Routing.cpp

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// -*- C++ -*-
#include <stdio.h>
#include <netdb.h>      // gethostbyname
#include <arpa/inet.h>  // inet_ntoa
#include <netinet/in.h> // sockaddr_in
#include <sys/wait.h>

#include <coil/Routing.h>
#include <coil/stringutil.h>
#include <coil/config_coil.h>

namespace coil
{
  bool dest_to_endpoint(std::string dest_addr, std::string& endpoint)
  {
    std::string dest_if;
    if (!find_dest_ifname(dest_addr, dest_if))
      {
        return false;
      }
    return ifname_to_ipaddr(dest_if, endpoint);
  }

  bool find_dest_ifname(std::string dest_addr, std::string& dest_if)
  {
    // This logic should be replaced by direct retrieving using
    // routing interface like AFROUTE or sysctl.
    struct ::hostent *hostent;
    struct ::sockaddr_in addr;
    
    hostent = gethostbyname(dest_addr.c_str());
    addr.sin_addr.s_addr = **(unsigned int **)(hostent->h_addr_list);
    dest_addr = inet_ntoa(addr.sin_addr);
    
#if defined(COIL_OS_FREEBSD) || defined(COIL_OS_DARWIN) || defined(COIL_OS_CYGWIN)
    std::string cmd("PATH=/bin:/sbin:/usr/bin:/usr/sbin "
                    "route get ");
    const char* match_str = "interface";
    const char* delimiter = ":";
    size_t ifname_pos(1);
    cmd += dest_addr;
    cmd += " 2> /dev/null";
#endif // COIL_OS_IS_FREEBSD || COIL_OS_DARWIN || COIL_OS_CYGWIN
#if defined(COIL_OS_LINUX)
    std::string cmd("PATH=/bin:/sbin:/usr/bin:/usr/sbin "
                    "ip route get ");
    const char* match_str = "dev ";
    const char* delimiter = " ";
    size_t ifname_pos(2);
    cmd += dest_addr;
    cmd += " 2> /dev/null";
#endif // COIL_OS_IS_LINUX    
    
    FILE* fp;
    if ((fp = popen(cmd.c_str(), "r")) == NULL)
      {
        return false;
      }

    do
      {
        char str[512];
        fgets(str, 512, fp);
        std::string line(str);
        
        if (std::string::npos == line.find(match_str)) { continue; }
        
        line.erase(line.end() - 1);
        coil::vstring vs(coil::split(line, delimiter));

#if defined(COIL_OS_FREEBSD) || defined(COIL_OS_DARWIN) || defined(COIL_OS_CYGWIN)
        if (vs.size() > ifname_pos)
          {
            dest_if = vs[ifname_pos];
            pclose(fp);
            wait(NULL);
            return true;
          }
#endif // COIL_OS_FREEBSD || COIL_OS_DARWIN || COIL_OS_CYGWIN
#if defined(COIL_OS_LINUX)
        for (int i(0); i < vs.size(); ++i)
          {
            if (vs[i] == "dev")
              {
                dest_if = vs[i + 1];
                return true;
              }
          }
#endif // COIL_OS_LINUX
      } while (!feof(fp));
    pclose(fp);
    wait(NULL);
    return false;
  }

  bool ifname_to_ipaddr(std::string ifname, std::string& ipaddr)
  {
    std::string cmd("ifconfig ");
    cmd += ifname;
    cmd += " 2> /dev/null";
    
    FILE* fp;
    if ((fp = popen(cmd.c_str(), "r")) == NULL)
      {
        return false;
      }
    
    do
      {
        char str[512];
        fgets(str, 512, fp);
        std::string line(str);
        
        if (std::string::npos == line.find("inet ")) { continue; }
        
        line.erase(line.end() - 1);
        coil::eraseHeadBlank(line);
        coil::vstring vs(coil::split(line, " "));
        if (vs.size() == 6)
          {
            ipaddr = vs[1];
            pclose(fp);
            wait(NULL);
            return true;
          }
      } while (!feof(fp));
    pclose(fp);
    wait(NULL);
    return false;
  }
  
}; // namespace coil