Implement possibility to declare private memory pools. This is useful to decouple some apps from the core (SNMP stack) or make contrib app useage simpler (httpserver_raw) .

2026-08-09 17:13:49 +08:00 · 2015-11-12 08:45:04 +01:00
parent d38db89626
commit c838e1ed5b
6 changed files with 370 additions and 281 deletions
--- a/src/core/mem.c
+++ b/src/core/mem.c
@@ -66,6 +66,11 @@
 #include <string.h>

 #if MEM_USE_POOLS
+
+#if MEMP_MEM_MALLOC
+#error MEM_USE_POOLS and MEMP_MEM_MALLOC cannot be used together
+#endif
+
 /* lwIP head implemented with different sized pools */

 /**
@@ -89,7 +94,7 @@ again:
 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
    /* is this pool big enough to hold an element of the required size
       plus a struct memp_malloc_helper that saves the pool this element came from? */
-    if (required_size <= memp_sizes[poolnr]) {
+    if (required_size <= memp_pools[poolnr]->size) {
      break;
    }
  }
@@ -119,7 +124,7 @@ again:
 #if MEMP_OVERFLOW_CHECK
  /* initialize unused memory */
  element->size = size;
-  memset((u8_t*)ret + size, 0xcd, memp_sizes[poolnr] - size);
+  memset((u8_t*)ret + size, 0xcd, memp_pools[poolnr]->size - size);
 #endif /* MEMP_OVERFLOW_CHECK */
  return ret;
 }
@@ -150,9 +155,9 @@ mem_free(void *rmem)
  {
     u16_t i;
     LWIP_ASSERT("MEM_USE_POOLS: invalid chunk size",
-        hmem->size <= memp_sizes[hmem->poolnr]);
+        hmem->size <= memp_pools[hmem->poolnr]->size);
     /* check that unused memory remained untouched */
-     for (i = hmem->size; i < memp_sizes[hmem->poolnr]; i++) {
+     for (i = hmem->size; i < memp_pools[hmem->poolnr]->size; i++) {
        u8_t data = *((u8_t*)rmem + i);
        LWIP_ASSERT("MEM_USE_POOLS: mem overflow detected", data == 0xcd);
     }
--- a/src/core/memp.c
+++ b/src/core/memp.c
@@ -64,155 +64,47 @@
 #include "lwip/nd6.h"
 #include "lwip/ip6_frag.h"
 #include "lwip/mld6.h"
+#include "lwip/tcp.h"
+#include "lwip/tcpip.h"
 #include "lwip/priv/tcp_priv.h"
 #include "lwip/priv/tcpip_priv.h"

 #include <string.h>

-#if !MEMP_MEM_MALLOC /* don't build if not configured for use in lwipopts.h */
+#define LWIP_MEMPOOL(name,num,size,desc) LWIP_MEMPOOL_DECLARE(name,num,size,desc)
+#include "lwip/priv/memp_std.h"

-struct memp {
-  struct memp *next;
-#if MEMP_OVERFLOW_CHECK
-  const char *file;
-  int line;
-#endif /* MEMP_OVERFLOW_CHECK */
-};
-
-#if MEMP_OVERFLOW_CHECK
-/* if MEMP_OVERFLOW_CHECK is turned on, we reserve some bytes at the beginning
- * and at the end of each element, initialize them as 0xcd and check
- * them later. */
-/* If MEMP_OVERFLOW_CHECK is >= 2, on every call to memp_malloc or memp_free,
- * every single element in each pool is checked!
- * This is VERY SLOW but also very helpful. */
-/* MEMP_SANITY_REGION_BEFORE and MEMP_SANITY_REGION_AFTER can be overridden in
- * lwipopts.h to change the amount reserved for checking. */
-#ifndef MEMP_SANITY_REGION_BEFORE
-#define MEMP_SANITY_REGION_BEFORE  16
-#endif /* MEMP_SANITY_REGION_BEFORE*/
-#if MEMP_SANITY_REGION_BEFORE > 0
-#define MEMP_SANITY_REGION_BEFORE_ALIGNED    LWIP_MEM_ALIGN_SIZE(MEMP_SANITY_REGION_BEFORE)
-#else
-#define MEMP_SANITY_REGION_BEFORE_ALIGNED    0
-#endif /* MEMP_SANITY_REGION_BEFORE*/
-#ifndef MEMP_SANITY_REGION_AFTER
-#define MEMP_SANITY_REGION_AFTER   16
-#endif /* MEMP_SANITY_REGION_AFTER*/
-#if MEMP_SANITY_REGION_AFTER > 0
-#define MEMP_SANITY_REGION_AFTER_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEMP_SANITY_REGION_AFTER)
-#else
-#define MEMP_SANITY_REGION_AFTER_ALIGNED     0
-#endif /* MEMP_SANITY_REGION_AFTER*/
-
-/* MEMP_SIZE: save space for struct memp and for sanity check */
-#define MEMP_SIZE          (LWIP_MEM_ALIGN_SIZE(sizeof(struct memp)) + MEMP_SANITY_REGION_BEFORE_ALIGNED)
-#define MEMP_ALIGN_SIZE(x) (LWIP_MEM_ALIGN_SIZE(x) + MEMP_SANITY_REGION_AFTER_ALIGNED)
-
-#else /* MEMP_OVERFLOW_CHECK */
-
-/* No sanity checks
- * We don't need to preserve the struct memp while not allocated, so we
- * can save a little space and set MEMP_SIZE to 0.
- */
-#define MEMP_SIZE           0
-#define MEMP_ALIGN_SIZE(x) (LWIP_MEM_ALIGN_SIZE(x))
-
-#endif /* MEMP_OVERFLOW_CHECK */
-
-/** This array holds the first free element of each pool.
- *  Elements form a linked list. */
-static struct memp *memp_tab[MEMP_MAX];
-
-#else /* MEMP_MEM_MALLOC */
-
-#define MEMP_ALIGN_SIZE(x) (LWIP_MEM_ALIGN_SIZE(x))
-
-#endif /* MEMP_MEM_MALLOC */
-
-/** This array holds the element sizes of each pool. */
-#if !MEM_USE_POOLS && !MEMP_MEM_MALLOC && !MEMP_USE_CUSTOM_POOLS
-static
-#endif
-const u16_t memp_sizes[MEMP_MAX] = {
-#define LWIP_MEMPOOL(name,num,size,desc)  LWIP_MEM_ALIGN_SIZE(size),
+const struct memp_desc *memp_pools[MEMP_MAX] = {
+#define LWIP_MEMPOOL(name,num,size,desc) &memp_ ## name,
 #include "lwip/priv/memp_std.h"
 };

 #if !MEMP_MEM_MALLOC /* don't build if not configured for use in lwipopts.h */

-/** This array holds the number of elements in each pool. */
-static const u16_t memp_num[MEMP_MAX] = {
-#define LWIP_MEMPOOL(name,num,size,desc)  (num),
-#include "lwip/priv/memp_std.h"
-};
-
-/** This array holds a textual description of each pool. */
-#ifdef LWIP_DEBUG
-static const char *memp_desc[MEMP_MAX] = {
-#define LWIP_MEMPOOL(name,num,size,desc)  (desc),
-#include "lwip/priv/memp_std.h"
-};
-#endif /* LWIP_DEBUG */
-
-#if MEMP_SEPARATE_POOLS
-
-/** This creates each memory pool. These are named memp_memory_XXX_base (where
- * XXX is the name of the pool defined in memp_std.h).
- * To relocate a pool, declare it as extern in cc.h. Example for GCC:
- *   extern u8_t __attribute__((section(".onchip_mem"))) memp_memory_UDP_PCB_base[];
- */
-#define LWIP_MEMPOOL(name,num,size,desc) u8_t memp_memory_ ## name ## _base \
-  [((num) * (MEMP_SIZE + MEMP_ALIGN_SIZE(size)))];
-#include "lwip/priv/memp_std.h"
-
-/** This array holds the base of each memory pool. */
-static u8_t *const memp_bases[] = {
-#define LWIP_MEMPOOL(name,num,size,desc) memp_memory_ ## name ## _base,
-#include "lwip/priv/memp_std.h"
-};
-
-#else /* MEMP_SEPARATE_POOLS */
-
-/** This is the actual memory used by the pools (all pools in one big block). */
-static u8_t memp_memory[MEM_ALIGNMENT - 1
-#define LWIP_MEMPOOL(name,num,size,desc) + ( (num) * (MEMP_SIZE + MEMP_ALIGN_SIZE(size) ) )
-#include "lwip/priv/memp_std.h"
-];
-
-#endif /* MEMP_SEPARATE_POOLS */
-
 #if MEMP_SANITY_CHECK
 /**
 * Check that memp-lists don't form a circle, using "Floyd's cycle-finding algorithm".
 */
 static int
-memp_sanity(void)
+memp_sanity(const struct memp_desc *desc)
 {
-  s16_t i;
  struct memp *t, *h;

-  for (i = 0; i < MEMP_MAX; i++) {
-    t = memp_tab[i];
-    if (t != NULL) {
-      for (h = t->next; (t != NULL) && (h != NULL); t = t->next,
-        h = (((h->next != NULL) && (h->next->next != NULL)) ? h->next->next : NULL)) {
-        if (t == h) {
-          return 0;
-        }
+  t = *desc->tab;
+  if (t != NULL) {
+    for (h = t->next; (t != NULL) && (h != NULL); t = t->next,
+      h = (((h->next != NULL) && (h->next->next != NULL)) ? h->next->next : NULL)) {
+      if (t == h) {
+        return 0;
      }
    }
  }
+
  return 1;
 }
 #endif /* MEMP_SANITY_CHECK*/
+
 #if MEMP_OVERFLOW_CHECK
-#if defined(LWIP_DEBUG) && MEMP_STATS
-static const char * memp_overflow_names[] = {
-#define LWIP_MEMPOOL(name,num,size,desc) "/"desc,
-#include "lwip/priv/memp_std.h"
-  };
-#endif

 /**
 * Check if a memp element was victim of an overflow
@@ -222,25 +114,16 @@ static const char * memp_overflow_names[] = {
 * @param memp_type the pool p comes from
 */
 static void
-memp_overflow_check_element_overflow(struct memp *p, u16_t memp_type)
+memp_overflow_check_element_overflow(struct memp *p, const struct memp_desc *desc)
 {
  u16_t k;
  u8_t *m;
 #if MEMP_SANITY_REGION_AFTER_ALIGNED > 0
-  m = (u8_t*)p + MEMP_SIZE + memp_sizes[memp_type];
+  m = (u8_t*)p + MEMP_SIZE + desc->size;
  for (k = 0; k < MEMP_SANITY_REGION_AFTER_ALIGNED; k++) {
    if (m[k] != 0xcd) {
      char errstr[128] = "detected memp overflow in pool ";
-      char digit[] = "0";
-      if (memp_type >= 10) {
-        digit[0] = '0' + (memp_type/10);
-        strcat(errstr, digit);
-      }
-      digit[0] = '0' + (memp_type%10);
-      strcat(errstr, digit);
-#if defined(LWIP_DEBUG) && MEMP_STATS
-      strcat(errstr, memp_overflow_names[memp_type]);
-#endif
+      strcat(errstr, desc->desc);
      LWIP_ASSERT(errstr, 0);
    }
  }
@@ -255,7 +138,7 @@ memp_overflow_check_element_overflow(struct memp *p, u16_t memp_type)
 * @param memp_type the pool p comes from
 */
 static void
-memp_overflow_check_element_underflow(struct memp *p, u16_t memp_type)
+memp_overflow_check_element_underflow(struct memp *p, const struct memp_desc *desc)
 {
  u16_t k;
  u8_t *m;
@@ -264,16 +147,7 @@ memp_overflow_check_element_underflow(struct memp *p, u16_t memp_type)
  for (k = 0; k < MEMP_SANITY_REGION_BEFORE_ALIGNED; k++) {
    if (m[k] != 0xcd) {
      char errstr[128] = "detected memp underflow in pool ";
-      char digit[] = "0";
-      if (memp_type >= 10) {
-        digit[0] = '0' + (memp_type/10);
-        strcat(errstr, digit);
-      }
-      digit[0] = '0' + (memp_type%10);
-      strcat(errstr, digit);
-#if defined(LWIP_DEBUG) && MEMP_STATS
-      strcat(errstr, memp_overflow_names[memp_type]);
-#endif
+      strcat(errstr, desc->desc);
      LWIP_ASSERT(errstr, 0);
    }
  }
@@ -291,28 +165,19 @@ memp_overflow_check_all(void)
  u16_t i, j;
  struct memp *p;

-#if !MEMP_SEPARATE_POOLS
-  p = (struct memp *)LWIP_MEM_ALIGN(memp_memory);
-#endif /* !MEMP_SEPARATE_POOLS */
  for (i = 0; i < MEMP_MAX; ++i) {
-#if MEMP_SEPARATE_POOLS
-    p = (struct memp *)(memp_bases[i]);
-#endif /* MEMP_SEPARATE_POOLS */
-    for (j = 0; j < memp_num[i]; ++j) {
-      memp_overflow_check_element_overflow(p, i);
-      p = (struct memp*)((u8_t*)p + MEMP_SIZE + memp_sizes[i] + MEMP_SANITY_REGION_AFTER_ALIGNED);
+    p = (struct memp *)(size_t)(memp_pools[i]->base);
+    for (j = 0; j < memp_pools[i]->num; ++j) {
+      memp_overflow_check_element_overflow(p, memp_pools[i]);
+      p = (struct memp*)(size_t)((u8_t*)p + MEMP_SIZE + memp_pools[i]->size + MEMP_SANITY_REGION_AFTER_ALIGNED);
    }
  }
-#if !MEMP_SEPARATE_POOLS
-  p = (struct memp *)LWIP_MEM_ALIGN(memp_memory);
-#endif /* !MEMP_SEPARATE_POOLS */
+
  for (i = 0; i < MEMP_MAX; ++i) {
-#if MEMP_SEPARATE_POOLS
-    p = (struct memp *)(memp_bases[i]);
-#endif /* MEMP_SEPARATE_POOLS */
-    for (j = 0; j < memp_num[i]; ++j) {
-      memp_overflow_check_element_underflow(p, i);
-      p = (struct memp*)((u8_t*)p + MEMP_SIZE + memp_sizes[i] + MEMP_SANITY_REGION_AFTER_ALIGNED);
+    p = (struct memp *)(size_t)(memp_pools[i]->base);
+    for (j = 0; j < memp_pools[i]->num; ++j) {
+      memp_overflow_check_element_underflow(p, memp_pools[i]);
+      p = (struct memp*)(size_t)((u8_t*)p + MEMP_SIZE + memp_pools[i]->size + MEMP_SANITY_REGION_AFTER_ALIGNED);
    }
  }
 }
@@ -321,34 +186,52 @@ memp_overflow_check_all(void)
 * Initialize the restricted areas of all memp elements in every pool.
 */
 static void
-memp_overflow_init(void)
+memp_overflow_init(const struct memp_desc *desc)
 {
-  u16_t i, j;
+  u16_t i;
  struct memp *p;
  u8_t *m;

-#if !MEMP_SEPARATE_POOLS
-  p = (struct memp *)LWIP_MEM_ALIGN(memp_memory);
-#endif /* !MEMP_SEPARATE_POOLS */
-  for (i = 0; i < MEMP_MAX; ++i) {
-#if MEMP_SEPARATE_POOLS
-    p = (struct memp *)(memp_bases[i]);
-#endif /* MEMP_SEPARATE_POOLS */
-    for (j = 0; j < memp_num[i]; ++j) {
+  p = (struct memp *)(size_t)(desc->base);
+  for (i = 0; i < desc->num; ++i) {
 #if MEMP_SANITY_REGION_BEFORE_ALIGNED > 0
-      m = (u8_t*)p + MEMP_SIZE - MEMP_SANITY_REGION_BEFORE_ALIGNED;
-      memset(m, 0xcd, MEMP_SANITY_REGION_BEFORE_ALIGNED);
+    m = (u8_t*)p + MEMP_SIZE - MEMP_SANITY_REGION_BEFORE_ALIGNED;
+    memset(m, 0xcd, MEMP_SANITY_REGION_BEFORE_ALIGNED);
 #endif
 #if MEMP_SANITY_REGION_AFTER_ALIGNED > 0
-      m = (u8_t*)p + MEMP_SIZE + memp_sizes[i];
-      memset(m, 0xcd, MEMP_SANITY_REGION_AFTER_ALIGNED);
+    m = (u8_t*)p + MEMP_SIZE + desc->size;
+    memset(m, 0xcd, MEMP_SANITY_REGION_AFTER_ALIGNED);
 #endif
-      p = (struct memp*)((u8_t*)p + MEMP_SIZE + memp_sizes[i] + MEMP_SANITY_REGION_AFTER_ALIGNED);
-    }
+    p = (struct memp*)(size_t)((u8_t*)p + MEMP_SIZE + desc->size + MEMP_SANITY_REGION_AFTER_ALIGNED);
  }
 }
 #endif /* MEMP_OVERFLOW_CHECK */

+
+void
+memp_init_pool(const struct memp_desc *desc)
+{
+  int i;
+  struct memp *memp;
+  
+  *desc->tab = NULL;
+  memp = (struct memp*)LWIP_MEM_ALIGN(desc->base);
+  /* create a linked list of memp elements */
+  for (i = 0; i < desc->num; ++i) {
+    memp->next = *desc->tab;
+    *desc->tab = memp;
+    memp = (struct memp *)(void *)((u8_t *)memp + MEMP_SIZE + desc->size
+#if MEMP_OVERFLOW_CHECK
+      + MEMP_SANITY_REGION_AFTER_ALIGNED
+#endif
+    );
+  }  
+
+#if MEMP_OVERFLOW_CHECK
+  memp_overflow_init(desc);
+#endif /* MEMP_OVERFLOW_CHECK */
+}
+
 /**
 * Initialize this module.
 *
@@ -357,43 +240,62 @@ memp_overflow_init(void)
 void
 memp_init(void)
 {
-  struct memp *memp;
-  u16_t i, j;
+  u16_t i;

  for (i = 0; i < MEMP_MAX; ++i) {
    MEMP_STATS_AVAIL(used, i, 0);
    MEMP_STATS_AVAIL(max, i, 0);
    MEMP_STATS_AVAIL(err, i, 0);
-    MEMP_STATS_AVAIL(avail, i, memp_num[i]);
+    MEMP_STATS_AVAIL(avail, i, memp_pools[i]->num);
  }

-#if !MEMP_SEPARATE_POOLS
-  memp = (struct memp *)LWIP_MEM_ALIGN(memp_memory);
-#endif /* !MEMP_SEPARATE_POOLS */
  /* for every pool: */
  for (i = 0; i < MEMP_MAX; ++i) {
-    memp_tab[i] = NULL;
-#if MEMP_SEPARATE_POOLS
-    memp = (struct memp*)LWIP_MEM_ALIGN(memp_bases[i]);
-#endif /* MEMP_SEPARATE_POOLS */
-    /* create a linked list of memp elements */
-    for (j = 0; j < memp_num[i]; ++j) {
-      memp->next = memp_tab[i];
-      memp_tab[i] = memp;
-      memp = (struct memp *)(void *)((u8_t *)memp + MEMP_SIZE + memp_sizes[i]
-#if MEMP_OVERFLOW_CHECK
-        + MEMP_SANITY_REGION_AFTER_ALIGNED
-#endif
-      );
-    }
+    memp_init_pool(memp_pools[i]);
  }
+
 #if MEMP_OVERFLOW_CHECK
-  memp_overflow_init();
  /* check everything a first time to see if it worked */
  memp_overflow_check_all();
 #endif /* MEMP_OVERFLOW_CHECK */
 }

+void *
+#if !MEMP_OVERFLOW_CHECK
+memp_malloc_pool(const struct memp_desc *desc)
+#else
+memp_malloc_pool_fn(const struct memp_desc *desc, const char* file, const int line)
+#endif
+{
+  struct memp *memp;
+  SYS_ARCH_DECL_PROTECT(old_level);
+
+  SYS_ARCH_PROTECT(old_level);
+
+  memp = *desc->tab;
+
+#if MEMP_OVERFLOW_CHECK == 1
+  memp_overflow_check_element_overflow(memp, desc);
+  memp_overflow_check_element_underflow(memp, desc);
+#endif /* MEMP_OVERFLOW_CHECK */
+
+  if (memp != NULL) {
+    *desc->tab = memp->next;
+#if MEMP_OVERFLOW_CHECK
+    memp->next = NULL;
+    memp->file = file;
+    memp->line = line;
+#endif /* MEMP_OVERFLOW_CHECK */
+    LWIP_ASSERT("memp_malloc: memp properly aligned",
+                ((mem_ptr_t)memp % MEM_ALIGNMENT) == 0);
+    memp = (struct memp*)(void *)((u8_t*)memp + MEMP_SIZE);
+  }
+
+  SYS_ARCH_UNPROTECT(old_level);
+
+  return memp;
+}
+
 /**
 * Get an element from a specific pool.
 *
@@ -412,31 +314,30 @@ memp_malloc(memp_t type)
 memp_malloc_fn(memp_t type, const char* file, const int line)
 #endif
 {
-  struct memp *memp;
+  void *memp;
  SYS_ARCH_DECL_PROTECT(old_level);

  LWIP_ERROR("memp_malloc: type < MEMP_MAX", (type < MEMP_MAX), return NULL;);

  SYS_ARCH_PROTECT(old_level);
+
 #if MEMP_OVERFLOW_CHECK >= 2
  memp_overflow_check_all();
 #endif /* MEMP_OVERFLOW_CHECK >= 2 */

-  memp = memp_tab[type];
+#if !MEMP_OVERFLOW_CHECK
+  memp = memp_malloc_pool(memp_pools[type]);
+#else
+  memp = memp_malloc_pool_fn(memp_pools[type], file, line);
+#endif

  if (memp != NULL) {
-    memp_tab[type] = memp->next;
-#if MEMP_OVERFLOW_CHECK
-    memp->next = NULL;
-    memp->file = file;
-    memp->line = line;
-#endif /* MEMP_OVERFLOW_CHECK */
-    MEMP_STATS_INC_USED(used, type);
-    LWIP_ASSERT("memp_malloc: memp properly aligned",
-                ((mem_ptr_t)memp % MEM_ALIGNMENT) == 0);
-    memp = (struct memp*)(void *)((u8_t*)memp + MEMP_SIZE);
+    MEMP_STATS_INC(used, type);
+    if(MEMP_STATS_GET(used, type) > MEMP_STATS_GET(max, type)) {
+      MEMP_STATS_AVAIL(max, type, MEMP_STATS_GET(used, type));
+    }
  } else {
-    LWIP_DEBUGF(MEMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("memp_malloc: out of memory in pool %s\n", memp_desc[type]));
+    LWIP_DEBUGF(MEMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("memp_malloc: out of memory in pool %s\n", memp_pools[type]->desc));
    MEMP_STATS_INC(err, type);
  }

@@ -445,14 +346,8 @@ memp_malloc_fn(memp_t type, const char* file, const int line)
  return memp;
 }

-/**
- * Put an element back into its pool.
- *
- * @param type the pool where to put mem
- * @param mem the memp element to free
- */
 void
-memp_free(memp_t type, void *mem)
+memp_free_pool(const struct memp_desc* desc, void *mem)
 {
  struct memp *memp;
 #ifdef LWIP_HOOK_MEMP_AVAILABLE
@@ -469,28 +364,53 @@ memp_free(memp_t type, void *mem)
  memp = (struct memp *)(void *)((u8_t*)mem - MEMP_SIZE);

  SYS_ARCH_PROTECT(old_level);
-#if MEMP_OVERFLOW_CHECK
-#if MEMP_OVERFLOW_CHECK >= 2
-  memp_overflow_check_all();
-#else
-  memp_overflow_check_element_overflow(memp, type);
-  memp_overflow_check_element_underflow(memp, type);
-#endif /* MEMP_OVERFLOW_CHECK >= 2 */
+
+#if MEMP_OVERFLOW_CHECK == 2
+  memp_overflow_check_element_overflow(memp, desc);
+  memp_overflow_check_element_underflow(memp, desc);
 #endif /* MEMP_OVERFLOW_CHECK */

-  MEMP_STATS_DEC(used, type);
-
-  memp->next = memp_tab[type];
+  memp->next = *desc->tab;
 #ifdef LWIP_HOOK_MEMP_AVAILABLE
-  old_first = memp_tab[type];
+  old_first = *desc->tab;
 #endif
-  memp_tab[type] = memp;
+  *desc->tab = memp;

 #if MEMP_SANITY_CHECK
-  LWIP_ASSERT("memp sanity", memp_sanity());
+  LWIP_ASSERT("memp sanity", memp_sanity(desc));
 #endif /* MEMP_SANITY_CHECK */

  SYS_ARCH_UNPROTECT(old_level);
+}
+
+/**
+ * Put an element back into its pool.
+ *
+ * @param type the pool where to put mem
+ * @param mem the memp element to free
+ */
+void
+memp_free(memp_t type, void *mem)
+{
+#ifdef LWIP_HOOK_MEMP_AVAILABLE
+  struct memp *old_first;
+#endif
+  SYS_ARCH_DECL_PROTECT(old_level);
+
+  LWIP_ERROR("memp_free: type < MEMP_MAX", (type < MEMP_MAX), return;);
+
+  SYS_ARCH_PROTECT(old_level);
+
+#if MEMP_OVERFLOW_CHECK >= 2
+  memp_overflow_check_all();
+#endif /* MEMP_OVERFLOW_CHECK >= 2 */
+
+  MEMP_STATS_DEC(used, type);
+
+  memp_free_pool(memp_pools[type], mem);
+
+  SYS_ARCH_UNPROTECT(old_level);
+
 #ifdef LWIP_HOOK_MEMP_AVAILABLE
  if (old_first == NULL) {
    LWIP_HOOK_MEMP_AVAILABLE(type);