[wireguard] Keep allowed IPs in a shared flash table (#20087)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

esphome/components/wireguard/__init__.py

@@ -121,16 +121,19 @@ async def to_code(config):
         )
     )
 
+    # Shared flash table ended by an empty entry, so the component stores only a pointer.
+    entries = [
+        cg.StructInitializer(
+            AllowedIP,
+            ("ip", str(ip.network_address)),
+            ("netmask", str(ip.netmask)),
+        )
+        for ip in allowed_ips
+    ]
+    end = cg.StructInitializer(AllowedIP, ("ip", cg.nullptr), ("netmask", cg.nullptr))
     cg.add(
         var.set_allowed_ips(
-            [
-                cg.StructInitializer(
-                    AllowedIP,
-                    ("ip", str(ip.network_address)),
-                    ("netmask", str(ip.netmask)),
-                )
-                for ip in allowed_ips
-            ]
+            cg.shared_progmem_array("wireguard_allowed_ips", AllowedIP, [*entries, end])
         )
     )
 

esphome/components/wireguard/wireguard.cpp

@@ -154,8 +154,8 @@ void Wireguard::dump_config() {
       (this->preshared_key_ != nullptr ? preshared_key_masked : LOG_STR_LITERAL("NOT IN USE")));
   // clang-format on
   ESP_LOGCONFIG(TAG, "  Peer Allowed IPs:");
-  for (const AllowedIP &allowed_ip : this->allowed_ips_) {
-    ESP_LOGCONFIG(TAG, "    - %s/%s", allowed_ip.ip, allowed_ip.netmask);
+  for (const AllowedIP *it = this->allowed_ips_; it != nullptr && it->ip != nullptr; it++) {
+    ESP_LOGCONFIG(TAG, "    - %s/%s", it->ip, it->netmask);
   }
   ESP_LOGCONFIG(TAG, "  Peer Persistent Keepalive: %d%s", this->keepalive_,
                 (this->keepalive_ > 0 ? LOG_STR_LITERAL("s") : LOG_STR_LITERAL(" (DISABLED)")));
@@ -249,8 +249,8 @@ void Wireguard::start_connection_() {
 
   ESP_LOGD(TAG, "Configuring allowed IPs list");
   bool allowed_ips_ok = true;
-  for (const AllowedIP &ip : this->allowed_ips_) {
-    allowed_ips_ok &= (esp_wireguard_add_allowed_ip(&(this->wg_ctx_), ip.ip, ip.netmask) == ESP_OK);
+  for (const AllowedIP *it = this->allowed_ips_; it != nullptr && it->ip != nullptr; it++) {
+    allowed_ips_ok &= (esp_wireguard_add_allowed_ip(&(this->wg_ctx_), it->ip, it->netmask) == ESP_OK);
   }
 
   if (allowed_ips_ok) {

esphome/components/wireguard/wireguard.h

@@ -2,7 +2,6 @@
 #include "esphome/core/defines.h"
 #ifdef USE_WIREGUARD
 #include <ctime>
-#include <initializer_list>
 
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
@@ -58,9 +57,8 @@ class Wireguard final : public PollingComponent {
   void set_peer_public_key(const std::string &key) = delete;
   void set_preshared_key(const std::string &key) = delete;
 
-  void set_allowed_ips(std::initializer_list<AllowedIP> ips) { this->allowed_ips_ = ips; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_allowed_ips(std::initializer_list<std::tuple<std::string, std::string>> ips) = delete;
+  /// Table ended by an entry with a null ip; must outlive the component.
+  void set_allowed_ips(const AllowedIP *ips) { this->allowed_ips_ = ips; }
 
   void set_keepalive(const uint16_t seconds) { this->keepalive_ = seconds; }
   void set_reboot_timeout(const uint32_t seconds) { this->reboot_timeout_ = seconds; }
@@ -105,7 +103,7 @@ class Wireguard final : public PollingComponent {
   const char *peer_public_key_{nullptr};
   const char *preshared_key_{nullptr};
 
-  FixedVector<AllowedIP> allowed_ips_;
+  const AllowedIP *allowed_ips_{nullptr};
 
   uint16_t peer_port_;
   uint16_t keepalive_;

tests/component_tests/wireguard/config/allowed_ips.yaml

@@ -0,0 +1,26 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: test
+  password: password1
+
+time:
+  - platform: sntp
+    id: sntp_time
+
+wireguard:
+  time_id: sntp_time
+  address: 172.16.34.100
+  netmask: 255.255.255.0
+  private_key: wPBMxtNYH3mChicrbpsRpZIasIdPq3yZuthn23FbGG8=
+  peer_public_key: Hs2JfikvYU03/Kv3YoAs1hrUIPPTEkpsZKSPUljE9yc=
+  peer_endpoint: wg.server.example
+  peer_allowed_ips:
+    - 172.16.34.0/24
+    - 192.168.0.0/16

tests/component_tests/wireguard/test_allowed_ips.py

@@ -0,0 +1,21 @@
+"""Tests for the wireguard allowed IPs codegen."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+
+def test_allowed_ips_are_a_progmem_table(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Allowed IPs live in a flash table ended by an empty entry instead of a heap vector."""
+    main_cpp = generate_main(component_config_path("allowed_ips.yaml"))
+
+    table = main_cpp.split(
+        "wireguard::AllowedIP wireguard_allowed_ips[] PROGMEM = ", 1
+    )[1]
+    table = table.split(";", 1)[0]
+    assert '.ip = "172.16.34.0"' in table
+    assert '.netmask = "255.255.0.0"' in table
+    assert ".ip = nullptr" in table
+    assert "->set_allowed_ips(wireguard_allowed_ips);" in main_cpp