pw_bluetooth_sapphire: Support creating LE dynamic channels in l2cap

Support creating (outbound-only as of this commit) LE dynamic channels
in the L2CAP layer using the LE credit-based flow control.

Test: fx test l2cap_tests
Bug: 42178956
GitOrigin-RevId: 99cd566731a287e1e39f68332209969c89e21491
Change-Id: If319a741ce4382c20a69eba66e490e16606ba28f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/240713
Docs-Not-Needed: Jason Graffius <[email protected]>
Reviewed-by: Ben Lawson <[email protected]>
Presubmit-Verified: CQ Bot Account <[email protected]>
Lint: Lint 🤖 <[email protected]>
Commit-Queue: Jason Graffius <[email protected]>

pw_bluetooth_sapphire/BUILD.bazel

@@ -180,6 +180,7 @@ cc_library(
         "public/pw_bluetooth_sapphire/internal/host/l2cap/fragmenter.h",
         "public/pw_bluetooth_sapphire/internal/host/l2cap/frame_headers.h",
         "public/pw_bluetooth_sapphire/internal/host/l2cap/l2cap_defs.h",
+        "public/pw_bluetooth_sapphire/internal/host/l2cap/le_dynamic_channel.h",
         "public/pw_bluetooth_sapphire/internal/host/l2cap/le_signaling_channel.h",
         "public/pw_bluetooth_sapphire/internal/host/l2cap/logical_link.h",
         "public/pw_bluetooth_sapphire/internal/host/l2cap/low_energy_command_handler.h",

pw_bluetooth_sapphire/BUILD.gn

@@ -215,6 +215,7 @@ pw_source_set("_public") {
     "public/pw_bluetooth_sapphire/internal/host/l2cap/fragmenter.h",
     "public/pw_bluetooth_sapphire/internal/host/l2cap/frame_headers.h",
     "public/pw_bluetooth_sapphire/internal/host/l2cap/l2cap_defs.h",
+    "public/pw_bluetooth_sapphire/internal/host/l2cap/le_dynamic_channel.h",
     "public/pw_bluetooth_sapphire/internal/host/l2cap/le_signaling_channel.h",
     "public/pw_bluetooth_sapphire/internal/host/l2cap/logical_link.h",
     "public/pw_bluetooth_sapphire/internal/host/l2cap/low_energy_command_handler.h",

pw_bluetooth_sapphire/host/l2cap/BUILD.bazel

@@ -50,6 +50,7 @@ cc_library(
         "enhanced_retransmission_mode_tx_engine.cc",
         "fcs.cc",
         "fragmenter.cc",
+        "le_dynamic_channel.cc",
         "le_signaling_channel.cc",
         "logical_link.cc",
         "low_energy_command_handler.cc",
@@ -139,6 +140,7 @@ pw_cc_test(
         "fcs_test.cc",
         "fragmenter_test.cc",
         "frame_headers_test.cc",
+        "le_dynamic_channel_test.cc",
         "le_signaling_channel_test.cc",
         "logical_link_test.cc",
         "low_energy_command_handler_test.cc",

pw_bluetooth_sapphire/host/l2cap/BUILD.gn

@@ -53,6 +53,7 @@ pw_source_set("l2cap") {
     "$dir_public_l2cap/enhanced_retransmission_mode_tx_engine.h",
     "$dir_public_l2cap/fcs.h",
     "$dir_public_l2cap/fragmenter.h",
+    "$dir_public_l2cap/le_dynamic_channel.h",
     "$dir_public_l2cap/le_signaling_channel.h",
     "$dir_public_l2cap/logical_link.h",
     "$dir_public_l2cap/low_energy_command_handler.h",
@@ -85,6 +86,7 @@ pw_source_set("l2cap") {
     "enhanced_retransmission_mode_tx_engine.cc",
     "fcs.cc",
     "fragmenter.cc",
+    "le_dynamic_channel.cc",
     "le_signaling_channel.cc",
     "logical_link.cc",
     "low_energy_command_handler.cc",
@@ -191,6 +193,7 @@ pw_test("l2cap_tests") {
     "fcs_test.cc",
     "fragmenter_test.cc",
     "frame_headers_test.cc",
+    "le_dynamic_channel_test.cc",
     "le_signaling_channel_test.cc",
     "logical_link_test.cc",
     "low_energy_command_handler_test.cc",

pw_bluetooth_sapphire/host/l2cap/channel.cc

@@ -25,6 +25,8 @@
 #include "pw_bluetooth_sapphire/internal/host/common/weak_self.h"
 #include "pw_bluetooth_sapphire/internal/host/l2cap/basic_mode_rx_engine.h"
 #include "pw_bluetooth_sapphire/internal/host/l2cap/basic_mode_tx_engine.h"
+#include "pw_bluetooth_sapphire/internal/host/l2cap/credit_based_flow_control_rx_engine.h"
+#include "pw_bluetooth_sapphire/internal/host/l2cap/credit_based_flow_control_tx_engine.h"
 #include "pw_bluetooth_sapphire/internal/host/l2cap/enhanced_retransmission_mode_engines.h"
 #include "pw_bluetooth_sapphire/internal/host/l2cap/l2cap_defs.h"
 #include "pw_bluetooth_sapphire/internal/host/l2cap/logical_link.h"
@@ -135,22 +137,35 @@ ChannelImpl::ChannelImpl(pw::async::Dispatcher& dispatcher,
   BT_ASSERT_MSG(
       info_.mode == RetransmissionAndFlowControlMode::kBasic ||
           info_.mode ==
-              RetransmissionAndFlowControlMode::kEnhancedRetransmission,
+              RetransmissionAndFlowControlMode::kEnhancedRetransmission ||
+          info.mode == CreditBasedFlowControlMode::kLeCreditBasedFlowControl,
       "Channel constructed with unsupported mode: %s\n",
       AnyChannelModeToString(info_.mode).c_str());
 
+  auto connection_failure_cb = [link] {
+    if (link.is_alive()) {
+      // |link| is expected to ignore this call if it has been closed.
+      link->SignalError();
+    }
+  };
+
   if (info_.mode == RetransmissionAndFlowControlMode::kBasic) {
     rx_engine_ = std::make_unique<BasicModeRxEngine>();
     tx_engine_ =
         std::make_unique<BasicModeTxEngine>(id, max_tx_sdu_size(), *this);
+  } else if (std::holds_alternative<CreditBasedFlowControlMode>(info_.mode)) {
+    BT_ASSERT(info_.remote_initial_credits.has_value());
+    auto mode = std::get<CreditBasedFlowControlMode>(info_.mode);
+    rx_engine_ = std::make_unique<CreditBasedFlowControlRxEngine>(
+        std::move(connection_failure_cb));
+    tx_engine_ = std::make_unique<CreditBasedFlowControlTxEngine>(
+        id,
+        max_tx_sdu_size(),
+        *this,
+        mode,
+        info_.max_tx_pdu_payload_size,
+        *info_.remote_initial_credits);
   } else {
-    // Must capture |link| and not |link_| to avoid having to take |mutex_|.
-    auto connection_failure_cb = [link] {
-      if (link.is_alive()) {
-        // |link| is expected to ignore this call if it has been closed.
-        link->SignalError();
-      }
-    };
     std::tie(rx_engine_, tx_engine_) =
         MakeLinkedEnhancedRetransmissionModeEngines(
             id,