git.ozlabs.org Git - ccan/blob - ccan/tdb/test/external-transaction.c

   1 #include "external-transaction.h"
   2 #include <sys/types.h>
   3 #include <sys/wait.h>
   4 #include <unistd.h>
   5 #include <err.h>
   6 #include <fcntl.h>
   7 #include <stdlib.h>
   8 #include <limits.h>
   9 #include <string.h>
  10 #include <errno.h>
  11 #include <ccan/tdb/tdb.h>
  12 #include <ccan/tap/tap.h>
  13
  14 static volatile sig_atomic_t alarmed;
  15 static void do_alarm(int signum)
  16 {
  17         alarmed++;
  18 }
  19
  20 static int do_operation(enum operation op, const char *name)
  21 {
  22         TDB_DATA k = { .dptr = (void *)"a", .dsize = 1 };
  23         TDB_DATA d = { .dptr = (void *)"b", .dsize = 1 };
  24         struct tdb_context *tdb;
  25
  26         tdb = tdb_open(name, 0, op == OPEN_WITH_CLEAR_IF_FIRST ?
  27                        TDB_CLEAR_IF_FIRST : TDB_DEFAULT, O_RDWR, 0);
  28         if (!tdb)
  29                 return -1;
  30
  31         if (op == OPEN || op == OPEN_WITH_CLEAR_IF_FIRST) {
  32                 tdb_close(tdb);
  33                 return 0;
  34         }
  35
  36         alarmed = 0;
  37         tdb_setalarm_sigptr(tdb, &alarmed);
  38
  39         alarm(1);
  40         if (tdb_transaction_start(tdb) != 0)
  41                 goto maybe_alarmed;
  42
  43         if (tdb_store(tdb, k, d, 0) != 0) {
  44                 tdb_transaction_cancel(tdb);
  45                 tdb_close(tdb);
  46                 return -2;
  47         }
  48
  49         if (tdb_transaction_commit(tdb) == 0) {
  50                 tdb_delete(tdb, k);
  51                 tdb_close(tdb);
  52                 return 1;
  53         }
  54
  55         tdb_delete(tdb, k);
  56 maybe_alarmed:
  57         tdb_close(tdb);
  58         if (alarmed)
  59                 return 0;
  60         return -3;
  61 }
  62
  63 struct agent {
  64         int cmdfd, responsefd;
  65 };
  66
  67 /* Do this before doing any tdb stuff.  Return handle, or NULL. */
  68 struct agent *prepare_external_agent(void)
  69 {
  70         int pid;
  71         int command[2], response[2];
  72         struct sigaction act = { .sa_handler = do_alarm };
  73         char name[1+PATH_MAX];
  74
  75         if (pipe(command) != 0 || pipe(response) != 0)
  76                 return NULL;
  77
  78         pid = fork();
  79         if (pid < 0)
  80                 return NULL;
  81
  82         if (pid != 0) {
  83                 struct agent *agent = malloc(sizeof(*agent));
  84
  85                 close(command[0]);
  86                 close(response[1]);
  87                 agent->cmdfd = command[1];
  88                 agent->responsefd = response[0];
  89                 return agent;
  90         }
  91
  92         close(command[1]);
  93         close(response[0]);
  94         sigaction(SIGALRM, &act, NULL);
  95
  96         while (read(command[0], name, sizeof(name)) != 0) {
  97                 int result;
  98
  99                 result = do_operation(name[0], name+1);
 100                 if (write(response[1], &result, sizeof(result))
 101                     != sizeof(result))
 102                         err(1, "Writing response");
 103         }
 104         exit(0);
 105 }
 106
 107 /* Ask the external agent to try to do an operation. */
 108 bool external_agent_operation(struct agent *agent,
 109                               enum operation op, const char *tdbname)
 110 {
 111         int res;
 112         char string[1 + strlen(tdbname) + 1];
 113
 114         string[0] = op;
 115         strcpy(string+1, tdbname);
 116
 117         if (write(agent->cmdfd, string, sizeof(string)) != sizeof(string))
 118                 err(1, "Writing to agent");
 119
 120         if (read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
 121                 err(1, "Reading from agent");
 122
 123         if (res > 1)
 124                 errx(1, "Agent returned %u\n", res);
 125
 126         return res;
 127 }
 128
 129 void external_agent_operation_start(struct agent *agent,
 130                                     enum operation op, const char *tdbname)
 131 {
 132         char string[1 + strlen(tdbname) + 1];
 133
 134         string[0] = op;
 135         strcpy(string+1, tdbname);
 136
 137         if (write(agent->cmdfd, string, sizeof(string)) != sizeof(string))
 138                 err(1, "Writing to agent");
 139 }
 140
 141 bool external_agent_operation_check(struct agent *agent, bool block, int *res)
 142 {
 143         int flags = fcntl(agent->responsefd, F_GETFL);
 144
 145         if (block)
 146                 fcntl(agent->responsefd, F_SETFL, flags & ~O_NONBLOCK);
 147         else
 148                 fcntl(agent->responsefd, F_SETFL, flags | O_NONBLOCK);
 149
 150         switch (read(agent->responsefd, res, sizeof(*res))) {
 151         case sizeof(*res):
 152                 break;
 153         case 0:
 154                 errx(1, "Agent died?");
 155         default:
 156                 if (!block && (errno == EAGAIN || errno == EWOULDBLOCK))
 157                         return false;
 158                 err(1, "%slocking reading from agent", block ? "B" : "Non-b");
 159         }
 160
 161         if (*res > 1)
 162                 errx(1, "Agent returned %u\n", *res);
 163
 164         return true;
 165 }