A Discrete-Event Network Simulator
API
netmap-device-creator.cc
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1 /*
2  * Copyright (c) University of Washington
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation;
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11  * GNU General Public License for more details.
12  *
13  * You should have received a copy of the GNU General Public License
14  * along with this program; if not, write to the Free Software
15  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
16  */
17 
18 #include "creator-utils.h"
19 
20 #include <arpa/inet.h>
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <iomanip>
24 #include <iostream>
25 #include <net/ethernet.h>
26 #include <net/if.h>
27 #include <netinet/in.h>
28 #include <sstream>
29 #include <stdlib.h>
30 #include <string>
31 #include <sys/ioctl.h>
32 #include <sys/socket.h>
33 #include <sys/un.h>
34 #include <unistd.h>
35 
36 #define EMU_MAGIC 65867
37 
38 using namespace ns3;
39 
40 int
41 main(int argc, char* argv[])
42 {
43  int c;
44  char* path = nullptr;
45 
46  opterr = 0;
47 
48  while ((c = getopt(argc, argv, "vp:")) != -1)
49  {
50  switch (c)
51  {
52  case 'v':
53  gVerbose = true;
54  break;
55  case 'p':
56  path = optarg;
57  break;
58  }
59  }
60 
61  //
62  // This program is spawned by an emu net device running in a simulation. It
63  // wants to create a raw socket as described below. We are going to do the
64  // work here since we're running suid root. Once we create the raw socket,
65  // we have to send it back to the emu net device. We do that over a Unix
66  // (local interprocess) socket. The emu net device created a socket to
67  // listen for our response on, and it is expected to have encoded the address
68  // information as a string and to have passed that string as an argument to
69  // us. We see it here as the "path" string. We can't do anything useful
70  // unless we have that string.
71  //
72  ABORT_IF(!path, "path is a required argument", 0);
73  LOG("Provided path is \"" << path << "\"");
74  //
75  // The whole reason for all of the hoops we went through to call out to this
76  // program will pay off here. We created this program to run as suid root
77  // in order to keep the main simulation program from having to be run with
78  // root privileges. We need root privileges to be able to open a raw socket
79  // though. So all of these hoops are to allow us to execute the following
80  // single line of code:
81  //
82  LOG("Creating netmap fd");
83  int sock = open("/dev/netmap", O_RDWR);
84  ABORT_IF(sock == -1, "CreateSocket(): Unable to open netmap fd", 1);
85 
86  //
87  // Send the socket back to the emu net device so it can go about its business
88  //
89  SendSocket(path, sock, EMU_MAGIC);
90 
91  return 0;
92 }
#define LOG(x)
Log to std::cout.
#define ABORT_IF(cond, msg, printErrno)
Definition: creator-utils.h:51
void SendSocket(const char *path, int fd, const int magic_number)
Send the file descriptor back to the code that invoked the creation.
Every class exported by the ns3 library is enclosed in the ns3 namespace.
bool gVerbose
Flag to enable / disable verbose log mode.
#define EMU_MAGIC