From a8ac37f419b7f8d451605d56b19b904e88d25bf2 Mon Sep 17 00:00:00 2001
From: goldsimon <goldsimon@gmx.de>
Date: Sat, 9 Sep 2017 21:41:06 +0200
Subject: [PATCH] refactor tcp_input a bit in preparation of a fix for bug
 #51937

---
 src/core/tcp_in.c | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index 747a0181..48d95c12 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -91,6 +91,8 @@ static void tcp_parseopt(struct tcp_pcb *pcb);
 static void tcp_listen_input(struct tcp_pcb_listen *pcb);
 static void tcp_timewait_input(struct tcp_pcb *pcb);
 
+static int tcp_input_delayed_close(struct tcp_pcb *pcb);
+
 #if LWIP_TCP_SACK_OUT
 static void tcp_add_sack(struct tcp_pcb *pcb, u32_t left, u32_t right);
 static void tcp_remove_sacks_lt(struct tcp_pcb *pcb, u32_t seq);
@@ -445,17 +447,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
           }
           recv_acked = 0;
         }
-        if (recv_flags & TF_CLOSED) {
-          /* The connection has been closed and we will deallocate the
-             PCB. */
-          if (!(pcb->flags & TF_RXCLOSED)) {
-            /* Connection closed although the application has only shut down the
-               tx side: call the PCB's err callback and indicate the closure to
-               ensure the application doesn't continue using the PCB. */
-            TCP_EVENT_ERR(pcb->state, pcb->errf, pcb->callback_arg, ERR_CLSD);
-          }
-          tcp_pcb_remove(&tcp_active_pcbs, pcb);
-          memp_free(MEMP_TCP_PCB, pcb);
+        if (tcp_input_delayed_close(pcb)) {
           goto aborted;
         }
 #if TCP_QUEUE_OOSEQ && LWIP_WND_SCALE
@@ -572,6 +564,30 @@ dropped:
   pbuf_free(p);
 }
 
+/** Called from tcp_input to check for TF_CLOSED flag. This results in closing
+ * and deallocating a pcb at the correct place to ensure noone references it
+ * any more.
+ * @returns 1 if the pcb has been closed and deallocated, 0 otherwise
+ */
+static int
+tcp_input_delayed_close(struct tcp_pcb *pcb)
+{
+  if (recv_flags & TF_CLOSED) {
+    /* The connection has been closed and we will deallocate the
+        PCB. */
+    if (!(pcb->flags & TF_RXCLOSED)) {
+      /* Connection closed although the application has only shut down the
+          tx side: call the PCB's err callback and indicate the closure to
+          ensure the application doesn't continue using the PCB. */
+      TCP_EVENT_ERR(pcb->state, pcb->errf, pcb->callback_arg, ERR_CLSD);
+    }
+    tcp_pcb_remove(&tcp_active_pcbs, pcb);
+    memp_free(MEMP_TCP_PCB, pcb);
+    return 1;
+  }
+  return 0;
+}
+
 /**
  * Called by tcp_input() when a segment arrives for a listening
  * connection (from tcp_input()).