/*
 * jabberd - Jabber Open Source Server
 * Copyright (c) 2002 Jeremie Miller, Thomas Muldowney,
 *                    Ryan Eatmon, Robert Norris
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA02111-1307USA
 */

/**
 * this plugin implements the traditional SSL "wrappermode" streams and
 * STARTTLS extension documented in xmpp-core
 */

#include "sx.h"

/* code stolen from SSL_CTX_set_verify(3) */
static int _sx_ssl_verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
{
    char    buf[256];
    X509   *err_cert;
    int     err, depth;
    SSL    *ssl;

    err_cert = X509_STORE_CTX_get_current_cert(ctx);
    err = X509_STORE_CTX_get_error(ctx);
    depth = X509_STORE_CTX_get_error_depth(ctx);

    /*
     * Retrieve the pointer to the SSL of the connection currently treated
     * and the application specific data stored into the SSL object.
     */
    ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
    X509_NAME_oneline(X509_get_subject_name(err_cert), buf, 256);

    if (!preverify_ok) {
        _sx_debug(ZONE, "verify error:num=%d:%s:depth=%d:%s\n", err,
                 X509_verify_cert_error_string(err), depth, buf);
    }
    else
    {
        _sx_debug(ZONE, "OK! depth=%d:%s", depth, buf);
    }

    /*
     * At this point, err contains the last verification error. We can use
     * it for something special
     */
    if (!preverify_ok && (err == X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT))
    {
      X509_NAME_oneline(X509_get_issuer_name(ctx->current_cert), buf, 256);
      _sx_debug(ZONE, "issuer= %s\n", buf);
    }

    return preverify_ok;
 }

static void _sx_ssl_starttls_notify_proceed(sx_t s, void *arg) {
    _sx_debug(ZONE, "preparing for starttls");

    _sx_reset(s);

    /* start listening */
    sx_server_init(s, s->flags | SX_SSL_WRAPPER);
}

static int _sx_ssl_process(sx_t s, sx_plugin_t p, nad_t nad) {
    int flags;
    char *ns = NULL, *to = NULL, *from = NULL, *version = NULL;
    sx_error_t sxe;

    /* not interested if we're a server and we never offered it */
    if(s->type == type_SERVER && !(s->flags & SX_SSL_STARTTLS_OFFER))
        return 1;

    /* only want tls packets */
    if(NAD_ENS(nad, 0) < 0 || NAD_NURI_L(nad, NAD_ENS(nad, 0)) != strlen(uri_TLS) || strncmp(NAD_NURI(nad, NAD_ENS(nad, 0)), uri_TLS, strlen(uri_TLS)) != 0)
        return 1;

    /* starttls from client */
    if(s->type == type_SERVER) {
        if(NAD_ENAME_L(nad, 0) == 8 && strncmp(NAD_ENAME(nad, 0), "starttls", 8) == 0) {
            nad_free(nad);
    
            /* can't go on if we've been here before */
            if(s->ssf > 0) {
                _sx_debug(ZONE, "starttls requested on already encrypted channel, dropping packet");
                return 0;
            }

            /* can't go on if we're on compressed stream */
            if(s->compressed > 0) {
                _sx_debug(ZONE, "starttls requested on already compressed channel, dropping packet");
                return 0;
            }

            _sx_debug(ZONE, "starttls requested, setting up");

            /* go ahead */
            jqueue_push(s->wbufq, _sx_buffer_new("<proceed xmlns='" uri_TLS "'/>", strlen(uri_TLS) + 19, _sx_ssl_starttls_notify_proceed, NULL), 0);
            s->want_write = 1;

            /* handled the packet */
            return 0;
        }
    }

    else if(s->type == type_CLIENT) {
        /* kick off the handshake */
        if(NAD_ENAME_L(nad, 0) == 7 && strncmp(NAD_ENAME(nad, 0), "proceed", 7) == 0) {
            nad_free(nad);

            /* save interesting bits */
            flags = s->flags;

            if(s->ns != NULL) ns = strdup(s->ns);

            if(s->req_to != NULL) to = strdup(s->req_to);
            if(s->req_from != NULL) from = strdup(s->req_from);
            if(s->req_version != NULL) version = strdup(s->req_version);

            /* reset state */
            _sx_reset(s);

            _sx_debug(ZONE, "server ready for ssl, starting");

            /* second time round */
            sx_client_init(s, flags | SX_SSL_WRAPPER, ns, to, from, version);

            /* free bits */
            if(ns != NULL) free(ns);
            if(to != NULL) free(to);
            if(from != NULL) free(from);
            if(version != NULL) free(version);

            return 0;
        }

        /* busted server */
        if(NAD_ENAME_L(nad, 0) == 7 && strncmp(NAD_ENAME(nad, 0), "failure", 7) == 0) {
            nad_free(nad);

            /* free the pemfile arg */
            if(s->plugin_data[p->index] != NULL) {
                if( ((_sx_ssl_conn_t)s->plugin_data[p->index])->pemfile != NULL )
                    free(((_sx_ssl_conn_t)s->plugin_data[p->index])->pemfile);
                free(s->plugin_data[p->index]);
                s->plugin_data[p->index] = NULL;
            }

            _sx_debug(ZONE, "server can't handle ssl, business as usual");

            _sx_gen_error(sxe, SX_ERR_STARTTLS_FAILURE, "STARTTLS failure", "Server was unable to prepare for the TLS handshake");
            _sx_event(s, event_ERROR, (void *) &sxe);

            return 0;
        }
    }

    _sx_debug(ZONE, "unknown starttls namespace element '%.*s', dropping packet", NAD_ENAME_L(nad, 0), NAD_ENAME(nad, 0));
    nad_free(nad);
    return 0;
}

static void _sx_ssl_features(sx_t s, sx_plugin_t p, nad_t nad) {
    int ns;

    /* if the session is already encrypted, or the app told us not to,
     * or session is compressed then we don't offer anything */
    if(s->state > state_STREAM || s->ssf > 0 || !(s->flags & SX_SSL_STARTTLS_OFFER) || s->compressed)
        return;

    _sx_debug(ZONE, "offering starttls");

    ns = nad_add_namespace(nad, uri_TLS, NULL);
    nad_append_elem(nad, ns, "starttls", 1);

    if(s->flags & SX_SSL_STARTTLS_REQUIRE)
        nad_append_elem(nad, ns, "required", 2);
}

static int _sx_ssl_handshake(sx_t s, _sx_ssl_conn_t sc) {
    int ret, err;
    char *errstring;
    sx_error_t sxe;

    /* work on establishing the channel */
    while(!SSL_is_init_finished(sc->ssl)) {
        _sx_debug(ZONE, "secure channel not established, handshake in progress");

        /* we can't handshake if they want to read, but there's nothing to read */
        if(sc->last_state == SX_SSL_STATE_WANT_READ && BIO_pending(sc->rbio) == 0)
            return 0;

        /* more handshake */
        if(s->type == type_CLIENT)
            ret = SSL_connect(sc->ssl);
        else
            ret = SSL_accept(sc->ssl);

        /* check if we're done */
        if(ret == 1) {
            _sx_debug(ZONE, "secure channel established");
            sc->last_state = SX_SSL_STATE_NONE;

            s->ssf = SSL_get_cipher_bits(sc->ssl, NULL);

            _sx_debug(ZONE, "using cipher %s (%d bits)", SSL_get_cipher_name(sc->ssl), s->ssf);

            return 1;
        }

        /* error checking */
        else if(ret <= 0) {
            err = SSL_get_error(sc->ssl, ret);

            if(err == SSL_ERROR_WANT_READ)
                sc->last_state = SX_SSL_STATE_WANT_READ;
            else if(err == SSL_ERROR_WANT_WRITE)
                sc->last_state = SX_SSL_STATE_WANT_WRITE;

            else {
                /* fatal error */
                sc->last_state = SX_SSL_STATE_ERROR;

                errstring = ERR_error_string(ERR_get_error(), NULL);
                _sx_debug(ZONE, "openssl error: %s", errstring);

                /* throw an error */
                _sx_gen_error(sxe, SX_ERR_SSL, "SSL handshake error", errstring);
                _sx_event(s, event_ERROR, (void *) &sxe);

                _sx_error(s, stream_err_INTERNAL_SERVER_ERROR, errstring);
                _sx_close(s);

                /* !!! drop queue */

                return -1;
            }
        }
    }

    return 1;
}

static int _sx_ssl_wio(sx_t s, sx_plugin_t p, sx_buf_t buf) {
    _sx_ssl_conn_t sc = (_sx_ssl_conn_t) s->plugin_data[p->index];
    int est, ret, err;
    sx_buf_t wbuf;
    char *errstring;
    sx_error_t sxe;

    /* sanity */
    if(sc->last_state == SX_SSL_STATE_ERROR)
        return -2;

    _sx_debug(ZONE, "in _sx_ssl_wio");

    /* queue the buffer */
    if(buf->len > 0) {
        _sx_debug(ZONE, "queueing buffer for write");

        jqueue_push(sc->wq, _sx_buffer_new(buf->data, buf->len, buf->notify, buf->notify_arg), 0);
        _sx_buffer_clear(buf);
        buf->notify = NULL;
        buf->notify_arg = NULL;
    }

    /* handshake */
    est = _sx_ssl_handshake(s, sc);
    if(est < 0)
        return -2;  /* fatal error */

    /* channel established, do some real writing */
    wbuf = NULL;
    if(est > 0 && jqueue_size(sc->wq) > 0) {
        _sx_debug(ZONE, "preparing queued buffer for write");

        wbuf = jqueue_pull(sc->wq);

        ret = SSL_write(sc->ssl, wbuf->data, wbuf->len);
        if(ret <= 0) {
            /* something's wrong */
            _sx_debug(ZONE, "write failed, requeuing buffer");

            /* requeue the buffer */
            jqueue_push(sc->wq, wbuf, (sc->wq->front != NULL) ? sc->wq->front->priority + 1 : 0);

            /* error checking */
            err = SSL_get_error(sc->ssl, ret);

            if(err == SSL_ERROR_ZERO_RETURN) {
                /* ssl channel closed, we're done */
                _sx_close(s);
            }

            if(err == SSL_ERROR_WANT_READ) {
                /* we'll be renegotiating next time */
                _sx_debug(ZONE, "renegotiation started");
                sc->last_state = SX_SSL_STATE_WANT_READ;
            }

            else {
                sc->last_state = SX_SSL_STATE_ERROR;

                /* something very bad */
                errstring = ERR_error_string(ERR_get_error(), NULL);
                _sx_debug(ZONE, "openssl error: %s", errstring);

                /* throw an error */
                _sx_gen_error(sxe, SX_ERR_SSL, "SSL handshake error", errstring);
                _sx_event(s, event_ERROR, (void *) &sxe);

                _sx_error(s, stream_err_INTERNAL_SERVER_ERROR, errstring);
                _sx_close(s);

                /* !!! drop queue */

                return -2;  /* fatal */
            }
        }
    }

    /* prepare the buffer with stuff to write */
    if(BIO_pending(sc->wbio) > 0) {
        int bytes_pending = BIO_pending(sc->wbio);
        assert(buf->len == 0);
        _sx_buffer_alloc_margin(buf, 0, bytes_pending);
        BIO_read(sc->wbio, buf->data, bytes_pending);
        buf->len += bytes_pending;

        /* restore notify and clean up */
        if(wbuf != NULL) {
            buf->notify = wbuf->notify;
            buf->notify_arg = wbuf->notify_arg;
            _sx_buffer_free(wbuf);
        }

        _sx_debug(ZONE, "prepared %d ssl bytes for write", buf->len);
    }

    /* flag if we want to read */
    if(sc->last_state == SX_SSL_STATE_WANT_READ || sc->last_state == SX_SSL_STATE_NONE)
        s->want_read = 1;

    return 1;
}

static int _sx_ssl_rio(sx_t s, sx_plugin_t p, sx_buf_t buf) {
    _sx_ssl_conn_t sc = (_sx_ssl_conn_t) s->plugin_data[p->index];
    int est, ret, err, pending;
    char *errstring;
    sx_error_t sxe;

    /* sanity */
    if(sc->last_state == SX_SSL_STATE_ERROR)
        return -1;

    _sx_debug(ZONE, "in _sx_ssl_rio");

    /* move the data into the ssl read buffer */
    if(buf->len > 0) {
        _sx_debug(ZONE, "loading %d bytes into ssl read buffer", buf->len);

        BIO_write(sc->rbio, buf->data, buf->len);

        _sx_buffer_clear(buf);
    }

    /* handshake */
    est = _sx_ssl_handshake(s, sc);
    if(est < 0)
        return -1;  /* fatal error */

    /* channel is up, slurp up the read buffer */
    if(est > 0) {

        pending = SSL_pending(sc->ssl);
        if(pending == 0)
            pending = BIO_pending(sc->rbio);

        /* get it all */
        while((pending = SSL_pending(sc->ssl)) > 0 || (pending = BIO_pending(sc->rbio)) > 0) {
            _sx_buffer_alloc_margin(buf, 0, pending);

            ret = SSL_read(sc->ssl, &(buf->data[buf->len]), pending);

            if (ret == 0)
            {
                /* ret will equal zero if the SSL stream was closed.
                   (See the SSL_read manpage.) */

                /* If the SSL Shutdown happened properly,
                   (i.e. we got an SSL "close notify")
                   then proccess the last packet recieved. */
                if (SSL_get_shutdown(sc->ssl) == SSL_RECEIVED_SHUTDOWN)
                {
                  _sx_close(s);
                  break;
                }

                /* If the SSL stream was just closed and not shutdown,
                   drop the last packet recieved.
                   WARNING: This may cause clients that use SSLv2 and
                   earlier to not log out properly. */

                err = SSL_get_error(sc->ssl, ret);

                _sx_buffer_clear(buf);


                if(err == SSL_ERROR_ZERO_RETURN) {
                    /* ssl channel closed, we're done */
                    _sx_close(s);
                }

                return -1;
            }
            else if(ret < 0) {
                /* ret will be negative if the SSL stream needs
                   more data, or if there was a SSL error.
                   (See the SSL_read manpage.) */
                err = SSL_get_error(sc->ssl, ret);

                /* ssl block incomplete, need more */
                if(err == SSL_ERROR_WANT_READ) {
                    sc->last_state = SX_SSL_STATE_WANT_READ;

                    break;
                }

                /* something's wrong */
                _sx_buffer_clear(buf);


                /* !!! need checks for renegotiation */

                sc->last_state = SX_SSL_STATE_ERROR;

                errstring = ERR_error_string(ERR_get_error(), NULL);
                _sx_debug(ZONE, "openssl error: %s", errstring);

                /* throw an error */
                _sx_gen_error(sxe, SX_ERR_SSL, "SSL handshake error", errstring);
                _sx_event(s, event_ERROR, (void *) &sxe);

                _sx_error(s, stream_err_INTERNAL_SERVER_ERROR, errstring);
                _sx_close(s);

                /* !!! drop queue */

                return -1;
            }

            buf->len += ret;
        }
    }

    /* flag if stuff to write */
    if(BIO_pending(sc->wbio) > 0 || (est > 0 && jqueue_size(sc->wq) > 0))
        s->want_write = 1;

    /* flag if we want to read */
    if(sc->last_state == SX_SSL_STATE_WANT_READ || sc->last_state == SX_SSL_STATE_NONE)
        s->want_read = 1;
    
    if(buf->len == 0)
        return 0;

    return 1;
}

static void _sx_ssl_client(sx_t s, sx_plugin_t p) {
    _sx_ssl_conn_t sc;
    char *pemfile = NULL;
    int ret;

    /* only bothering if they asked for wrappermode */
    if(!(s->flags & SX_SSL_WRAPPER) || s->ssf > 0)
        return;

    _sx_debug(ZONE, "preparing for ssl connect for %d", s->tag);

    sc = (_sx_ssl_conn_t) malloc(sizeof(struct _sx_ssl_conn_st));
    memset(sc, 0, sizeof(struct _sx_ssl_conn_st));

    /* create the buffers */
    sc->rbio = BIO_new(BIO_s_mem());
    sc->wbio = BIO_new(BIO_s_mem());

    /* new ssl conn */
    sc->ssl = SSL_new((SSL_CTX *) p->private);
    SSL_set_bio(sc->ssl, sc->rbio, sc->wbio);
    SSL_set_connect_state(sc->ssl);

    /* empty external_id */
    sc->external_id = NULL;

    /* alternate pemfile */
    /* !!! figure out how to error correctly here - just returning will cause
     *     us to send a normal unencrypted stream start while the server is
     *     waiting for ClientHelo. the server will flag an error, but it won't
     *     help the admin at all to figure out what happened */
    if(s->plugin_data[p->index] != NULL) {
        pemfile = ((_sx_ssl_conn_t)s->plugin_data[p->index])->pemfile;
        free(s->plugin_data[p->index]);
        s->plugin_data[p->index] = NULL;
    }
    if(pemfile != NULL) {
        /* load the certificate */
        ret = SSL_use_certificate_file(sc->ssl, pemfile, SSL_FILETYPE_PEM);
        if(ret != 1) {
            _sx_debug(ZONE, "couldn't load alternate certificate from %s", pemfile);
            SSL_free(sc->ssl);
            free(sc);
            free(pemfile);
            return;
        }

        /* load the private key */
        ret = SSL_use_PrivateKey_file(sc->ssl, pemfile, SSL_FILETYPE_PEM);
        if(ret != 1) {
            _sx_debug(ZONE, "couldn't load alternate private key from %s", pemfile);
            SSL_free(sc->ssl);
            free(sc);
            free(pemfile);
            return;
        }

        /* check the private key matches the certificate */
        ret = SSL_check_private_key(sc->ssl);
        if(ret != 1) {
            _sx_debug(ZONE, "private key does not match certificate public key");
            SSL_free(sc->ssl);
            free(sc);
            free(pemfile);
            return;
        }

        _sx_debug(ZONE, "loaded alternate pemfile %s", pemfile);

        free(pemfile);
    }

    /* buffer queue */
    sc->wq = jqueue_new();

    s->plugin_data[p->index] = (void *) sc;

    /* bring the plugin online */
    _sx_chain_io_plugin(s, p);
}

static void _sx_ssl_server(sx_t s, sx_plugin_t p) {
    _sx_ssl_conn_t sc;

    /* only bothering if they asked for wrappermode */
    if(!(s->flags & SX_SSL_WRAPPER) || s->ssf > 0)
        return;

    _sx_debug(ZONE, "preparing for ssl accept for %d", s->tag);

    sc = (_sx_ssl_conn_t) malloc(sizeof(struct _sx_ssl_conn_st));
    memset(sc, 0, sizeof(struct _sx_ssl_conn_st));

    /* create the buffers */
    sc->rbio = BIO_new(BIO_s_mem());
    sc->wbio = BIO_new(BIO_s_mem());

    /* new ssl conn */
    sc->ssl = SSL_new((SSL_CTX *) p->private);
    SSL_set_bio(sc->ssl, sc->rbio, sc->wbio);
    SSL_set_accept_state(sc->ssl);

    /* empty external_id */
    sc->external_id = NULL;

    /* buffer queue */
    sc->wq = jqueue_new();

    s->plugin_data[p->index] = (void *) sc;

    /* bring the plugin online */
    _sx_chain_io_plugin(s, p);
}

/** cleanup */
static void _sx_ssl_free(sx_t s, sx_plugin_t p) {
    _sx_ssl_conn_t sc = (_sx_ssl_conn_t) s->plugin_data[p->index];
    sx_buf_t buf;

    if(sc == NULL)
        return;

    log_debug(ZONE, "cleaning up conn state");

    if(s->type == type_NONE) {
        free(sc);
        return;
    }

    if(sc->external_id != NULL) free(sc->external_id);
    if(sc->pemfile != NULL) free(sc->pemfile);

    if(sc->ssl != NULL) SSL_free(sc->ssl);      /* frees wbio and rbio too */

    if(sc->wq != NULL) {
        while((buf = jqueue_pull(sc->wq)) != NULL)
            _sx_buffer_free(buf);

        jqueue_free(sc->wq);
    }

    free(sc);
    
    s->plugin_data[p->index] = NULL;
}

static void _sx_ssl_unload(sx_plugin_t p) {
    SSL_CTX_free((SSL_CTX *) p->private);
}

int sx_openssl_initialized = 0;

/** args: pemfile, cachain, mode */
int sx_ssl_init(sx_env_t env, sx_plugin_t p, va_list args) {
    char *pemfile, *cachain;
    SSL_CTX *ctx;
    int ret;
    int mode;

    _sx_debug(ZONE, "initialising ssl plugin");

    pemfile = va_arg(args, char *);
    if(pemfile == NULL)
        return 1;

    if(p->private != NULL)
        return 1;

    cachain = va_arg(args, char *);
    mode = va_arg(args, int);

    /* !!! output openssl error messages to the debug log */

    /* openssl startup */
    SSL_library_init();
    SSL_load_error_strings();

    sx_openssl_initialized = 1;

    /* create the context */
    ctx = SSL_CTX_new(SSLv23_method());
    if(ctx == NULL) {
        _sx_debug(ZONE, "ssl context creation failed");
        return 1;
    }
    
    /* Load the CA chain, if configured */
    if (cachain != NULL) {
        ret = SSL_CTX_load_verify_locations (ctx, cachain, NULL);
        if(ret != 1) {
            _sx_debug(ZONE, "WARNING: couldn't load CA chain: %s", cachain);
        }
    }

    /* load the certificate */
    ret = SSL_CTX_use_certificate_chain_file(ctx, pemfile);
    if(ret != 1) {
        _sx_debug(ZONE, "couldn't load certificate from %s", pemfile);
        SSL_CTX_free(ctx);
        return 1;
    }

    /* load the private key */
    ret = SSL_CTX_use_PrivateKey_file(ctx, pemfile, SSL_FILETYPE_PEM);
    if(ret != 1) {
        _sx_debug(ZONE, "couldn't load private key from %s", pemfile);
        SSL_CTX_free(ctx);
        return 1;
    }

    /* check the private key matches the certificate */
    ret = SSL_CTX_check_private_key(ctx);
    if(ret != 1) {
        _sx_debug(ZONE, "private key does not match certificate public key");
        SSL_CTX_free(ctx);
        return 1;
    }

    _sx_debug(ZONE, "Setting verify mode to %02x", mode);
    SSL_CTX_set_verify(ctx, mode, _sx_ssl_verify_callback);

    /* its good */
    _sx_debug(ZONE, "ssl context initialised; certificate and key loaded from %s", pemfile);

    p->magic = SX_SSL_MAGIC;

    p->private = (void *) ctx;

    p->unload = _sx_ssl_unload;

    p->client = _sx_ssl_client;
    p->server = _sx_ssl_server;
    p->rio = _sx_ssl_rio;
    p->wio = _sx_ssl_wio;
    p->features = _sx_ssl_features;
    p->process = _sx_ssl_process;
    p->free = _sx_ssl_free;

    return 0;
}

int sx_ssl_client_starttls(sx_plugin_t p, sx_t s, char *pemfile) {
    assert((int) (p != NULL));
    assert((int) (s != NULL));

    /* sanity */
    if(s->type != type_CLIENT || s->state != state_STREAM) {
        _sx_debug(ZONE, "wrong conn type or state for client starttls");
        return 1;
    }

    /* check if we're already encrypted or compressed */
    if(s->ssf > 0 || s->compressed) {
        _sx_debug(ZONE, "encrypted channel already established");
        return 1;
    }

    _sx_debug(ZONE, "initiating starttls sequence");

    /* save the given pemfile for later */
    if(pemfile != NULL) {
        s->plugin_data[p->index] = (_sx_ssl_conn_t) malloc(sizeof(struct _sx_ssl_conn_st));
        memset(s->plugin_data[p->index], 0, sizeof(struct _sx_ssl_conn_st));
        ((_sx_ssl_conn_t)s->plugin_data[p->index])->pemfile = strdup(pemfile);
    }

    /* go */
    jqueue_push(s->wbufq, _sx_buffer_new("<starttls xmlns='" uri_TLS "'/>", strlen(uri_TLS) + 20, NULL, NULL), 0);
    s->want_write = 1;
    _sx_event(s, event_WANT_WRITE, NULL);

    return 0;
}