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