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[mdns] Guard LEAmDNS main loop calls against lwIP re-entrancy on ESP8266 (#18990)

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This commit is contained in:
J. Nick Koston
2026-09-07 10:46:21 +12:00
committed by Jesse Hills
parent c1aa41f276
commit 5d2ddc658c
2 changed files with 47 additions and 6 deletions
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esphome/components/mdns/__init__.py
+2
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@@ -192,6 +192,8 @@ async def to_code(config: ConfigType) -> None:
if CORE.using_arduino:
if CORE.is_esp8266:
cg.add_library("ESP8266mDNS", None)
# No MDNS global in the build; mdns_esp8266.cpp owns a guarded MDNSResponder
cg.add_build_flag("-DNO_GLOBAL_MDNS")
elif CORE.is_rp2:
cg.add_library("LEAmDNS", None)
esphome/components/mdns/mdns_esp8266.cpp
+45 -6
View File
@@ -13,8 +13,47 @@
namespace esphome::mdns {
// Main-loop calls into LEAmDNS that send (update() and close(); begin(), addService() and
// the scheduled restart never reach a send) can yield inside UdpContext::sendTimeout(); a
// packet arriving then re-enters LEAmDNS from lwIP on the same UdpContext and both sides
// free the same tx pbufs (#18760). Received packets stay queued during such a call and are
// processed from the main loop afterwards.
class GuardedMDNSResponder : public ::esp8266::MDNSImplementation::MDNSResponder {
public:
void update_guarded() { this->run_guarded_(&GuardedMDNSResponder::update); }
void close_guarded() { this->run_guarded_(&GuardedMDNSResponder::close); }
private:
void run_guarded_(bool (GuardedMDNSResponder::*fn)()) {
UdpContext *ctx = this->m_pUDPContext;
if (ctx == nullptr) {
(this->*fn)();
return;
}
// Set every time: a restart replaces the context together with its stock handler. Only
// begin() and the scheduled netif callback restart, never update() or close(), so the
// context cannot change underneath this call.
ctx->onRx([this]() {
if (!this->in_loop_call_) {
this->_callProcess();
}
});
this->in_loop_call_ = true;
(this->*fn)();
// close() releases the context; a yield in here queues further packets for this loop too
while (this->m_pUDPContext != nullptr && this->m_pUDPContext->next()) {
this->_parseMessage();
}
this->in_loop_call_ = false;
}
volatile bool in_loop_call_{false};
};
static GuardedMDNSResponder mdns_responder; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services) {
MDNS.begin(App.get_name().c_str());
mdns_responder.begin(App.get_name().c_str());
for (const auto &service : services) {
// Strip the leading underscore from the proto and service_type. While it is
@@ -30,10 +69,10 @@ static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SER
service_type++;
}
uint16_t port = service.port.value();
MDNS.addService(FPSTR(service_type), FPSTR(proto), port);
mdns_responder.addService(FPSTR(service_type), FPSTR(proto), port);
for (const auto &record : service.txt_records) {
MDNS.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
FPSTR(MDNS_STR_ARG(record.value)));
mdns_responder.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
FPSTR(MDNS_STR_ARG(record.value)));
}
}
}
@@ -52,7 +91,7 @@ void MDNSComponent::start_polling_window_() {
if (wifi->is_roaming() || (!wifi->is_connected() && !wifi->is_ap_active()))
return;
#endif
MDNS.update();
mdns_responder.update_guarded();
});
this->set_timeout(MDNS_POLL_STOP_ID, MDNS_POLL_WINDOW_MS, [this]() { this->cancel_interval(MDNS_POLL_ID); });
}
@@ -81,7 +120,7 @@ void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::
#endif
void MDNSComponent::on_shutdown() {
MDNS.close();
mdns_responder.close_guarded();
delay(10);
}