src
+  REQUIRES
+    bt
+    esp_netif
+)
+
+idf_component_get_property(lwip lwip COMPONENT_LIB)
+target_sources(
+    ${lwip}
+    PRIVATE
+    "$ENV{IDF_PATH}/components/lwip/lwip/src/netif/lowpan6.c"
+    "$ENV{IDF_PATH}/components/lwip/lwip/src/netif/lowpan6_ble.c"
+    "$ENV{IDF_PATH}/components/lwip/lwip/src/netif/lowpan6_common.c"
+)

components/netif_6lowpan_ble/LICENSE

@@ -0,0 +1,202 @@
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components/netif_6lowpan_ble/README.md

@@ -0,0 +1,93 @@
+# LoWPAN6 BLE Netif
+
+This component provides a custom ESP-NETIF layer for
+[RFC7668](https://datatracker.ietf.org/doc/html/rfc7668), allowing devices to
+transport IPv6 over Bluetooth Low Energy links.
+
+> :warning: This is an experimental library, developed for a pretty narrow
+> use-case. In particular, we just needed to connect to a peripheral using
+> LoWPAN6 for local communications so have not really tested this component as
+> a LoWPAN6 client. This component does not implement any routing capabilities:
+> this won't allow you to route packets from your personal area network to the
+> public internet, for example.
+
+## Usage
+
+This component only supports the NimBLE stack. It also requires support for
+L2CAP COC connections. This means your project's `sdkconfig` needs at least:
+* NimBLE as the Bluetooth stack (`CONFIG_BT_NIMBLE_ENABLED=y`)
+* `CONFIG_BT_NIMBLE_L2CAP_COC_MAX_NUM` set to a non-zero value
+
+There is some boilerplate required to set up this netif layer.
+```c
+// Initialize the lowpan6_ble module
+ESP_ERROR_CHECK(lowpan6_ble_init());
+
+// Configure a new esp_netif to use the lowpan6_ble netstack
+esp_netif_inherent_config_t base_cfg = ESP_NETIF_INHERENT_DEFAULT_LOWPAN6_BLE();
+esp_netif_config_t cfg = {
+    .base   = &base_cfg,
+    .driver = NULL,
+    .stack  = netstack_default_lowpan6_ble,
+};
+esp_netif_t* lowpan6_ble_netif = esp_netif_new(&cfg);
+
+// Create a lowpan6_ble driver instance. Note that each driver instance only
+// supports a single LoWPAN6 BLE channel.
+s_l6ble_handle = lowpan6_ble_create();
+if (s_l6ble_handle != NULL)
+{
+    // Finally, attach the driver instance to the netif you created above.
+    ESP_ERROR_CHECK(esp_netif_attach(lowpan6_ble_netif, s_l6ble_handle));
+}
+```
+
+All that is left to bring this netif up is to connect to a BLE peer that
+supports LoWPAN6 BLE. You can discover potential peers during, e.g., GAP discovery:
+
+```c
+// Note: no error handling included for brevity's sake
+static int on_gap_event(struct ble_gap_event* event, void* arg)
+{
+    switch (event->type)
+    {
+    case BLE_GAP_EVENT_DISC:
+        // Verify that the discovered peer supports LoWPAN6 BLE
+        if (lowpan6_ble_connectable(&event->disc))
+        {
+            // Cancel the current discovery process so we can connect
+            ble_gap_disc_cancel();
+
+            lowpan6_ble_connect(
+                s_l6ble_handle,       // handle to the driver we created above
+                &event->disc.addr,    // peer's BLE address
+                BLE_CONNECT_TIMEOUT,  // GAP connect timeout in ms
+                on_lowpan6_ble_event, // user-defined callback
+                NULL                  // user-defined callback argument
+            );
+        }
+    }
+}
+```
+
+Once that netif is up, you should be able to communicate to the BLE peer with
+generic network interfaces. For example, a UDP socket listening for messages
+from any address using LwIP's BSD sockets API:
+
+```c
+struct sockaddr_in6 server_addr;
+
+server_addr.sin6_family = AF_INET6;
+server_addr.sin6_addr   = in6addr_any;
+server_addr.sin6_port   = htons(PORT);
+
+int s = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+bind(s, (struct sockaddr*)&server_addr, sizeof(server_addr));
+int rc = recvfrom(s, buf, len, 0, client_addr, addr_len);
+```
+
+> :warning: If using LwIP's Raw API, be careful to separate message receipt
+> from further communications. Raw API callbacks are serviced by the NimBLE
+> event handler, which means that trying to send data in a callback can and
+> will deadlock as the event handler waits for a BLE unstalled event that will
+> never arrive.

components/netif_6lowpan_ble/examples/.build-test-rules.yml

@@ -0,0 +1,5 @@
+components/netif_6lowpan_ble/examples:
+  disable:
+    - if: IDF_TARGET in ["esp32p4", "esp32h2"]
+      temporary: false
+      reason: No BLE support