libcli/echo/echo.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Echo example async client library
   5
   6    Copyright (C) 2010 Kai Blin  <kai@samba.org>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "replace.h"
  23 #include "system/network.h"
  24 #include <tevent.h>
  25 #include "lib/tsocket/tsocket.h"
  26 #include "libcli/util/ntstatus.h"
  27 #include "libcli/echo/libecho.h"
  28 #include "lib/util/tevent_ntstatus.h"
  29 #include "libcli/util/error.h"
  30
  31 /*
  32  * Following the Samba convention for async functions, set up a state struct
  33  * for this set of calls. The state is always called function_name_state for
  34  * the set of async functions related to function_name_send().
  35  */
  36 struct echo_request_state {
  37         struct tevent_context *ev;
  38         ssize_t orig_len;
  39         struct tdgram_context *dgram;
  40         char *message;
  41 };
  42
  43 /* Declare callback functions used below. */
  44 static void echo_request_get_reply(struct tevent_req *subreq);
  45 static void echo_request_done(struct tevent_req *subreq);
  46
  47 struct tevent_req *echo_request_send(TALLOC_CTX *mem_ctx,
  48                                      struct tevent_context *ev,
  49                                      const char *server_addr_string,
  50                                      const char *message)
  51 {
  52         struct tevent_req *req, *subreq;
  53         struct echo_request_state *state;
  54         struct tsocket_address *local_addr, *server_addr;
  55         struct tdgram_context *dgram;
  56         int ret;
  57
  58         /*
  59          * Creating the initial tevent_req is the only place where returning
  60          * NULL is allowed. Everything after that should return a more
  61          * meaningful error using tevent_req_post().
  62          */
  63         req = tevent_req_create(mem_ctx, &state, struct echo_request_state);
  64         if (req == NULL) {
  65                 return NULL;
  66         }
  67
  68         /*
  69          * We need to dispatch new async functions in the callbacks, hold
  70          * on to the event context.
  71          */
  72         state->ev = ev;
  73
  74         /* libecho uses connected UDP sockets, take care of this here */
  75         ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0,
  76                                                 &local_addr);
  77         if (ret != 0) {
  78                 tevent_req_nterror(req, map_nt_error_from_unix(ret));
  79                 return tevent_req_post(req, ev);
  80         }
  81
  82         ret = tsocket_address_inet_from_strings(state, "ip", server_addr_string,
  83                                                 ECHO_PORT, &server_addr);
  84         if (ret != 0) {
  85                 tevent_req_nterror(req, map_nt_error_from_unix(ret));
  86                 return tevent_req_post(req, ev);
  87         }
  88
  89         ret = tdgram_inet_udp_socket(local_addr, server_addr, state, &dgram);
  90         if (ret != 0) {
  91                 tevent_req_nterror(req, map_nt_error_from_unix(ret));
  92                 return tevent_req_post(req, ev);
  93         }
  94
  95         state->dgram = dgram;
  96         state->orig_len = strlen(message) + 1;
  97
  98         /* Start of a subrequest for the actual data sending */
  99         subreq = tdgram_sendto_send(state, ev, dgram,
 100                                     (const uint8_t *) message,
 101                                     state->orig_len, NULL);
 102         if (tevent_req_nomem(subreq, req)) {
 103                 return tevent_req_post(req, ev);
 104         }
 105
 106         /*
 107          * And tell tevent what to call when the subreq is done. Note that the
 108          * original req structure is passed into the callback as callback data.
 109          * This is used to get to the state struct in callbacks.
 110          */
 111         tevent_req_set_callback(subreq, echo_request_get_reply, req);
 112         return req;
 113 }
 114
 115 /*
 116  * The following two callbacks both demonstrate the way of getting back the
 117  * state struct in a callback function.
 118  */
 119
 120 static void echo_request_get_reply(struct tevent_req *subreq)
 121 {
 122         /* Get the parent request struct from the callback data */
 123         struct tevent_req *req = tevent_req_callback_data(subreq,
 124                                                 struct tevent_req);
 125         /* And get the state struct from the parent request struct */
 126         struct echo_request_state *state = tevent_req_data(req,
 127                                                 struct echo_request_state);
 128         ssize_t len;
 129         int err = 0;
 130
 131         len = tdgram_sendto_recv(subreq, &err);
 132         TALLOC_FREE(subreq);
 133
 134         if (len == -1 && err != 0) {
 135                 tevent_req_nterror(req, map_nt_error_from_unix(err));
 136                 return;
 137         }
 138
 139         if (len != state->orig_len) {
 140                 tevent_req_nterror(req, NT_STATUS_UNEXPECTED_NETWORK_ERROR);
 141                 return;
 142         }
 143
 144         /* Send off the second subreq here, this time to receive the reply */
 145         subreq = tdgram_recvfrom_send(state, state->ev, state->dgram);
 146         if (tevent_req_nomem(subreq, req)) {
 147                 return;
 148         }
 149
 150         /* And set the new callback */
 151         tevent_req_set_callback(subreq, echo_request_done, req);
 152         return;
 153 }
 154
 155 static void echo_request_done(struct tevent_req *subreq)
 156 {
 157         struct tevent_req *req = tevent_req_callback_data(subreq,
 158                                                 struct tevent_req);
 159         struct echo_request_state *state = tevent_req_data(req,
 160                                                 struct echo_request_state);
 161
 162         ssize_t len;
 163         int err = 0;
 164
 165         len = tdgram_recvfrom_recv(subreq, &err, state,
 166                                    (uint8_t **)&state->message,
 167                                    NULL);
 168         TALLOC_FREE(subreq);
 169
 170         if (len == -1 && err != 0) {
 171                 tevent_req_nterror(req, map_nt_error_from_unix(err));
 172                 return;
 173         }
 174
 175         state->message[len] = '\0';
 176         /* Once the async function has completed, set tevent_req_done() */
 177         tevent_req_done(req);
 178 }
 179
 180 /*
 181  * In the recv function, we usually need to move the data from the state struct
 182  * to the memory area owned by the caller. Also, the function
 183  * tevent_req_received() is called to take care of freeing the memory still
 184  * associated with the request.
 185  */
 186
 187 NTSTATUS echo_request_recv(struct tevent_req *req,
 188                            TALLOC_CTX *mem_ctx,
 189                            char **message)
 190 {
 191         struct echo_request_state *state = tevent_req_data(req,
 192                         struct echo_request_state);
 193         NTSTATUS status;
 194
 195         if (tevent_req_is_nterror(req, &status)) {
 196                 tevent_req_received(req);
 197                 return status;
 198         }
 199
 200         *message = talloc_move(mem_ctx, &state->message);
 201         tevent_req_received(req);
 202
 203         return NT_STATUS_OK;
 204 }