dlmod.c

snmp的源代码,已经在我的ubuntu下编译通过

/*
 *  Dynamic Loadable Agent Modules MIB (UCD-DLMOD-MIB) - dlmod.c
 *
 */
#include <net-snmp/net-snmp-config.h>

#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <stdio.h>
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <ctype.h>

#if HAVE_WINSOCK_H
#include <winsock.h>
#endif

#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>

#include "struct.h"
#include "util_funcs.h"

#if defined(HAVE_DLFCN_H) && ( defined(HAVE_DLOPEN) || defined(HAVE_LIBDL) )

#include <dlfcn.h>
#include "dlmod.h"

static struct dlmod *dlmods = NULL;
static int      dlmod_next_index = 1;
static char     dlmod_path[1024];

static void     dlmod_parse_config(const char *, char *);
static void     dlmod_free_config(void);

/*
 * this variable defines function callbacks and type return
 * information for the dlmod mib
 */
static struct variable4 dlmod_variables[] = {
    {DLMODNEXTINDEX, ASN_INTEGER, RONLY, var_dlmod, 1, {1}},
    {DLMODNAME, ASN_OCTET_STR, RWRITE, var_dlmodEntry, 3, {2, 1, 2}},
    {DLMODPATH, ASN_OCTET_STR, RWRITE, var_dlmodEntry, 3, {2, 1, 3}},
    {DLMODERROR, ASN_OCTET_STR, RONLY, var_dlmodEntry, 3, {2, 1, 4}},
    {DLMODSTATUS, ASN_INTEGER, RWRITE, var_dlmodEntry, 3, {2, 1, 5}},
};

static oid      dlmod_variables_oid[] = { 1, 3, 6, 1, 4, 1, 2021, 13, 14 };
static int      dlmod_variables_oid_len = 9;

void
init_dlmod(void)
{
    char           *p;
    int             len;

    REGISTER_MIB("dlmod", dlmod_variables, variable4, dlmod_variables_oid);

    /*
     * TODO: REGISTER_SYSOR_ENTRY 
     */

    DEBUGMSGTL(("dlmod", "register mib\n"));

    snmpd_register_config_handler("dlmod", dlmod_parse_config,
                                  dlmod_free_config,
                                  "module-name module-path");

    p = getenv("SNMPDLMODPATH");
    strncpy(dlmod_path, SNMPDLMODPATH, sizeof(dlmod_path));
    dlmod_path[ sizeof(dlmod_path)-1 ] = 0;
    if (p) {
        if (p[0] == ':') {
            len = strlen(dlmod_path);
            if (dlmod_path[len - 1] != ':') {
                strncat(dlmod_path, ":", sizeof(dlmod_path) - len -1);
                len++;
            }
            strncat(dlmod_path, p + 1,   sizeof(dlmod_path) - len);
        } else
            strncpy(dlmod_path, p, sizeof(dlmod_path));
    }
    dlmod_path[ sizeof(dlmod_path)-1 ] = 0;
    DEBUGMSGTL(("dlmod", "dlmod_path: %s\n", dlmod_path));
}

void
deinit_dlmod(void)
{
    unregister_mib(dlmod_variables_oid, dlmod_variables_oid_len);
    snmpd_unregister_config_handler("dlmod");
}

struct dlmod   *
dlmod_create_module(void)
{
    struct dlmod  **pdlmod, *dlm;

    DEBUGMSGTL(("dlmod", "dlmod_create_module\n"));
    dlm = (struct dlmod *) calloc(1, sizeof(struct dlmod));
    if (dlm == NULL)
        return NULL;

    dlm->index = dlmod_next_index++;
    dlm->status = DLMOD_UNLOADED;

    for (pdlmod = &dlmods; *pdlmod != NULL; pdlmod = &((*pdlmod)->next));
    (*pdlmod) = dlm;

    return dlm;
}

void
dlmod_delete_module(struct dlmod *dlm)
{
    struct dlmod  **pdlmod;

    DEBUGMSGTL(("dlmod", "dlmod_delete_module\n"));
    if (!dlm || dlm->status != DLMOD_UNLOADED)
        return;

    for (pdlmod = &dlmods; *pdlmod; pdlmod = &((*pdlmod)->next))
        if (*pdlmod == dlm) {
            *pdlmod = dlm->next;
            free(dlm);
            return;
        }
}

void
dlmod_load_module(struct dlmod *dlm)
{
    char            sym_init[64];
    char           *p, tmp_path[255];
    int             (*dl_init) (void);
    char           *st;

    DEBUGMSGTL(("dlmod", "dlmod_load_module %s: %s\n", dlm->name,
                dlm->path));

    if (!dlm || !dlm->path || !dlm->name ||
        (dlm->status != DLMOD_UNLOADED && dlm->status != DLMOD_ERROR))
        return;

    if (dlm->path[0] == '/') {
#ifdef RTLD_NOW
        dlm->handle = dlopen(dlm->path, RTLD_NOW);
#else
        dlm->handle = dlopen(dlm->path, RTLD_LAZY);
#endif
        if (dlm->handle == NULL) {
            snprintf(dlm->error, sizeof(dlm->error),
                     "dlopen failed: %s", dlerror());
            dlm->status = DLMOD_ERROR;
            return;
        }
    } else {
        for (p = strtok_r(dlmod_path, ":", &st); p; p = strtok_r(NULL, ":", &st)) {
            snprintf(tmp_path, sizeof(tmp_path), "%s/%s.so", p, dlm->path);
            DEBUGMSGTL(("dlmod", "p: %s tmp_path: %s\n", p, tmp_path));
#ifdef RTLD_NOW
            dlm->handle = dlopen(tmp_path, RTLD_NOW);
#else
            dlm->handle = dlopen(tmp_path, RTLD_LAZY);
#endif
            if (dlm->handle == NULL) {
                snprintf(dlm->error, sizeof(dlm->error),
                         "dlopen failed: %s", dlerror());
                dlm->status = DLMOD_ERROR;
            }
        }
        strncpy(dlm->path, tmp_path, sizeof(dlm->path));
        if (dlm->status == DLMOD_ERROR)
            return;
    }
    snprintf(sym_init, sizeof(sym_init), "init_%s", dlm->name);
    dl_init = dlsym(dlm->handle, sym_init);
    if (dl_init == NULL) {
        dlclose(dlm->handle);
        snprintf(dlm->error, sizeof(dlm->error),
                 "dlsym failed: can't find \'%s\'", sym_init);
        dlm->status = DLMOD_ERROR;
        return;
    }

    dl_init();
    dlm->error[0] = '\0';
    dlm->status = DLMOD_LOADED;
}

void
dlmod_unload_module(struct dlmod *dlm)
{
    char            sym_deinit[64];
    int             (*dl_deinit) (void);

    if (!dlm || dlm->status != DLMOD_LOADED)
        return;

    snprintf(sym_deinit, sizeof(sym_deinit), "deinit_%s", dlm->name);
    dl_deinit = dlsym(dlm->handle, sym_deinit);
    if (dl_deinit == NULL) {
        snprintf(dlm->error, sizeof(dlm->error),
                 "dlsym failed: can't find \'%s\'", sym_deinit);
    } else {
        dl_deinit();
    }
    dlclose(dlm->handle);
    dlm->status = DLMOD_UNLOADED;
    DEBUGMSGTL(("dlmod", "Module %s unloaded\n", dlm->name));
}

struct dlmod   *
dlmod_get_by_index(int iindex)
{
    struct dlmod   *dlmod;

    for (dlmod = dlmods; dlmod; dlmod = dlmod->next)
        if (dlmod->index == iindex)
            return dlmod;

    return NULL;
}

static void
dlmod_parse_config(const char *token, char *cptr)
{
    char           *dlm_name, *dlm_path;
    struct dlmod   *dlm;
    char           *st;

    if (cptr == NULL) {
        config_perror("Bad dlmod line");
        return;
    }
    /*
     * remove comments 
     */
    *(cptr + strcspn(cptr, "#;\r\n")) = '\0';

    dlm = dlmod_create_module();
    if (!dlm)
        return;

    /*
     * dynamic module name 
     */
    dlm_name = strtok_r(cptr, "\t ", &st);
    if (dlm_name == NULL) {
        config_perror("Bad dlmod line");
        dlmod_delete_module(dlm);
        return;
    }
    strncpy(dlm->name, dlm_name, sizeof(dlm->name));

    /*
     * dynamic module path 
     */
    dlm_path = strtok_r(NULL, "\t ", &st);
    if (dlm_path)
        strncpy(dlm->path, dlm_path, sizeof(dlm->path));
    else
        strncpy(dlm->path, dlm_name, sizeof(dlm->path));

    dlmod_load_module(dlm);

    if (dlm->status == DLMOD_ERROR)
        snmp_log(LOG_ERR, "%s\n", dlm->error);
}

static void
dlmod_free_config(void)
{
    struct dlmod   *dtmp, *dtmp2;

    for (dtmp = dlmods; dtmp != NULL;) {
        dtmp2 = dtmp;
        dtmp = dtmp->next;
        dlmod_unload_module(dtmp2);
        free(dtmp2);
    }
    dlmods = NULL;
}


/*
 * header_dlmod(...
 * Arguments:
 * vp     IN      - pointer to variable entry that points here
 * name    IN/OUT  - IN/name requested, OUT/name found