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 void (*external_agent_free)(void *) = free;
  21
  22 static enum TDB_ERROR clear_if_first(int fd, void *arg)
  23 {
  24 /* We hold a lock offset 4 always, so we can tell if anyone is holding it.
  25  * (This is compatible with tdb1's TDB_CLEAR_IF_FIRST flag).  */
  26         struct flock fl;
  27
  28         fl.l_type = F_WRLCK;
  29         fl.l_whence = SEEK_SET;
  30         fl.l_start = 4;
  31         fl.l_len = 1;
  32
  33         if (fcntl(fd, F_SETLK, &fl) == 0) {
  34                 /* We must be first ones to open it! */
  35                 diag("agent truncating file!");
  36                 if (ftruncate(fd, 0) != 0) {
  37                         return TDB_ERR_IO;
  38                 }
  39         }
  40         fl.l_type = F_RDLCK;
  41         if (fcntl(fd, F_SETLKW, &fl) != 0) {
  42                 return TDB_ERR_IO;
  43         }
  44         return TDB_SUCCESS;
  45 }
  46
  47 static enum agent_return do_operation(enum operation op, const char *name)
  48 {
  49         TDB_DATA k;
  50         enum agent_return ret;
  51         TDB_DATA data;
  52         enum TDB_ERROR ecode;
  53         union tdb_attribute cif;
  54
  55         if (op != OPEN && op != OPEN_WITH_HOOK && !tdb) {
  56                 diag("external: No tdb open!");
  57                 return OTHER_FAILURE;
  58         }
  59
  60         diag("external: %s", operation_name(op));
  61
  62         k = tdb_mkdata(name, strlen(name));
  63
  64         locking_would_block = 0;
  65         switch (op) {
  66         case OPEN:
  67                 if (tdb) {
  68                         diag("Already have tdb %s open", tdb->name);
  69                         return OTHER_FAILURE;
  70                 }
  71                 tdb = tdb_open(name, TDB_DEFAULT, O_RDWR, 0, &tap_log_attr);
  72                 if (!tdb) {
  73                         if (!locking_would_block)
  74                                 diag("Opening tdb gave %s", strerror(errno));
  75                         forget_locking();
  76                         ret = OTHER_FAILURE;
  77                 } else
  78                         ret = SUCCESS;
  79                 break;
  80         case OPEN_WITH_HOOK:
  81                 if (tdb) {
  82                         diag("Already have tdb %s open", tdb->name);
  83                         return OTHER_FAILURE;
  84                 }
  85                 cif.openhook.base.attr = TDB_ATTRIBUTE_OPENHOOK;
  86                 cif.openhook.base.next = &tap_log_attr;
  87                 cif.openhook.fn = clear_if_first;
  88                 tdb = tdb_open(name, TDB_DEFAULT, O_RDWR, 0, &cif);
  89                 if (!tdb) {
  90                         if (!locking_would_block)
  91                                 diag("Opening tdb gave %s", strerror(errno));
  92                         forget_locking();
  93                         ret = OTHER_FAILURE;
  94                 } else
  95                         ret = SUCCESS;
  96                 break;
  97         case FETCH:
  98                 ecode = tdb_fetch(tdb, k, &data);
  99                 if (ecode == TDB_ERR_NOEXIST) {
 100                         ret = FAILED;
 101                 } else if (ecode < 0) {
 102                         ret = OTHER_FAILURE;
 103                 } else if (!tdb_deq(data, k)) {
 104                         ret = OTHER_FAILURE;
 105                         external_agent_free(data.dptr);
 106                 } else {
 107                         ret = SUCCESS;
 108                         external_agent_free(data.dptr);
 109                 }
 110                 break;
 111         case STORE:
 112                 ret = tdb_store(tdb, k, k, 0) == 0 ? SUCCESS : OTHER_FAILURE;
 113                 break;
 114         case TRANSACTION_START:
 115                 ret = tdb_transaction_start(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
 116                 break;
 117         case TRANSACTION_COMMIT:
 118                 ret = tdb_transaction_commit(tdb)==0 ? SUCCESS : OTHER_FAILURE;
 119                 break;
 120         case NEEDS_RECOVERY:
 121                 if (tdb->flags & TDB_VERSION1)
 122                         ret = tdb1_needs_recovery(tdb) ? SUCCESS : FAILED;
 123                 else
 124                         ret = tdb_needs_recovery(tdb) ? SUCCESS : FAILED;
 125                 break;
 126         case CHECK:
 127                 ret = tdb_check(tdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
 128                 break;
 129         case CLOSE:
 130                 ret = tdb_close(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
 131                 tdb = NULL;
 132                 break;
 133         case SEND_SIGNAL:
 134                 /* We do this async */
 135                 ret = SUCCESS;
 136                 break;
 137         default:
 138                 ret = OTHER_FAILURE;
 139         }
 140
 141         if (locking_would_block)
 142                 ret = WOULD_HAVE_BLOCKED;
 143
 144         return ret;
 145 }
 146
 147 struct agent {
 148         int cmdfd, responsefd;
 149 };
 150
 151 /* Do this before doing any tdb stuff.  Return handle, or NULL. */
 152 struct agent *prepare_external_agent(void)
 153 {
 154         int pid, ret;
 155         int command[2], response[2];
 156         char name[1+PATH_MAX];
 157
 158         if (pipe(command) != 0 || pipe(response) != 0)
 159                 return NULL;
 160
 161         pid = fork();
 162         if (pid < 0)
 163                 return NULL;
 164
 165         if (pid != 0) {
 166                 struct agent *agent = malloc(sizeof(*agent));
 167
 168                 close(command[0]);
 169                 close(response[1]);
 170                 agent->cmdfd = command[1];
 171                 agent->responsefd = response[0];
 172                 return agent;
 173         }
 174
 175         close(command[1]);
 176         close(response[0]);
 177
 178         /* We want to fail, not block. */
 179         nonblocking_locks = true;
 180         log_prefix = "external: ";
 181         while ((ret = read(command[0], name, sizeof(name))) > 0) {
 182                 enum agent_return result;
 183
 184                 result = do_operation(name[0], name+1);
 185                 if (write(response[1], &result, sizeof(result))
 186                     != sizeof(result))
 187                         err(1, "Writing response");
 188                 if (name[0] == SEND_SIGNAL) {
 189                         struct timeval ten_ms;
 190                         ten_ms.tv_sec = 0;
 191                         ten_ms.tv_usec = 10000;
 192                         select(0, NULL, NULL, NULL, &ten_ms);
 193                         kill(getppid(), SIGUSR1);
 194                 }
 195         }
 196         exit(0);
 197 }
 198
 199 /* Ask the external agent to try to do an operation. */
 200 enum agent_return external_agent_operation(struct agent *agent,
 201                                            enum operation op,
 202                                            const char *name)
 203 {
 204         enum agent_return res;
 205         unsigned int len;
 206         char *string;
 207
 208         if (!name)
 209                 name = "";
 210         len = 1 + strlen(name) + 1;
 211         string = malloc(len);
 212
 213         string[0] = op;
 214         strcpy(string+1, name);
 215
 216         if (write(agent->cmdfd, string, len) != len
 217             || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
 218                 res = AGENT_DIED;
 219
 220         free(string);
 221         return res;
 222 }
 223
 224 const char *agent_return_name(enum agent_return ret)
 225 {
 226         return ret == SUCCESS ? "SUCCESS"
 227                 : ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
 228                 : ret == AGENT_DIED ? "AGENT_DIED"
 229                 : ret == FAILED ? "FAILED"
 230                 : ret == OTHER_FAILURE ? "OTHER_FAILURE"
 231                 : "**INVALID**";
 232 }
 233
 234 const char *operation_name(enum operation op)
 235 {
 236         switch (op) {
 237         case OPEN: return "OPEN";
 238         case OPEN_WITH_HOOK: return "OPEN_WITH_HOOK";
 239         case FETCH: return "FETCH";
 240         case STORE: return "STORE";
 241         case CHECK: return "CHECK";
 242         case TRANSACTION_START: return "TRANSACTION_START";
 243         case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
 244         case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
 245         case SEND_SIGNAL: return "SEND_SIGNAL";
 246         case CLOSE: return "CLOSE";
 247         }
 248         return "**INVALID**";
 249 }
 250
 251 void free_external_agent(struct agent *agent)
 252 {
 253         close(agent->cmdfd);
 254         close(agent->responsefd);
 255         free(agent);
 256 }