From 3a788b6e8b4b39e07a2cc700c7cf7f0291ee52dd Mon Sep 17 00:00:00 2001
From: Simon Goldschmidt <goldsimon@gmx.de>
Date: Wed, 12 May 2021 21:04:46 +0200
Subject: [PATCH] dhcp: remove acd handle when stopping dhcp

see bug #57706
---
 src/core/ipv4/acd.c    | 28 ++++++++++++++++++++++++++++
 src/core/ipv4/dhcp.c   |  8 ++++++++
 src/include/lwip/acd.h |  7 +------
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/core/ipv4/acd.c b/src/core/ipv4/acd.c
index 90e0decf..8f4b54a0 100644
--- a/src/core/ipv4/acd.c
+++ b/src/core/ipv4/acd.c
@@ -141,6 +141,34 @@ acd_add(struct netif *netif, struct acd *acd,
   return ERR_OK;
 }
 
+/**
+ * @ingroup acd
+ * Remvoe ACD client from the client list
+ *
+ * @param netif network interface from which to remove the acd client
+ * @param acd   acd module to be removed from the list
+ */
+void
+acd_remove(struct netif *netif, struct acd *acd)
+{
+  struct acd *acd2, *prev = NULL;
+
+  LWIP_ASSERT_CORE_LOCKED();
+
+  for (acd2 = netif->acd_list; acd2 != NULL; acd2 = acd2->next) {
+    if (acd2 == acd) {
+      if (prev) {
+        prev->next = acd->next;
+      } else {
+        netif->acd_list = acd->next;
+      }
+      return;
+    }
+  }
+  LWIP_ASSERT(0, ("acd_remove(): acd not on list\n"));
+}
+
+
 /**
  * @ingroup acd
  * Start ACD client
diff --git a/src/core/ipv4/dhcp.c b/src/core/ipv4/dhcp.c
index e05a093b..21979d20 100644
--- a/src/core/ipv4/dhcp.c
+++ b/src/core/ipv4/dhcp.c
@@ -308,6 +308,9 @@ dhcp_conflict_callback(struct netif *netif, acd_callback_enum_t state)
   struct dhcp *dhcp = netif_dhcp_data(netif);
   u16_t msecs;
 
+  LWIP_ASSERT("DHCP should be enabled at this point, but it is not!",
+              (dhcp != NULL) && (dhcp->state != DHCP_STATE_OFF));
+
   switch (state) {
     case ACD_IP_OK:
       dhcp_bind(netif);
@@ -1361,6 +1364,11 @@ dhcp_release_and_stop(struct netif *netif)
      dhcp_set_state(dhcp, DHCP_STATE_OFF);
   }
 
+#if LWIP_DHCP_DOES_ACD_CHECK
+  /* stop acd because we may be in checking state and the callback would trigger a bind */
+  acd_remove(netif, &dhcp->acd);
+#endif
+
   if (dhcp->pcb_allocated != 0) {
     dhcp_dec_pcb_refcount(); /* free DHCP PCB if not needed any more */
     dhcp->pcb_allocated = 0;
diff --git a/src/include/lwip/acd.h b/src/include/lwip/acd.h
index a5f36586..e2e6cddf 100644
--- a/src/include/lwip/acd.h
+++ b/src/include/lwip/acd.h
@@ -91,17 +91,12 @@ struct acd
 
 err_t acd_add(struct netif *netif, struct acd *acd,
               acd_conflict_callback_t acd_conflict_callback);
-
+void acd_remove(struct netif *netif, struct acd *acd);
 err_t acd_start(struct netif *netif, struct acd *acd, ip4_addr_t ipaddr);
-
 err_t acd_stop(struct acd *acd);
-
 void acd_arp_reply(struct netif *netif, struct etharp_hdr *hdr);
-
 void acd_tmr(void);
-
 void acd_network_changed_link_down(struct netif *netif);
-
 void acd_netif_ip_addr_changed(struct netif *netif, const ip_addr_t *old_addr,
                                const ip_addr_t *new_addr);