modules/remotebackend/pipeconnector.cc

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #ifdef HAVE_CONFIG_H
  23 #include "config.h"
  24 #endif
  25 #include "remotebackend.hh"
  26
  27 PipeConnector::PipeConnector(std::map<std::string,std::string> optionsMap) {
  28   if (optionsMap.count("command") == 0) {
  29     L<<Logger::Error<<"Cannot find 'command' option in connection string"<<endl;
  30     throw PDNSException();
  31   }
  32   this->command = optionsMap.find("command")->second;
  33   this->options = optionsMap;
  34   d_timeout=2000;
  35
  36   if (optionsMap.find("timeout") != optionsMap.end()) {
  37      d_timeout = std::stoi(optionsMap.find("timeout")->second);
  38   }
  39
  40   d_pid = -1;
  41   d_fp = NULL;
  42   d_fd1[0] = d_fd1[1] = -1;
  43   d_fd2[0] = d_fd2[1] = -1;
  44 }
  45
  46 PipeConnector::~PipeConnector(){
  47   int status;
  48   // just in case...
  49   if (d_pid == -1) return;
  50
  51   if(!waitpid(d_pid, &status, WNOHANG)) {
  52     kill(d_pid, 9);
  53     waitpid(d_pid, &status, 0);
  54   }
  55
  56   close(d_fd1[1]);
  57   if (d_fp != NULL) fclose(d_fp);
  58 }
  59
  60 void PipeConnector::launch() {
  61   // no relaunch
  62   if (d_pid > 0 && checkStatus()) return;
  63
  64   std::vector <std::string> v;
  65   split(v, command, is_any_of(" "));
  66
  67   std::vector<const char *>argv(v.size()+1);
  68   argv[v.size()]=0;
  69
  70   for (size_t n = 0; n < v.size(); n++)
  71     argv[n]=v[n].c_str();
  72
  73   signal(SIGPIPE, SIG_IGN);
  74
  75   if(access(argv[0],X_OK)) // check before fork so we can throw
  76     throw PDNSException("Command '"+string(argv[0])+"' cannot be executed: "+stringerror());
  77
  78   if(pipe(d_fd1)<0 || pipe(d_fd2)<0)
  79     throw PDNSException("Unable to open pipe for coprocess: "+string(strerror(errno)));
  80
  81   if((d_pid=fork())<0)
  82     throw PDNSException("Unable to fork for coprocess: "+stringerror());
  83   else if(d_pid>0) { // parent speaking
  84     close(d_fd1[0]);
  85     setCloseOnExec(d_fd1[1]);
  86     close(d_fd2[1]);
  87     setCloseOnExec(d_fd2[0]);
  88     if(!(d_fp=fdopen(d_fd2[0],"r")))
  89       throw PDNSException("Unable to associate a file pointer with pipe: "+stringerror());
  90     if (d_timeout)
  91       setbuf(d_fp,0); // no buffering please, confuses select
  92   }
  93   else if(!d_pid) { // child
  94     signal(SIGCHLD, SIG_DFL); // silence a warning from perl
  95     close(d_fd1[1]);
  96     close(d_fd2[0]);
  97
  98     if(d_fd1[0]!= 0) {
  99       dup2(d_fd1[0], 0);
 100       close(d_fd1[0]);
 101     }
 102
 103     if(d_fd2[1]!= 1) {
 104       dup2(d_fd2[1], 1);
 105       close(d_fd2[1]);
 106     }
 107
 108     // stdin & stdout are now connected, fire up our coprocess!
 109
 110     if(execv(argv[0], const_cast<char * const *>(argv.data()))<0) // now what
 111       exit(123);
 112
 113     /* not a lot we can do here. We shouldn't return because that will leave a forked process around.
 114        no way to log this either - only thing we can do is make sure that our parent catches this soonest! */
 115   }
 116
 117   Json::array parameters;
 118   Json msg = Json(Json::object{
 119     { "method", "initialize" },
 120     { "parameters", Json(options) },
 121   });
 122
 123   this->send(msg);
 124   msg = nullptr;
 125   if (this->recv(msg)==false) {
 126     L<<Logger::Error<<"Failed to initialize coprocess"<<std::endl;
 127   }
 128 }
 129
 130 int PipeConnector::send_message(const Json& input)
 131 {
 132    auto line = input.dump();
 133    launch();
 134
 135    line.append(1,'\n');
 136
 137    unsigned int sent=0;
 138    int bytes;
 139
 140    // writen routine - socket may not accept al data in one go
 141    while(sent<line.size()) {
 142      bytes=write(d_fd1[1],line.c_str()+sent,line.length()-sent);
 143      if(bytes<0)
 144        throw PDNSException("Writing to coprocess failed: "+std::string(strerror(errno)));
 145
 146      sent+=bytes;
 147    }
 148    return sent;
 149 }
 150
 151 int PipeConnector::recv_message(Json& output)
 152 {
 153    std::string receive;
 154    std::string err;
 155    std::string s_output;
 156    launch();
 157
 158    while(1) {
 159      receive.clear();
 160      if(d_timeout) {
 161        struct timeval tv;
 162        tv.tv_sec = d_timeout/1000;
 163        tv.tv_usec = (d_timeout % 1000) * 1000;
 164        fd_set rds;
 165        FD_ZERO(&rds);
 166        FD_SET(fileno(d_fp),&rds);
 167        int ret=select(fileno(d_fp)+1,&rds,0,0,&tv);
 168        if(ret<0)
 169          throw PDNSException("Error waiting on data from coprocess: "+stringerror());
 170        if(!ret)
 171          throw PDNSException("Timeout waiting for data from coprocess");
 172      }
 173
 174      if(!stringfgets(d_fp, receive))
 175        throw PDNSException("Child closed pipe");
 176
 177       s_output.append(receive);
 178       // see if it can be parsed
 179       output = Json::parse(s_output, err);
 180       if (output != nullptr) return s_output.size();
 181    }
 182    return 0;
 183 }
 184
 185 bool PipeConnector::checkStatus()
 186 {
 187   int status;
 188   int ret=waitpid(d_pid, &status, WNOHANG);
 189   if(ret<0)
 190     throw PDNSException("Unable to ascertain status of coprocess "+itoa(d_pid)+" from "+itoa(getpid())+": "+string(strerror(errno)));
 191   else if(ret) {
 192     if(WIFEXITED(status)) {
 193       int exitStatus=WEXITSTATUS(status);
 194       throw PDNSException("Coprocess exited with code "+itoa(exitStatus));
 195     }
 196     if(WIFSIGNALED(status)) {
 197       int sig=WTERMSIG(status);
 198       string reason="CoProcess died on receiving signal "+itoa(sig);
 199 #ifdef WCOREDUMP
 200       if(WCOREDUMP(status))
 201         reason+=". Dumped core";
 202 #endif
 203
 204       throw PDNSException(reason);
 205     }
 206   }
 207   return true;
 208 }