Index: /trunk/src/VBox/Devices/Network/slirp/ip_icmp.c
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/ip_icmp.c	(revision 55855)
+++ /trunk/src/VBox/Devices/Network/slirp/ip_icmp.c	(revision 55856)
@@ -90,5 +90,4 @@
 };
 
-static void icmp_cache_clean(PNATState pData, int iEntries);
 
 int
@@ -99,4 +98,6 @@
 
 #ifndef RT_OS_WINDOWS
+    TAILQ_INIT(&pData->icmp_msg_head);
+
     if (iIcmpCacheLimit < 0)
     {
@@ -129,7 +130,4 @@
     fd_nonblock(pData->icmp_socket.s);
     NSOCK_INC();
-
-    LIST_INIT(&pData->icmp_msg_head);
-
 #else /* RT_OS_WINDOWS */
     if (icmpwin_init(pData) != 0)
@@ -149,10 +147,109 @@
     icmpwin_finit(pData);
 #else
-    icmp_cache_clean(pData, -1);
+    while (!TAILQ_EMPTY(&pData->icmp_msg_head))
+    {
+        struct icmp_msg *icm = TAILQ_FIRST(&pData->icmp_msg_head);
+        icmp_msg_delete(pData, icm);
+    }
     closesocket(pData->icmp_socket.s);
 #endif
 }
 
+
 #if !defined(RT_OS_WINDOWS)
+static struct icmp_msg *
+icmp_msg_alloc(PNATState pData)
+{
+    struct icmp_msg *icm;
+
+#ifdef DEBUG
+    {
+        int iTally = 0;
+        TAILQ_FOREACH(icm, &pData->icmp_msg_head, im_queue)
+            ++iTally;
+        Assert(pData->cIcmpCacheSize == iTally);
+    }
+#endif
+
+    if (pData->cIcmpCacheSize >= pData->iIcmpCacheLimit)
+    {
+        int cTargetCacheSize = pData->iIcmpCacheLimit/2;
+
+        while (pData->cIcmpCacheSize > cTargetCacheSize)
+        {
+            icm = TAILQ_FIRST(&pData->icmp_msg_head);
+            icmp_msg_delete(pData, icm);
+        }
+    }
+
+    icm = RTMemAlloc(sizeof(struct icmp_msg));
+    if (RT_UNLIKELY(icm == NULL))
+        return NULL;
+
+    TAILQ_INSERT_TAIL(&pData->icmp_msg_head, icm, im_queue);
+    pData->cIcmpCacheSize++;
+
+    return icm;
+}
+
+
+static void
+icmp_attach(PNATState pData, struct mbuf *m)
+{
+    struct icmp_msg *icm;
+
+#ifdef DEBUG
+    {
+        /* only used for ping */
+        struct ip *ip = mtod(m, struct ip *);
+        Assert(ip->ip_p == IPPROTO_ICMP);
+    }
+#endif
+
+    icm = icmp_msg_alloc(pData);
+    if (RT_UNLIKELY(icm == NULL))
+        return;
+
+    icm->im_so = &pData->icmp_socket;
+    icm->im_m = m;
+}
+
+
+void
+icmp_msg_delete(PNATState pData, struct icmp_msg *icm)
+{
+    if (RT_UNLIKELY(icm == NULL))
+        return;
+
+#ifdef DEBUG
+    {
+        struct icmp_msg *existing;
+        int iTally = 0;
+
+        TAILQ_FOREACH(existing, &pData->icmp_msg_head, im_queue)
+            ++iTally;
+        Assert(pData->cIcmpCacheSize == iTally);
+
+        Assert(pData->cIcmpCacheSize > 0);
+        TAILQ_FOREACH(existing, &pData->icmp_msg_head, im_queue)
+        {
+            if (existing == icm)
+                break;
+        }
+        Assert(existing != NULL);
+    }
+#endif
+
+    TAILQ_REMOVE(&pData->icmp_msg_head, icm, im_queue);
+    pData->cIcmpCacheSize--;
+
+    icm->im_so->so_m = NULL;
+    if (icm->im_m != NULL)
+        m_freem(pData, icm->im_m);
+
+    RTMemFree(icm);
+}
+
+
 /*
  * ip here is ip header + 64bytes readed from ICMP packet
@@ -185,5 +282,5 @@
         case IPPROTO_ICMP:
             icp = (struct icmp *)((char *)ip + (ip->ip_hl << 2));
-            LIST_FOREACH(icm, &pData->icmp_msg_head, im_list)
+            TAILQ_FOREACH(icm, &pData->icmp_msg_head, im_queue)
             {
                 m0 = icm->im_m;
@@ -250,5 +347,5 @@
                 found = 1;
                 so = last_socket;
-                goto sofound;
+                break;
             }
             for (so = head_socket->so_prev; so != head_socket; so = so->so_prev)
@@ -269,89 +366,55 @@
             Log(("NAT:ICMP: unsupported protocol(%d)\n", ip->ip_p));
     }
-    sofound:
-    if (found == 1 && icm == NULL)
-    {
+
+#ifdef DEBUG
+    if (found)
+        Assert((icm != NULL) ^ (so != NULL));
+#endif
+
+    if (found && icm == NULL)
+    {
+        /*
+         * XXX: Implies this is not a pong, found socket.  This is, of
+         * course, wasteful since the caller will delete icmp_msg
+         * immediately after processing, so there's not much reason to
+         * clutter up the queue with it.
+         */
+        AssertReturn(so != NULL, NULL);
+
+        /*
+         * XXX: FIXME: If the very first send(2) fails, the socket is
+         * still in SS_NOFDREF and so we will not report this too.
+         */
         if (so->so_state == SS_NOFDREF)
         {
-            /* socket is shutdowning we've already sent ICMP on it.*/
-            Log(("NAT: Received icmp on shutdowning socket (probably corresponding ICMP socket has been already sent)\n"));
+            /* socket is shutting down we've already sent ICMP on it. */
+            Log(("NAT:ICMP: disconnected %R[natsock]\n", so));
+            LogFlowFunc(("LEAVE: icm:NULL\n"));
             return NULL;
         }
-        icm = RTMemAlloc(sizeof(struct icmp_msg));
+
+        if (so->so_m == NULL)
+        {
+            Log(("NAT:ICMP: no saved mbuf for %R[natsock]\n", so));
+            LogFlowFunc(("LEAVE: icm:NULL\n"));
+            return NULL;
+        }
+
+        icm = icmp_msg_alloc(pData);
+        if (RT_UNLIKELY(icm == NULL))
+        {
+            LogFlowFunc(("LEAVE: icm:NULL\n"));
+            return NULL;
+        }
+
+        Log(("NAT:ICMP: for %R[natsock]\n", so));
+        icm->im_so = so;
         icm->im_m = so->so_m;
-        icm->im_so = so;
-        found = 1;
-        Log(("hit:%R[natsock]\n", so));
-        /*XXX: this storage not very long,
-         * better add flag if it should removed from lis
-         */
-        LIST_INSERT_HEAD(&pData->icmp_msg_head, icm, im_list);
-        pData->cIcmpCacheSize++;
-        if (pData->cIcmpCacheSize > pData->iIcmpCacheLimit)
-            icmp_cache_clean(pData, pData->iIcmpCacheLimit/2);
-        LogFlowFunc(("LEAVE: icm:%p\n", icm));
-        return (icm);
-    }
-    if (found == 1)
-    {
-        LogFlowFunc(("LEAVE: icm:%p\n", icm));
-        return icm;
-    }
-
-    LogFlowFunc(("LEAVE: NULL\n"));
-    return NULL;
-}
-
-/**
- * iEntries how many entries to leave, if iEntries < 0, clean all
- */
-static void icmp_cache_clean(PNATState pData, int iEntries)
-{
-    int iIcmpCount = 0;
-    struct icmp_msg *icm = NULL;
-    LogFlowFunc(("iEntries:%d\n", iEntries));
-    if (iEntries > pData->cIcmpCacheSize)
-    {
-        LogFlowFuncLeave();
-        return;
-    }
-    while(!LIST_EMPTY(&pData->icmp_msg_head))
-    {
-        icm = LIST_FIRST(&pData->icmp_msg_head);
-        if (    iEntries > 0
-            &&  iIcmpCount < iEntries)
-        {
-            iIcmpCount++;
-            continue;
-        }
-
-        LIST_REMOVE(icm, im_list);
-        if (icm->im_m)
-        {
-            pData->cIcmpCacheSize--;
-            m_freem(pData, icm->im_m);
-        }
-        RTMemFree(icm);
-    }
-    LogFlowFuncLeave();
-}
-
-static int
-icmp_attach(PNATState pData, struct mbuf *m)
-{
-    struct icmp_msg *icm;
-    struct ip *ip;
-    ip = mtod(m, struct ip *);
-    Assert(ip->ip_p == IPPROTO_ICMP);
-    icm = RTMemAlloc(sizeof(struct icmp_msg));
-    icm->im_m = m;
-    icm->im_so = m->m_so;
-    LIST_INSERT_HEAD(&pData->icmp_msg_head, icm, im_list);
-    pData->cIcmpCacheSize++;
-    if (pData->cIcmpCacheSize > pData->iIcmpCacheLimit)
-        icmp_cache_clean(pData, pData->iIcmpCacheLimit/2);
-    return 0;
+    }
+    LogFlowFunc(("LEAVE: icm:%p\n", icm));
+    return icm;
 }
 #endif /* !RT_OS_WINDOWS */
+
 
 /*
@@ -480,5 +543,4 @@
                     if (rc >= 0)
                     {
-                        m->m_so = &pData->icmp_socket;
                         icmp_attach(pData, m);
                         /* don't let m_freem at the end free atached buffer */
Index: /trunk/src/VBox/Devices/Network/slirp/ip_icmp.h
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/ip_icmp.h	(revision 55855)
+++ /trunk/src/VBox/Devices/Network/slirp/ip_icmp.h	(revision 55856)
@@ -192,14 +192,15 @@
 struct icmp_msg
 {
-    LIST_ENTRY(icmp_msg) im_list;
+    TAILQ_ENTRY(icmp_msg) im_queue;
     struct mbuf *im_m;
     struct socket *im_so;
 };
 
-LIST_HEAD(icmp_storage, icmp_msg);
+TAILQ_HEAD(icmp_storage, icmp_msg);
 
 int icmp_init (PNATState , int);
 void icmp_finit (PNATState );
 struct icmp_msg * icmp_find_original_mbuf (PNATState , struct ip *);
+void icmp_msg_delete(PNATState, struct icmp_msg *);
 
 #ifdef RT_OS_WINDOWS
Index: /trunk/src/VBox/Devices/Network/slirp/socket.c
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/socket.c	(revision 55855)
+++ /trunk/src/VBox/Devices/Network/slirp/socket.c	(revision 55856)
@@ -1228,7 +1228,5 @@
     {
         LogFunc(("%R[natsock] hasn't stored it's mbuf on sent\n", icm->im_so));
-        LIST_REMOVE(icm, im_list);
-        RTMemFree(icm);
-        return;
+        goto done;
     }
 
@@ -1241,5 +1239,5 @@
         {
             Log(("NAT: we haven't found echo for this reply\n"));
-            return;
+            goto done;
         }
         /*
@@ -1254,5 +1252,5 @@
             Log(("NAT: ECHO(%d) lenght doesn't match ECHOREPLY(%d)\n",
                 (ip->ip_len - hlen), (ip0->ip_len - (ip0->ip_hl << 2))));
-            return;
+            goto done;
         }
     }
@@ -1297,8 +1295,7 @@
     /* m was freed */
     icm->im_m = NULL;
-    icm->im_so->so_m = NULL;
-    LIST_REMOVE(icm, im_list);
-    pData->cIcmpCacheSize--;
-    RTMemFree(icm);
+
+  done:
+    icmp_msg_delete(pData, icm);
 }