fix the bug that TCP connections don't abort when IP changed

components/lwip/Kconfig

@@ -329,6 +329,16 @@ config TCP_QUEUE_OOSEQ
         Disable this option to save some RAM during TCP sessions, at the expense
         of increased retransmissions if segments arrive out of order.
 
+config ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
+    bool "Keep TCP connections when IP changed"
+    default n
+    help
+        This option is enabled when the following scenario happen:
+        network dropped and reconnected, IP changes is like: 192.168.0.2->0.0.0.0->192.168.0.2
+        
+        Disable this option to keep consistent with the original LWIP code behavior.
+
+
 choice TCP_OVERSIZE
     prompt "Pre-allocate transmit PBUF size"
     default TCP_OVERSIZE_MSS

components/lwip/core/netif.c

@@ -453,10 +453,10 @@ void
 netif_set_ipaddr(struct netif *netif, const ip4_addr_t *ipaddr)
 {
   ip4_addr_t new_addr = (ipaddr ? *ipaddr : *IP4_ADDR_ANY);
-#if ESP_LWIP
+#if ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
   ip4_addr_t *last_addr = ip_2_ip4(&netif->last_ip_addr);
 #else
-  ip4_addr_t *last_addr = netif_ip4_addr(netif);
+  ip4_addr_t *last_addr = ip_2_ip4(&(netif->ip_addr));
 #endif
 
   /* address is actually being changed? */

components/lwip/core/tcp.c

@@ -1929,6 +1929,31 @@ tcp_eff_send_mss_impl(u16_t sendmss, const ip_addr_t *dest
 }
 #endif /* TCP_CALCULATE_EFF_SEND_MSS */
 
+/** Helper function for tcp_netif_ip4_addr_changed() that iterates a pcb list */
+static void
+tcp_netif_ip_addr_changed_pcblist(const ip4_addr_t* old_addr, struct tcp_pcb* pcb_list)
+{
+  struct tcp_pcb *pcb;
+  pcb = pcb_list;
+  while (pcb != NULL) {
+    /* PCB bound to current local interface address? */
+    if (ip4_addr_cmp(ip_2_ip4(&pcb->local_ip), old_addr)
+#if LWIP_AUTOIP
+      /* connections to link-local addresses must persist (RFC3927 ch. 1.9) */
+      && (!IP_IS_V4_VAL(pcb->local_ip) || !ip4_addr_islinklocal(ip_2_ip4(&pcb->local_ip)))
+#endif /* LWIP_AUTOIP */
+      ) {
+        /* this connection must be aborted */
+        struct tcp_pcb *next = pcb->next;
+        LWIP_DEBUGF(NETIF_DEBUG | LWIP_DBG_STATE, ("netif_set_ipaddr: aborting TCP pcb %p\n", (void *)pcb));
+        tcp_abort(pcb);
+        pcb = next;
+    } else {
+      pcb = pcb->next;
+    }
+  }
+}
+
 #if LWIP_IPV4
 /** This function is called from netif.c when address is changed or netif is removed
  *
@@ -1939,6 +1964,16 @@ void tcp_netif_ipv4_addr_changed(const ip4_addr_t* old_addr, const ip4_addr_t* n
 {
   struct tcp_pcb_listen *lpcb, *next;
 
+  if (!ip4_addr_isany(old_addr)) {
+#if ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
+    if ((new_addr == NULL) || ((!ip4_addr_isany_val(*new_addr)) && (!ip4_addr_cmp(old_addr, new_addr)))) {
+#endif
+      tcp_netif_ip_addr_changed_pcblist(old_addr, tcp_active_pcbs);
+      tcp_netif_ip_addr_changed_pcblist(old_addr, tcp_bound_pcbs);
+#if ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
+    }
+#endif
+
     if (!ip4_addr_isany(new_addr)) {
       /* PCB bound to current local interface address? */
       for (lpcb = tcp_listen_pcbs.listen_pcbs; lpcb != NULL; lpcb = next) {
@@ -1956,6 +1991,7 @@ void tcp_netif_ipv4_addr_changed(const ip4_addr_t* old_addr, const ip4_addr_t* n
       }
     }
   }
+}
 #endif /* LWIP_IPV4 */
 
 const char*

components/lwip/include/lwip/port/lwipopts.h

@@ -296,6 +296,12 @@
  */
 #define TCP_QUEUE_OOSEQ                 CONFIG_TCP_QUEUE_OOSEQ
 
+/**
+ * ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES==1: Keep TCP connection when IP changed
+ * scenario happens: 192.168.0.2 -> 0.0.0.0 -> 192.168.0.2 or 192.168.0.2 -> 0.0.0.0
+ */
+
+#define ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES  CONFIG_ESP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES 
 /*
  *     LWIP_EVENT_API==1: The user defines lwip_tcp_event() to receive all
  *         events (accept, sent, etc) that happen in the system.