/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2000 Paycounter, Inc.
 * Copyright (c) 2005 Robert N. M. Watson
 * Author: Alfred Perlstein <alfred@paycounter.com>, <alfred@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#define ACCEPT_FILTER_MOD

#include "opt_param.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/domain.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/protosw.h>
#include <sys/sysctl.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/queue.h>

static struct mtx accept_filter_mtx;
MTX_SYSINIT(accept_filter, &accept_filter_mtx, "accept_filter_mtx",
        MTX_DEF);
#define ACCEPT_FILTER_LOCK()    mtx_lock(&accept_filter_mtx)
#define ACCEPT_FILTER_UNLOCK()  mtx_unlock(&accept_filter_mtx)

static SLIST_HEAD(, accept_filter) accept_filtlsthd =
        SLIST_HEAD_INITIALIZER(accept_filtlsthd);

MALLOC_DEFINE(M_ACCF, "accf", "accept filter data");

static int unloadable = 0;

SYSCTL_NODE(_net, OID_AUTO, accf, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Accept filters");
SYSCTL_INT(_net_accf, OID_AUTO, unloadable, CTLFLAG_RW, &unloadable, 0,
        "Allow unload of accept filters (not recommended)");

/*
 * Must be passed a malloc'd structure so we don't explode if the kld is
 * unloaded, we leak the struct on deallocation to deal with this, but if a
 * filter is loaded with the same name as a leaked one we re-use the entry.
 */
int
accept_filt_add(struct accept_filter *filt)
{
        struct accept_filter *p;

        ACCEPT_FILTER_LOCK();
        SLIST_FOREACH(p, &accept_filtlsthd, accf_next)
                if (strcmp(p->accf_name, filt->accf_name) == 0)  {
                        if (p->accf_callback != NULL) {
                                ACCEPT_FILTER_UNLOCK();
                                return (EEXIST);
                        } else {
                                p->accf_callback = filt->accf_callback;
                                ACCEPT_FILTER_UNLOCK();
                                free(filt, M_ACCF);
                                return (0);
                        }
                }
                                
        if (p == NULL)
                SLIST_INSERT_HEAD(&accept_filtlsthd, filt, accf_next);
        ACCEPT_FILTER_UNLOCK();
        return (0);
}

int
accept_filt_del(char *name)
{
        struct accept_filter *p;

        p = accept_filt_get(name);
        if (p == NULL)
                return (ENOENT);

        p->accf_callback = NULL;
        return (0);
}

struct accept_filter *
accept_filt_get(char *name)
{
        struct accept_filter *p;

        ACCEPT_FILTER_LOCK();
        SLIST_FOREACH(p, &accept_filtlsthd, accf_next)
                if (strcmp(p->accf_name, name) == 0)
                        break;
        ACCEPT_FILTER_UNLOCK();

        return (p);
}

int
accept_filt_generic_mod_event(module_t mod, int event, void *data)
{
        struct accept_filter *p;
        struct accept_filter *accfp = (struct accept_filter *) data;
        int error;

        switch (event) {
        case MOD_LOAD:
                p = malloc(sizeof(*p), M_ACCF, M_WAITOK);
                bcopy(accfp, p, sizeof(*p));
                error = accept_filt_add(p);
                break;

        case MOD_UNLOAD:
                /*
                 * Do not support unloading yet. we don't keep track of
                 * refcounts and unloading an accept filter callback and then
                 * having it called is a bad thing.  A simple fix would be to
                 * track the refcount in the struct accept_filter.
                 */
                if (unloadable != 0) {
                        error = accept_filt_del(accfp->accf_name);
                } else
                        error = EOPNOTSUPP;
                break;

        case MOD_SHUTDOWN:
                error = 0;
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        return (error);
}

int
accept_filt_getopt(struct socket *so, struct sockopt *sopt)
{
        struct accept_filter_arg *afap;
        int error;

        error = 0;
        afap = malloc(sizeof(*afap), M_TEMP, M_WAITOK | M_ZERO);
        SOCK_LOCK(so);
        if (!SOLISTENING(so)) {
                error = EINVAL;
                goto out;
        }
        if (so->sol_accept_filter == NULL) {
                error = EINVAL;
                goto out;
        }
        strcpy(afap->af_name, so->sol_accept_filter->accf_name);
        if (so->sol_accept_filter_str != NULL)
                strcpy(afap->af_arg, so->sol_accept_filter_str);
out:
        SOCK_UNLOCK(so);
        if (error == 0)
                error = sooptcopyout(sopt, afap, sizeof(*afap));
        free(afap, M_TEMP);
        return (error);
}

int
accept_filt_setopt(struct socket *so, struct sockopt *sopt)
{
        struct accept_filter_arg *afap;
        struct accept_filter *afp;
        char *accept_filter_str = NULL;
        void *accept_filter_arg = NULL;
        int error;

        /*
         * Handle the simple delete case first.
         */
        if (sopt == NULL || sopt->sopt_val == NULL) {
                struct socket *sp, *sp1;
                int wakeup;

                SOCK_LOCK(so);
                if (!SOLISTENING(so)) {
                        SOCK_UNLOCK(so);
                        return (EINVAL);
                }
                if (so->sol_accept_filter == NULL) {
                        SOCK_UNLOCK(so);
                        return (0);
                }
                if (so->sol_accept_filter->accf_destroy != NULL)
                        so->sol_accept_filter->accf_destroy(so);
                if (so->sol_accept_filter_str != NULL)
                        free(so->sol_accept_filter_str, M_ACCF);
                so->sol_accept_filter = NULL;
                so->sol_accept_filter_arg = NULL;
                so->sol_accept_filter_str = NULL;
                so->so_options &= ~SO_ACCEPTFILTER;

                /*
                 * Move from incomplete queue to complete only those
                 * connections, that are blocked by us.
                 */
                wakeup = 0;
                TAILQ_FOREACH_SAFE(sp, &so->sol_incomp, so_list, sp1) {
                        SOCK_LOCK(sp);
                        if (sp->so_options & SO_ACCEPTFILTER) {
                                TAILQ_REMOVE(&so->sol_incomp, sp, so_list);
                                TAILQ_INSERT_TAIL(&so->sol_comp, sp, so_list);
                                sp->so_qstate = SQ_COMP;
                                sp->so_options &= ~SO_ACCEPTFILTER;
                                so->sol_incqlen--;
                                so->sol_qlen++;
                                wakeup = 1;
                        }
                        SOCK_UNLOCK(sp);
                }
                if (wakeup)
                        solisten_wakeup(so);  /* unlocks */
                else
                        SOLISTEN_UNLOCK(so);
                return (0);
        }

        /*
         * Pre-allocate any memory we may need later to avoid blocking at
         * untimely moments.  This does not optimize for invalid arguments.
         */
        afap = malloc(sizeof(*afap), M_TEMP, M_WAITOK);
        error = sooptcopyin(sopt, afap, sizeof *afap, sizeof *afap);
        afap->af_name[sizeof(afap->af_name)-1] = '\0';
        afap->af_arg[sizeof(afap->af_arg)-1] = '\0';
        if (error) {
                free(afap, M_TEMP);
                return (error);
        }
        afp = accept_filt_get(afap->af_name);
        if (afp == NULL) {
                free(afap, M_TEMP);
                return (ENOENT);
        }
        if (afp->accf_create != NULL && afap->af_name[0] != '\0') {
                size_t len = strlen(afap->af_name) + 1;
                accept_filter_str = malloc(len, M_ACCF, M_WAITOK);
                strcpy(accept_filter_str, afap->af_name);
        }

        /*
         * Require a listen socket; don't try to replace an existing filter
         * without first removing it.
         */
        SOCK_LOCK(so);
        if (__predict_false(!SOLISTENING(so))) {
                error = EINVAL;
                goto out;
        }
        if (__predict_false(so->sol_accept_filter != NULL)) {
                error = EBUSY;
                goto out;
        }

        /*
         * Invoke the accf_create() method of the filter if required.  The
         * socket mutex is held over this call, so create methods for filters
         * can't block.
         */
        if (afp->accf_create != NULL) {
                accept_filter_arg = afp->accf_create(so, afap->af_arg);
                if (accept_filter_arg == NULL) {
                        error = EINVAL;
                        goto out;
                }
        }
        so->sol_accept_filter = afp;
        so->sol_accept_filter_arg = accept_filter_arg;
        so->sol_accept_filter_str = accept_filter_str;
        accept_filter_str = NULL;
        so->so_options |= SO_ACCEPTFILTER;
out:
        SOCK_UNLOCK(so);
        if (accept_filter_str != NULL)
                free(accept_filter_str, M_ACCF);
        free(afap, M_TEMP);
        return (error);
}