src/tcpmaxrt.c

   1 // gcc tcpmaxrt.c -fPIC -shared -ldl -o tcpmaxrt.so
   2
   3 #include <stdlib.h>
   4 #include <stdio.h>
   5 #include <dlfcn.h>
   6 #include <sys/types.h>
   7 #include <sys/socket.h>
   8 #include <linux/tcp.h>
   9
  10
  11 int setsockopt(int sockfd, int level, int optname, const void *optval, socklen_t optlen)
  12 {
  13
  14         int (*real_setsockopt)(int sockfd, int level, int optname, const void *optval, socklen_t optlen) = NULL;
  15         int real_setsockopt_return;
  16         int i1 = 1;
  17
  18         if (real_setsockopt == NULL) {
  19                 void *handle = dlopen("/lib/libc.so.6", RTLD_LAZY);
  20                 if (handle == NULL) {
  21                         fprintf(stderr, "dlopen: %s\n", dlerror());
  22                         exit(1);
  23                 }
  24                 real_setsockopt = dlsym(handle, "setsockopt");
  25                 if (real_setsockopt == NULL) {
  26                         fprintf(stderr, "dlsym: %s\n", dlerror());
  27                         exit(1);
  28                 }
  29         }
  30
  31         fprintf(stderr, "setsockopt: optname=%d optval=%d\n", optname, optval);
  32         fflush(stderr);
  33
  34         real_setsockopt_return = real_setsockopt(sockfd, level, optname, optval, optlen);
  35         fprintf(stderr, "setsockopt %d\n",
  36                 real_setsockopt(sockfd, level, TCP_, (const void *)&i1, optlen)
  37         );
  38         fflush(stderr);
  39
  40         return real_setsockopt_return;
  41 }