lib/ntdb/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 ntdb_context *ntdb;
  18
  19 void (*external_agent_free)(void *) = free;
  20
  21 static enum NTDB_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 tdb'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 NTDB_ERR_IO;
  37                 }
  38         }
  39         fl.l_type = F_RDLCK;
  40         if (fcntl(fd, F_SETLKW, &fl) != 0) {
  41                 return NTDB_ERR_IO;
  42         }
  43         return NTDB_SUCCESS;
  44 }
  45
  46 static enum agent_return do_operation(enum operation op, const char *name)
  47 {
  48         NTDB_DATA k, d;
  49         enum agent_return ret;
  50         NTDB_DATA data;
  51         enum NTDB_ERROR ecode;
  52         union ntdb_attribute cif;
  53         const char *eq;
  54
  55         if (op != OPEN && op != OPEN_WITH_HOOK && !ntdb) {
  56                 diag("external: No ntdb open!");
  57                 return OTHER_FAILURE;
  58         }
  59
  60         diag("external: %s", operation_name(op));
  61
  62         eq = strchr(name, '=');
  63         if (eq) {
  64                 k = ntdb_mkdata(name, eq - name);
  65                 d = ntdb_mkdata(eq + 1, strlen(eq+1));
  66         } else {
  67                 k = ntdb_mkdata(name, strlen(name));
  68                 d.dsize = 0;
  69                 d.dptr = NULL;
  70         }
  71
  72         locking_would_block = 0;
  73         switch (op) {
  74         case OPEN:
  75                 if (ntdb) {
  76                         diag("Already have ntdb %s open", ntdb_name(ntdb));
  77                         return OTHER_FAILURE;
  78                 }
  79                 ntdb = ntdb_open(name, MAYBE_NOSYNC, O_RDWR, 0, &tap_log_attr);
  80                 if (!ntdb) {
  81                         if (!locking_would_block)
  82                                 diag("Opening ntdb gave %s", strerror(errno));
  83                         forget_locking();
  84                         ret = OTHER_FAILURE;
  85                 } else
  86                         ret = SUCCESS;
  87                 break;
  88         case OPEN_WITH_HOOK:
  89                 if (ntdb) {
  90                         diag("Already have ntdb %s open", ntdb_name(ntdb));
  91                         return OTHER_FAILURE;
  92                 }
  93                 cif.openhook.base.attr = NTDB_ATTRIBUTE_OPENHOOK;
  94                 cif.openhook.base.next = &tap_log_attr;
  95                 cif.openhook.fn = clear_if_first;
  96                 ntdb = ntdb_open(name, MAYBE_NOSYNC, O_RDWR, 0, &cif);
  97                 if (!ntdb) {
  98                         if (!locking_would_block)
  99                                 diag("Opening ntdb gave %s", strerror(errno));
 100                         forget_locking();
 101                         ret = OTHER_FAILURE;
 102                 } else
 103                         ret = SUCCESS;
 104                 break;
 105         case FETCH:
 106                 ecode = ntdb_fetch(ntdb, k, &data);
 107                 if (ecode == NTDB_ERR_NOEXIST) {
 108                         ret = FAILED;
 109                 } else if (ecode < 0) {
 110                         ret = OTHER_FAILURE;
 111                 } else if (!ntdb_deq(data, d)) {
 112                         ret = OTHER_FAILURE;
 113                         external_agent_free(data.dptr);
 114                 } else {
 115                         ret = SUCCESS;
 116                         external_agent_free(data.dptr);
 117                 }
 118                 break;
 119         case STORE:
 120                 ret = ntdb_store(ntdb, k, d, 0) == 0 ? SUCCESS : OTHER_FAILURE;
 121                 break;
 122         case TRANSACTION_START:
 123                 ret = ntdb_transaction_start(ntdb) == 0 ? SUCCESS : OTHER_FAILURE;
 124                 break;
 125         case TRANSACTION_COMMIT:
 126                 ret = ntdb_transaction_commit(ntdb)==0 ? SUCCESS : OTHER_FAILURE;
 127                 break;
 128         case NEEDS_RECOVERY:
 129                 ret = external_agent_needs_rec(ntdb);
 130                 break;
 131         case CHECK:
 132                 ret = ntdb_check(ntdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
 133                 break;
 134         case CLOSE:
 135                 ret = ntdb_close(ntdb) == 0 ? SUCCESS : OTHER_FAILURE;
 136                 ntdb = NULL;
 137                 break;
 138         case SEND_SIGNAL:
 139                 /* We do this async */
 140                 ret = SUCCESS;
 141                 break;
 142         default:
 143                 ret = OTHER_FAILURE;
 144         }
 145
 146         if (locking_would_block)
 147                 ret = WOULD_HAVE_BLOCKED;
 148
 149         return ret;
 150 }
 151
 152 struct agent {
 153         int cmdfd, responsefd;
 154 };
 155
 156 /* Do this before doing any ntdb stuff.  Return handle, or NULL. */
 157 struct agent *prepare_external_agent(void)
 158 {
 159         int pid, ret;
 160         int command[2], response[2];
 161         char name[1+PATH_MAX];
 162
 163         if (pipe(command) != 0 || pipe(response) != 0)
 164                 return NULL;
 165
 166         pid = fork();
 167         if (pid < 0)
 168                 return NULL;
 169
 170         if (pid != 0) {
 171                 struct agent *agent = malloc(sizeof(*agent));
 172
 173                 close(command[0]);
 174                 close(response[1]);
 175                 agent->cmdfd = command[1];
 176                 agent->responsefd = response[0];
 177                 return agent;
 178         }
 179
 180         close(command[1]);
 181         close(response[0]);
 182
 183         /* We want to fail, not block. */
 184         nonblocking_locks = true;
 185         log_prefix = "external: ";
 186         while ((ret = read(command[0], name, sizeof(name))) > 0) {
 187                 enum agent_return result;
 188
 189                 result = do_operation(name[0], name+1);
 190                 if (write(response[1], &result, sizeof(result))
 191                     != sizeof(result))
 192                         err(1, "Writing response");
 193                 if (name[0] == SEND_SIGNAL) {
 194                         struct timeval ten_ms;
 195                         ten_ms.tv_sec = 0;
 196                         ten_ms.tv_usec = 10000;
 197                         select(0, NULL, NULL, NULL, &ten_ms);
 198                         kill(getppid(), SIGUSR1);
 199                 }
 200         }
 201         exit(0);
 202 }
 203
 204 /* Ask the external agent to try to do an operation. */
 205 enum agent_return external_agent_operation(struct agent *agent,
 206                                            enum operation op,
 207                                            const char *name)
 208 {
 209         enum agent_return res;
 210         unsigned int len;
 211         char *string;
 212
 213         if (!name)
 214                 name = "";
 215         len = 1 + strlen(name) + 1;
 216         string = malloc(len);
 217
 218         string[0] = op;
 219         strcpy(string+1, name);
 220
 221         if (write(agent->cmdfd, string, len) != len
 222             || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
 223                 res = AGENT_DIED;
 224
 225         free(string);
 226         return res;
 227 }
 228
 229 const char *agent_return_name(enum agent_return ret)
 230 {
 231         return ret == SUCCESS ? "SUCCESS"
 232                 : ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
 233                 : ret == AGENT_DIED ? "AGENT_DIED"
 234                 : ret == FAILED ? "FAILED"
 235                 : ret == OTHER_FAILURE ? "OTHER_FAILURE"
 236                 : "**INVALID**";
 237 }
 238
 239 const char *operation_name(enum operation op)
 240 {
 241         switch (op) {
 242         case OPEN: return "OPEN";
 243         case OPEN_WITH_HOOK: return "OPEN_WITH_HOOK";
 244         case FETCH: return "FETCH";
 245         case STORE: return "STORE";
 246         case CHECK: return "CHECK";
 247         case TRANSACTION_START: return "TRANSACTION_START";
 248         case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
 249         case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
 250         case SEND_SIGNAL: return "SEND_SIGNAL";
 251         case CLOSE: return "CLOSE";
 252         }
 253         return "**INVALID**";
 254 }
 255
 256 void free_external_agent(struct agent *agent)
 257 {
 258         close(agent->cmdfd);
 259         close(agent->responsefd);
 260         free(agent);
 261 }