git.ozlabs.org Git - ccan/blob - ccan/tdb/test/external-agent.c

   1 #include "external-agent.h"
   2 #include "lock-tracking.h"
   3 #include "logging.h"
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6 #include <unistd.h>
   7 #include <err.h>
   8 #include <fcntl.h>
   9 #include <stdlib.h>
  10 #include <limits.h>
  11 #include <string.h>
  12 #include <errno.h>
  13 #include <ccan/tdb/tdb.h>
  14 #include <ccan/tdb/tdb_private.h>
  15 #include <ccan/tap/tap.h>
  16 #include <stdio.h>
  17 #include <stdarg.h>
  18
  19 static struct tdb_context *tdb;
  20
  21 static enum agent_return do_operation(enum operation op, const char *name)
  22 {
  23         TDB_DATA k;
  24         enum agent_return ret;
  25         TDB_DATA data;
  26
  27         if (op != OPEN && op != OPEN_WITH_CLEAR_IF_FIRST && !tdb) {
  28                 diag("external: No tdb open!");
  29                 return OTHER_FAILURE;
  30         }
  31
  32         k.dptr = (void *)name;
  33         k.dsize = strlen(name);
  34
  35         locking_would_block = 0;
  36         switch (op) {
  37         case OPEN:
  38                 if (tdb) {
  39                         diag("Already have tdb %s open", tdb_name(tdb));
  40                         return OTHER_FAILURE;
  41                 }
  42                 tdb = tdb_open_ex(name, 0, TDB_DEFAULT, O_RDWR, 0,
  43                                   &taplogctx, NULL);
  44                 if (!tdb) {
  45                         if (!locking_would_block)
  46                                 diag("Opening tdb gave %s", strerror(errno));
  47                         ret = OTHER_FAILURE;
  48                 } else
  49                         ret = SUCCESS;
  50                 break;
  51         case OPEN_WITH_CLEAR_IF_FIRST:
  52                 if (tdb)
  53                         return OTHER_FAILURE;
  54                 tdb = tdb_open_ex(name, 0, TDB_CLEAR_IF_FIRST, O_RDWR, 0,
  55                                   &taplogctx, NULL);
  56                 ret = tdb ? SUCCESS : OTHER_FAILURE;
  57                 break;
  58         case TRANSACTION_START:
  59                 ret = tdb_transaction_start(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
  60                 break;
  61         case FETCH:
  62                 data = tdb_fetch(tdb, k);
  63                 if (data.dptr == NULL) {
  64                         if (tdb_error(tdb) == TDB_ERR_NOEXIST)
  65                                 ret = FAILED;
  66                         else
  67                                 ret = OTHER_FAILURE;
  68                 } else if (data.dsize != k.dsize
  69                            || memcmp(data.dptr, k.dptr, k.dsize) != 0) {
  70                         ret = OTHER_FAILURE;
  71                 } else {
  72                         ret = SUCCESS;
  73                 }
  74                 free(data.dptr);
  75                 break;
  76         case STORE:
  77                 ret = tdb_store(tdb, k, k, 0) == 0 ? SUCCESS : OTHER_FAILURE;
  78                 break;
  79         case TRANSACTION_COMMIT:
  80                 ret = tdb_transaction_commit(tdb)==0 ? SUCCESS : OTHER_FAILURE;
  81                 break;
  82         case CHECK:
  83                 ret = tdb_check(tdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
  84                 break;
  85         case NEEDS_RECOVERY:
  86                 ret = tdb_needs_recovery(tdb) ? SUCCESS : FAILED;
  87                 break;
  88         case CLOSE:
  89                 ret = tdb_close(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
  90                 tdb = NULL;
  91                 break;
  92         default:
  93                 ret = OTHER_FAILURE;
  94         }
  95
  96         if (locking_would_block)
  97                 ret = WOULD_HAVE_BLOCKED;
  98
  99         return ret;
 100 }
 101
 102 struct agent {
 103         int cmdfd, responsefd;
 104 };
 105
 106 /* Do this before doing any tdb stuff.  Return handle, or NULL. */
 107 struct agent *prepare_external_agent(void)
 108 {
 109         int pid, ret;
 110         int command[2], response[2];
 111         char name[1+PATH_MAX];
 112
 113         if (pipe(command) != 0 || pipe(response) != 0)
 114                 return NULL;
 115
 116         pid = fork();
 117         if (pid < 0)
 118                 return NULL;
 119
 120         if (pid != 0) {
 121                 struct agent *agent = malloc(sizeof(*agent));
 122
 123                 close(command[0]);
 124                 close(response[1]);
 125                 agent->cmdfd = command[1];
 126                 agent->responsefd = response[0];
 127                 return agent;
 128         }
 129
 130         close(command[1]);
 131         close(response[0]);
 132
 133         /* We want to fail, not block. */
 134         nonblocking_locks = true;
 135         log_prefix = "external: ";
 136         while ((ret = read(command[0], name, sizeof(name))) > 0) {
 137                 enum agent_return result;
 138
 139                 result = do_operation(name[0], name+1);
 140                 if (write(response[1], &result, sizeof(result))
 141                     != sizeof(result))
 142                         err(1, "Writing response");
 143         }
 144         exit(0);
 145 }
 146
 147 /* Ask the external agent to try to do an operation. */
 148 enum agent_return external_agent_operation(struct agent *agent,
 149                                            enum operation op,
 150                                            const char *name)
 151 {
 152         enum agent_return res;
 153         unsigned int len;
 154         char *string;
 155
 156         if (!name)
 157                 name = "";
 158         len = 1 + strlen(name) + 1;
 159         string = malloc(len);
 160
 161         string[0] = op;
 162         strcpy(string+1, name);
 163
 164         if (write(agent->cmdfd, string, len) != len
 165             || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
 166                 res = AGENT_DIED;
 167
 168         free(string);
 169         return res;
 170 }
 171
 172 const char *agent_return_name(enum agent_return ret)
 173 {
 174         return ret == SUCCESS ? "SUCCESS"
 175                 : ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
 176                 : ret == AGENT_DIED ? "AGENT_DIED"
 177                 : ret == FAILED ? "FAILED"
 178                 : ret == OTHER_FAILURE ? "OTHER_FAILURE"
 179                 : "**INVALID**";
 180 }
 181
 182 const char *operation_name(enum operation op)
 183 {
 184         switch (op) {
 185         case OPEN: return "OPEN";
 186         case OPEN_WITH_CLEAR_IF_FIRST: return "OPEN_WITH_CLEAR_IF_FIRST";
 187         case TRANSACTION_START: return "TRANSACTION_START";
 188         case FETCH: return "FETCH";
 189         case STORE: return "STORE";
 190         case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
 191         case CHECK: return "CHECK";
 192         case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
 193         case CLOSE: return "CLOSE";
 194         }
 195         return "**INVALID**";
 196 }