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snmp_recv: don't peek the UDP header, p->tot_len does the same; no need for the extra checks at the beginning; don't use so many if/else but if/return instead to make the code more readable

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This commit is contained in:
goldsimon 2010-01-27 17:36:37 +00:00
parent 0644c4c08e
commit 853e33bdb4
1 changed files with 67 additions and 105 deletions
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172
src/core/snmp/msg_in.c
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@ -808,121 +808,83 @@ snmp_msg_event(u8_t request_id)
static void
snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
{
struct udp_hdr *udphdr;
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);
/* peek in the UDP header (goto IP payload) */
if(pbuf_header(p, UDP_HLEN)){
LWIP_ASSERT("Can't move to UDP header", 0);
/* 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;
}
udphdr = p->payload;
/* check if datagram is really directed at us (including broadcast requests) */
if ((pcb == snmp1_pcb) && (ntohs(udphdr->dest) == SNMP_IN_PORT))
/* 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)) )
{
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 */
/* 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);
}
/**