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 oid SNMPAgent::snmpTrapOID[] = { 1, 3, 6, 1, 6, 3, 1, 1, 4, 1, 0 };
  29 const size_t SNMPAgent::snmpTrapOIDLen = OID_LENGTH(SNMPAgent::snmpTrapOID);
  30
  31 int SNMPAgent::setCounter64Value(netsnmp_request_info* request,
  32                                  uint64_t value)
  33 {
  34   struct counter64 val64;
  35   val64.high = value >> 32;
  36   val64.low = value & 0xffffffff;
  37   snmp_set_var_typed_value(request->requestvb,
  38                            ASN_COUNTER64,
  39                            &val64,
  40                            sizeof(val64));
  41   return SNMP_ERR_NOERROR;
  42 }
  43
  44 bool SNMPAgent::sendTrap(int fd,
  45                          netsnmp_variable_list* varList)
  46 {
  47   ssize_t written = write(fd, &varList, sizeof(varList));
  48
  49   if (written != sizeof(varList)) {
  50     snmp_free_varbind(varList);
  51     return false;
  52   }
  53   return true;
  54 }
  55
  56 void SNMPAgent::handleTrapsEvent()
  57 {
  58   netsnmp_variable_list* varList = nullptr;
  59   ssize_t got = 0;
  60
  61   do {
  62     got = read(d_trapPipe[0], &varList, sizeof(varList));
  63
  64     if (got == sizeof(varList)) {
  65       send_v2trap(varList);
  66       snmp_free_varbind(varList);
  67     }
  68   }
  69   while (got > 0);
  70 }
  71
  72 void SNMPAgent::handleSNMPQueryEvent(int fd)
  73 {
  74   netsnmp_large_fd_set fdset;
  75   netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
  76   NETSNMP_LARGE_FD_ZERO(&fdset);
  77   NETSNMP_LARGE_FD_SET(fd, &fdset);
  78   snmp_read2(&fdset);
  79 }
  80
  81 void SNMPAgent::handleTrapsCB(int fd, FDMultiplexer::funcparam_t& var)
  82 {
  83   SNMPAgent** agent = boost::any_cast<SNMPAgent*>(&var);
  84   if (!agent || !*agent)
  85     throw std::runtime_error("Invalid value received in SNMP trap callback");
  86
  87   (*agent)->handleTrapsEvent();
  88 }
  89
  90 void SNMPAgent::handleSNMPQueryCB(int fd, FDMultiplexer::funcparam_t& var)
  91 {
  92   SNMPAgent** agent = boost::any_cast<SNMPAgent*>(&var);
  93   if (!agent || !*agent)
  94     throw std::runtime_error("Invalid value received in SNMP trap callback");
  95
  96   (*agent)->handleSNMPQueryEvent(fd);
  97 }
  98
  99 #endif /* HAVE_NET_SNMP */
 100
 101 void SNMPAgent::worker()
 102 {
 103 #ifdef HAVE_NET_SNMP
 104   FDMultiplexer* mplexer = FDMultiplexer::getMultiplexerSilent();
 105   if (mplexer == nullptr) {
 106     throw std::runtime_error("No FD multiplexer found for the SNMP agent!");
 107   }
 108
 109 #ifdef RECURSOR
 110   string threadName = "pdns-r/SNMP";
 111 #else
 112   string threadName = "dnsdist/SNMP";
 113 #endif
 114   setThreadName(threadName);
 115
 116   int maxfd = 0;
 117   int block = 1;
 118   netsnmp_large_fd_set fdset;
 119   struct timeval timeout = { 0, 0 };
 120   struct timeval now;
 121
 122   /* we want to be notified if a trap is waiting
 123    to be sent */
 124   mplexer->addReadFD(d_trapPipe[0], &handleTrapsCB, this);
 125
 126   while(true) {
 127     netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
 128     NETSNMP_LARGE_FD_ZERO(&fdset);
 129
 130     block = 1;
 131     timeout = { 0, 0 };
 132     snmp_select_info2(&maxfd, &fdset, &timeout, &block);
 133
 134     for (int fd = 0; fd < maxfd; fd++) {
 135       if (NETSNMP_LARGE_FD_ISSET(fd, &fdset)) {
 136         mplexer->addReadFD(fd, &handleSNMPQueryCB, this);
 137       }
 138     }
 139
 140     /* run updates now */
 141     int res = mplexer->run(&now, (timeout.tv_sec * 1000) + (timeout.tv_usec / 1000));
 142
 143     /* we handle timeouts here, the rest has already been handled by callbacks */
 144     if (res == 0) {
 145       snmp_timeout();
 146       run_alarms();
 147     }
 148
 149     for (int fd = 0; fd < maxfd; fd++) {
 150       if (NETSNMP_LARGE_FD_ISSET(fd, &fdset)) {
 151         try {
 152           mplexer->removeReadFD(fd);
 153         }
 154         catch(const FDMultiplexerException& e) {
 155           /* we might get an exception when removing a closed file descriptor,
 156              just ignore it */
 157         }
 158       }
 159     }
 160   }
 161 #endif /* HAVE_NET_SNMP */
 162 }
 163
 164 SNMPAgent::SNMPAgent(const std::string& name, const std::string& masterSocket)
 165 {
 166 #ifdef HAVE_NET_SNMP
 167   netsnmp_enable_subagent();
 168   snmp_disable_log();
 169   if (!masterSocket.empty()) {
 170     netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID,
 171                           NETSNMP_DS_AGENT_X_SOCKET,
 172                           masterSocket.c_str());
 173   }
 174   /* no need to load any MIBS,
 175      and it causes import errors if some modules are not present */
 176   setenv("MIBS", "", 1);
 177
 178   init_agent(name.c_str());
 179
 180   /* we use select() so don't use SIGALARM to handle alarms.
 181      Note that we need to handle alarms for automatic reconnection
 182      to the master to work.
 183   */
 184   netsnmp_ds_set_boolean(NETSNMP_DS_LIBRARY_ID,
 185                          NETSNMP_DS_LIB_ALARM_DONT_USE_SIG,
 186                          1);
 187
 188   init_snmp(name.c_str());
 189
 190   if (pipe(d_trapPipe) < 0)
 191     unixDie("Creating pipe");
 192
 193   if (!setNonBlocking(d_trapPipe[0])) {
 194     close(d_trapPipe[0]);
 195     close(d_trapPipe[1]);
 196     unixDie("Setting pipe non-blocking");
 197   }
 198
 199   if (!setNonBlocking(d_trapPipe[1])) {
 200     close(d_trapPipe[0]);
 201     close(d_trapPipe[1]);
 202     unixDie("Setting pipe non-blocking");
 203   }
 204
 205 #endif /* HAVE_NET_SNMP */
 206 }