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diff --git a/geekos/src/lwip/core/sys.c b/geekos/src/lwip/core/sys.c
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+++ b/geekos/src/lwip/core/sys.c
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+/**
+ * @file
+ * lwIP Operating System abstraction
+ *
+ */
+
+/*
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+ * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ *
+ * This file is part of the lwIP TCP/IP stack.
+ *
+ * Author: Adam Dunkels <adam@sics.se>
+ *
+ */
+
+#include "lwip/opt.h"
+
+#if (NO_SYS == 0) /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/sys.h"
+#include "lwip/def.h"
+#include "lwip/memp.h"
+#include "lwip/tcpip.h"
+
+/**
+ * Struct used for sys_sem_wait_timeout() to tell wether the time
+ * has run out or the semaphore has really become available.
+ */
+struct sswt_cb
+{
+  s16_t timeflag;
+  sys_sem_t *psem;
+};
+
+/**
+ * Wait (forever) for a message to arrive in an mbox.
+ * While waiting, timeouts (for this thread) are processed.
+ *
+ * @param mbox the mbox to fetch the message from
+ * @param msg the place to store the message
+ */
+void
+sys_mbox_fetch(sys_mbox_t mbox, void **msg)
+{
+  u32_t time;
+  struct sys_timeouts *timeouts;
+  struct sys_timeo *tmptimeout;
+  sys_timeout_handler h;
+  void *arg;
+
+ again:
+  timeouts = sys_arch_timeouts();
+
+  if (!timeouts || !timeouts->next) {
+    UNLOCK_TCPIP_CORE();
+    time = sys_arch_mbox_fetch(mbox, msg, 0);
+    LOCK_TCPIP_CORE();
+  } else {
+    if (timeouts->next->time > 0) {
+      UNLOCK_TCPIP_CORE();
+      time = sys_arch_mbox_fetch(mbox, msg, timeouts->next->time);
+      LOCK_TCPIP_CORE();
+    } else {
+      time = SYS_ARCH_TIMEOUT;
+    }
+
+    if (time == SYS_ARCH_TIMEOUT) {
+      /* If time == SYS_ARCH_TIMEOUT, a timeout occured before a message
+         could be fetched. We should now call the timeout handler and
+         deallocate the memory allocated for the timeout. */
+      tmptimeout = timeouts->next;
+      timeouts->next = tmptimeout->next;
+      h   = tmptimeout->h;
+      arg = tmptimeout->arg;
+      memp_free(MEMP_SYS_TIMEOUT, tmptimeout);
+      if (h != NULL) {
+        LWIP_DEBUGF(SYS_DEBUG, ("smf calling h=%p(%p)\n", (void*)&h, arg));
+        h(arg);
+      }
+
+      /* We try again to fetch a message from the mbox. */
+      goto again;
+    } else {
+      /* If time != SYS_ARCH_TIMEOUT, a message was received before the timeout
+         occured. The time variable is set to the number of
+         milliseconds we waited for the message. */
+      if (time < timeouts->next->time) {
+        timeouts->next->time -= time;
+      } else {
+        timeouts->next->time = 0;
+      }
+    }
+  }
+}
+
+/**
+ * Wait (forever) for a semaphore to become available.
+ * While waiting, timeouts (for this thread) are processed.
+ *
+ * @param sem semaphore to wait for
+ */
+void
+sys_sem_wait(sys_sem_t sem)
+{
+  u32_t time;
+  struct sys_timeouts *timeouts;
+  struct sys_timeo *tmptimeout;
+  sys_timeout_handler h;
+  void *arg;
+
+ again:
+
+  timeouts = sys_arch_timeouts();
+
+  if (!timeouts || !timeouts->next) {
+    sys_arch_sem_wait(sem, 0);
+  } else {
+    if (timeouts->next->time > 0) {
+      time = sys_arch_sem_wait(sem, timeouts->next->time);
+    } else {
+      time = SYS_ARCH_TIMEOUT;
+    }
+
+    if (time == SYS_ARCH_TIMEOUT) {
+      /* If time == SYS_ARCH_TIMEOUT, a timeout occured before a message
+        could be fetched. We should now call the timeout handler and
+        deallocate the memory allocated for the timeout. */
+      tmptimeout = timeouts->next;
+      timeouts->next = tmptimeout->next;
+      h = tmptimeout->h;
+      arg = tmptimeout->arg;
+      memp_free(MEMP_SYS_TIMEOUT, tmptimeout);
+      if (h != NULL) {
+        LWIP_DEBUGF(SYS_DEBUG, ("ssw h=%p(%p)\n", (void*)&h, (void *)arg));
+        h(arg);
+      }
+
+      /* We try again to fetch a message from the mbox. */
+      goto again;
+    } else {
+      /* If time != SYS_ARCH_TIMEOUT, a message was received before the timeout
+         occured. The time variable is set to the number of
+         milliseconds we waited for the message. */
+      if (time < timeouts->next->time) {
+        timeouts->next->time -= time;
+      } else {
+        timeouts->next->time = 0;
+      }
+    }
+  }
+}
+
+/**
+ * Create a one-shot timer (aka timeout). Timeouts are processed in the
+ * following cases:
+ * - while waiting for a message using sys_mbox_fetch()
+ * - while waiting for a semaphore using sys_sem_wait() or sys_sem_wait_timeout()
+ * - while sleeping using the inbuilt sys_msleep()
+ *
+ * @param msecs time in milliseconds after that the timer should expire
+ * @param h callback function to call when msecs have elapsed
+ * @param arg argument to pass to the callback function
+ */
+void
+sys_timeout(u32_t msecs, sys_timeout_handler h, void *arg)
+{
+  struct sys_timeouts *timeouts;
+  struct sys_timeo *timeout, *t;
+
+  timeout = memp_malloc(MEMP_SYS_TIMEOUT);
+  if (timeout == NULL) {
+    LWIP_ASSERT("sys_timeout: timeout != NULL", timeout != NULL);
+    return;
+  }
+  timeout->next = NULL;
+  timeout->h = h;
+  timeout->arg = arg;
+  timeout->time = msecs;
+
+  timeouts = sys_arch_timeouts();
+
+  LWIP_DEBUGF(SYS_DEBUG, ("sys_timeout: %p msecs=%"U32_F" h=%p arg=%p\n",
+    (void *)timeout, msecs, (void*)&h, (void *)arg));
+
+  if (timeouts == NULL) {
+    LWIP_ASSERT("sys_timeout: timeouts != NULL", timeouts != NULL);
+    return;
+  }
+
+  if (timeouts->next == NULL) {
+    timeouts->next = timeout;
+    return;
+  }
+
+  if (timeouts->next->time > msecs) {
+    timeouts->next->time -= msecs;
+    timeout->next = timeouts->next;
+    timeouts->next = timeout;
+  } else {
+    for(t = timeouts->next; t != NULL; t = t->next) {
+      timeout->time -= t->time;
+      if (t->next == NULL || t->next->time > timeout->time) {
+        if (t->next != NULL) {
+          t->next->time -= timeout->time;
+        }
+        timeout->next = t->next;
+        t->next = timeout;
+        break;
+      }
+    }
+  }
+}
+
+/**
+ * Go through timeout list (for this task only) and remove the first matching
+ * entry, even though the timeout has not triggered yet.
+ *
+ * @note This function only works as expected if there is only one timeout
+ * calling 'h' in the list of timeouts.
+ *
+ * @param h callback function that would be called by the timeout
+ * @param arg callback argument that would be passed to h
+*/
+void
+sys_untimeout(sys_timeout_handler h, void *arg)
+{
+  struct sys_timeouts *timeouts;
+  struct sys_timeo *prev_t, *t;
+
+  timeouts = sys_arch_timeouts();
+
+  if (timeouts == NULL) {
+    LWIP_ASSERT("sys_untimeout: timeouts != NULL", timeouts != NULL);
+    return;
+  }
+  if (timeouts->next == NULL) {
+    return;
+  }
+
+  for (t = timeouts->next, prev_t = NULL; t != NULL; prev_t = t, t = t->next) {
+    if ((t->h == h) && (t->arg == arg)) {
+      /* We have a match */
+      /* Unlink from previous in list */
+      if (prev_t == NULL)
+        timeouts->next = t->next;
+      else
+        prev_t->next = t->next;
+      /* If not the last one, add time of this one back to next */
+      if (t->next != NULL)
+        t->next->time += t->time;
+      memp_free(MEMP_SYS_TIMEOUT, t);
+      return;
+    }
+  }
+  return;
+}
+
+/**
+ * Timeout handler function for sys_sem_wait_timeout()
+ *
+ * @param arg struct sswt_cb* used to signal a semaphore and end waiting.
+ */
+static void
+sswt_handler(void *arg)
+{
+  struct sswt_cb *sswt_cb = (struct sswt_cb *) arg;
+
+  /* Timeout. Set flag to TRUE and signal semaphore */
+  sswt_cb->timeflag = 1;
+  sys_sem_signal(*(sswt_cb->psem));
+}
+
+/**
+ * Wait for a semaphore with timeout (specified in ms)
+ *
+ * @param sem semaphore to wait
+ * @param timeout timeout in ms (0: wait forever)
+ * @return 0 on timeout, 1 otherwise
+ */
+int
+sys_sem_wait_timeout(sys_sem_t sem, u32_t timeout)
+{
+  struct sswt_cb sswt_cb;
+
+  sswt_cb.psem = &sem;
+  sswt_cb.timeflag = 0;
+
+  /* If timeout is zero, then just wait forever */
+  if (timeout > 0) {
+    /* Create a timer and pass it the address of our flag */
+    sys_timeout(timeout, sswt_handler, &sswt_cb);
+  }
+  sys_sem_wait(sem);
+  /* Was it a timeout? */
+  if (sswt_cb.timeflag) {
+    /* timeout */
+    return 0;
+  } else {
+    /* Not a timeout. Remove timeout entry */
+    sys_untimeout(sswt_handler, &sswt_cb);
+    return 1;
+  }
+}
+
+/**
+ * Sleep for some ms. Timeouts are processed while sleeping.
+ *
+ * @param ms number of milliseconds to sleep
+ */
+void
+sys_msleep(u32_t ms)
+{
+  sys_sem_t delaysem = sys_sem_new(0);
+
+  sys_sem_wait_timeout(delaysem, ms);
+
+  sys_sem_free(delaysem);
+}
+
+
+#endif /* NO_SYS */