src/tomd/main.c

   1 /* Copyright (C) 2018 Thomas Balzer */
   2
   3 /* This file is part of tomd. */
   4
   5 /* tomd is free software: you can redistribute it and/or modify */
   6 /* it under the terms of the GNU General Public License as published by */
   7 /* the Free Software Foundation, either version 3 of the License, or */
   8 /* (at your option) any later version. */
   9
  10 /* tomd is distributed in the hope that it will be useful, */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the */
  13 /* GNU General Public License for more details. */
  14
  15 /* You should have received a copy of the GNU General Public License */
  16 /* along with tomd.  If not, see <http://www.gnu.org/licenses/>. */
  17
  18 #include <stddef.h>
  19 #include <stdio.h>
  20 #include <errno.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <string.h>
  24 #include <sys/un.h>
  25 #include <sys/stat.h>
  26 #include <sys/socket.h>
  27
  28 static void header(void)
  29 {
  30   printf("[tomd] Tom's Daemon, Copyright (C) 2018 Thomas Balzer\n");
  31   printf("[tomd] GPL v3 or later license.\n");
  32 }
  33
  34 static int sfd;
  35 static char socket_dirname[100];
  36 static char socket_filename[100];
  37
  38 static void gen_socket_filename(void)
  39 {
  40   uid_t this_user_id =
  41     getuid();
  42   sprintf(socket_dirname,
  43           "/run/user/%d/tomd",
  44           this_user_id);
  45   sprintf(socket_filename,
  46           "/run/user/%d/tomd/socket",
  47           this_user_id);
  48
  49   printf("[tomd] making dir '%s'\n", socket_dirname);
  50   /* lazy way */
  51   char buf[100];
  52   sprintf(buf, "mkdir -p %s", socket_dirname);
  53   system(buf);
  54   /* if(mkdir(socket_dirname, S_IRWXU) != 0){ */
  55   /*   perror("socket mkdir"); */
  56   /*   exit(EXIT_FAILURE); */
  57   /* } */
  58
  59   printf("[tomd] removing file '%s'\n", socket_filename);
  60   if(unlink(socket_filename) != 0){
  61     if(errno == ENOENT){
  62       printf("[tomd] socket file doesn't exist\n");
  63     }else{
  64       perror("[tomd] socket unlink");
  65       exit(EXIT_FAILURE);
  66     }
  67   }
  68 }
  69
  70 static void init(void)
  71 {
  72   gen_socket_filename();
  73
  74   /* listen on socket, respond to requests. */
  75   /* perform all registered 'tick' operations */
  76   sfd =
  77     socket(PF_LOCAL,         /* namespace - local unix socket */
  78            SOCK_STREAM,      /* style */
  79            0);               /* protocol */
  80
  81   if(sfd < 0){
  82     perror("[tomd] socket");
  83     exit(EXIT_FAILURE);
  84   }
  85
  86   struct sockaddr_un name;
  87   size_t size;
  88
  89   name.sun_family = AF_LOCAL;
  90   strncpy(name.sun_path,
  91           socket_filename,
  92           sizeof(name.sun_path));
  93
  94   size = SUN_LEN(&name);
  95   printf("[tomd] attempting to bind to '%s'\n",
  96          socket_filename);
  97   if(bind(sfd,
  98           (struct sockaddr *) &name,
  99           size) < 0){
 100     perror("[tomd] bind");
 101     exit(EXIT_FAILURE);
 102   }
 103
 104   printf("[tomd] initialized tomd socket connections\n");
 105 }
 106
 107 /* These defines are here to improve the local readability */
 108 #define CHDIR            0
 109 #define DONT_CHDIR       1
 110 #define CLOSE_PIPES      0
 111 #define DONT_CLOSE_PIPES 1
 112
 113 static void daemonize(void)
 114 {
 115   /* daemon is in unistd. */
 116   /* arg1 - 0 changes dir to / */
 117   /* arg2 - 0 closes all pipes (/dev/null) */
 118   /* WARNING > THIS BEHAVIOR IS SILENT AND EASY TO MISPLACE THE
 119      PROCESS  */
 120   daemon(DONT_CHDIR, DONT_CLOSE_PIPES);
 121 }
 122
 123 static void run(void)
 124 {
 125   /* loop: */
 126   /*  1 listen */
 127   /*  2 accept/select */
 128   /*  3 handle dgram */
 129   int listen_bool =
 130     listen(sfd,
 131            10); /* max connection limit is 10 for arbitrary reasons */
 132   if(listen_bool == -1){
 133     perror("[tomd] listen");
 134     exit(EXIT_FAILURE);
 135   }
 136
 137   for(;;){
 138     struct sockaddr addr;
 139     socklen_t size;
 140     int accept_sfd =
 141       accept(sfd,
 142              &addr,             /* requester info */
 143              &size);            /* len of requester info */
 144     if(accept_sfd < 0){
 145       perror("[tomd] accept socket");
 146       exit(EXIT_FAILURE);
 147     }
 148
 149     /* int getsockname(accept_sfd, */
 150     /*                 addr, */
 151     /*                 size); */
 152
 153     printf("[tomd] accepted socket connection from '%s'\n",
 154            ((struct sockaddr_un *) &addr)->sun_path);
 155
 156     char accept_buf[100] = {};
 157
 158     read(accept_sfd, accept_buf, 100);
 159     printf("[tomd] got message '%s'\n, accept_buf");
 160     close(accept_sfd);
 161   }
 162 }
 163
 164 static void cleanup(void)
 165 {
 166   if(sfd >= 0){
 167     close(sfd);
 168   }
 169 }
 170
 171 int main(int argc, char **argv)
 172 {
 173   header();
 174   init();
 175   daemonize();
 176   run();
 177   cleanup();
 178
 179   return EXIT_SUCCESS;
 180 }