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[wifi] Remove dhcp_renew() entirely — it can never run usefully

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The dhcp_renew() loop was cargo-culted from Arduino ESP8266's
WiFi.hostname() which was designed for changing the hostname on
an already-connected system with multiple interfaces (WiFi+Ethernet).

In ESPHome, wifi_apply_hostname_() is only called from:
  - setup_() — before WiFi connects (link never up)
  - wifi_sta_connect_() — after wifi_disconnect_() (link always down)

The hostname is fixed at compile time and never changes at runtime.
Setting intf->hostname is sufficient — lwIP automatically includes
it in DHCP DISCOVER/REQUEST packets via LWIP_NETIF_HOSTNAME.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
J. Nick Koston
2026-02-14 05:22:39 -07:00
co-authored by Claude Opus 4.6
parent 8abb472c3a
commit f7705c8589
1 changed files with 6 additions and 24 deletions
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esphome/components/wifi/wifi_component_esp8266.cpp
+6 -24
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@@ -16,8 +16,7 @@ extern "C" {
#include "lwip/err.h"
#include "lwip/dns.h"
#include "lwip/dhcp.h"
#include "lwip/prot/dhcp.h" // DHCP_STATE_BOUND
#include "lwip/init.h" // LWIP_VERSION_
#include "lwip/init.h" // LWIP_VERSION_
#include "lwip/apps/sntp.h"
#include "lwip/netif.h" // struct netif
#include <AddrList.h>
@@ -217,34 +216,17 @@ bool WiFiComponent::wifi_apply_hostname_() {
ESP_LOGV(TAG, "Set hostname failed");
}
// inform dhcp server of hostname change using dhcp_renew()
// Update hostname on all lwIP interfaces so DHCP packets include it.
// No dhcp_renew() call here — the hostname is fixed at compile time and
// this function is only called during setup() or wifi_sta_connect_() when
// the interface is always disconnected. lwIP includes the hostname in
// DHCP DISCOVER/REQUEST automatically via LWIP_NETIF_HOSTNAME.
for (netif *intf = netif_list; intf; intf = intf->next) {
// unconditionally update all known interfaces
#if LWIP_VERSION_MAJOR == 1
intf->hostname = (char *) wifi_station_get_hostname();
#else
intf->hostname = wifi_station_get_hostname();
#endif
struct dhcp *dhcp_data = netif_dhcp_data(intf);
if (dhcp_data != nullptr && dhcp_data->state == DHCP_STATE_BOUND && netif_is_link_up(intf)) {
// Renew already-bound DHCP leases to inform server of hostname change.
// Both conditions are required:
// - DHCP must be BOUND (have an active lease to renew)
// - Interface must have link (able to send packets)
// During reconnection, DHCP can remain BOUND from a previous connection
// while the link is down. Calling dhcp_renew() without link corrupts
// lwIP's DHCP state machine (it unconditionally sets state to RENEWING
// before attempting to send, and never rolls back on failure). This
// causes dhcp_network_changed() to call dhcp_reboot() instead of
// dhcp_discover() when WiFi later connects, sending a bogus DHCP REQUEST
// for IP 0.0.0.0 that can put some routers into a persistent bad state.
err_t lwipret = dhcp_renew(intf);
if (lwipret != ERR_OK) {
ESP_LOGW(TAG, "wifi_apply_hostname_(%s): lwIP error %d on interface %c%c (index %d)", intf->hostname,
(int) lwipret, intf->name[0], intf->name[1], intf->num);
ret = false;
}
}
}
return ret;