Diff: lwip/core/snmp/mib_structs.c

Revision:

0:350011bf8be7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lwip/core/snmp/mib_structs.c	Tue Nov 23 14:15:36 2010 +0000
@@ -0,0 +1,1174 @@
+/**
+ * @file
+ * MIB tree access/construction functions.
+ */
+
+/*
+ * Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.
+ * 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.
+ *
+ * Author: Christiaan Simons <christiaan.simons@axon.tv>
+ */
+
+#include "lwip/opt.h"
+
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/snmp_structs.h"
+#include "lwip/memp.h"
+#include "lwip/netif.h"
+
+/** .iso.org.dod.internet address prefix, @see snmp_iso_*() */
+const s32_t prefix[4] = {1, 3, 6, 1};
+
+#define NODE_STACK_SIZE (LWIP_SNMP_OBJ_ID_LEN)
+/** node stack entry (old news?) */
+struct nse
+{
+  /** right child */
+  struct mib_node* r_ptr;
+  /** right child identifier */
+  s32_t r_id;
+  /** right child next level */
+  u8_t r_nl;
+};
+static u8_t node_stack_cnt;
+static struct nse node_stack[NODE_STACK_SIZE];
+
+/**
+ * Pushes nse struct onto stack.
+ */
+static void
+push_node(struct nse* node)
+{
+  LWIP_ASSERT("node_stack_cnt < NODE_STACK_SIZE",node_stack_cnt < NODE_STACK_SIZE);
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("push_node() node=%p id=%"S32_F"\n",(void*)(node->r_ptr),node->r_id));
+  if (node_stack_cnt < NODE_STACK_SIZE)
+  {
+    node_stack[node_stack_cnt] = *node;
+    node_stack_cnt++;
+  }
+}
+
+/**
+ * Pops nse struct from stack.
+ */
+static void
+pop_node(struct nse* node)
+{
+  if (node_stack_cnt > 0)
+  {
+    node_stack_cnt--;
+    *node = node_stack[node_stack_cnt];
+  }
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("pop_node() node=%p id=%"S32_F"\n",(void *)(node->r_ptr),node->r_id));
+}
+
+/**
+ * Conversion from ifIndex to lwIP netif
+ * @param ifindex is a s32_t object sub-identifier
+ * @param netif points to returned netif struct pointer
+ */
+void
+snmp_ifindextonetif(s32_t ifindex, struct netif **netif)
+{
+  struct netif *nif = netif_list;
+  s32_t i, ifidx;
+
+  ifidx = ifindex - 1;
+  i = 0;
+  while ((nif != NULL) && (i < ifidx))
+  {
+    nif = nif->next;
+    i++;
+  }
+  *netif = nif;
+}
+
+/**
+ * Conversion from lwIP netif to ifIndex
+ * @param netif points to a netif struct
+ * @param ifidx points to s32_t object sub-identifier
+ */
+void
+snmp_netiftoifindex(struct netif *netif, s32_t *ifidx)
+{
+  struct netif *nif = netif_list;
+  u16_t i;
+
+  i = 0;
+  while ((nif != NULL) && (nif != netif))
+  {
+    nif = nif->next;
+    i++;
+  }
+  *ifidx = i+1;
+}
+
+/**
+ * Conversion from oid to lwIP ip_addr
+ * @param ident points to s32_t ident[4] input
+ * @param ip points to output struct
+ */
+void
+snmp_oidtoip(s32_t *ident, ip_addr_t *ip)
+{
+  IP4_ADDR(ip, ident[0], ident[1], ident[2], ident[3]);
+}
+
+/**
+ * Conversion from lwIP ip_addr to oid
+ * @param ip points to input struct
+ * @param ident points to s32_t ident[4] output
+ */
+void
+snmp_iptooid(ip_addr_t *ip, s32_t *ident)
+{
+  ident[0] = ip4_addr1(ip);
+  ident[1] = ip4_addr2(ip);
+  ident[2] = ip4_addr3(ip);
+  ident[3] = ip4_addr4(ip);
+}
+
+struct mib_list_node *
+snmp_mib_ln_alloc(s32_t id)
+{
+  struct mib_list_node *ln;
+
+  ln = (struct mib_list_node *)memp_malloc(MEMP_SNMP_NODE);
+  if (ln != NULL)
+  {
+    ln->prev = NULL;
+    ln->next = NULL;
+    ln->objid = id;
+    ln->nptr = NULL;
+  }
+  return ln;
+}
+
+void
+snmp_mib_ln_free(struct mib_list_node *ln)
+{
+  memp_free(MEMP_SNMP_NODE, ln);
+}
+
+struct mib_list_rootnode *
+snmp_mib_lrn_alloc(void)
+{
+  struct mib_list_rootnode *lrn;
+
+  lrn = (struct mib_list_rootnode*)memp_malloc(MEMP_SNMP_ROOTNODE);
+  if (lrn != NULL)
+  {
+    lrn->get_object_def = noleafs_get_object_def;
+    lrn->get_value = noleafs_get_value;
+    lrn->set_test = noleafs_set_test;
+    lrn->set_value = noleafs_set_value;
+    lrn->node_type = MIB_NODE_LR;
+    lrn->maxlength = 0;
+    lrn->head = NULL;
+    lrn->tail = NULL;
+    lrn->count = 0;
+  }
+  return lrn;
+}
+
+void
+snmp_mib_lrn_free(struct mib_list_rootnode *lrn)
+{
+  memp_free(MEMP_SNMP_ROOTNODE, lrn);
+}
+
+/**
+ * Inserts node in idx list in a sorted
+ * (ascending order) fashion and
+ * allocates the node if needed.
+ *
+ * @param rn points to the root node
+ * @param objid is the object sub identifier
+ * @param insn points to a pointer to the inserted node
+ *   used for constructing the tree.
+ * @return -1 if failed, 1 if inserted, 2 if present.
+ */
+s8_t
+snmp_mib_node_insert(struct mib_list_rootnode *rn, s32_t objid, struct mib_list_node **insn)
+{
+  struct mib_list_node *nn;
+  s8_t insert;
+
+  LWIP_ASSERT("rn != NULL",rn != NULL);
+
+  /* -1 = malloc failure, 0 = not inserted, 1 = inserted, 2 = was present */
+  insert = 0;
+  if (rn->head == NULL)
+  {
+    /* empty list, add first node */
+    LWIP_DEBUGF(SNMP_MIB_DEBUG,("alloc empty list objid==%"S32_F"\n",objid));
+    nn = snmp_mib_ln_alloc(objid);
+    if (nn != NULL)
+    {
+      rn->head = nn;
+      rn->tail = nn;
+      *insn = nn;
+      insert = 1;
+    }
+    else
+    {
+      insert = -1;
+    }
+  }
+  else
+  {
+    struct mib_list_node *n;
+    /* at least one node is present */
+    n = rn->head;
+    while ((n != NULL) && (insert == 0))
+    {
+      if (n->objid == objid)
+      {
+        /* node is already there */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("node already there objid==%"S32_F"\n",objid));
+        *insn = n;
+        insert = 2;
+      }
+      else if (n->objid < objid)
+      {
+        if (n->next == NULL)
+        {
+          /* alloc and insert at the tail */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("alloc ins tail objid==%"S32_F"\n",objid));
+          nn = snmp_mib_ln_alloc(objid);
+          if (nn != NULL)
+          {
+            nn->next = NULL;
+            nn->prev = n;
+            n->next = nn;
+            rn->tail = nn;
+            *insn = nn;
+            insert = 1;
+          }
+          else
+          {
+            /* insertion failure */
+            insert = -1;
+          }
+        }
+        else
+        {
+          /* there's more to explore: traverse list */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("traverse list\n"));
+          n = n->next;
+        }
+      }
+      else
+      {
+        /* n->objid > objid */
+        /* alloc and insert between n->prev and n */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("alloc ins n->prev, objid==%"S32_F", n\n",objid));
+        nn = snmp_mib_ln_alloc(objid);
+        if (nn != NULL)
+        {
+          if (n->prev == NULL)
+          {
+            /* insert at the head */
+            nn->next = n;
+            nn->prev = NULL;
+            rn->head = nn;
+            n->prev = nn;
+          }
+          else
+          {
+            /* insert in the middle */
+            nn->next = n;
+            nn->prev = n->prev;
+            n->prev->next = nn;
+            n->prev = nn;
+          }
+          *insn = nn;
+          insert = 1;
+        }
+        else
+        {
+          /* insertion failure */
+          insert = -1;
+        }
+      }
+    }
+  }
+  if (insert == 1)
+  {
+    rn->count += 1;
+  }
+  LWIP_ASSERT("insert != 0",insert != 0);
+  return insert;
+}
+
+/**
+ * Finds node in idx list and returns deletion mark.
+ *
+ * @param rn points to the root node
+ * @param objid  is the object sub identifier
+ * @param fn returns pointer to found node
+ * @return 0 if not found, 1 if deletable,
+ *   2 can't delete (2 or more children), 3 not a list_node
+ */
+s8_t
+snmp_mib_node_find(struct mib_list_rootnode *rn, s32_t objid, struct mib_list_node **fn)
+{
+  s8_t fc;
+  struct mib_list_node *n;
+
+  LWIP_ASSERT("rn != NULL",rn != NULL);
+  n = rn->head;
+  while ((n != NULL) && (n->objid != objid))
+  {
+    n = n->next;
+  }
+  if (n == NULL)
+  {
+    fc = 0;
+  }
+  else if (n->nptr == NULL)
+  {
+    /* leaf, can delete node */
+    fc = 1;
+  }
+  else
+  {
+    struct mib_list_rootnode *r;
+
+    if (n->nptr->node_type == MIB_NODE_LR)
+    {
+      r = (struct mib_list_rootnode *)n->nptr;
+      if (r->count > 1)
+      {
+        /* can't delete node */
+        fc = 2;
+      }
+      else
+      {
+        /* count <= 1, can delete node */
+        fc = 1;
+      }
+    }
+    else
+    {
+      /* other node type */
+      fc = 3;
+    }
+  }
+  *fn = n;
+  return fc;
+}
+
+/**
+ * Removes node from idx list
+ * if it has a single child left.
+ *
+ * @param rn points to the root node
+ * @param n points to the node to delete
+ * @return the nptr to be freed by caller
+ */
+struct mib_list_rootnode *
+snmp_mib_node_delete(struct mib_list_rootnode *rn, struct mib_list_node *n)
+{
+  struct mib_list_rootnode *next;
+
+  LWIP_ASSERT("rn != NULL",rn != NULL);
+  LWIP_ASSERT("n != NULL",n != NULL);
+
+  /* caller must remove this sub-tree */
+  next = (struct mib_list_rootnode*)(n->nptr);
+  rn->count -= 1;
+
+  if (n == rn->head)
+  {
+    rn->head = n->next;
+    if (n->next != NULL)
+    {
+      /* not last node, new list begin */
+      n->next->prev = NULL;
+    }
+  }
+  else if (n == rn->tail)
+  {
+    rn->tail = n->prev;
+    if (n->prev != NULL)
+    {
+      /* not last node, new list end */
+      n->prev->next = NULL;
+    }
+  }
+  else
+  {
+    /* node must be in the middle */
+    n->prev->next = n->next;
+    n->next->prev = n->prev;
+  }
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("free list objid==%"S32_F"\n",n->objid));
+  snmp_mib_ln_free(n);
+  if (rn->count == 0)
+  {
+    rn->head = NULL;
+    rn->tail = NULL;
+  }
+  return next;
+}
+
+
+
+/**
+ * Searches tree for the supplied (scalar?) object identifier.
+ *
+ * @param node points to the root of the tree ('.internet')
+ * @param ident_len the length of the supplied object identifier
+ * @param ident points to the array of sub identifiers
+ * @param np points to the found object instance (return)
+ * @return pointer to the requested parent (!) node if success, NULL otherwise
+ */
+struct mib_node *
+snmp_search_tree(struct mib_node *node, u8_t ident_len, s32_t *ident, struct snmp_name_ptr *np)
+{
+  u8_t node_type, ext_level;
+
+  ext_level = 0;
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("node==%p *ident==%"S32_F"\n",(void*)node,*ident));
+  while (node != NULL)
+  {
+    node_type = node->node_type;
+    if ((node_type == MIB_NODE_AR) || (node_type == MIB_NODE_RA))
+    {
+      struct mib_array_node *an;
+      u16_t i;
+
+      if (ident_len > 0)
+      {
+        /* array node (internal ROM or RAM, fixed length) */
+        an = (struct mib_array_node *)node;
+        i = 0;
+        while ((i < an->maxlength) && (an->objid[i] != *ident))
+        {
+          i++;
+        }
+        if (i < an->maxlength)
+        {
+          /* found it, if available proceed to child, otherwise inspect leaf */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("an->objid[%"U16_F"]==%"S32_F" *ident==%"S32_F"\n",i,an->objid[i],*ident));
+          if (an->nptr[i] == NULL)
+          {
+            /* a scalar leaf OR table,
+               inspect remaining instance number / table index */
+            np->ident_len = ident_len;
+            np->ident = ident;
+            return (struct mib_node*)an;
+          }
+          else
+          {
+            /* follow next child pointer */
+            ident++;
+            ident_len--;
+            node = an->nptr[i];
+          }
+        }
+        else
+        {
+          /* search failed, identifier mismatch (nosuchname) */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("an search failed *ident==%"S32_F"\n",*ident));
+          return NULL;
+        }
+      }
+      else
+      {
+        /* search failed, short object identifier (nosuchname) */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("an search failed, short object identifier\n"));
+        return NULL;
+      }
+    }
+    else if(node_type == MIB_NODE_LR)
+    {
+      struct mib_list_rootnode *lrn;
+      struct mib_list_node *ln;
+
+      if (ident_len > 0)
+      {
+        /* list root node (internal 'RAM', variable length) */
+        lrn = (struct mib_list_rootnode *)node;
+        ln = lrn->head;
+        /* iterate over list, head to tail */
+        while ((ln != NULL) && (ln->objid != *ident))
+        {
+          ln = ln->next;
+        }
+        if (ln != NULL)
+        {
+          /* found it, proceed to child */;
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("ln->objid==%"S32_F" *ident==%"S32_F"\n",ln->objid,*ident));
+          if (ln->nptr == NULL)
+          {
+            np->ident_len = ident_len;
+            np->ident = ident;
+            return (struct mib_node*)lrn;
+          }
+          else
+          {
+            /* follow next child pointer */
+            ident_len--;
+            ident++;
+            node = ln->nptr;
+          }
+        }
+        else
+        {
+          /* search failed */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("ln search failed *ident==%"S32_F"\n",*ident));
+          return NULL;
+        }
+      }
+      else
+      {
+        /* search failed, short object identifier (nosuchname) */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("ln search failed, short object identifier\n"));
+        return NULL;
+      }
+    }
+    else if(node_type == MIB_NODE_EX)
+    {
+      struct mib_external_node *en;
+      u16_t i, len;
+
+      if (ident_len > 0)
+      {
+        /* external node (addressing and access via functions) */
+        en = (struct mib_external_node *)node;
+
+        i = 0;
+        len = en->level_length(en->addr_inf,ext_level);
+        while ((i < len) && (en->ident_cmp(en->addr_inf,ext_level,i,*ident) != 0))
+        {
+          i++;
+        }
+        if (i < len)
+        {
+          s32_t debug_id;
+
+          en->get_objid(en->addr_inf,ext_level,i,&debug_id);
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("en->objid==%"S32_F" *ident==%"S32_F"\n",debug_id,*ident));
+          if ((ext_level + 1) == en->tree_levels)
+          {
+            np->ident_len = ident_len;
+            np->ident = ident;
+            return (struct mib_node*)en;
+          }
+          else
+          {
+            /* found it, proceed to child */
+            ident_len--;
+            ident++;
+            ext_level++;
+          }
+        }
+        else
+        {
+          /* search failed */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("en search failed *ident==%"S32_F"\n",*ident));
+          return NULL;
+        }
+      }
+      else
+      {
+        /* search failed, short object identifier (nosuchname) */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("en search failed, short object identifier\n"));
+        return NULL;
+      }
+    }
+    else if (node_type == MIB_NODE_SC)
+    {
+      mib_scalar_node *sn;
+
+      sn = (mib_scalar_node *)node;
+      if ((ident_len == 1) && (*ident == 0))
+      {
+        np->ident_len = ident_len;
+        np->ident = ident;
+        return (struct mib_node*)sn;
+      }
+      else
+      {
+        /* search failed, short object identifier (nosuchname) */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("search failed, invalid object identifier length\n"));
+        return NULL;
+      }
+    }
+    else
+    {
+      /* unknown node_type */
+      LWIP_DEBUGF(SNMP_MIB_DEBUG,("search failed node_type %"U16_F" unkown\n",(u16_t)node_type));
+      return NULL;
+    }
+  }
+  /* done, found nothing */
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("search failed node==%p\n",(void*)node));
+  return NULL;
+}
+
+/**
+ * Test table for presence of at least one table entry.
+ */
+static u8_t
+empty_table(struct mib_node *node)
+{
+  u8_t node_type;
+  u8_t empty = 0;
+
+  if (node != NULL)
+  {
+    node_type = node->node_type;
+    if (node_type == MIB_NODE_LR)
+    {
+      struct mib_list_rootnode *lrn;
+      lrn = (struct mib_list_rootnode *)node;
+      if ((lrn->count == 0) || (lrn->head == NULL))
+      {
+        empty = 1;
+      }
+    }
+    else if ((node_type == MIB_NODE_AR) || (node_type == MIB_NODE_RA))
+    {
+      struct mib_array_node *an;
+      an = (struct mib_array_node *)node;
+      if ((an->maxlength == 0) || (an->nptr == NULL))
+      {
+        empty = 1;
+      }
+    }
+    else if (node_type == MIB_NODE_EX)
+    {
+      struct mib_external_node *en;
+      en = (struct mib_external_node *)node;
+      if (en->tree_levels == 0)
+      {
+        empty = 1;
+      }
+    }
+  }
+  return empty;
+}
+
+/**
+ * Tree expansion.
+ */
+struct mib_node *
+snmp_expand_tree(struct mib_node *node, u8_t ident_len, s32_t *ident, struct snmp_obj_id *oidret)
+{
+  u8_t node_type, ext_level, climb_tree;
+
+  ext_level = 0;
+  /* reset node stack */
+  node_stack_cnt = 0;
+  while (node != NULL)
+  {
+    climb_tree = 0;
+    node_type = node->node_type;
+    if ((node_type == MIB_NODE_AR) || (node_type == MIB_NODE_RA))
+    {
+      struct mib_array_node *an;
+      u16_t i;
+
+      /* array node (internal ROM or RAM, fixed length) */
+      an = (struct mib_array_node *)node;
+      if (ident_len > 0)
+      {
+        i = 0;
+        while ((i < an->maxlength) && (an->objid[i] < *ident))
+        {
+          i++;
+        }
+        if (i < an->maxlength)
+        {
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("an->objid[%"U16_F"]==%"S32_F" *ident==%"S32_F"\n",i,an->objid[i],*ident));
+          /* add identifier to oidret */
+          oidret->id[oidret->len] = an->objid[i];
+          (oidret->len)++;
+
+          if (an->nptr[i] == NULL)
+          {
+            LWIP_DEBUGF(SNMP_MIB_DEBUG,("leaf node\n"));
+            /* leaf node (e.g. in a fixed size table) */
+            if (an->objid[i] > *ident)
+            {
+              return (struct mib_node*)an;
+            }
+            else if ((i + 1) < an->maxlength)
+            {
+              /* an->objid[i] == *ident */
+              (oidret->len)--;
+              oidret->id[oidret->len] = an->objid[i + 1];
+              (oidret->len)++;
+              return (struct mib_node*)an;
+            }
+            else
+            {
+              /* (i + 1) == an->maxlength */
+              (oidret->len)--;
+              climb_tree = 1;
+            }
+          }
+          else
+          {
+            u8_t j;
+            struct nse cur_node;
+
+            LWIP_DEBUGF(SNMP_MIB_DEBUG,("non-leaf node\n"));
+            /* non-leaf, store right child ptr and id */
+            LWIP_ASSERT("i < 0xff", i < 0xff);
+            j = (u8_t)i + 1;
+            while ((j < an->maxlength) && (empty_table(an->nptr[j])))
+            {
+              j++;
+            }
+            if (j < an->maxlength)
+            {
+              cur_node.r_ptr = an->nptr[j];
+              cur_node.r_id = an->objid[j];
+              cur_node.r_nl = 0;
+            }
+            else
+            {
+              cur_node.r_ptr = NULL;
+            }
+            push_node(&cur_node);
+            if (an->objid[i] == *ident)
+            {
+              ident_len--;
+              ident++;
+            }
+            else
+            {
+              /* an->objid[i] < *ident */
+              ident_len = 0;
+            }
+            /* follow next child pointer */
+            node = an->nptr[i];
+          }
+        }
+        else
+        {
+          /* i == an->maxlength */
+          climb_tree = 1;
+        }
+      }
+      else
+      {
+        u8_t j;
+        /* ident_len == 0, complete with leftmost '.thing' */
+        j = 0;
+        while ((j < an->maxlength) && empty_table(an->nptr[j]))
+        {
+          j++;
+        }
+        if (j < an->maxlength)
+        {
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("left an->objid[j]==%"S32_F"\n",an->objid[j]));
+          oidret->id[oidret->len] = an->objid[j];
+          (oidret->len)++;
+          if (an->nptr[j] == NULL)
+          {
+            /* leaf node */
+            return (struct mib_node*)an;
+          }
+          else
+          {
+            /* no leaf, continue */
+            node = an->nptr[j];
+          }
+        }
+        else
+        {
+          /* j == an->maxlength */
+          climb_tree = 1;
+        }
+      }
+    }
+    else if(node_type == MIB_NODE_LR)
+    {
+      struct mib_list_rootnode *lrn;
+      struct mib_list_node *ln;
+
+      /* list root node (internal 'RAM', variable length) */
+      lrn = (struct mib_list_rootnode *)node;
+      if (ident_len > 0)
+      {
+        ln = lrn->head;
+        /* iterate over list, head to tail */
+        while ((ln != NULL) && (ln->objid < *ident))
+        {
+          ln = ln->next;
+        }
+        if (ln != NULL)
+        {
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("ln->objid==%"S32_F" *ident==%"S32_F"\n",ln->objid,*ident));
+          oidret->id[oidret->len] = ln->objid;
+          (oidret->len)++;
+          if (ln->nptr == NULL)
+          {
+            /* leaf node */
+            if (ln->objid > *ident)
+            {
+              return (struct mib_node*)lrn;
+            }
+            else if (ln->next != NULL)
+            {
+              /* ln->objid == *ident */
+              (oidret->len)--;
+              oidret->id[oidret->len] = ln->next->objid;
+              (oidret->len)++;
+              return (struct mib_node*)lrn;
+            }
+            else
+            {
+              /* ln->next == NULL */
+              (oidret->len)--;
+              climb_tree = 1;
+            }
+          }
+          else
+          {
+            struct mib_list_node *jn;
+            struct nse cur_node;
+
+            /* non-leaf, store right child ptr and id */
+            jn = ln->next;
+            while ((jn != NULL) && empty_table(jn->nptr))
+            {
+              jn = jn->next;
+            }
+            if (jn != NULL)
+            {
+              cur_node.r_ptr = jn->nptr;
+              cur_node.r_id = jn->objid;
+              cur_node.r_nl = 0;
+            }
+            else
+            {
+              cur_node.r_ptr = NULL;
+            }
+            push_node(&cur_node);
+            if (ln->objid == *ident)
+            {
+              ident_len--;
+              ident++;
+            }
+            else
+            {
+              /* ln->objid < *ident */
+              ident_len = 0;
+            }
+            /* follow next child pointer */
+            node = ln->nptr;
+          }
+
+        }
+        else
+        {
+          /* ln == NULL */
+          climb_tree = 1;
+        }
+      }
+      else
+      {
+        struct mib_list_node *jn;
+        /* ident_len == 0, complete with leftmost '.thing' */
+        jn = lrn->head;
+        while ((jn != NULL) && empty_table(jn->nptr))
+        {
+          jn = jn->next;
+        }
+        if (jn != NULL)
+        {
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("left jn->objid==%"S32_F"\n",jn->objid));
+          oidret->id[oidret->len] = jn->objid;
+          (oidret->len)++;
+          if (jn->nptr == NULL)
+          {
+            /* leaf node */
+            LWIP_DEBUGF(SNMP_MIB_DEBUG,("jn->nptr == NULL\n"));
+            return (struct mib_node*)lrn;
+          }
+          else
+          {
+            /* no leaf, continue */
+            node = jn->nptr;
+          }
+        }
+        else
+        {
+          /* jn == NULL */
+          climb_tree = 1;
+        }
+      }
+    }
+    else if(node_type == MIB_NODE_EX)
+    {
+      struct mib_external_node *en;
+      s32_t ex_id;
+
+      /* external node (addressing and access via functions) */
+      en = (struct mib_external_node *)node;
+      if (ident_len > 0)
+      {
+        u16_t i, len;
+
+        i = 0;
+        len = en->level_length(en->addr_inf,ext_level);
+        while ((i < len) && (en->ident_cmp(en->addr_inf,ext_level,i,*ident) < 0))
+        {
+          i++;
+        }
+        if (i < len)
+        {
+          /* add identifier to oidret */
+          en->get_objid(en->addr_inf,ext_level,i,&ex_id);
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("en->objid[%"U16_F"]==%"S32_F" *ident==%"S32_F"\n",i,ex_id,*ident));
+          oidret->id[oidret->len] = ex_id;
+          (oidret->len)++;
+
+          if ((ext_level + 1) == en->tree_levels)
+          {
+            LWIP_DEBUGF(SNMP_MIB_DEBUG,("leaf node\n"));
+            /* leaf node */
+            if (ex_id > *ident)
+            {
+              return (struct mib_node*)en;
+            }
+            else if ((i + 1) < len)
+            {
+              /* ex_id == *ident */
+              en->get_objid(en->addr_inf,ext_level,i + 1,&ex_id);
+              (oidret->len)--;
+              oidret->id[oidret->len] = ex_id;
+              (oidret->len)++;
+              return (struct mib_node*)en;
+            }
+            else
+            {
+              /* (i + 1) == len */
+              (oidret->len)--;
+              climb_tree = 1;
+            }
+          }
+          else
+          {
+            u8_t j;
+            struct nse cur_node;
+
+            LWIP_DEBUGF(SNMP_MIB_DEBUG,("non-leaf node\n"));
+            /* non-leaf, store right child ptr and id */
+            LWIP_ASSERT("i < 0xff", i < 0xff);
+            j = (u8_t)i + 1;
+            if (j < len)
+            {
+              /* right node is the current external node */
+              cur_node.r_ptr = node;
+              en->get_objid(en->addr_inf,ext_level,j,&cur_node.r_id);
+              cur_node.r_nl = ext_level + 1;
+            }
+            else
+            {
+              cur_node.r_ptr = NULL;
+            }
+            push_node(&cur_node);
+            if (en->ident_cmp(en->addr_inf,ext_level,i,*ident) == 0)
+            {
+              ident_len--;
+              ident++;
+            }
+            else
+            {
+              /* external id < *ident */
+              ident_len = 0;
+            }
+            /* proceed to child */
+            ext_level++;
+          }
+        }
+        else
+        {
+          /* i == len (en->level_len()) */
+          climb_tree = 1;
+        }
+      }
+      else
+      {
+        /* ident_len == 0, complete with leftmost '.thing' */
+        en->get_objid(en->addr_inf,ext_level,0,&ex_id);
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("left en->objid==%"S32_F"\n",ex_id));
+        oidret->id[oidret->len] = ex_id;
+        (oidret->len)++;
+        if ((ext_level + 1) == en->tree_levels)
+        {
+          /* leaf node */
+          LWIP_DEBUGF(SNMP_MIB_DEBUG,("(ext_level + 1) == en->tree_levels\n"));
+          return (struct mib_node*)en;
+        }
+        else
+        {
+          /* no leaf, proceed to child */
+          ext_level++;
+        }
+      }
+    }
+    else if(node_type == MIB_NODE_SC)
+    {
+      mib_scalar_node *sn;
+
+      /* scalar node  */
+      sn = (mib_scalar_node *)node;
+      if (ident_len > 0)
+      {
+        /* at .0 */
+        climb_tree = 1;
+      }
+      else
+      {
+        /* ident_len == 0, complete object identifier */
+        oidret->id[oidret->len] = 0;
+        (oidret->len)++;
+        /* leaf node */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("completed scalar leaf\n"));
+        return (struct mib_node*)sn;
+      }
+    }
+    else
+    {
+      /* unknown/unhandled node_type */
+      LWIP_DEBUGF(SNMP_MIB_DEBUG,("expand failed node_type %"U16_F" unkown\n",(u16_t)node_type));
+      return NULL;
+    }
+
+    if (climb_tree)
+    {
+      struct nse child;
+
+      /* find right child ptr */
+      child.r_ptr = NULL;
+      child.r_id = 0;
+      child.r_nl = 0;
+      while ((node_stack_cnt > 0) && (child.r_ptr == NULL))
+      {
+        pop_node(&child);
+        /* trim returned oid */
+        (oidret->len)--;
+      }
+      if (child.r_ptr != NULL)
+      {
+        /* incoming ident is useless beyond this point */
+        ident_len = 0;
+        oidret->id[oidret->len] = child.r_id;
+        oidret->len++;
+        node = child.r_ptr;
+        ext_level = child.r_nl;
+      }
+      else
+      {
+        /* tree ends here ... */
+        LWIP_DEBUGF(SNMP_MIB_DEBUG,("expand failed, tree ends here\n"));
+        return NULL;
+      }
+    }
+  }
+  /* done, found nothing */
+  LWIP_DEBUGF(SNMP_MIB_DEBUG,("expand failed node==%p\n",(void*)node));
+  return NULL;
+}
+
+/**
+ * Test object identifier for the iso.org.dod.internet prefix.
+ *
+ * @param ident_len the length of the supplied object identifier
+ * @param ident points to the array of sub identifiers
+ * @return 1 if it matches, 0 otherwise
+ */
+u8_t
+snmp_iso_prefix_tst(u8_t ident_len, s32_t *ident)
+{
+  if ((ident_len > 3) &&
+      (ident[0] == 1) && (ident[1] == 3) &&
+      (ident[2] == 6) && (ident[3] == 1))
+  {
+    return 1;
+  }
+  else
+  {
+    return 0;
+  }
+}
+
+/**
+ * Expands object identifier to the iso.org.dod.internet
+ * prefix for use in getnext operation.
+ *
+ * @param ident_len the length of the supplied object identifier
+ * @param ident points to the array of sub identifiers
+ * @param oidret points to returned expanded object identifier
+ * @return 1 if it matches, 0 otherwise
+ *
+ * @note ident_len 0 is allowed, expanding to the first known object id!!
+ */
+u8_t
+snmp_iso_prefix_expand(u8_t ident_len, s32_t *ident, struct snmp_obj_id *oidret)
+{
+  const s32_t *prefix_ptr;
+  s32_t *ret_ptr;
+  u8_t i;
+
+  i = 0;
+  prefix_ptr = &prefix[0];
+  ret_ptr = &oidret->id[0];
+  ident_len = ((ident_len < 4)?ident_len:4);
+  while ((i < ident_len) && ((*ident) <= (*prefix_ptr)))
+  {
+    *ret_ptr++ = *prefix_ptr++;
+    ident++;
+    i++;
+  }
+  if (i == ident_len)
+  {
+    /* match, complete missing bits */
+    while (i < 4)
+    {
+      *ret_ptr++ = *prefix_ptr++;
+      i++;
+    }
+    oidret->len = i;
+    return 1;
+  }
+  else
+  {
+    /* i != ident_len */
+    return 0;
+  }
+}
+
+#endif /* LWIP_SNMP */