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mirror of https://gitlab.nic.cz/labs/bird.git synced 2024-12-23 10:11:53 +00:00
bird/proto/snmp/subagent.c
2024-07-23 13:48:20 +02:00

1420 lines
39 KiB
C

/*
* BIRD -- Simple Network Management Protocol (SNMP)
*
* (c) 2022 Vojtech Vilimek <vojtech.vilimek@nic.cz>
* (c) 2022 CZ.NIC z.s.p.o
*
* Can be freely distributed and used under the terms of the GNU GPL.
*
*/
#include "lib/unaligned.h"
#include "subagent.h"
#include "mib_tree.h"
#include "snmp_utils.h"
#include "bgp4_mib.h"
/*
* Goals:
* In current situation, we do not handle the dynamic BGP case.
*/
/**
*
*
*
*
* Handling of malformed packet:
*
* When we find an error in PDU data, we create and send a response with error
* defined by the RFC. We await until the packet is send and then we close the
* communication socket. This implicitly closes the established session. We
* chose this approach because we cannot easily mark the boundary between packets.
* When we are reseting the connection, we change the snmp_state to SNMP_RESET.
* In SNMP_RESET state we skip all received bytes and wait for snmp_tx_skip()
* to be called. The socket's tx_hook is called when the TX-buffer is empty,
* meaning our response (agentx-Response-PDU) was send.
*
*
* Partial parsing:
*
* It may happen that we received only staring part of some PDU from the
* communication socket. In most cases, if we recognize this situation we
* immediately return, waiting for rest of the PDU to arrive. But for packets
* like agentx-Get-PDU, agentx-GetNext-PDU and agentx-GetBulk-PDU it could be
* costly as they could hold many VarBinds. We don't want to process these
* packet twice because it is a lot work. We parse all VarBinds until we hit the
* first incomplete one. The logic behind this is to release as much as
* possible space from receive buffer. When we hit the first incomplete VarBind,
* we store information about the parsing state and move the header inside the
* receive buffer.
*
* Transmit packet context
*
*/
static uint parse_response(struct snmp_proto *p, byte *buf);
static void do_response(struct snmp_proto *p, byte *buf);
static uint parse_gets_pdu(struct snmp_proto *p, byte *pkt);
static struct agentx_response *prepare_response(struct snmp_proto *p, struct snmp_pdu *c);
static void response_err_ind(struct snmp_proto *p, struct agentx_response *res, enum agentx_response_errs err, u16 ind);
static uint update_packet_size(struct agentx_header *start, byte *end);
/* standard SNMP internet prefix (.1.3.6.1) */
const u32 snmp_internet[] = { SNMP_ISO, SNMP_ORG, SNMP_DOD, SNMP_INTERNET };
static inline int
snmp_is_active(struct snmp_proto *p)
{
/* Note: states in which we have opened socket */
return p->state == SNMP_OPEN || p->state == SNMP_REGISTER ||
p->state == SNMP_CONN;
}
/*
* snmp_header - store packet information into buffer
* @h: pointer to created packet header in TX-buffer
* @type: created PDU type
* @flags: set flags
*
* Payload length is set to zero legth. Padding is also zeroed. Real stored
* flags are dependent on compile-time message byte-order configuration.
*/
static inline void
snmp_header(struct agentx_header *h, enum agentx_pdu_types type, u8 flags)
{
STORE_U8(h->version, AGENTX_VERSION);
STORE_U8(h->type, type);
STORE_U8(h->flags, flags | SNMP_ORDER);
STORE_U8(h->reserved, 0);
STORE_U32(h->payload, 0);
}
/*
* snmp_blank_header - create header with no flags except default
* @h: pointer to created header in TX-buffer
* @type: create PDU type
*
* Only flag possibly set may be packet byte order configuration.
*/
static inline void
snmp_blank_header(struct agentx_header *h, enum agentx_pdu_types type)
{
snmp_header(h, type, (u8) 0);
}
/*
* snmp_register_ack - handle registration response
* @p: SNMP protocol instance
* @res: header of agentx-Response-PDU
* @mib: MIB subtree identifier
*/
void
snmp_register_ack(struct snmp_proto *p, struct agentx_response *res, const struct oid *oid)
{
enum agentx_mibs mib = agentx_get_mib(oid);
struct snmp_registration *reg;
WALK_LIST(reg, p->registration_queue)
{
if (snmp_registration_match(reg, &res->h, mib))
{
rem_node(&reg->n);
p->registrations_to_ack--;
if (res->error == AGENTX_RES_NO_ERROR)
reg->reg_hook_ok(p, (const struct agentx_response *) res, reg);
else
reg->reg_hook_fail(p, (const struct agentx_response *) res, reg);
mb_free(reg->oid);
mb_free(reg);
return;
}
}
}
/*
* snmp_simple_response - send an agentx-Response-PDU with no data payload
* @p: SNMP protocol instance
* @error: response PDU error fields value
* @index: response PDU error index field value
*
* This function assumes that the buffer has enough space to fill in the AgentX
* Response PDU. So it is the responsibility of the caller to provide that.
*/
static void
snmp_simple_response(struct snmp_proto *p, enum agentx_response_errs error, u16 index)
{
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
ASSUME(c.size >= sizeof(struct agentx_response));
struct agentx_response *res = prepare_response(p, &c);
response_err_ind(p, res, error, index);
sk_send(sk, sizeof(struct agentx_response));
}
/*
* open_pdu - send an agentx-Open-PDU
* @p: SNMP protocol instance
* @oid: PDU OID description field value
*
* Other fields are filled based on @p configuration (timeout, subagent string
* description)
*/
static void
open_pdu(struct snmp_proto *p, struct oid *oid)
{
const struct snmp_config *cf = SKIP_BACK(struct snmp_config, cf, p->p.cf);
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
#define TIMEOUT_SIZE sizeof(u32) /* 1B timeout, 3B zero padding */
/* Make sure that we have enough space in TX-buffer */
uint s = AGENTX_HEADER_SIZE + TIMEOUT_SIZE + snmp_oid_size(oid) +
snmp_str_size(cf->description);
if (snmp_tbuf_reserve(&c, s))
snmp_log("agentx-Open-PDU small buffer");
struct agentx_header *h = (void *) c.buffer;
ADVANCE(c.buffer, c.size, AGENTX_HEADER_SIZE);
snmp_blank_header(h, AGENTX_OPEN_PDU);
STORE_U32(h->session_id, 1);
STORE_U32(h->transaction_id, 1);
STORE_U32(h->packet_id, 1);
c.size -= (4 + snmp_oid_size(oid) + snmp_str_size(cf->description));
if (p->timeout >= 1 S && p->timeout <= 255 S)
/* use p->timeout ceiled up to whole second */
c.buffer = snmp_put_fbyte(c.buffer,
(p->timeout % (1 S) == 0) ? p->timeout TO_S : p->timeout TO_S + 1);
/* out of range fallbacks */
else if (p->timeout < 1 TO_US)
c.buffer = snmp_put_fbyte(c.buffer, (u8) 1);
else /* p->timeout > 255 TO_US */
c.buffer = snmp_put_fbyte(c.buffer, (u8) 255);
c.buffer = snmp_put_oid(c.buffer, oid);
c.buffer = snmp_put_str(c.buffer, cf->description);
s = update_packet_size(h, c.buffer);
sk_send(sk, s);
#undef TIMEOUT_SIZE
}
/*
* send_notify_pdu - send an agentx-Notify-PDU
* @p: SNMP protocol instance
* @oid: PDU notification Varbind name (OID)
* @data: PDU Varbind payload
* @size - PDU Varbind payload size
* @include_uptime: flag enabling inclusion of sysUpTime.0 OID
*/
void
snmp_notify_pdu(struct snmp_proto *p, struct oid *oid, void *data, uint size, int include_uptime)
{
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
#define UPTIME_SIZE sizeof(STATIC_OID(4)) /* see sys_up_time_0 */
#define TRAP0_HEADER_SIZE sizeof(STATIC_OID(6)) /* see snmp_trap_oid_0 */
uint sz = AGENTX_HEADER_SIZE + TRAP0_HEADER_SIZE + snmp_oid_size(oid) \
+ size;
if (include_uptime)
sz += UPTIME_SIZE;
/* Make sure that we have enough space in TX-buffer */
if (snmp_tbuf_reserve(&c, sz))
snmp_log("agentx-Notify-PDU small buffer");
struct agentx_header *h = (void *) c.buffer;
ADVANCE(c.buffer, c.size, AGENTX_HEADER_SIZE);
snmp_blank_header(h, AGENTX_NOTIFY_PDU);
p->packet_id++; /* New packet id */
snmp_session(p, h);
if (include_uptime)
{
/* sysUpTime.0 oid */
STATIC_OID(4) sys_up_time_0 = {
.n_subid = 4,
.prefix = SNMP_MGMT,
.include = 0,
.reserved = 0,
.ids = { SNMP_MIB_2, SNMP_SYSTEM, SNMP_SYS_UP_TIME, 0 },
};
struct oid *uptime_0 = (struct oid *) &sys_up_time_0;
struct agentx_varbind *vb = snmp_create_varbind(c.buffer, uptime_0);
for (uint i = 0; i < uptime_0->n_subid; i++)
STORE_U32(vb->name.ids[i], uptime_0->ids[i]);
/* TODO use time from last reconfiguration instead? [config->load_time] */
btime uptime = current_time() - boot_time;
snmp_varbind_ticks(&c, (uptime TO_S) / 100);
ASSUME(snmp_test_varbind(vb));
ADVANCE(c.buffer, c.size, snmp_varbind_size_unsafe(vb));
}
/* snmpTrapOID.0 oid */
STATIC_OID(6) snmp_trap_oid_0 = {
.n_subid = 6,
.prefix = SNMP_V2,
.include = 0,
.reserved = 0,
.ids = { SNMP_MODULES, SNMP_ALARM_NEXT_INDEX, SNMP_MIB_OBJECTS, SNMP_TRAP, SNMP_TRAP_OID, 0 },
};
struct oid *trap_0 = (struct oid *) &snmp_trap_oid_0;
struct agentx_varbind *trap_vb = snmp_create_varbind(c.buffer, trap_0);
for (uint i = 0; i < trap_0->n_subid; i++)
STORE_U32(trap_vb->name.ids[i], trap_0->ids[i]);
trap_vb->type = AGENTX_OBJECT_ID;
snmp_put_oid(snmp_varbind_data(trap_vb), oid);
ADVANCE(c.buffer, c.size, snmp_varbind_size_unsafe(trap_vb));
memcpy(c.buffer, data, size);
ADVANCE(c.buffer, c.size, size);
uint s = update_packet_size(h, c.buffer);
sk_send(sk, s);
#undef TRAP0_HEADER_SIZE
#undef UPTIME_SIZE
}
/*
* un_register_pdu - common functionality for registration PDUs
* @p: SNMP protocol instance
* @oid: OID to register/unregister
* @bound: OIDs registration upper bound
* @index: OIDs registration n_subid index
* @type: register/unregister PDU type
* @is_instance: flag enabling instance registration (used only for register)
* @contid: context ID to register in (currently unsupported)
*
* Both register and unregister PDUs are capable of specifing a number of OIDs
* by using pair of index and upper bound. The index (r.range_subid) points into
* the OID's n_subid array to ID being threated as variable. The upper bound
* (r.upper_bound) determins maximal value for n_subid selected by index.
* The index and upper bound are passed as @index, and @bound respectively.
*
* Zero value for @is_instance means we want to register/unregister OID as a MIB
* subtree, for nonzero value we are registering MIB tree an instance (leaf).
*
* This function in internal and shoulnd't be used outside the SNMP module,
* see snmp_register() and snmp_unregister() functions.
*/
static void
un_register_pdu(struct snmp_proto *p, struct oid *oid, u32 bound, uint index, enum agentx_pdu_types type, u8 is_instance, uint UNUSED contid)
{
/* used for agentx-Register-PDU and agentx-Unregister-PDU */
const struct snmp_config *cf = SKIP_BACK(struct snmp_config, cf, p->p.cf);
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
#define BOUND_SIZE sizeof(u32)
/* conditional +4 for upper-bound (optinal field) */
uint sz = AGENTX_HEADER_SIZE + snmp_oid_size(oid) +
((bound > 1) ? BOUND_SIZE : 0);
if (snmp_tbuf_reserve(&c, sz))
snmp_log("agentx-Register-PDU small buffer");
struct agentx_header *h = (void *) c.buffer;
ADVANCE(c.buffer, c.size, AGENTX_HEADER_SIZE);
snmp_header(h, type, is_instance ? AGENTX_FLAG_INSTANCE_REGISTRATION : 0);
p->packet_id++;
snmp_session(p, h);
struct agentx_un_register_hdr *ur = (struct agentx_un_register_hdr *) c.buffer;
/* 0 = do not override session message timeout */
STORE_U8(ur->timeout, 0);
/* use selected priority */
STORE_U8(ur->priority, cf->priority);
STORE_U8(ur->range_subid, (bound > 1) ? index : 0);
STORE_U8(ur->reserved, 0);
ADVANCE(c.buffer, c.size, sizeof(struct agentx_un_register_hdr));
snmp_put_oid(c.buffer, oid);
ADVANCE(c.buffer, c.size, snmp_oid_size(oid));
/* place upper-bound if needed */
if (bound > 1)
{
STORE_PTR(c.buffer, bound);
ADVANCE(c.buffer, c.size, BOUND_SIZE);
}
uint s = update_packet_size(h, c.buffer);
sk_send(sk, s);
#undef BOUND_SIZE
}
/*
* snmp_register - send an agentx-Register-PDU
* @p: SNMP protocol instance
* @oid: OID to register
* @bound: OIDs registration upper bound
* @index: OIDs registration n_subid index
* @is_instance: flag enabling instance registration
* @contid: context ID to register in (currently unsupported)
*
* For more detailed description see un_register_pdu() function.
*/
void
snmp_register(struct snmp_proto *p, struct oid *oid, u32 bound, uint index, u8 is_instance, uint contid)
{
un_register_pdu(p, oid, bound, index, AGENTX_REGISTER_PDU, is_instance, contid);
}
/*
* snmp_unregister - send an agentx-Unregister-PDU
* @p: SNMP protocol instance
* @oid: OID to uregister
* @bound: OIDs unregistration upper bound
* @index: OIDs unregistration n_subid index
* @contid: context ID to unregister from (currently unsupported)
*
* For more detailed description see un_register_pdu() function.
*/
void
snmp_unregister(struct snmp_proto *p, struct oid *oid, u32 bound, uint index, uint contid)
{
un_register_pdu(p, oid, bound, index, AGENTX_UNREGISTER_PDU, 0, contid);
}
/*
* close_pdu - send an agentx-Close-PDU
* @p: SNMP protocol instance
* @reason: reason for closure
*/
static void
close_pdu(struct snmp_proto *p, enum agentx_close_reasons reason)
{
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
#define REASON_SIZE sizeof(u32)
if (snmp_tbuf_reserve(&c, AGENTX_HEADER_SIZE + REASON_SIZE))
snmp_log("agentx-Close-PDU small buffer");
struct agentx_header *h = (void *) c.buffer;
ADVANCE(c.buffer, c.size, AGENTX_HEADER_SIZE);
snmp_blank_header(h, AGENTX_CLOSE_PDU);
p->packet_id++;
snmp_session(p, h);
snmp_put_fbyte(c.buffer, (u8) reason);
ADVANCE(c.buffer, c.size, 4);
uint s = update_packet_size(h, c.buffer);
sk_send(sk, s);
#undef REASON_SIZE
}
/*
* parse_close_pdu - parse an agentx-Close-PDU
* @p: SNMP protocol instance
* @pkt_start: pointer to first byte of PDU
*
* Return number of bytes parsed from RX-buffer.
*/
static uint
parse_close_pdu(struct snmp_proto *p, byte * const pkt_start)
{
TRACE(D_PACKETS, "SNMP received agentx-Close-PDU");
byte *pkt = pkt_start;
struct agentx_close_pdu *pdu = (void *) pkt;
pkt += sizeof(struct agentx_close_pdu);
uint pkt_size = pdu->h.payload;
if (pkt_size != sizeof(struct agentx_close_pdu))
{
TRACE(D_PACKETS, "SNMP malformed agentx-Close-PDU, closing anyway");
snmp_simple_response(p, AGENTX_RES_GEN_ERROR, 0);
snmp_set_state(p, SNMP_RESET);
return MIN(pkt_size + AGENTX_HEADER_SIZE, sizeof(struct agentx_close_pdu));
}
if (!snmp_test_close_reason(pdu->reason))
{
TRACE(D_PACKETS, "SNMP invalid close reason %u", pdu->reason);
snmp_simple_response(p, AGENTX_RES_GEN_ERROR, 0);
snmp_set_state(p, SNMP_RESET);
return pkt_size + AGENTX_HEADER_SIZE;
}
enum agentx_close_reasons reason = (enum agentx_close_reasons) pdu->reason;
TRACE(D_PACKETS, "SNMP close reason %u", reason);
snmp_simple_response(p, AGENTX_RES_NO_ERROR, 0);
snmp_set_state(p, SNMP_RESET);
return pkt_size + AGENTX_HEADER_SIZE;
}
/*
* refresh_ids - Copy current ids from packet to protocol
* @p: SNMP protocol instance
* @h: PDU header with new transaction_id and packet_id ids.
*/
static inline void
refresh_ids(struct snmp_proto *p, struct agentx_header *h)
{
p->transaction_id = LOAD_U32(h->transaction_id);
p->packet_id = LOAD_U32(h->packet_id);
}
/*
* parse_test_set_pdu - parse an agentx-TestSet-PDU in buffer
* @p: SNMP protocol instance
* @pkt_start: first byte of test set PDU
* @size: number of bytes received from a socket
*
* Return number of bytes parsed from RX-buffer.
*/
static inline uint
parse_test_set_pdu(struct snmp_proto *p, byte * const pkt_start)
{
TRACE(D_PACKETS, "SNMP received agentx-TestSet-PDU");
byte *pkt = pkt_start; /* pointer to agentx-TestSet-PDU in RX-buffer */
uint s; /* final packat size */
struct agentx_response *res; /* pointer to reponse in TX-buffer */
struct agentx_header *h = (void *) pkt;
pkt += AGENTX_HEADER_SIZE;
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
if (snmp_tbuf_reserve(&c, AGENTX_HEADER_SIZE))
snmp_log("agentx-TestSet-PDU small buffer");
res = prepare_response(p, &c);
/* 0 if there is piece, that we cannot set */
int all_possible = 0;
/* the all_possible is currently hard-coded with no support for writing to mib
* variables, when implementing the mentioned support, change the initializer
* to 1
*/
s = update_packet_size(h, c.buffer);
if (c.error != AGENTX_RES_NO_ERROR)
{
response_err_ind(p, res, c.error, c.index + 1);
snmp_reset(p); // error
}
else if (all_possible)
{
response_err_ind(p, res, AGENTX_RES_NO_ERROR, 0);
}
else
{
TRACE(D_PACKETS, "SNMP SET action failed (not writable)");
/* This is a recoverable error, we do not need to reset the connection */
response_err_ind(p, res, AGENTX_RES_NOT_WRITABLE, c.index + 1);
}
sk_send(sk, s);
return pkt - pkt_start;
}
/*
* parse_sets_pdu - common functionality for commit set and undo set PDUs
* @p: SNMP protocol instance
* @pkt_start: pointer to first byte of on of set related PDU
* @error: error status to use
*
* Return number of bytes parsed from RX-buffer.
*/
static uint
parse_sets_pdu(struct snmp_proto *p, byte * const pkt_start, enum agentx_response_errs err)
{
byte *pkt = pkt_start;
struct agentx_header *h = (void *) pkt;
pkt += AGENTX_HEADER_SIZE;
uint pkt_size = LOAD_U32(h->payload);
if (pkt_size != 0)
{
TRACE(D_PACKETS, "SNMP received malformed set PDU (size)");
snmp_simple_response(p, AGENTX_RES_PARSE_ERROR, 0);
// TODO best solution for possibly malicious pkt_size
return AGENTX_HEADER_SIZE;
}
struct snmp_pdu c;
snmp_pdu_context(&c, p, p->sock);
if (snmp_tbuf_reserve(&c, sizeof(struct agentx_response)))
snmp_log("parse_sets_pdu small buffer");
struct agentx_response *r = prepare_response(p, &c);
// TODO free resource allocated by parse_test_set_pdu()
// TODO do something meaningful
//mb_free(tr);
c.error = err;
TRACE(D_PACKETS, "SNMP received set PDU with error %u", c.error);
response_err_ind(p, r, c.error, 0);
sk_send(p->sock, AGENTX_HEADER_SIZE);
/* Reset the connection on unrecoverable error */
if (c.error != AGENTX_RES_NO_ERROR && c.error != err)
snmp_reset(p); /* error */
return pkt - pkt_start;
}
/*
* parse_commit_set_pdu - parse an agentx-CommitSet-PDU
* @p: SNMP protocol instance
* @pkt: pointer to first byte of PDU inside RX-buffer
*
* Return number of bytes parsed from RX-buffer.
*/
static inline uint
parse_commit_set_pdu(struct snmp_proto *p, byte *pkt)
{
// don't forget to free resoures allocated by parse_test_set_pdu()
//mb_free(tr);
TRACE(D_PACKETS, "SNMP received agentx-CommitSet-PDU");
return parse_sets_pdu(p, pkt, AGENTX_RES_COMMIT_FAILED);
}
/*
* parse_undo_set_pdu - parse an agentx-UndoSet-PDU
* @p: SNMP protocol instance
* @pkt: pointer to first byte of PDU inside RX-buffer
*
* Return number of bytes parsed from buffer.
*/
static inline uint
parse_undo_set_pdu(struct snmp_proto *p, byte *pkt)
{
// don't forget to free resources allocated by parse_test_set_pdu()
//mb_free(tr);
TRACE(D_PACKETS, "SNMP received agentx-UndoSet-PDU");
return parse_sets_pdu(p, pkt, AGENTX_RES_UNDO_FAILED);
}
/*
* parse_cleanup_set_pdu - parse an agentx-CleanupSet-PDU
* @p: SNMP protocol instance
* @pkt_start: pointer to first byte of PDU inside RX-buffer
*
* Return number of bytes parsed from RX-buffer.
*/
static uint
parse_cleanup_set_pdu(struct snmp_proto *p, byte * const pkt_start)
{
TRACE(D_PACKETS, "SNMP received agentx-CleanupSet-PDU");
(void)p;
// TODO don't forget to free resources allocated by parse_test_set_pdu()
//mb_free(p->tr);
byte *pkt = pkt_start;
struct agentx_header *h = (void *) pkt;
uint pkt_size = LOAD_U32(h->payload);
/* errors are dropped silently, we must not send any agentx-Response-PDU */
if (pkt_size != 0)
{
// TODO should we free even for malformed packets ??
// TODO -> check that data is not freed
return AGENTX_HEADER_SIZE;
}
/* No agentx-Response-PDU is sent in response to agentx-CleanupSet-PDU */
return pkt_size;
}
/*
* space_for_response - check if TX-buffer has space for agentx-Response-PDU
* @sk: communication socket owned by SNMP protocol instance
*
* In some cases we send only the AgentX header but if we want to signal an
* error, we need at least space for agentx-Response-PDU. This simplifies the
* PDU space requirements testing.
*/
static inline int
space_for_response(const sock *sk)
{
return (
(uint) (sk->tbuf + sk->tbsize - sk->tpos) >= sizeof(struct agentx_response)
);
}
/**
* parse_pkt - parse received AgentX packet
* @p: SNMP protocol instance
* @pkt: first byte of PDU inside RX-buffer
* @size: number of bytes received from a socket
*
* Return number of bytes parsed from RX-buffer.
*/
static uint
parse_pkt(struct snmp_proto *p, byte *pkt, uint size)
{
snmp_log("parse_pkt %t", current_time());
/* TX-buffer free space */
if (size < AGENTX_HEADER_SIZE)
return 0;
struct agentx_header *h = (void *) pkt;
if (h->flags & AGENTX_NETWORK_BYTE_ORDER)
{
TRACE(D_PACKETS, "SNMP received PDU with unexpected byte order");
snmp_reset(p);
return 0;
}
uint pkt_size = LOAD_U32(h->payload);
/* RX side checks - too big packet */
if (pkt_size > SNMP_PKT_SIZE_MAX)
{
snmp_simple_response(p, AGENTX_RES_GEN_ERROR, 0);
snmp_reset(p);
return 0; /* no bytes parsed */
}
/* This guarantees that we have the full packet already received */
if (size < pkt_size + AGENTX_HEADER_SIZE)
return 0; /* no bytes parsed */
/* We need to see the responses for PDU such as
* agentx-Open-PDU, agentx-Register-PDU, ...
* even when we are outside the SNMP_CONNECTED state
*/
if (h->type == AGENTX_RESPONSE_PDU)
return parse_response(p, pkt);
ASSERT(snmp_is_active(p));
if (p->state != SNMP_CONN ||
p->session_id != LOAD_U32(h->session_id))
{
struct agentx_header copy = {
.session_id = p->session_id,
.transaction_id = p->transaction_id,
.packet_id = p->packet_id,
};
TRACE(D_PACKETS, "SNMP received PDU with unknown session id");
snmp_simple_response(p, AGENTX_RES_NOT_OPEN, 0);
p->session_id = copy.session_id;
p->transaction_id = copy.transaction_id;
p->packet_id = copy.packet_id;
snmp_log("restoring packet_id %u from temporal state", p->packet_id);
/*
* After unexpected state, we simply reset the session
* only sending the agentx-Response-PDU.
*/
snmp_reset(p);
return 0;
}
if (h->flags & AGENTX_NON_DEFAULT_CONTEXT)
{
TRACE(D_PACKETS, "SNMP received PDU with non-default context");
snmp_simple_response(p, AGENTX_RES_UNSUPPORTED_CONTEXT, 0);
return pkt_size + AGENTX_HEADER_SIZE;
}
refresh_ids(p, h);
switch (h->type)
{
case AGENTX_GET_PDU:
case AGENTX_GET_NEXT_PDU:
case AGENTX_GET_BULK_PDU:
return parse_gets_pdu(p, pkt);
case AGENTX_CLOSE_PDU:
return parse_close_pdu(p, pkt);
case AGENTX_TEST_SET_PDU:
return parse_test_set_pdu(p, pkt);
case AGENTX_COMMIT_SET_PDU:
return parse_commit_set_pdu(p, pkt);
case AGENTX_UNDO_SET_PDU:
return parse_undo_set_pdu(p, pkt);
case AGENTX_CLEANUP_SET_PDU:
return parse_cleanup_set_pdu(p, pkt);
default:
/* We reset the connection for malformed packet (Unknown packet type) */
TRACE(D_PACKETS, "SNMP received unknown packet with type %u", h->type);
snmp_set_state(p, SNMP_RESET);
return 0;
}
}
/*
* parse_response - parse an agentx-Response-PDU
* @p: SNMP protocol instance
* @res: pointer of agentx-Response-PDU header in RX-buffer
*
* Return number of bytes parsed from RX-buffer.
*/
static uint
parse_response(struct snmp_proto *p, byte *res)
{
struct agentx_response *r = (void *) res;
struct agentx_header *h = (void *) r;
// todo reject not compiled byte order
uint pkt_size = LOAD_U32(h->payload);
switch (r->error)
{
case AGENTX_RES_NO_ERROR:
TRACE(D_PACKETS, "SNMP received agetnx-Response-PDU");
do_response(p, res);
break;
/* Registration errors */
case AGENTX_RES_DUPLICATE_REGISTER:
case AGENTX_RES_REQUEST_DENIED:
case AGENTX_RES_UNKNOWN_REGISTER:
// TODO more direct path to mib-specific code
TRACE(D_PACKETS, "SNMP received agentx-Response-PDU with error %u", r->error);
byte *pkt = res + sizeof(struct agentx_response);
struct oid *failed = (struct oid *) pkt;
snmp_register_ack(p, r, failed);
break;
/*
* We found ourselves in an unexpected situation. To enter a well defined
* state as well as give the AgentX master agent room to fix the errors on
* his side, we perform a hard reset of the connections.
*/
case AGENTX_RES_NOT_OPEN:
case AGENTX_RES_OPEN_FAILED:
case AGENTX_RES_UNKNOWN_AGENT_CAPS:
case AGENTX_RES_UNSUPPORTED_CONTEXT: /* currently we don't use contexts */
case AGENTX_RES_PARSE_ERROR:
case AGENTX_RES_PROCESSING_ERR:
default:
DBG("SNMP agentx-Response-PDU with unexpected error %u", r->error);
snmp_set_state(p, SNMP_DOWN);
break;
}
return pkt_size + AGENTX_HEADER_SIZE;
}
/*
* snmp_register_mibs - register all MIB subtrees
* @p: SNMP protocol instance
*/
void
snmp_register_mibs(struct snmp_proto *p)
{
snmp_bgp4_register(p);
}
/*
* do_response - act on agentx-Response-PDU and protocol state
* @p: SNMP protocol instance
* @pkt: RX-buffer with PDU bytes
*
* Return number of bytes parsed from RX-buffer.
*/
static void
do_response(struct snmp_proto *p, byte *pkt)
{
struct agentx_response *r = (void *) pkt;
struct agentx_header *h = (void *) r;
switch (p->state)
{
case SNMP_INIT:
case SNMP_LOCKED:
/* silent drop of received packet */
break;
case SNMP_OPEN:
/* copy session info from received packet */
p->session_id = LOAD_U32(h->session_id);
refresh_ids(p, h);
tm_start(p->ping_timer, 0);
/* the state needs to be changed before sending registering PDUs to
* use correct do_response action on them
*/
snmp_set_state(p, SNMP_REGISTER);
break;
case SNMP_REGISTER:;
pkt += AGENTX_HEADER_SIZE;
const struct oid *oid = (struct oid *) pkt;
snmp_register_ack(p, r, oid);
if (p->registrations_to_ack == 0)
snmp_set_state(p, SNMP_CONN);
break;
case SNMP_CONN:
break;
case SNMP_STOP:
break;
default:
die("unkonwn SNMP state");
}
}
static inline struct oid *
snmp_oid_prefixize_unsafe(struct oid *dest, const struct oid *src)
{
u8 subids = LOAD_U8(src->n_subid) - 5;
dest->n_subid = subids;
STORE_U8(dest->prefix, (u8) LOAD_U32(src->ids[ARRAY_SIZE(snmp_internet)]));
STORE_U8(dest->include, (LOAD_U8(src->include)) ? 1 : 0);
STORE_U8(dest->reserved, 0);
/* The LOAD_U32() and STORE_U32() cancel out */
memcpy(&dest->ids[0], &src->ids[5], subids * sizeof(u32));
return dest;
}
/*
* snmp_vb_to_tx - create varbind from RX buffer OID
* @c: PDU context
* @oid: object identifier located in RX buffer
*
* Create NULL initialized VarBind inside TX buffer (from @c) whose vb->name is
* @oid. The @oid prefixed if possible. The result is stored in @c->sr_vb_start.
*/
void
snmp_vb_to_tx(struct snmp_pdu *c, const struct oid *oid)
{
uint vb_hdr_size = snmp_varbind_hdr_size_from_oid(oid);
if (snmp_tbuf_reserve(c, vb_hdr_size))
snmp_log("SNMP vb_to_tx small buffer");
ASSERT(c->size >= vb_hdr_size);
struct agentx_varbind *vb = (void *) c->buffer;
ADVANCE(c->buffer, c->size, sizeof(struct agentx_varbind) - sizeof(struct oid));
/* Move the c->buffer so that is points at &vb->name */
snmp_set_varbind_type(vb, AGENTX_NULL);
if (snmp_oid_is_prefixable(oid) && !snmp_oid_is_prefixed(oid))
{
u8 subids = LOAD_U8(oid->n_subid) - 5;
ADVANCE(c->buffer, c->size, snmp_oid_size_from_len(subids));
(void) snmp_oid_prefixize_unsafe(&vb->name, oid);
c->sr_vb_start = vb;
return;
}
ADVANCE(c->buffer, c->size, snmp_oid_size(oid));
snmp_oid_copy2(&vb->name, oid);
c->sr_vb_start = vb;
}
/*
* update_packet_size - set PDU size
* @start - pointer to PDU data start (excluding header size)
* @end - pointer after the last PDU byte
*
* Return number of bytes in TX-buffer (including header size).
*/
static inline uint
update_packet_size(struct agentx_header *start, byte *end)
{
uint s = snmp_pkt_len((byte *) start, end);
STORE_U32(start->payload, s);
return AGENTX_HEADER_SIZE + s;
}
/*
* response_err_ind - update response error and index
* @p: SNMP protocol instance
* @res: response PDU header
* @err: error status
* @ind: index of error, ignored for noAgentXError
*
* Update agentx-Response-PDU header fields res.error and it's res.index. If the
* error is not noError, also set the corrent response PDU payload size.
*/
static inline void
response_err_ind(struct snmp_proto *p, struct agentx_response *res, enum agentx_response_errs err, u16 ind)
{
STORE_U32(res->error, (u16) err);
// TODO deal with auto-incrementing of snmp_pdu context c.ind
if (err != AGENTX_RES_NO_ERROR && err != AGENTX_RES_GEN_ERROR)
{
TRACE(D_PACKETS, "Last PDU resulted in error %u", err);
STORE_U32(res->index, ind);
TRACE(D_PACKETS, "Storing packet size %u (was %u)", sizeof(struct agentx_response) - AGENTX_HEADER_SIZE, LOAD_U32(res->h.payload));
STORE_U32(res->h.payload,
sizeof(struct agentx_response) - AGENTX_HEADER_SIZE);
}
else if (err == AGENTX_RES_GEN_ERROR)
{
TRACE(D_PACKETS, "Last PDU resulted in error %u genErr", err);
STORE_U32(res->index, 0);
TRACE(D_PACKETS, "Storing packet size %u (was %u)", sizeof(struct agentx_response) - AGENTX_HEADER_SIZE, LOAD_U32(res->h.payload));
STORE_U32(res->h.payload,
sizeof(struct agentx_response) - AGENTX_HEADER_SIZE);
}
else
STORE_U32(res->index, 0);
}
static inline uint
parse_gets_error(struct snmp_proto *p, struct snmp_pdu *c, uint len)
{
TRACE(D_PACKETS, "SNMP error %u while parsing gets PDU", c->error);
if (c->index > UINT16_MAX)
snmp_simple_response(p, AGENTX_RES_GEN_ERROR, UINT16_MAX);
else
snmp_simple_response(p, AGENTX_RES_GEN_ERROR, c->index);
return len + AGENTX_HEADER_SIZE;
}
/*
* AgentX GetPDU, GetNextPDU and GetBulkPDU
*/
/* agentx-Get-PDU */
void
snmp_get_pdu(struct snmp_proto *p, struct snmp_pdu *c, const struct oid *o_start, struct mib_walk_state *walk)
{
snmp_log("snmp_get_pdu()");
struct mib_leaf *leaf;
leaf = snmp_walk_init(p->mib_tree, walk, o_start, c);
snmp_log("found node %p", leaf);
enum snmp_search_res res;
res = snmp_walk_fill(leaf, walk, c);
snmp_log("fill result %u", res);
if (res != SNMP_SEARCH_OK)
snmp_set_varbind_type(c->sr_vb_start, snmp_search_res_to_type(res));
}
/* agentx-GetNext-PDU */
int
snmp_get_next_pdu(struct snmp_proto *p, struct snmp_pdu *c, const struct oid *o_start, struct mib_walk_state *walk)
{
(void) snmp_walk_init(p->mib_tree, walk, o_start, c);
struct mib_leaf *leaf = snmp_walk_next(p->mib_tree, walk, c);
enum snmp_search_res res;
res = snmp_walk_fill(leaf, walk, c);
if (res != SNMP_SEARCH_OK)
snmp_set_varbind_type(c->sr_vb_start, AGENTX_END_OF_MIB_VIEW);
return res == SNMP_SEARCH_OK;
}
/* agentx-GetBulk-PDU */
void
snmp_get_bulk_pdu(struct snmp_proto *p, struct snmp_pdu *c, const struct oid *o_start, struct mib_walk_state *walk, struct agentx_bulk_state *bulk)
{
if (c->index >= bulk->getbulk.non_repeaters)
bulk->repeaters++;
// store the o_start and o_end
bulk->has_any |= snmp_get_next_pdu(p, c, o_start, walk);
}
static inline const struct oid *
snmp_load_oids(byte **pkt_ptr, uint *pkt_sz, struct snmp_pdu *c)
{
byte *pkt = *pkt_ptr;
uint pkt_size = *pkt_sz;
uint sz;
const struct oid *start = (const struct oid *) pkt;
if ((sz = snmp_oid_size(start)) > pkt_size)
{
snmp_log("load_oids start %u / %u", sz, pkt_size);
c->error = AGENTX_RES_PARSE_ERROR;
*pkt_ptr = pkt;
*pkt_sz = pkt_size;
return NULL;
}
ADVANCE(pkt, pkt_size, sz);
const struct oid *end = (const struct oid *) pkt;
if ((sz = snmp_oid_size(end)) > pkt_size)
{
snmp_log("load_oids end %u / %u", sz, pkt_size);
c->error = AGENTX_RES_PARSE_ERROR;
*pkt_ptr = pkt;
*pkt_sz = pkt_size;
return NULL;
}
ADVANCE(pkt, pkt_size, sz);
if (!snmp_is_oid_empty(end) &&
snmp_oid_compare(start, end) > 0)
{
c->error = AGENTX_RES_GEN_ERROR;
*pkt_ptr = pkt;
*pkt_sz = pkt_size;
return NULL;
}
ASSERT(start != NULL);
ASSERT(end != NULL);
c->sr_o_end = end;
*pkt_ptr = pkt;
*pkt_sz = pkt_size;
return start;
}
/*
* parse_gets_pdu - parse received gets PDUs
* @p: SNMP protocol instance
* @pkt_start: pointer to first byte of received PDU
*
* Gets PDUs are agentx-Get-PDU, agentx-GetNext-PDU, agentx-GetBulk-PDU.
*
* Return number of bytes parsed from RX-buffer
*/
static uint
parse_gets_pdu(struct snmp_proto *p, byte * const pkt_start)
{
snmp_log("parse_gets_pdu msg");
// TODO checks for c.size underflow
struct mib_walk_state walk;
byte *pkt = pkt_start;
struct agentx_header *h = (void *) pkt;
pkt += AGENTX_HEADER_SIZE;
uint pkt_size = LOAD_U32(h->payload);
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
/*
* Get-Bulk processing stops if all the varbind have type END_OF_MIB_VIEW
* has_any is true if some varbind has type other than END_OF_MIB_VIEW
*/
struct agentx_bulk_state bulk_state = { 0 };
if (h->type == AGENTX_GET_BULK_PDU)
{
if (pkt_size < sizeof(struct agentx_getbulk))
{
snmp_log("parse_gets GetBulkPDU prepare");
c.error = AGENTX_RES_PARSE_ERROR;
c.index = 0;
return parse_gets_error(p, &c, pkt_size);
}
struct agentx_getbulk *bulk_info = (void *) pkt;
ADVANCE(pkt, pkt_size, sizeof(struct agentx_getbulk));
bulk_state = (struct agentx_bulk_state) {
.getbulk = {
.non_repeaters = LOAD_U32(bulk_info->non_repeaters),
.max_repetitions = LOAD_U32(bulk_info->max_repetitions),
},
/* In contrast to the RFC, we use 0-based indices. */
.index = 0,
.repetition = 0,
.has_any = 0,
};
}
struct agentx_response *response_header = prepare_response(p, &c);
lp_state tmps;
lp_save(tmp_linpool, &tmps);
while (c.error == AGENTX_RES_NO_ERROR && pkt_size > 0)
{
lp_restore(tmp_linpool, &tmps);
const struct oid *start_rx;
if (!(start_rx = snmp_load_oids(&pkt, &pkt_size, &c)))
{
snmp_log("snmp_load_oid ends with an error");
return parse_gets_error(p, &c, pkt_size);
}
switch (h->type)
{
case AGENTX_GET_PDU:
snmp_get_pdu(p, &c, start_rx, &walk);
break;
case AGENTX_GET_NEXT_PDU:
snmp_get_next_pdu(p, &c, start_rx, &walk);
break;
case AGENTX_GET_BULK_PDU:
snmp_get_bulk_pdu(p, &c, start_rx, &walk, &bulk_state);
break;
default:
die("implementation failure");
}
c.sr_vb_start = NULL;
c.sr_o_end = NULL;
c.index++;
} /* while (c.error == AGENTX_RES_NO_ERROR && size > 0) */
lp_restore(tmp_linpool, &tmps);
if (h->type == AGENTX_GET_BULK_PDU)
{
// TODO: an error for now
}
/* We update the error, index pair on the beginning of the packet. */
response_err_ind(p, response_header, c.error, c.index + 1);
uint s = update_packet_size(&response_header->h, c.buffer);
/* We send the message in TX-buffer. */
sk_send(sk, s);
snmp_log("gets send %t", current_time());
// TODO think through the error state
/* number of bytes parsed from RX-buffer */
return pkt - pkt_start;
}
/*
* snmp_start_subagent - send session open request
* @p: SNMP protocol instance
*
* Send agentx-Open-PDU with configured OID and string description.
*/
void
snmp_start_subagent(struct snmp_proto *p)
{
ASSUME(p->state == SNMP_OPEN);
/* blank oid means unsupported */
STATIC_OID(0) blank = { 0 };
open_pdu(p, (struct oid *) &blank);
}
/*
* snmp_stop_subagent - close established session
* @p: SNMP protocol instance
*
* Send agentx-Close-PDU on established session.
*/
void
snmp_stop_subagent(struct snmp_proto *p)
{
tm_stop(p->ping_timer);
/* This cause problems with net-snmp daemon witch halts afterwards */
close_pdu(p, AGENTX_CLOSE_SHUTDOWN);
}
/*
* snmp_rx - handle received PDUs in RX-buffer in normal operation
* @sk: communication socket
* @size: number of bytes received
*/
int
snmp_rx(sock *sk, uint size)
{
snmp_log("snmp_rx with size %u", size);
struct snmp_proto *p = sk->data;
byte *pkt_start = sk->rbuf;
byte *end = pkt_start + size;
while (snmp_is_active(p) && end >= pkt_start + AGENTX_HEADER_SIZE)
{
uint parsed_len = parse_pkt(p, pkt_start, size);
if (parsed_len == 0)
break;
pkt_start += parsed_len;
size -= parsed_len;
}
/* We flush the RX-buffer on errors */
if (!snmp_is_active(p) || pkt_start == end)
return 1; /* The whole RX-buffer was consumed */
/* Incomplete packet parsing */
memmove(sk->rbuf, pkt_start, size);
sk->rpos = sk->rbuf + size;
return 0;
}
/*
* snmp_tx - handle TX-buffer
* @sk: communication socket owned by SNMP protocol instance
*
* The snmp_tx hook is used only to delay the processing in cases we don't have
* enough space in TX-buffer. Therefore we simply call the snmp_rx hook.
*/
void
snmp_tx(sock *sk)
{
snmp_log("snmp_tx()");
/* We still not have enough space */
if (!space_for_response(sk))
return;
/* There is nothing to process, no bytes in RX-buffer */
if (sk_tx_buffer_empty(sk))
return;
snmp_rx(sk, sk->tpos - sk->tbuf);
}
/*
* snmp_ping - send an agentx-Ping-PDU
* @p: SNMP protocol instance
*/
void
snmp_ping(struct snmp_proto *p)
{
if (!snmp_is_active(p))
return;
sock *sk = p->sock;
struct snmp_pdu c;
snmp_pdu_context(&c, p, sk);
if (c.size < AGENTX_HEADER_SIZE)
return;
int unused = sk->tbuf + sk->tbsize - c.buffer;
if (unused < AGENTX_HEADER_SIZE)
return;
struct agentx_header *h = (void *) c.buffer;
ADVANCE(c.buffer, c.size, AGENTX_HEADER_SIZE);
snmp_blank_header(h, AGENTX_PING_PDU);
p->packet_id++;
snmp_log("incrementing packet_id to %u (ping)", p->packet_id);
snmp_session(p, h);
/* sending only header */
uint s = update_packet_size(h, (byte *) h + AGENTX_HEADER_SIZE);
sk_send(sk, s);
}
/**
* snmp_search_check_end_oid - check if oid is before SearchRange end
*
* @found: best oid found in MIB tree
* @bound: upper bound specified in SearchRange
*
* check if found oid meet the SearchRange upper bound condition in
* lexicographical order, returns boolean value
*/
int
snmp_search_check_end_oid(const struct oid *found, const struct oid *bound)
{
if (snmp_is_oid_empty(bound))
return 1;
return (snmp_oid_compare(found, bound) < 0);
}
/*
* snmp_tbuf_reserve - TODO
*
*/
int
snmp_tbuf_reserve(struct snmp_pdu *c, size_t size)
{
if (size >= c->size)
{
struct snmp_proto *p = c->p;
sock *sk = p->sock;
int diff;
if (c->sr_vb_start != NULL)
diff = (char *) c->sr_vb_start - (char *) sk->tbuf;
snmp_log("snmp_tbuf_reserve()");
sk_set_tbsize(sk, sk->tbsize + 2048);
c->size += 2048;
if (c->sr_vb_start != NULL)
c->sr_vb_start = (struct agentx_varbind *) (sk->tbuf + diff);
return 1;
}
return 0;
}
/*
* prepare_response - fill buffer with AgentX PDU header
* @p: SNMP protocol instance
* @c: transmit PDU context to use
*
* Prepare known parts of AgentX packet header into the TX-buffer held by @c.
*/
static struct agentx_response *
prepare_response(struct snmp_proto *p, struct snmp_pdu *c)
{
struct agentx_response *r = (void *) c->buffer;
struct agentx_header *h = &r->h;
snmp_blank_header(h, AGENTX_RESPONSE_PDU);
snmp_session(p, h);
/* protocol doesn't care about subagent upTime */
STORE_U32(r->uptime, 0);
STORE_U16(r->error, AGENTX_RES_NO_ERROR);
STORE_U16(r->index, 0);
ADVANCE(c->buffer, c->size, sizeof(struct agentx_response));
return r;
}