mark/mark.c

   1 /******************************************************************************
   2  * mark.c
   3  *****************************************************************************/
   4
   5 #define _GNU_SOURCE
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <sys/socket.h>
  10 #include <unistd.h>
  11 #include <arpa/inet.h>
  12 #include <dlfcn.h>
  13
  14 #include "mark.h"
  15
  16
  17 #define SO_MARK 36
  18
  19
  20 real_socket_t real_socket;
  21 int default_mark = 1;
  22
  23
  24 void lib_init(void)
  25 {
  26     char *temp;
  27
  28     *(void **) (&real_socket) = dlsym(RTLD_NEXT, "socket");
  29     if(!real_socket)
  30     {
  31         fprintf(stderr, "Cannot load symbol 'socket' %s\n", dlerror());
  32         _exit(1);
  33     }
  34
  35     temp = getenv("MARK");
  36     if(temp) default_mark = (int) strtoul(temp, NULL, 10);
  37 }
  38
  39
  40 int socket(int domain, int type, int protocol)
  41 {
  42     int err2, mark = default_mark;
  43     int err = real_socket(domain, type, protocol);
  44
  45     if(domain != PF_INET || err == -1) return err;
  46
  47     err2 = setsockopt(err, SOL_SOCKET, SO_MARK, (void *) &mark, sizeof (int));
  48     if(err2 == -1) { perror("setsockopt(... SO_MARK ...)"); exit(1); }
  49
  50     return err;
  51 }
  52
  53