source: vendor/current/lib/tdb/test/external-agent.c

#include "external-agent.h"
#include "lock-tracking.h"
#include "logging.h"
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <errno.h>
#include "../common/tdb_private.h"
#include "tap-interface.h"
#include <stdio.h>
#include <stdarg.h>

static struct tdb_context *tdb;

static enum agent_return do_operation(enum operation op, const char *name)
{
        TDB_DATA k;
        enum agent_return ret;
        TDB_DATA data;

        if (op != OPEN && op != OPEN_WITH_CLEAR_IF_FIRST && !tdb) {
                diag("external: No tdb open!");
                return OTHER_FAILURE;
        }

        k.dptr = discard_const_p(uint8_t, name);
        k.dsize = strlen(name);

        locking_would_block = 0;
        switch (op) {
        case OPEN:
                if (tdb) {
                        diag("Already have tdb %s open", tdb_name(tdb));
                        return OTHER_FAILURE;
                }
                tdb = tdb_open_ex(name, 0, TDB_DEFAULT, O_RDWR, 0,
                                  &taplogctx, NULL);
                if (!tdb) {
                        if (!locking_would_block)
                                diag("Opening tdb gave %s", strerror(errno));
                        ret = OTHER_FAILURE;
                } else
                        ret = SUCCESS;
                break;
        case OPEN_WITH_CLEAR_IF_FIRST:
                if (tdb)
                        return OTHER_FAILURE;
                tdb = tdb_open_ex(name, 0, TDB_CLEAR_IF_FIRST, O_RDWR, 0,
                                  &taplogctx, NULL);
                ret = tdb ? SUCCESS : OTHER_FAILURE;
                break;
        case TRANSACTION_START:
                ret = tdb_transaction_start(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
                break;
        case FETCH:
                data = tdb_fetch(tdb, k);
                if (data.dptr == NULL) {
                        if (tdb_error(tdb) == TDB_ERR_NOEXIST)
                                ret = FAILED;
                        else
                                ret = OTHER_FAILURE;
                } else if (data.dsize != k.dsize
                           || memcmp(data.dptr, k.dptr, k.dsize) != 0) {
                        ret = OTHER_FAILURE;
                } else {
                        ret = SUCCESS;
                }
                free(data.dptr);
                break;
        case STORE:
                ret = tdb_store(tdb, k, k, 0) == 0 ? SUCCESS : OTHER_FAILURE;
                break;
        case TRANSACTION_COMMIT:
                ret = tdb_transaction_commit(tdb)==0 ? SUCCESS : OTHER_FAILURE;
                break;
        case CHECK:
                ret = tdb_check(tdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
                break;
        case NEEDS_RECOVERY:
                ret = tdb_needs_recovery(tdb) ? SUCCESS : FAILED;
                break;
        case CLOSE:
                ret = tdb_close(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
                tdb = NULL;
                break;
        case PING:
                ret = SUCCESS;
                break;
        case UNMAP:
                ret = tdb_munmap(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
                if (ret == SUCCESS) {
                        tdb->flags |= TDB_NOMMAP;
                }
                break;
        default:
                ret = OTHER_FAILURE;
        }

        if (locking_would_block)
                ret = WOULD_HAVE_BLOCKED;

        return ret;
}

struct agent {
        int cmdfd, responsefd;
        pid_t pid;
};

/* Do this before doing any tdb stuff.  Return handle, or NULL. */
struct agent *prepare_external_agent(void)
{
        int ret;
        int command[2], response[2];
        char name[1+PATH_MAX];
        struct agent *agent = malloc(sizeof(*agent));

        if (pipe(command) != 0 || pipe(response) != 0) {
                fprintf(stderr, "pipe failed: %s\n", strerror(errno));
                exit(1);
        }

        agent->pid = fork();
        if (agent->pid < 0) {
                fprintf(stderr, "fork failed: %s\n", strerror(errno));
                exit(1);
        }

        if (agent->pid != 0) {
                close(command[0]);
                close(response[1]);
                agent->cmdfd = command[1];
                agent->responsefd = response[0];
                return agent;
        }

        close(command[1]);
        close(response[0]);

        /* We want to fail, not block. */
        nonblocking_locks = true;
        log_prefix = "external: ";
        while ((ret = read(command[0], name, sizeof(name))) > 0) {
                enum agent_return result;

                result = do_operation(name[0], name+1);
                if (write(response[1], &result, sizeof(result))
                    != sizeof(result))
                        abort();
        }
        exit(0);
}

void shutdown_agent(struct agent *agent)
{
        pid_t p;

        close(agent->cmdfd);
        close(agent->responsefd);
        p = waitpid(agent->pid, NULL, WNOHANG);
        if (p == 0) {
                kill(agent->pid, SIGKILL);
        }
        waitpid(agent->pid, NULL, 0);
        free(agent);
}

/* Ask the external agent to try to do an operation. */
enum agent_return external_agent_operation(struct agent *agent,
                                           enum operation op,
                                           const char *name)
{
        enum agent_return res;
        unsigned int len;
        char *string;

        if (!name)
                name = "";
        len = 1 + strlen(name) + 1;
        string = malloc(len);

        string[0] = op;
        strcpy(string+1, name);

        if (write(agent->cmdfd, string, len) != len
            || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
                res = AGENT_DIED;

        free(string);
        return res;
}

const char *agent_return_name(enum agent_return ret)
{
        return ret == SUCCESS ? "SUCCESS"
                : ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
                : ret == AGENT_DIED ? "AGENT_DIED"
                : ret == FAILED ? "FAILED"
                : ret == OTHER_FAILURE ? "OTHER_FAILURE"
                : "**INVALID**";
}

const char *operation_name(enum operation op)
{
        switch (op) {
        case OPEN: return "OPEN";
        case OPEN_WITH_CLEAR_IF_FIRST: return "OPEN_WITH_CLEAR_IF_FIRST";
        case TRANSACTION_START: return "TRANSACTION_START";
        case FETCH: return "FETCH";
        case STORE: return "STORE";
        case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
        case CHECK: return "CHECK";
        case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
        case CLOSE: return "CLOSE";
        case PING: return "PING";
        case UNMAP: return "UNMAP";
        }
        return "**INVALID**";
}