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