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/**
* @brief SNMP Agent implementation.
*
* This file is part of sila-snmp project.
*
* Copyright (c) 2022 SILA
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include "config.h"
#include "tracing.hpp"
#include <sdeventplus/clock.hpp>
#include <sdeventplus/event.hpp>
#include <sdeventplus/source/event.hpp>
#include <sdeventplus/source/io.hpp>
#include <sdeventplus/source/time.hpp>
#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>
#include <map>
constexpr auto clockId = sdeventplus::ClockId::Monotonic;
using Clock = sdeventplus::Clock<clockId>;
using Time = sdeventplus::source::Time<clockId>;
// list of snmp file descriptors attached to sd_event loop.
static std::map<int, sdeventplus::source::IO> snmp_fds;
/** @brief Called when snmp file descriptors have data for reading. */
static void sdevent_snmp_read(sdeventplus::source::IO& /*source*/, int fd,
uint32_t /*revents*/)
{
DEBUGMSGTL(("snmpagent:handle", "Handle fd=%d\n", fd));
fd_set fdset;
FD_ZERO(&fdset);
FD_SET(fd, &fdset);
snmp_read(&fdset);
}
/** @brief Refresh list of snmp file descriptors. */
static void sdevent_snmp_update(const sdeventplus::Event& event)
{
netsnmp_check_outstanding_agent_requests();
int maxfd = 0;
int is_blocked = 1;
fd_set fdset;
timeval timeout;
FD_ZERO(&fdset);
snmp_select_info(&maxfd, &fdset, &timeout, &is_blocked);
static Time snmpTimer(event, {}, std::chrono::microseconds{1},
[](Time&, Time::TimePoint) {
DEBUGMSGTL(("snmpagent:handle", "Time out\n"));
snmp_timeout();
run_alarms();
});
if (timeout.tv_sec || timeout.tv_usec)
{
snmpTimer.set_time(Clock(event).now() +
std::chrono::seconds{timeout.tv_sec} +
std::chrono::microseconds{timeout.tv_usec});
snmpTimer.set_enabled(sdeventplus::source::Enabled::OneShot);
}
// We need to untrack any event whose FD is not in `fdset` anymore.
for (auto it = snmp_fds.begin(); it != snmp_fds.end();)
{
if (it->first >= maxfd || (!FD_ISSET(it->first, &fdset)))
{
DEBUGMSGTL(
("snmpagent:handle", "Remove fd=%d from set.\n", it->first));
it->second.set_enabled(sdeventplus::source::Enabled::Off);
it = snmp_fds.erase(it);
}
else
{
FD_CLR(it->first, &fdset);
++it;
}
}
// Invariant: FD in `fdset` are not in `snmp_fds`
for (int fd = 0; fd < maxfd; ++fd)
{
if (FD_ISSET(fd, &fdset))
{
DEBUGMSGTL(("snmpagent:handle", "Add fd=%d to set.\n", fd));
snmp_fds.emplace(fd, sdeventplus::source::IO(event, fd, EPOLLIN,
sdevent_snmp_read));
}
}
}
/** @brief Initialize snmp agent */
void snmpagent_init(const sdeventplus::Event& event)
{
// make us a agentx client
netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_ROLE, 1);
// initialize tcpip, if necessary
SOCK_STARTUP;
// initialize the agent library
init_agent(PACKAGE_NAME);
// We will be used to read <PACKAGE_NAME>.conf files.
init_snmp(PACKAGE_NAME);
// This is run before the event loop will sleep and wait for new events.
static sdeventplus::source::Post post(
event, [](sdeventplus::source::EventBase& source) {
sdevent_snmp_update(source.get_event());
});
sdevent_snmp_update(event);
}
/** @brief Deinitialize snmp agen */
void snmpagent_destroy()
{
snmp_shutdown(PACKAGE_NAME);
SOCK_CLEANUP;
}
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