1 files changed, 140 insertions, 0 deletions
diff --git a/agent/snmp.cpp b/agent/snmp.cpp
new file mode 100644
index 0000000..b6a2881
--- /dev/null
+++ b/agent/snmp.cpp
@@ -0,0 +1,140 @@
+/**
+ * @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;
+}