git.ozlabs.org Git - ccan/blob - ccan/tdb2/test/external-agent.c

   1 #include "external-agent.h"
   2 #include "logging.h"
   3 #include "lock-tracking.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/tdb2/tdb1_private.h>
  14 #include <ccan/tap/tap.h>
  15 #include <stdio.h>
  16 #include <stdarg.h>
  17
  18 static struct tdb_context *tdb;
  19
  20 static enum TDB_ERROR clear_if_first(int fd, void *arg)
  21 {
  22 /* We hold a lock offset 4 always, so we can tell if anyone is holding it.
  23  * (This is compatible with tdb1's TDB_CLEAR_IF_FIRST flag).  */
  24         struct flock fl;
  25
  26         fl.l_type = F_WRLCK;
  27         fl.l_whence = SEEK_SET;
  28         fl.l_start = 4;
  29         fl.l_len = 1;
  30
  31         if (fcntl(fd, F_SETLK, &fl) == 0) {
  32                 /* We must be first ones to open it! */
  33                 diag("agent truncating file!");
  34                 if (ftruncate(fd, 0) != 0) {
  35                         return TDB_ERR_IO;
  36                 }
  37         }
  38         fl.l_type = F_RDLCK;
  39         if (fcntl(fd, F_SETLKW, &fl) != 0) {
  40                 return TDB_ERR_IO;
  41         }
  42         return TDB_SUCCESS;
  43 }
  44
  45 static enum agent_return do_operation(enum operation op, const char *name)
  46 {
  47         TDB_DATA k;
  48         enum agent_return ret;
  49         TDB_DATA data;
  50         enum TDB_ERROR ecode;
  51         union tdb_attribute cif;
  52
  53         if (op != OPEN && op != OPEN_WITH_HOOK && !tdb) {
  54                 diag("external: No tdb open!");
  55                 return OTHER_FAILURE;
  56         }
  57
  58         diag("external: %s", operation_name(op));
  59
  60         k = tdb_mkdata(name, strlen(name));
  61
  62         locking_would_block = 0;
  63         switch (op) {
  64         case OPEN:
  65                 if (tdb) {
  66                         diag("Already have tdb %s open", tdb->name);
  67                         return OTHER_FAILURE;
  68                 }
  69                 tdb = tdb_open(name, TDB_DEFAULT, O_RDWR, 0, &tap_log_attr);
  70                 if (!tdb) {
  71                         if (!locking_would_block)
  72                                 diag("Opening tdb gave %s", strerror(errno));
  73                         forget_locking();
  74                         ret = OTHER_FAILURE;
  75                 } else
  76                         ret = SUCCESS;
  77                 break;
  78         case OPEN_WITH_HOOK:
  79                 if (tdb) {
  80                         diag("Already have tdb %s open", tdb->name);
  81                         return OTHER_FAILURE;
  82                 }
  83                 cif.openhook.base.attr = TDB_ATTRIBUTE_OPENHOOK;
  84                 cif.openhook.base.next = &tap_log_attr;
  85                 cif.openhook.fn = clear_if_first;
  86                 tdb = tdb_open(name, TDB_DEFAULT, O_RDWR, 0, &cif);
  87                 if (!tdb) {
  88                         if (!locking_would_block)
  89                                 diag("Opening tdb gave %s", strerror(errno));
  90                         forget_locking();
  91                         ret = OTHER_FAILURE;
  92                 } else
  93                         ret = SUCCESS;
  94                 break;
  95         case FETCH:
  96                 ecode = tdb_fetch(tdb, k, &data);
  97                 if (ecode == TDB_ERR_NOEXIST) {
  98                         ret = FAILED;
  99                 } else if (ecode < 0) {
 100                         ret = OTHER_FAILURE;
 101                 } else if (!tdb_deq(data, k)) {
 102                         ret = OTHER_FAILURE;
 103                         free(data.dptr);
 104                 } else {
 105                         ret = SUCCESS;
 106                         free(data.dptr);
 107                 }
 108                 break;
 109         case STORE:
 110                 ret = tdb_store(tdb, k, k, 0) == 0 ? SUCCESS : OTHER_FAILURE;
 111                 break;
 112         case TRANSACTION_START:
 113                 ret = tdb_transaction_start(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
 114                 break;
 115         case TRANSACTION_COMMIT:
 116                 ret = tdb_transaction_commit(tdb)==0 ? SUCCESS : OTHER_FAILURE;
 117                 break;
 118         case NEEDS_RECOVERY:
 119                 if (tdb->flags & TDB_VERSION1)
 120                         ret = tdb1_needs_recovery(tdb) ? SUCCESS : FAILED;
 121                 else
 122                         ret = tdb_needs_recovery(tdb) ? SUCCESS : FAILED;
 123                 break;
 124         case CHECK:
 125                 ret = tdb_check(tdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
 126                 break;
 127         case CLOSE:
 128                 ret = tdb_close(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
 129                 tdb = NULL;
 130                 break;
 131         case SEND_SIGNAL:
 132                 /* We do this async */
 133                 ret = SUCCESS;
 134                 break;
 135         default:
 136                 ret = OTHER_FAILURE;
 137         }
 138
 139         if (locking_would_block)
 140                 ret = WOULD_HAVE_BLOCKED;
 141
 142         return ret;
 143 }
 144
 145 struct agent {
 146         int cmdfd, responsefd;
 147 };
 148
 149 /* Do this before doing any tdb stuff.  Return handle, or NULL. */
 150 struct agent *prepare_external_agent(void)
 151 {
 152         int pid, ret;
 153         int command[2], response[2];
 154         char name[1+PATH_MAX];
 155
 156         if (pipe(command) != 0 || pipe(response) != 0)
 157                 return NULL;
 158
 159         pid = fork();
 160         if (pid < 0)
 161                 return NULL;
 162
 163         if (pid != 0) {
 164                 struct agent *agent = malloc(sizeof(*agent));
 165
 166                 close(command[0]);
 167                 close(response[1]);
 168                 agent->cmdfd = command[1];
 169                 agent->responsefd = response[0];
 170                 return agent;
 171         }
 172
 173         close(command[1]);
 174         close(response[0]);
 175
 176         /* We want to fail, not block. */
 177         nonblocking_locks = true;
 178         log_prefix = "external: ";
 179         while ((ret = read(command[0], name, sizeof(name))) > 0) {
 180                 enum agent_return result;
 181
 182                 result = do_operation(name[0], name+1);
 183                 if (write(response[1], &result, sizeof(result))
 184                     != sizeof(result))
 185                         err(1, "Writing response");
 186                 if (name[0] == SEND_SIGNAL) {
 187                         struct timeval ten_ms;
 188                         ten_ms.tv_sec = 0;
 189                         ten_ms.tv_usec = 10000;
 190                         select(0, NULL, NULL, NULL, &ten_ms);
 191                         kill(getppid(), SIGUSR1);
 192                 }
 193         }
 194         exit(0);
 195 }
 196
 197 /* Ask the external agent to try to do an operation. */
 198 enum agent_return external_agent_operation(struct agent *agent,
 199                                            enum operation op,
 200                                            const char *name)
 201 {
 202         enum agent_return res;
 203         unsigned int len;
 204         char *string;
 205
 206         if (!name)
 207                 name = "";
 208         len = 1 + strlen(name) + 1;
 209         string = malloc(len);
 210
 211         string[0] = op;
 212         strcpy(string+1, name);
 213
 214         if (write(agent->cmdfd, string, len) != len
 215             || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
 216                 res = AGENT_DIED;
 217
 218         free(string);
 219         return res;
 220 }
 221
 222 const char *agent_return_name(enum agent_return ret)
 223 {
 224         return ret == SUCCESS ? "SUCCESS"
 225                 : ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
 226                 : ret == AGENT_DIED ? "AGENT_DIED"
 227                 : ret == FAILED ? "FAILED"
 228                 : ret == OTHER_FAILURE ? "OTHER_FAILURE"
 229                 : "**INVALID**";
 230 }
 231
 232 const char *operation_name(enum operation op)
 233 {
 234         switch (op) {
 235         case OPEN: return "OPEN";
 236         case OPEN_WITH_HOOK: return "OPEN_WITH_HOOK";
 237         case FETCH: return "FETCH";
 238         case STORE: return "STORE";
 239         case CHECK: return "CHECK";
 240         case TRANSACTION_START: return "TRANSACTION_START";
 241         case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
 242         case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
 243         case SEND_SIGNAL: return "SEND_SIGNAL";
 244         case CLOSE: return "CLOSE";
 245         }
 246         return "**INVALID**";
 247 }
 248
 249 void free_external_agent(struct agent *agent)
 250 {
 251         close(agent->cmdfd);
 252         close(agent->responsefd);
 253         free(agent);
 254 }