Diff: EthernetInterface/lwip/core/snmp/msg_in.c

Revision:

0:0ed2a7c7190c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/EthernetInterface/lwip/core/snmp/msg_in.c	Fri May 31 04:09:54 2013 +0000
@@ -0,0 +1,1437 @@
+/**
+ * @file
+ * SNMP input message processing (RFC1157).
+ */
+
+/*
+ * 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.h"
+#include "lwip/snmp_asn1.h"
+#include "lwip/snmp_msg.h"
+#include "lwip/snmp_structs.h"
+#include "lwip/ip_addr.h"
+#include "lwip/memp.h"
+#include "lwip/udp.h"
+#include "lwip/stats.h"
+
+#include <string.h>
+
+/* public (non-static) constants */
+/** SNMP v1 == 0 */
+const s32_t snmp_version = 0;
+/** default SNMP community string */
+const char snmp_publiccommunity[7] = "public";
+
+/* statically allocated buffers for SNMP_CONCURRENT_REQUESTS */
+struct snmp_msg_pstat msg_input_list[SNMP_CONCURRENT_REQUESTS];
+/* UDP Protocol Control Block */
+struct udp_pcb *snmp1_pcb;
+
+static void snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);
+static err_t snmp_pdu_header_check(struct pbuf *p, u16_t ofs, u16_t pdu_len, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat);
+static err_t snmp_pdu_dec_varbindlist(struct pbuf *p, u16_t ofs, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat);
+
+
+/**
+ * Starts SNMP Agent.
+ * Allocates UDP pcb and binds it to IP_ADDR_ANY port 161.
+ */
+void
+snmp_init(void)
+{
+  struct snmp_msg_pstat *msg_ps;
+  u8_t i;
+
+  snmp1_pcb = udp_new();
+  if (snmp1_pcb != NULL)
+  {
+    udp_recv(snmp1_pcb, snmp_recv, (void *)SNMP_IN_PORT);
+    udp_bind(snmp1_pcb, IP_ADDR_ANY, SNMP_IN_PORT);
+  }
+  msg_ps = &msg_input_list[0];
+  for (i=0; i<SNMP_CONCURRENT_REQUESTS; i++)
+  {
+    msg_ps->state = SNMP_MSG_EMPTY;
+    msg_ps->error_index = 0;
+    msg_ps->error_status = SNMP_ES_NOERROR;
+    msg_ps++;
+  }
+  trap_msg.pcb = snmp1_pcb;
+
+#ifdef SNMP_PRIVATE_MIB_INIT
+  /* If defined, rhis must be a function-like define to initialize the
+   * private MIB after the stack has been initialized.
+   * The private MIB can also be initialized in tcpip_callback (or after
+   * the stack is initialized), this define is only for convenience. */
+  SNMP_PRIVATE_MIB_INIT();
+#endif /* SNMP_PRIVATE_MIB_INIT */
+
+  /* The coldstart trap will only be output
+     if our outgoing interface is up & configured  */
+  snmp_coldstart_trap();
+}
+
+static void
+snmp_error_response(struct snmp_msg_pstat *msg_ps, u8_t error)
+{
+  snmp_varbind_list_free(&msg_ps->outvb);
+  msg_ps->outvb = msg_ps->invb;
+  msg_ps->invb.head = NULL;
+  msg_ps->invb.tail = NULL;
+  msg_ps->invb.count = 0;
+  msg_ps->error_status = error;
+  msg_ps->error_index = 1 + msg_ps->vb_idx;
+  snmp_send_response(msg_ps);
+  snmp_varbind_list_free(&msg_ps->outvb);
+  msg_ps->state = SNMP_MSG_EMPTY;
+}
+
+static void
+snmp_ok_response(struct snmp_msg_pstat *msg_ps)
+{
+  err_t err_ret;
+
+  err_ret = snmp_send_response(msg_ps);
+  if (err_ret == ERR_MEM)
+  {
+    /* serious memory problem, can't return tooBig */
+  }
+  else
+  {
+    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_event = %"S32_F"\n",msg_ps->error_status));
+  }
+  /* free varbinds (if available) */
+  snmp_varbind_list_free(&msg_ps->invb);
+  snmp_varbind_list_free(&msg_ps->outvb);
+  msg_ps->state = SNMP_MSG_EMPTY;
+}
+
+/**
+ * Service an internal or external event for SNMP GET.
+ *
+ * @param request_id identifies requests from 0 to (SNMP_CONCURRENT_REQUESTS-1)
+ * @param msg_ps points to the assosicated message process state
+ */
+static void
+snmp_msg_get_event(u8_t request_id, struct snmp_msg_pstat *msg_ps)
+{
+  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_get_event: msg_ps->state==%"U16_F"\n",(u16_t)msg_ps->state));
+
+  if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_OBJDEF)
+  {
+    struct mib_external_node *en;
+    struct snmp_name_ptr np;
+
+    /* get_object_def() answer*/
+    en = msg_ps->ext_mib_node;
+    np = msg_ps->ext_name_ptr;
+
+    /* translate answer into a known lifeform */
+    en->get_object_def_a(request_id, np.ident_len, np.ident, &msg_ps->ext_object_def);
+    if ((msg_ps->ext_object_def.instance != MIB_OBJECT_NONE) &&
+        (msg_ps->ext_object_def.access & MIB_ACCESS_READ))
+    {
+      msg_ps->state = SNMP_MSG_EXTERNAL_GET_VALUE;
+      en->get_value_q(request_id, &msg_ps->ext_object_def);
+    }
+    else
+    {
+      en->get_object_def_pc(request_id, np.ident_len, np.ident);
+      /* search failed, object id points to unknown object (nosuchname) */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  else if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_VALUE)
+  {
+    struct mib_external_node *en;
+    struct snmp_varbind *vb;
+
+    /* get_value() answer */
+    en = msg_ps->ext_mib_node;
+
+    /* allocate output varbind */
+    vb = (struct snmp_varbind *)memp_malloc(MEMP_SNMP_VARBIND);
+    LWIP_ASSERT("vb != NULL",vb != NULL);
+    if (vb != NULL)
+    {
+      vb->next = NULL;
+      vb->prev = NULL;
+
+      /* move name from invb to outvb */
+      vb->ident = msg_ps->vb_ptr->ident;
+      vb->ident_len = msg_ps->vb_ptr->ident_len;
+      /* ensure this memory is refereced once only */
+      msg_ps->vb_ptr->ident = NULL;
+      msg_ps->vb_ptr->ident_len = 0;
+
+      vb->value_type = msg_ps->ext_object_def.asn_type;
+      LWIP_ASSERT("invalid length", msg_ps->ext_object_def.v_len <= 0xff);
+      vb->value_len = (u8_t)msg_ps->ext_object_def.v_len;
+      if (vb->value_len > 0)
+      {
+        LWIP_ASSERT("SNMP_MAX_OCTET_STRING_LEN is configured too low", vb->value_len <= SNMP_MAX_VALUE_SIZE);
+        vb->value = memp_malloc(MEMP_SNMP_VALUE);
+        LWIP_ASSERT("vb->value != NULL",vb->value != NULL);
+        if (vb->value != NULL)
+        {
+          en->get_value_a(request_id, &msg_ps->ext_object_def, vb->value_len, vb->value);
+          snmp_varbind_tail_add(&msg_ps->outvb, vb);
+          /* search again (if vb_idx < msg_ps->invb.count) */
+          msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+          msg_ps->vb_idx += 1;
+        }
+        else
+        {
+          en->get_value_pc(request_id, &msg_ps->ext_object_def);
+          LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_event: no variable space\n"));
+          msg_ps->vb_ptr->ident = vb->ident;
+          msg_ps->vb_ptr->ident_len = vb->ident_len;
+          memp_free(MEMP_SNMP_VARBIND, vb);
+          snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+        }
+      }
+      else
+      {
+        /* vb->value_len == 0, empty value (e.g. empty string) */
+        en->get_value_a(request_id, &msg_ps->ext_object_def, 0, NULL);
+        vb->value = NULL;
+        snmp_varbind_tail_add(&msg_ps->outvb, vb);
+        /* search again (if vb_idx < msg_ps->invb.count) */
+        msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+        msg_ps->vb_idx += 1;
+      }
+    }
+    else
+    {
+      en->get_value_pc(request_id, &msg_ps->ext_object_def);
+      LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_event: no outvb space\n"));
+      snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+    }
+  }
+
+  while ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+         (msg_ps->vb_idx < msg_ps->invb.count))
+  {
+    struct mib_node *mn;
+    struct snmp_name_ptr np;
+
+    if (msg_ps->vb_idx == 0)
+    {
+      msg_ps->vb_ptr = msg_ps->invb.head;
+    }
+    else
+    {
+      msg_ps->vb_ptr = msg_ps->vb_ptr->next;
+    }
+    /** test object identifier for .iso.org.dod.internet prefix */
+    if (snmp_iso_prefix_tst(msg_ps->vb_ptr->ident_len,  msg_ps->vb_ptr->ident))
+    {
+      mn = snmp_search_tree((struct mib_node*)&internet, msg_ps->vb_ptr->ident_len - 4,
+                             msg_ps->vb_ptr->ident + 4, &np);
+      if (mn != NULL)
+      {
+        if (mn->node_type == MIB_NODE_EX)
+        {
+          /* external object */
+          struct mib_external_node *en = (struct mib_external_node*)mn;
+
+          msg_ps->state = SNMP_MSG_EXTERNAL_GET_OBJDEF;
+          /* save en && args in msg_ps!! */
+          msg_ps->ext_mib_node = en;
+          msg_ps->ext_name_ptr = np;
+
+          en->get_object_def_q(en->addr_inf, request_id, np.ident_len, np.ident);
+        }
+        else
+        {
+          /* internal object */
+          struct obj_def object_def;
+
+          msg_ps->state = SNMP_MSG_INTERNAL_GET_OBJDEF;
+          mn->get_object_def(np.ident_len, np.ident, &object_def);
+          if ((object_def.instance != MIB_OBJECT_NONE) &&
+            (object_def.access & MIB_ACCESS_READ))
+          {
+            mn = mn;
+          }
+          else
+          {
+            /* search failed, object id points to unknown object (nosuchname) */
+            mn =  NULL;
+          }
+          if (mn != NULL)
+          {
+            struct snmp_varbind *vb;
+
+            msg_ps->state = SNMP_MSG_INTERNAL_GET_VALUE;
+            /* allocate output varbind */
+            vb = (struct snmp_varbind *)memp_malloc(MEMP_SNMP_VARBIND);
+            LWIP_ASSERT("vb != NULL",vb != NULL);
+            if (vb != NULL)
+            {
+              vb->next = NULL;
+              vb->prev = NULL;
+
+              /* move name from invb to outvb */
+              vb->ident = msg_ps->vb_ptr->ident;
+              vb->ident_len = msg_ps->vb_ptr->ident_len;
+              /* ensure this memory is refereced once only */
+              msg_ps->vb_ptr->ident = NULL;
+              msg_ps->vb_ptr->ident_len = 0;
+
+              vb->value_type = object_def.asn_type;
+              LWIP_ASSERT("invalid length", object_def.v_len <= 0xff);
+              vb->value_len = (u8_t)object_def.v_len;
+              if (vb->value_len > 0)
+              {
+                LWIP_ASSERT("SNMP_MAX_OCTET_STRING_LEN is configured too low",
+                  vb->value_len <= SNMP_MAX_VALUE_SIZE);
+                vb->value = memp_malloc(MEMP_SNMP_VALUE);
+                LWIP_ASSERT("vb->value != NULL",vb->value != NULL);
+                if (vb->value != NULL)
+                {
+                  mn->get_value(&object_def, vb->value_len, vb->value);
+                  snmp_varbind_tail_add(&msg_ps->outvb, vb);
+                  msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+                  msg_ps->vb_idx += 1;
+                }
+                else
+                {
+                  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_event: couldn't allocate variable space\n"));
+                  msg_ps->vb_ptr->ident = vb->ident;
+                  msg_ps->vb_ptr->ident_len = vb->ident_len;
+                  memp_free(MEMP_SNMP_VARBIND, vb);
+                  snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+                }
+              }
+              else
+              {
+                /* vb->value_len == 0, empty value (e.g. empty string) */
+                vb->value = NULL;
+                snmp_varbind_tail_add(&msg_ps->outvb, vb);
+                msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+                msg_ps->vb_idx += 1;
+              }
+            }
+            else
+            {
+              LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_event: couldn't allocate outvb space\n"));
+              snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+            }
+          }
+        }
+      }
+    }
+    else
+    {
+      mn = NULL;
+    }
+    if (mn == NULL)
+    {
+      /* mn == NULL, noSuchName */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  if ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+      (msg_ps->vb_idx == msg_ps->invb.count))
+  {
+    snmp_ok_response(msg_ps);
+  }
+}
+
+/**
+ * Service an internal or external event for SNMP GETNEXT.
+ *
+ * @param request_id identifies requests from 0 to (SNMP_CONCURRENT_REQUESTS-1)
+ * @param msg_ps points to the assosicated message process state
+ */
+static void
+snmp_msg_getnext_event(u8_t request_id, struct snmp_msg_pstat *msg_ps)
+{
+  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_getnext_event: msg_ps->state==%"U16_F"\n",(u16_t)msg_ps->state));
+
+  if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_OBJDEF)
+  {
+    struct mib_external_node *en;
+
+    /* get_object_def() answer*/
+    en = msg_ps->ext_mib_node;
+
+    /* translate answer into a known lifeform */
+    en->get_object_def_a(request_id, 1, &msg_ps->ext_oid.id[msg_ps->ext_oid.len - 1], &msg_ps->ext_object_def);
+    if (msg_ps->ext_object_def.instance != MIB_OBJECT_NONE)
+    {
+      msg_ps->state = SNMP_MSG_EXTERNAL_GET_VALUE;
+      en->get_value_q(request_id, &msg_ps->ext_object_def);
+    }
+    else
+    {
+      en->get_object_def_pc(request_id, 1, &msg_ps->ext_oid.id[msg_ps->ext_oid.len - 1]);
+      /* search failed, object id points to unknown object (nosuchname) */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  else if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_VALUE)
+  {
+    struct mib_external_node *en;
+    struct snmp_varbind *vb;
+
+    /* get_value() answer */
+    en = msg_ps->ext_mib_node;
+
+    LWIP_ASSERT("invalid length", msg_ps->ext_object_def.v_len <= 0xff);
+    vb = snmp_varbind_alloc(&msg_ps->ext_oid,
+                            msg_ps->ext_object_def.asn_type,
+                            (u8_t)msg_ps->ext_object_def.v_len);
+    if (vb != NULL)
+    {
+      en->get_value_a(request_id, &msg_ps->ext_object_def, vb->value_len, vb->value);
+      snmp_varbind_tail_add(&msg_ps->outvb, vb);
+      msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+      msg_ps->vb_idx += 1;
+    }
+    else
+    {
+      en->get_value_pc(request_id, &msg_ps->ext_object_def);
+      LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_getnext_event: couldn't allocate outvb space\n"));
+      snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+    }
+  }
+
+  while ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+         (msg_ps->vb_idx < msg_ps->invb.count))
+  {
+    struct mib_node *mn;
+    struct snmp_obj_id oid;
+
+    if (msg_ps->vb_idx == 0)
+    {
+      msg_ps->vb_ptr = msg_ps->invb.head;
+    }
+    else
+    {
+      msg_ps->vb_ptr = msg_ps->vb_ptr->next;
+    }
+    if (snmp_iso_prefix_expand(msg_ps->vb_ptr->ident_len, msg_ps->vb_ptr->ident, &oid))
+    {
+      if (msg_ps->vb_ptr->ident_len > 3)
+      {
+        /* can offset ident_len and ident */
+        mn = snmp_expand_tree((struct mib_node*)&internet,
+                              msg_ps->vb_ptr->ident_len - 4,
+                              msg_ps->vb_ptr->ident + 4, &oid);
+      }
+      else
+      {
+        /* can't offset ident_len -4, ident + 4 */
+        mn = snmp_expand_tree((struct mib_node*)&internet, 0, NULL, &oid);
+      }
+    }
+    else
+    {
+      mn = NULL;
+    }
+    if (mn != NULL)
+    {
+      if (mn->node_type == MIB_NODE_EX)
+      {
+        /* external object */
+        struct mib_external_node *en = (struct mib_external_node*)mn;
+
+        msg_ps->state = SNMP_MSG_EXTERNAL_GET_OBJDEF;
+        /* save en && args in msg_ps!! */
+        msg_ps->ext_mib_node = en;
+        msg_ps->ext_oid = oid;
+
+        en->get_object_def_q(en->addr_inf, request_id, 1, &oid.id[oid.len - 1]);
+      }
+      else
+      {
+        /* internal object */
+        struct obj_def object_def;
+        struct snmp_varbind *vb;
+
+        msg_ps->state = SNMP_MSG_INTERNAL_GET_OBJDEF;
+        mn->get_object_def(1, &oid.id[oid.len - 1], &object_def);
+
+        LWIP_ASSERT("invalid length", object_def.v_len <= 0xff);
+        vb = snmp_varbind_alloc(&oid, object_def.asn_type, (u8_t)object_def.v_len);
+        if (vb != NULL)
+        {
+          msg_ps->state = SNMP_MSG_INTERNAL_GET_VALUE;
+          mn->get_value(&object_def, object_def.v_len, vb->value);
+          snmp_varbind_tail_add(&msg_ps->outvb, vb);
+          msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+          msg_ps->vb_idx += 1;
+        }
+        else
+        {
+          LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_recv couldn't allocate outvb space\n"));
+          snmp_error_response(msg_ps,SNMP_ES_TOOBIG);
+        }
+      }
+    }
+    if (mn == NULL)
+    {
+      /* mn == NULL, noSuchName */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  if ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+      (msg_ps->vb_idx == msg_ps->invb.count))
+  {
+    snmp_ok_response(msg_ps);
+  }
+}
+
+/**
+ * Service an internal or external event for SNMP SET.
+ *
+ * @param request_id identifies requests from 0 to (SNMP_CONCURRENT_REQUESTS-1)
+ * @param msg_ps points to the assosicated message process state
+ */
+static void
+snmp_msg_set_event(u8_t request_id, struct snmp_msg_pstat *msg_ps)
+{
+  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_msg_set_event: msg_ps->state==%"U16_F"\n",(u16_t)msg_ps->state));
+
+  if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_OBJDEF)
+  {
+    struct mib_external_node *en;
+    struct snmp_name_ptr np;
+
+    /* get_object_def() answer*/
+    en = msg_ps->ext_mib_node;
+    np = msg_ps->ext_name_ptr;
+
+    /* translate answer into a known lifeform */
+    en->get_object_def_a(request_id, np.ident_len, np.ident, &msg_ps->ext_object_def);
+    if (msg_ps->ext_object_def.instance != MIB_OBJECT_NONE)
+    {
+      msg_ps->state = SNMP_MSG_EXTERNAL_SET_TEST;
+      en->set_test_q(request_id, &msg_ps->ext_object_def);
+    }
+    else
+    {
+      en->get_object_def_pc(request_id, np.ident_len, np.ident);
+      /* search failed, object id points to unknown object (nosuchname) */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  else if (msg_ps->state == SNMP_MSG_EXTERNAL_SET_TEST)
+  {
+    struct mib_external_node *en;
+
+    /* set_test() answer*/
+    en = msg_ps->ext_mib_node;
+
+    if (msg_ps->ext_object_def.access & MIB_ACCESS_WRITE)
+    {
+       if ((msg_ps->ext_object_def.asn_type == msg_ps->vb_ptr->value_type) &&
+           (en->set_test_a(request_id,&msg_ps->ext_object_def,
+                           msg_ps->vb_ptr->value_len,msg_ps->vb_ptr->value) != 0))
+      {
+        msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+        msg_ps->vb_idx += 1;
+      }
+      else
+      {
+        en->set_test_pc(request_id,&msg_ps->ext_object_def);
+        /* bad value */
+        snmp_error_response(msg_ps,SNMP_ES_BADVALUE);
+      }
+    }
+    else
+    {
+      en->set_test_pc(request_id,&msg_ps->ext_object_def);
+      /* object not available for set */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+  else if (msg_ps->state == SNMP_MSG_EXTERNAL_GET_OBJDEF_S)
+  {
+    struct mib_external_node *en;
+    struct snmp_name_ptr np;
+
+    /* get_object_def() answer*/
+    en = msg_ps->ext_mib_node;
+    np = msg_ps->ext_name_ptr;
+
+    /* translate answer into a known lifeform */
+    en->get_object_def_a(request_id, np.ident_len, np.ident, &msg_ps->ext_object_def);
+    if (msg_ps->ext_object_def.instance != MIB_OBJECT_NONE)
+    {
+      msg_ps->state = SNMP_MSG_EXTERNAL_SET_VALUE;
+      en->set_value_q(request_id, &msg_ps->ext_object_def,
+                      msg_ps->vb_ptr->value_len,msg_ps->vb_ptr->value);
+    }
+    else
+    {
+      en->get_object_def_pc(request_id, np.ident_len, np.ident);
+      /* set_value failed, object has disappeared for some odd reason?? */
+      snmp_error_response(msg_ps,SNMP_ES_GENERROR);
+    }
+  }
+  else if (msg_ps->state == SNMP_MSG_EXTERNAL_SET_VALUE)
+  {
+    struct mib_external_node *en;
+
+    /** set_value_a() */
+    en = msg_ps->ext_mib_node;
+    en->set_value_a(request_id, &msg_ps->ext_object_def,
+      msg_ps->vb_ptr->value_len, msg_ps->vb_ptr->value);
+
+    /** @todo use set_value_pc() if toobig */
+    msg_ps->state = SNMP_MSG_INTERNAL_SET_VALUE;
+    msg_ps->vb_idx += 1;
+  }
+
+  /* test all values before setting */
+  while ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+         (msg_ps->vb_idx < msg_ps->invb.count))
+  {
+    struct mib_node *mn;
+    struct snmp_name_ptr np;
+
+    if (msg_ps->vb_idx == 0)
+    {
+      msg_ps->vb_ptr = msg_ps->invb.head;
+    }
+    else
+    {
+      msg_ps->vb_ptr = msg_ps->vb_ptr->next;
+    }
+    /** test object identifier for .iso.org.dod.internet prefix */
+    if (snmp_iso_prefix_tst(msg_ps->vb_ptr->ident_len,  msg_ps->vb_ptr->ident))
+    {
+      mn = snmp_search_tree((struct mib_node*)&internet, msg_ps->vb_ptr->ident_len - 4,
+                             msg_ps->vb_ptr->ident + 4, &np);
+      if (mn != NULL)
+      {
+        if (mn->node_type == MIB_NODE_EX)
+        {
+          /* external object */
+          struct mib_external_node *en = (struct mib_external_node*)mn;
+
+          msg_ps->state = SNMP_MSG_EXTERNAL_GET_OBJDEF;
+          /* save en && args in msg_ps!! */
+          msg_ps->ext_mib_node = en;
+          msg_ps->ext_name_ptr = np;
+
+          en->get_object_def_q(en->addr_inf, request_id, np.ident_len, np.ident);
+        }
+        else
+        {
+          /* internal object */
+          struct obj_def object_def;
+
+          msg_ps->state = SNMP_MSG_INTERNAL_GET_OBJDEF;
+          mn->get_object_def(np.ident_len, np.ident, &object_def);
+          if (object_def.instance != MIB_OBJECT_NONE)
+          {
+            mn = mn;
+          }
+          else
+          {
+            /* search failed, object id points to unknown object (nosuchname) */
+            mn = NULL;
+          }
+          if (mn != NULL)
+          {
+            msg_ps->state = SNMP_MSG_INTERNAL_SET_TEST;
+
+            if (object_def.access & MIB_ACCESS_WRITE)
+            {
+              if ((object_def.asn_type == msg_ps->vb_ptr->value_type) &&
+                  (mn->set_test(&object_def,msg_ps->vb_ptr->value_len,msg_ps->vb_ptr->value) != 0))
+              {
+                msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+                msg_ps->vb_idx += 1;
+              }
+              else
+              {
+                /* bad value */
+                snmp_error_response(msg_ps,SNMP_ES_BADVALUE);
+              }
+            }
+            else
+            {
+              /* object not available for set */
+              snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+            }
+          }
+        }
+      }
+    }
+    else
+    {
+      mn = NULL;
+    }
+    if (mn == NULL)
+    {
+      /* mn == NULL, noSuchName */
+      snmp_error_response(msg_ps,SNMP_ES_NOSUCHNAME);
+    }
+  }
+
+  if ((msg_ps->state == SNMP_MSG_SEARCH_OBJ) &&
+      (msg_ps->vb_idx == msg_ps->invb.count))
+  {
+    msg_ps->vb_idx = 0;
+    msg_ps->state = SNMP_MSG_INTERNAL_SET_VALUE;
+  }
+
+  /* set all values "atomically" (be as "atomic" as possible) */
+  while ((msg_ps->state == SNMP_MSG_INTERNAL_SET_VALUE) &&
+         (msg_ps->vb_idx < msg_ps->invb.count))
+  {
+    struct mib_node *mn;
+    struct snmp_name_ptr np;
+
+    if (msg_ps->vb_idx == 0)
+    {
+      msg_ps->vb_ptr = msg_ps->invb.head;
+    }
+    else
+    {
+      msg_ps->vb_ptr = msg_ps->vb_ptr->next;
+    }
+    /* skip iso prefix test, was done previously while settesting() */
+    mn = snmp_search_tree((struct mib_node*)&internet, msg_ps->vb_ptr->ident_len - 4,
+                           msg_ps->vb_ptr->ident + 4, &np);
+    /* check if object is still available
+       (e.g. external hot-plug thingy present?) */
+    if (mn != NULL)
+    {
+      if (mn->node_type == MIB_NODE_EX)
+      {
+        /* external object */
+        struct mib_external_node *en = (struct mib_external_node*)mn;
+
+        msg_ps->state = SNMP_MSG_EXTERNAL_GET_OBJDEF_S;
+        /* save en && args in msg_ps!! */
+        msg_ps->ext_mib_node = en;
+        msg_ps->ext_name_ptr = np;
+
+        en->get_object_def_q(en->addr_inf, request_id, np.ident_len, np.ident);
+      }
+      else
+      {
+        /* internal object */
+        struct obj_def object_def;
+
+        msg_ps->state = SNMP_MSG_INTERNAL_GET_OBJDEF_S;
+        mn->get_object_def(np.ident_len, np.ident, &object_def);
+        msg_ps->state = SNMP_MSG_INTERNAL_SET_VALUE;
+        mn->set_value(&object_def,msg_ps->vb_ptr->value_len,msg_ps->vb_ptr->value);
+        msg_ps->vb_idx += 1;
+      }
+    }
+  }
+  if ((msg_ps->state == SNMP_MSG_INTERNAL_SET_VALUE) &&
+      (msg_ps->vb_idx == msg_ps->invb.count))
+  {
+    /* simply echo the input if we can set it
+       @todo do we need to return the actual value?
+       e.g. if value is silently modified or behaves sticky? */
+    msg_ps->outvb = msg_ps->invb;
+    msg_ps->invb.head = NULL;
+    msg_ps->invb.tail = NULL;
+    msg_ps->invb.count = 0;
+    snmp_ok_response(msg_ps);
+  }
+}
+
+
+/**
+ * Handle one internal or external event.
+ * Called for one async event. (recv external/private answer)
+ *
+ * @param request_id identifies requests from 0 to (SNMP_CONCURRENT_REQUESTS-1)
+ */
+void
+snmp_msg_event(u8_t request_id)
+{
+  struct snmp_msg_pstat *msg_ps;
+
+  if (request_id < SNMP_CONCURRENT_REQUESTS)
+  {
+    msg_ps = &msg_input_list[request_id];
+    if (msg_ps->rt == SNMP_ASN1_PDU_GET_NEXT_REQ)
+    {
+      snmp_msg_getnext_event(request_id, msg_ps);
+    }
+    else if (msg_ps->rt == SNMP_ASN1_PDU_GET_REQ)
+    {
+      snmp_msg_get_event(request_id, msg_ps);
+    }
+    else if(msg_ps->rt == SNMP_ASN1_PDU_SET_REQ)
+    {
+      snmp_msg_set_event(request_id, msg_ps);
+    }
+  }
+}
+
+
+/* lwIP UDP receive callback function */
+static void
+snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
+{
+  struct snmp_msg_pstat *msg_ps;
+  u8_t req_idx;
+  err_t err_ret;
+  u16_t payload_len = p->tot_len;
+  u16_t payload_ofs = 0;
+  u16_t varbind_ofs = 0;
+
+  /* suppress unused argument warning */
+  LWIP_UNUSED_ARG(arg);
+
+  /* traverse input message process list, look for SNMP_MSG_EMPTY */
+  msg_ps = &msg_input_list[0];
+  req_idx = 0;
+  while ((req_idx < SNMP_CONCURRENT_REQUESTS) && (msg_ps->state != SNMP_MSG_EMPTY))
+  {
+    req_idx++;
+    msg_ps++;
+  }
+  if (req_idx == SNMP_CONCURRENT_REQUESTS)
+  {
+    /* exceeding number of concurrent requests */
+    pbuf_free(p);
+    return;
+  }
+
+  /* accepting request */
+  snmp_inc_snmpinpkts();
+  /* record used 'protocol control block' */
+  msg_ps->pcb = pcb;
+  /* source address (network order) */
+  msg_ps->sip = *addr;
+  /* source port (host order (lwIP oddity)) */
+  msg_ps->sp = port;
+
+  /* check total length, version, community, pdu type */
+  err_ret = snmp_pdu_header_check(p, payload_ofs, payload_len, &varbind_ofs, msg_ps);
+  /* Only accept requests and requests without error (be robust) */
+  /* Reject response and trap headers or error requests as input! */
+  if ((err_ret != ERR_OK) ||
+      ((msg_ps->rt != SNMP_ASN1_PDU_GET_REQ) &&
+       (msg_ps->rt != SNMP_ASN1_PDU_GET_NEXT_REQ) &&
+       (msg_ps->rt != SNMP_ASN1_PDU_SET_REQ)) ||
+      ((msg_ps->error_status != SNMP_ES_NOERROR) ||
+       (msg_ps->error_index != 0)) )
+  {
+    /* header check failed drop request silently, do not return error! */
+    pbuf_free(p);
+    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_header_check() failed\n"));
+    return;
+  }
+  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_recv ok, community %s\n", msg_ps->community));
+
+  /* Builds a list of variable bindings. Copy the varbinds from the pbuf
+    chain to glue them when these are divided over two or more pbuf's. */
+  err_ret = snmp_pdu_dec_varbindlist(p, varbind_ofs, &varbind_ofs, msg_ps);
+  /* we've decoded the incoming message, release input msg now */
+  pbuf_free(p);
+  if ((err_ret != ERR_OK) || (msg_ps->invb.count == 0))
+  {
+    /* varbind-list decode failed, or varbind list empty.
+       drop request silently, do not return error!
+       (errors are only returned for a specific varbind failure) */
+    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_dec_varbindlist() failed\n"));
+    return;
+  }
+
+  msg_ps->error_status = SNMP_ES_NOERROR;
+  msg_ps->error_index = 0;
+  /* find object for each variable binding */
+  msg_ps->state = SNMP_MSG_SEARCH_OBJ;
+  /* first variable binding from list to inspect */
+  msg_ps->vb_idx = 0;
+
+  LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_recv varbind cnt=%"U16_F"\n",(u16_t)msg_ps->invb.count));
+
+  /* handle input event and as much objects as possible in one go */
+  snmp_msg_event(req_idx);
+}
+
+/**
+ * Checks and decodes incoming SNMP message header, logs header errors.
+ *
+ * @param p points to pbuf chain of SNMP message (UDP payload)
+ * @param ofs points to first octet of SNMP message
+ * @param pdu_len the length of the UDP payload
+ * @param ofs_ret returns the ofset of the variable bindings
+ * @param m_stat points to the current message request state return
+ * @return
+ * - ERR_OK SNMP header is sane and accepted
+ * - ERR_ARG SNMP header is either malformed or rejected
+ */
+static err_t
+snmp_pdu_header_check(struct pbuf *p, u16_t ofs, u16_t pdu_len, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
+{
+  err_t derr;
+  u16_t len, ofs_base;
+  u8_t  len_octets;
+  u8_t  type;
+  s32_t version;
+
+  ofs_base = ofs;
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) ||
+      (pdu_len != (1 + len_octets + len)) ||
+      (type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)))
+  {
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets);
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
+  {
+    /* can't decode or no integer (version) */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &version);
+  if (derr != ERR_OK)
+  {
+    /* can't decode */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  if (version != 0)
+  {
+    /* not version 1 */
+    snmp_inc_snmpinbadversions();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets + len);
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR)))
+  {
+    /* can't decode or no octet string (community) */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, SNMP_COMMUNITY_STR_LEN, m_stat->community);
+  if (derr != ERR_OK)
+  {
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  /* add zero terminator */
+  len = ((len < (SNMP_COMMUNITY_STR_LEN))?(len):(SNMP_COMMUNITY_STR_LEN));
+  m_stat->community[len] = 0;
+  m_stat->com_strlen = (u8_t)len;
+  if (strncmp(snmp_publiccommunity, (const char*)m_stat->community, SNMP_COMMUNITY_STR_LEN) != 0)
+  {
+    /** @todo: move this if we need to check more names */
+    snmp_inc_snmpinbadcommunitynames();
+    snmp_authfail_trap();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets + len);
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if (derr != ERR_OK)
+  {
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  switch(type)
+  {
+    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_REQ):
+      /* GetRequest PDU */
+      snmp_inc_snmpingetrequests();
+      derr = ERR_OK;
+      break;
+    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_NEXT_REQ):
+      /* GetNextRequest PDU */
+      snmp_inc_snmpingetnexts();
+      derr = ERR_OK;
+      break;
+    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_RESP):
+      /* GetResponse PDU */
+      snmp_inc_snmpingetresponses();
+      derr = ERR_ARG;
+      break;
+    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_SET_REQ):
+      /* SetRequest PDU */
+      snmp_inc_snmpinsetrequests();
+      derr = ERR_OK;
+      break;
+    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_TRAP):
+      /* Trap PDU */
+      snmp_inc_snmpintraps();
+      derr = ERR_ARG;
+      break;
+    default:
+      snmp_inc_snmpinasnparseerrs();
+      derr = ERR_ARG;
+      break;
+  }
+  if (derr != ERR_OK)
+  {
+    /* unsupported input PDU for this agent (no parse error) */
+    return ERR_ARG;
+  }
+  m_stat->rt = type & 0x1F;
+  ofs += (1 + len_octets);
+  if (len != (pdu_len - (ofs - ofs_base)))
+  {
+    /* decoded PDU length does not equal actual payload length */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
+  {
+    /* can't decode or no integer (request ID) */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->rid);
+  if (derr != ERR_OK)
+  {
+    /* can't decode */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets + len);
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
+  {
+    /* can't decode or no integer (error-status) */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  /* must be noError (0) for incoming requests.
+     log errors for mib-2 completeness and for debug purposes */
+  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_status);
+  if (derr != ERR_OK)
+  {
+    /* can't decode */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  switch (m_stat->error_status)
+  {
+    case SNMP_ES_TOOBIG:
+      snmp_inc_snmpintoobigs();
+      break;
+    case SNMP_ES_NOSUCHNAME:
+      snmp_inc_snmpinnosuchnames();
+      break;
+    case SNMP_ES_BADVALUE:
+      snmp_inc_snmpinbadvalues();
+      break;
+    case SNMP_ES_READONLY:
+      snmp_inc_snmpinreadonlys();
+      break;
+    case SNMP_ES_GENERROR:
+      snmp_inc_snmpingenerrs();
+      break;
+  }
+  ofs += (1 + len_octets + len);
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
+  {
+    /* can't decode or no integer (error-index) */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  /* must be 0 for incoming requests.
+     decode anyway to catch bad integers (and dirty tricks) */
+  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_index);
+  if (derr != ERR_OK)
+  {
+    /* can't decode */
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets + len);
+  *ofs_ret = ofs;
+  return ERR_OK;
+}
+
+static err_t
+snmp_pdu_dec_varbindlist(struct pbuf *p, u16_t ofs, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
+{
+  err_t derr;
+  u16_t len, vb_len;
+  u8_t  len_octets;
+  u8_t type;
+
+  /* variable binding list */
+  snmp_asn1_dec_type(p, ofs, &type);
+  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &vb_len);
+  if ((derr != ERR_OK) ||
+      (type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)))
+  {
+    snmp_inc_snmpinasnparseerrs();
+    return ERR_ARG;
+  }
+  ofs += (1 + len_octets);
+
+  /* start with empty list */
+  m_stat->invb.count = 0;
+  m_stat->invb.head = NULL;
+  m_stat->invb.tail = NULL;
+
+  while (vb_len > 0)
+  {
+    struct snmp_obj_id oid, oid_value;
+    struct snmp_varbind *vb;
+
+    snmp_asn1_dec_type(p, ofs, &type);
+    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+    if ((derr != ERR_OK) ||
+        (type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)) ||
+        (len == 0) || (len > vb_len))
+    {
+      snmp_inc_snmpinasnparseerrs();
+      /* free varbinds (if available) */
+      snmp_varbind_list_free(&m_stat->invb);
+      return ERR_ARG;
+    }
+    ofs += (1 + len_octets);
+    vb_len -= (1 + len_octets);
+
+    snmp_asn1_dec_type(p, ofs, &type);
+    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+    if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID)))
+    {
+      /* can't decode object name length */
+      snmp_inc_snmpinasnparseerrs();
+      /* free varbinds (if available) */
+      snmp_varbind_list_free(&m_stat->invb);
+      return ERR_ARG;
+    }
+    derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid);
+    if (derr != ERR_OK)
+    {
+      /* can't decode object name */
+      snmp_inc_snmpinasnparseerrs();
+      /* free varbinds (if available) */
+      snmp_varbind_list_free(&m_stat->invb);
+      return ERR_ARG;
+    }
+    ofs += (1 + len_octets + len);
+    vb_len -= (1 + len_octets + len);
+
+    snmp_asn1_dec_type(p, ofs, &type);
+    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
+    if (derr != ERR_OK)
+    {
+      /* can't decode object value length */
+      snmp_inc_snmpinasnparseerrs();
+      /* free varbinds (if available) */
+      snmp_varbind_list_free(&m_stat->invb);
+      return ERR_ARG;
+    }
+
+    switch (type)
+    {
+      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG):
+        vb = snmp_varbind_alloc(&oid, type, sizeof(s32_t));
+        if (vb != NULL)
+        {
+          s32_t *vptr = (s32_t*)vb->value;
+
+          derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, vptr);
+          snmp_varbind_tail_add(&m_stat->invb, vb);
+        }
+        else
+        {
+          derr = ERR_ARG;
+        }
+        break;
+      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_COUNTER):
+      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_GAUGE):
+      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS):
+        vb = snmp_varbind_alloc(&oid, type, sizeof(u32_t));
+        if (vb != NULL)
+        {
+          u32_t *vptr = (u32_t*)vb->value;
+
+          derr = snmp_asn1_dec_u32t(p, ofs + 1 + len_octets, len, vptr);
+          snmp_varbind_tail_add(&m_stat->invb, vb);
+        }
+        else
+        {
+          derr = ERR_ARG;
+        }
+        break;
+      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR):
+      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_OPAQUE):
+        LWIP_ASSERT("invalid length", len <= 0xff);
+        vb = snmp_varbind_alloc(&oid, type, (u8_t)len);
+        if (vb != NULL)
+        {
+          derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, (u8_t*)vb->value);
+          snmp_varbind_tail_add(&m_stat->invb, vb);
+        }
+        else
+        {
+          derr = ERR_ARG;
+        }
+        break;
+      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_NUL):
+        vb = snmp_varbind_alloc(&oid, type, 0);
+        if (vb != NULL)
+        {
+          snmp_varbind_tail_add(&m_stat->invb, vb);
+          derr = ERR_OK;
+        }
+        else
+        {
+          derr = ERR_ARG;
+        }
+        break;
+      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID):
+        derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid_value);
+        if (derr == ERR_OK)
+        {
+          vb = snmp_varbind_alloc(&oid, type, oid_value.len * sizeof(s32_t));
+          if (vb != NULL)
+          {
+            u8_t i = oid_value.len;
+            s32_t *vptr = (s32_t*)vb->value;
+
+            while(i > 0)
+            {
+              i--;
+              vptr[i] = oid_value.id[i];
+            }
+            snmp_varbind_tail_add(&m_stat->invb, vb);
+            derr = ERR_OK;
+          }
+          else
+          {
+            derr = ERR_ARG;
+          }
+        }
+        break;
+      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_IPADDR):
+        if (len == 4)
+        {
+          /* must be exactly 4 octets! */
+          vb = snmp_varbind_alloc(&oid, type, 4);
+          if (vb != NULL)
+          {
+            derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, (u8_t*)vb->value);
+            snmp_varbind_tail_add(&m_stat->invb, vb);
+          }
+          else
+          {
+            derr = ERR_ARG;
+          }
+        }
+        else
+        {
+          derr = ERR_ARG;
+        }
+        break;
+      default:
+        derr = ERR_ARG;
+        break;
+    }
+    if (derr != ERR_OK)
+    {
+      snmp_inc_snmpinasnparseerrs();
+      /* free varbinds (if available) */
+      snmp_varbind_list_free(&m_stat->invb);
+      return ERR_ARG;
+    }
+    ofs += (1 + len_octets + len);
+    vb_len -= (1 + len_octets + len);
+  }
+
+  if (m_stat->rt == SNMP_ASN1_PDU_SET_REQ)
+  {
+    snmp_add_snmpintotalsetvars(m_stat->invb.count);
+  }
+  else
+  {
+    snmp_add_snmpintotalreqvars(m_stat->invb.count);
+  }
+
+  *ofs_ret = ofs;
+  return ERR_OK;
+}
+
+struct snmp_varbind*
+snmp_varbind_alloc(struct snmp_obj_id *oid, u8_t type, u8_t len)
+{
+  struct snmp_varbind *vb;
+
+  vb = (struct snmp_varbind *)memp_malloc(MEMP_SNMP_VARBIND);
+  LWIP_ASSERT("vb != NULL",vb != NULL);
+  if (vb != NULL)
+  {
+    u8_t i;
+
+    vb->next = NULL;
+    vb->prev = NULL;
+    i = oid->len;
+    vb->ident_len = i;
+    if (i > 0)
+    {
+      LWIP_ASSERT("SNMP_MAX_TREE_DEPTH is configured too low", i <= SNMP_MAX_TREE_DEPTH);
+      /* allocate array of s32_t for our object identifier */
+      vb->ident = (s32_t*)memp_malloc(MEMP_SNMP_VALUE);
+      LWIP_ASSERT("vb->ident != NULL",vb->ident != NULL);
+      if (vb->ident == NULL)
+      {
+        memp_free(MEMP_SNMP_VARBIND, vb);
+        return NULL;
+      }
+      while(i > 0)
+      {
+        i--;
+        vb->ident[i] = oid->id[i];
+      }
+    }
+    else
+    {
+      /* i == 0, pass zero length object identifier */
+      vb->ident = NULL;
+    }
+    vb->value_type = type;
+    vb->value_len = len;
+    if (len > 0)
+    {
+      LWIP_ASSERT("SNMP_MAX_OCTET_STRING_LEN is configured too low", vb->value_len <= SNMP_MAX_VALUE_SIZE);
+      /* allocate raw bytes for our object value */
+      vb->value = memp_malloc(MEMP_SNMP_VALUE);
+      LWIP_ASSERT("vb->value != NULL",vb->value != NULL);
+      if (vb->value == NULL)
+      {
+        if (vb->ident != NULL)
+        {
+          memp_free(MEMP_SNMP_VALUE, vb->ident);
+        }
+        memp_free(MEMP_SNMP_VARBIND, vb);
+        return NULL;
+      }
+    }
+    else
+    {
+      /* ASN1_NUL type, or zero length ASN1_OC_STR */
+      vb->value = NULL;
+    }
+  }
+  return vb;
+}
+
+void
+snmp_varbind_free(struct snmp_varbind *vb)
+{
+  if (vb->value != NULL )
+  {
+    memp_free(MEMP_SNMP_VALUE, vb->value);
+  }
+  if (vb->ident != NULL )
+  {
+    memp_free(MEMP_SNMP_VALUE, vb->ident);
+  }
+  memp_free(MEMP_SNMP_VARBIND, vb);
+}
+
+void
+snmp_varbind_list_free(struct snmp_varbind_root *root)
+{
+  struct snmp_varbind *vb, *prev;
+
+  vb = root->tail;
+  while ( vb != NULL )
+  {
+    prev = vb->prev;
+    snmp_varbind_free(vb);
+    vb = prev;
+  }
+  root->count = 0;
+  root->head = NULL;
+  root->tail = NULL;
+}
+
+void
+snmp_varbind_tail_add(struct snmp_varbind_root *root, struct snmp_varbind *vb)
+{
+  if (root->count == 0)
+  {
+    /* add first varbind to list */
+    root->head = vb;
+    root->tail = vb;
+  }
+  else
+  {
+    /* add nth varbind to list tail */
+    root->tail->next = vb;
+    vb->prev = root->tail;
+    root->tail = vb;
+  }
+  root->count += 1;
+}
+
+struct snmp_varbind*
+snmp_varbind_tail_remove(struct snmp_varbind_root *root)
+{
+  struct snmp_varbind* vb;
+
+  if (root->count > 0)
+  {
+    /* remove tail varbind */
+    vb = root->tail;
+    root->tail = vb->prev;
+    vb->prev->next = NULL;
+    root->count -= 1;
+  }
+  else
+  {
+    /* nothing to remove */
+    vb = NULL;
+  }
+  return vb;
+}
+
+#endif /* LWIP_SNMP */