stm32/eth: Consolidate DHCP restart logic and fix static IP.

Static IP configured before active(True) was being overwritten when MAC
speed/duplex reconfiguration occurred (~2s after link up). The MAC
reconfiguration code restarted DHCP whenever a DHCP struct existed,
without checking if a static IP was configured.

Created eth_dhcp_restart_if_needed() helper function that checks if IP
is 0.0.0.0 before restarting DHCP. Consolidated 3 locations with
duplicated DHCP restart logic to use this helper, reducing code size
by 30 lines while fixing the bug.

This ensures static IP is preserved through MAC reconfiguration, cable
unplug/replug, and interface activation.

Signed-off-by: Andrew Leech <[email protected]>

Author: pi-anl

ports/stm32/eth.c

@@ -768,6 +768,16 @@ static void eth_lwip_init(eth_t *self) {
     MICROPY_PY_LWIP_EXIT
 }
 
+// Restart DHCP if no static IP is configured
+// Used when link comes up, MAC is reconfigured, or interface starts
+static void eth_dhcp_restart_if_needed(struct netif *netif) {
+    if (netif_is_up(netif) && ip4_addr_isany_val(*netif_ip4_addr(netif))) {
+        if (netif_dhcp_data(netif)) {
+            dhcp_stop(netif);
+        }
+        dhcp_start(netif);
+    }
+}
 
 void eth_phy_link_status_poll() {
     eth_t *self = &eth_instance;
@@ -795,14 +805,8 @@ void eth_phy_link_status_poll() {
             self->mac_speed_configured = false;
             self->autoneg_start_ms = mp_hal_ticks_ms();
 
-            // Start or restart DHCP if interface is up and no static IP
-            if (netif_is_up(netif) && ip4_addr_isany_val(*netif_ip4_addr(netif))) {
-                // No static IP configured, ensure DHCP is started fresh
-                if (netif_dhcp_data(netif)) {
-                    dhcp_stop(netif);  // Clean up any existing DHCP state
-                }
-                dhcp_start(netif);
-            }
+            // Start or restart DHCP if no static IP configured
+            eth_dhcp_restart_if_needed(netif);
         } else {
             // Cable is physically disconnected
             netif_set_link_down(netif);
@@ -897,14 +901,10 @@ void eth_phy_link_status_poll() {
             // Mark as configured
             self->mac_speed_configured = true;
 
-            // Restart DHCP since MAC was reconfigured
+            // Restart DHCP if no static IP configured (since MAC was reconfigured)
             struct netif *netif = &self->netif;
             MICROPY_PY_LWIP_ENTER
-            if (netif_is_up(netif) && netif_dhcp_data(netif)) {
-                // Use stop+start instead of renew to handle all DHCP states reliably
-                dhcp_stop(netif);
-                dhcp_start(netif);
-            }
+            eth_dhcp_restart_if_needed(netif);
             MICROPY_PY_LWIP_EXIT
         }
     }
@@ -992,12 +992,8 @@ int eth_start(eth_t *self) {
     // Do an initial link status poll after PHY has had time to initialize
     eth_phy_link_status_poll();
 
-    // Start DHCP if no static IP has been configured
-    if (ip4_addr_isany_val(*netif_ip4_addr(n))) {
-        // No static IP configured, start DHCP regardless of link status
-        // DHCP will wait for link to come up before sending packets
-        dhcp_start(n);
-    }
+    // Start DHCP if no static IP configured
+    eth_dhcp_restart_if_needed(n);
 
     MICROPY_PY_LWIP_EXIT