/**
* @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/ip_addr.h"
#include "lwip/mem.h"
#include "lwip/udp.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "lwip/snmp_asn1.h"
#include "lwip/snmp_msg.h"
#include "lwip/snmp_structs.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] = "public1";
/* 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, struct ip_addr *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;
/* 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->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 *)mem_malloc(sizeof(struct 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;
vb->value_len = msg_ps->ext_object_def.v_len;
if (vb->value_len > 0)
{
vb->value = mem_malloc(vb->value_len);
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;
mem_free(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)
{
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 *)mem_malloc(sizeof(struct 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;
vb->value_len = object_def.v_len;
if (vb->value_len > 0)
{
vb->value = mem_malloc(vb->value_len);
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;
mem_free(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;
vb = snmp_varbind_alloc(&msg_ps->ext_oid,
msg_ps->ext_object_def.asn_type,
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);
vb = snmp_varbind_alloc(&oid, object_def.asn_type, 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_OBJECT_READ_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_OBJECT_READ_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, struct ip_addr *addr, u16_t port)
{
struct udp_hdr *udphdr;
/* suppress unused argument warning */
LWIP_UNUSED_ARG(arg);
/* peek in the UDP header (goto IP payload) */
if(pbuf_header(p, UDP_HLEN)){
LWIP_ASSERT("Can't move to UDP header", 0);
pbuf_free(p);
return;
}
udphdr = p->payload;
/* check if datagram is really directed at us (including broadcast requests) */
if ((pcb == snmp1_pcb) && (ntohs(udphdr->dest) == SNMP_IN_PORT))
{
struct snmp_msg_pstat *msg_ps;
u8_t req_idx;
/* 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)
{
err_t err_ret;
u16_t payload_len;
u16_t payload_ofs;
u16_t varbind_ofs = 0;
/* 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;
/* read UDP payload length from UDP header */
payload_len = ntohs(udphdr->len) - UDP_HLEN;
/* adjust to UDP payload */
payload_ofs = UDP_HLEN;
/* check total length, version, community, pdu type */
err_ret = snmp_pdu_header_check(p, payload_ofs, payload_len, &varbind_ofs, msg_ps);
if (((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)) )
{
/* Only accept requests and requests without error (be robust) */
err_ret = err_ret;
}
else
{
/* Reject response and trap headers or error requests as input! */
err_ret = ERR_ARG;
}
if (err_ret == ERR_OK)
{
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);
if ((err_ret == ERR_OK) && (msg_ps->invb.count > 0))
{
/* we've decoded the incoming message, release input msg now */
pbuf_free(p);
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);
}
else
{
/* varbind-list decode failed, or varbind list empty.
drop request silently, do not return error!
(errors are only returned for a specific varbind failure) */
pbuf_free(p);
LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_dec_varbindlist() failed\n"));
}
}
else
{
/* header check failed
drop request silently, do not return error! */
pbuf_free(p);
LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_header_check() failed\n"));
}
}
else
{
/* exceeding number of concurrent requests */
pbuf_free(p);
}
}
else
{
/* datagram not for us */
pbuf_free(p);
}
}
/**
* 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 = 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 = 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 = 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):
vb = snmp_varbind_alloc(&oid, type, len);
if (vb != NULL)
{
derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, 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 = 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, 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 *)mem_malloc(sizeof(struct 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)
{
/* allocate array of s32_t for our object identifier */
vb->ident = (s32_t*)mem_malloc(sizeof(s32_t) * i);
LWIP_ASSERT("vb->ident != NULL",vb->ident != NULL);
if (vb->ident == NULL)
{
mem_free(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)
{
/* allocate raw bytes for our object value */
vb->value = mem_malloc(len);
LWIP_ASSERT("vb->value != NULL",vb->value != NULL);
if (vb->value == NULL)
{
if (vb->ident != NULL)
{
mem_free(vb->ident);
}
mem_free(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 )
{
mem_free(vb->value);
}
if (vb->ident != NULL )
{
mem_free(vb->ident);
}
mem_free(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 */