pdns/snmp-agent.cc

   1 #include "snmp-agent.hh"
   2 #include "misc.hh"
   3 #include "threadname.hh"
   4 #ifdef RECURSOR
   5 #include "logger.hh"
   6 #else
   7 #include "dolog.hh"
   8 #endif
   9
  10 #ifdef HAVE_NET_SNMP
  11
  12 #ifndef HAVE_SNMP_SELECT_INFO2
  13 /* that's terrible, because it means we are going to have trouble with large
  14    FD numbers at some point.. */
  15 # define netsnmp_large_fd_set fd_set
  16 # define snmp_read2 snmp_read
  17 # define snmp_select_info2 snmp_select_info
  18 # define netsnmp_large_fd_set_init(...)
  19 # define netsnmp_large_fd_set_cleanup(...)
  20 # define NETSNMP_LARGE_FD_SET FD_SET
  21 # define NETSNMP_LARGE_FD_CLR FD_CLR
  22 # define NETSNMP_LARGE_FD_ZERO FD_ZERO
  23 # define NETSNMP_LARGE_FD_ISSET FD_ISSET
  24 #else
  25 # include <net-snmp/library/large_fd_set.h>
  26 #endif
  27
  28 const std::array<oid, 11> SNMPAgent::snmpTrapOID = { 1, 3, 6, 1, 6, 3, 1, 1, 4, 1, 0 };
  29
  30 int SNMPAgent::setCounter64Value(netsnmp_request_info* request,
  31                                  uint64_t value)
  32 {
  33   struct counter64 val64;
  34   val64.high = value >> 32;
  35   val64.low = value & 0xffffffff;
  36   snmp_set_var_typed_value(request->requestvb,
  37                            ASN_COUNTER64,
  38                            &val64,
  39                            sizeof(val64));
  40   return SNMP_ERR_NOERROR;
  41 }
  42
  43 bool SNMPAgent::sendTrap(pdns::channel::Sender<netsnmp_variable_list, void(*)(netsnmp_variable_list*)>& sender,
  44                          netsnmp_variable_list* varList)
  45 {
  46   try  {
  47     auto obj = std::unique_ptr<netsnmp_variable_list, void(*)(netsnmp_variable_list*)>(varList, snmp_free_varbind);
  48     return sender.send(std::move(obj));
  49   }
  50   catch (...) {
  51     return false;
  52   }
  53 }
  54
  55 void SNMPAgent::handleTrapsEvent()
  56 {
  57   try {
  58     while (true) {
  59       auto obj = d_receiver.receive(snmp_free_varbind);
  60       if (!obj) {
  61         break;
  62       }
  63       send_v2trap(obj->get());
  64     }
  65   }
  66   catch (const std::exception& e) {
  67   }
  68 }
  69
  70 void SNMPAgent::handleSNMPQueryEvent(int fd)
  71 {
  72   netsnmp_large_fd_set fdset;
  73   netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
  74   NETSNMP_LARGE_FD_ZERO(&fdset);
  75   NETSNMP_LARGE_FD_SET(fd, &fdset);
  76   snmp_read2(&fdset);
  77 }
  78
  79 void SNMPAgent::handleTrapsCB(int /* fd */, FDMultiplexer::funcparam_t& var)
  80 {
  81   SNMPAgent** agent = boost::any_cast<SNMPAgent*>(&var);
  82   if (!agent || !*agent)
  83     throw std::runtime_error("Invalid value received in SNMP trap callback");
  84
  85   (*agent)->handleTrapsEvent();
  86 }
  87
  88 void SNMPAgent::handleSNMPQueryCB(int fd, FDMultiplexer::funcparam_t& var)
  89 {
  90   SNMPAgent** agent = boost::any_cast<SNMPAgent*>(&var);
  91   if (!agent || !*agent)
  92     throw std::runtime_error("Invalid value received in SNMP trap callback");
  93
  94   (*agent)->handleSNMPQueryEvent(fd);
  95 }
  96
  97 #endif /* HAVE_NET_SNMP */
  98
  99 void SNMPAgent::worker()
 100 {
 101 #ifdef HAVE_NET_SNMP
 102   FDMultiplexer* mplexer = FDMultiplexer::getMultiplexerSilent();
 103   if (mplexer == nullptr) {
 104     throw std::runtime_error("No FD multiplexer found for the SNMP agent!");
 105   }
 106
 107 #ifdef RECURSOR
 108   string threadName = "rec/snmp";
 109 #else
 110   string threadName = "dnsdist/SNMP";
 111 #endif
 112   setThreadName(threadName);
 113
 114   int maxfd = 0;
 115   int block = 1;
 116   netsnmp_large_fd_set fdset;
 117   struct timeval timeout = { 0, 0 };
 118   struct timeval now;
 119
 120   /* we want to be notified if a trap is waiting
 121    to be sent */
 122   mplexer->addReadFD(d_receiver.getDescriptor(), &handleTrapsCB, this);
 123
 124   while(true) {
 125     netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
 126     NETSNMP_LARGE_FD_ZERO(&fdset);
 127
 128     block = 1;
 129     timeout = { 0, 0 };
 130     snmp_select_info2(&maxfd, &fdset, &timeout, &block);
 131
 132     for (int fd = 0; fd < maxfd; fd++) {
 133       if (NETSNMP_LARGE_FD_ISSET(fd, &fdset)) {
 134         mplexer->addReadFD(fd, &handleSNMPQueryCB, this);
 135       }
 136     }
 137
 138     /* run updates now */
 139     int res = mplexer->run(&now, (timeout.tv_sec * 1000) + (timeout.tv_usec / 1000));
 140
 141     /* we handle timeouts here, the rest has already been handled by callbacks */
 142     if (res == 0) {
 143       snmp_timeout();
 144       run_alarms();
 145     }
 146
 147     for (int fd = 0; fd < maxfd; fd++) {
 148       if (NETSNMP_LARGE_FD_ISSET(fd, &fdset)) {
 149         try {
 150           mplexer->removeReadFD(fd);
 151         }
 152         catch(const FDMultiplexerException& e) {
 153           /* we might get an exception when removing a closed file descriptor,
 154              just ignore it */
 155         }
 156       }
 157     }
 158   }
 159 #endif /* HAVE_NET_SNMP */
 160 }
 161
 162 SNMPAgent::SNMPAgent([[maybe_unused]] const std::string& name, [[maybe_unused]] const std::string& daemonSocket)
 163 {
 164 #ifdef HAVE_NET_SNMP
 165   netsnmp_enable_subagent();
 166   snmp_disable_log();
 167   if (!daemonSocket.empty()) {
 168     netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID,
 169                           NETSNMP_DS_AGENT_X_SOCKET,
 170                           daemonSocket.c_str());
 171   }
 172   /* no need to load any MIBS,
 173      and it causes import errors if some modules are not present */
 174   setenv("MIBS", "", 1);
 175
 176   init_agent(name.c_str());
 177
 178   /* we use select() so don't use SIGALARM to handle alarms.
 179      Note that we need to handle alarms for automatic reconnection
 180      to the daemon to work.
 181   */
 182   netsnmp_ds_set_boolean(NETSNMP_DS_LIBRARY_ID,
 183                          NETSNMP_DS_LIB_ALARM_DONT_USE_SIG,
 184                          1);
 185
 186   init_snmp(name.c_str());
 187
 188   auto [sender, receiver] = pdns::channel::createObjectQueue<netsnmp_variable_list, void(*)(netsnmp_variable_list*)>();
 189   d_sender = std::move(sender);
 190   d_receiver = std::move(receiver);
 191 #endif /* HAVE_NET_SNMP */
 192 }