http_filters.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

     * we don't want to send out 0 Content-Lengths if it is a head request.
     * This happens when modules try to outsmart the server, and return
     * if they see a HEAD request.  Apache 1.3 handlers were supposed to
     * just return in that situation, and the core handled the HEAD.  In
     * 2.0, if a handler returns, then the core sends an EOS bucket down
     * the filter stack, and the content-length filter computes a C-L of
     * zero and that gets put in the headers, and we end up sending a
     * zero C-L to the client.  We can't just remove the C-L filter,
     * because well behaved 2.0 handlers will send their data down the stack,
     * and we will compute a real C-L for the head request. RBB
     */
    if (r->header_only
        && (clheader = apr_table_get(r->headers_out, "Content-Length"))
        && !strcmp(clheader, "0")) {
        apr_table_unset(r->headers_out, "Content-Length");
    }

    b2 = apr_brigade_create(r->pool, c->bucket_alloc);
    basic_http_header(r, b2, protocol);

    h.pool = r->pool;
    h.bb = b2;

    if (r->status == HTTP_NOT_MODIFIED) {
        apr_table_do((int (*)(void *, const char *, const char *)) form_header_field,
                     (void *) &h, r->headers_out,
                     "Connection",
                     "Keep-Alive",
                     "ETag",
                     "Content-Location",
                     "Expires",
                     "Cache-Control",
                     "Vary",
                     "Warning",
                     "WWW-Authenticate",
                     "Proxy-Authenticate",
                     "Set-Cookie",
                     "Set-Cookie2",
                     NULL);
    }
    else {
        send_all_header_fields(&h, r);
    }

    terminate_header(b2);

    ap_pass_brigade(f->next, b2);

    if (r->header_only) {
        apr_brigade_destroy(b);
        ctx->headers_sent = 1;
        return OK;
    }

    r->sent_bodyct = 1;         /* Whatever follows is real body stuff... */

    if (r->chunked) {
        /* We can't add this filter until we have already sent the headers.
         * If we add it before this point, then the headers will be chunked
         * as well, and that is just wrong.
         */
        ap_add_output_filter("CHUNK", NULL, r, r->connection);
    }

    /* Don't remove this filter until after we have added the CHUNK filter.
     * Otherwise, f->next won't be the CHUNK filter and thus the first
     * brigade won't be chunked properly.
     */
    ap_remove_output_filter(f);
    return ap_pass_brigade(f->next, b);
}

/* In HTTP/1.1, any method can have a body.  However, most GET handlers
 * wouldn't know what to do with a request body if they received one.
 * This helper routine tests for and reads any message body in the request,
 * simply discarding whatever it receives.  We need to do this because
 * failing to read the request body would cause it to be interpreted
 * as the next request on a persistent connection.
 *
 * Since we return an error status if the request is malformed, this
 * routine should be called at the beginning of a no-body handler, e.g.,
 *
 *    if ((retval = ap_discard_request_body(r)) != OK) {
 *        return retval;
 *    }
 */
AP_DECLARE(int) ap_discard_request_body(request_rec *r)
{
    apr_bucket_brigade *bb;
    int rv, seen_eos;

    /* Sometimes we'll get in a state where the input handling has
     * detected an error where we want to drop the connection, so if
     * that's the case, don't read the data as that is what we're trying
     * to avoid.
     *
     * This function is also a no-op on a subrequest.
     */
    if (r->main || r->connection->keepalive == AP_CONN_CLOSE ||
        ap_status_drops_connection(r->status)) {
        return OK;
    }

    bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);
    seen_eos = 0;
    do {
        apr_bucket *bucket;

        rv = ap_get_brigade(r->input_filters, bb, AP_MODE_READBYTES,
                            APR_BLOCK_READ, HUGE_STRING_LEN);

        if (rv != APR_SUCCESS) {
            /* FIXME: If we ever have a mapping from filters (apr_status_t)
             * to HTTP error codes, this would be a good place for them.
             *
             * If we received the special case AP_FILTER_ERROR, it means
             * that the filters have already handled this error.
             * Otherwise, we should assume we have a bad request.
             */
            if (rv == AP_FILTER_ERROR) {
                apr_brigade_destroy(bb);
                return rv;
            }
            else {
                apr_brigade_destroy(bb);
                return HTTP_BAD_REQUEST;
            }
        }

        for (bucket = APR_BRIGADE_FIRST(bb);
             bucket != APR_BRIGADE_SENTINEL(bb);
             bucket = APR_BUCKET_NEXT(bucket))
        {
            const char *data;
            apr_size_t len;

            if (APR_BUCKET_IS_EOS(bucket)) {
                seen_eos = 1;
                break;
            }

            /* These are metadata buckets. */
            if (bucket->length == 0) {
                continue;
            }

            /* We MUST read because in case we have an unknown-length
             * bucket or one that morphs, we want to exhaust it.
             */
            rv = apr_bucket_read(bucket, &data, &len, APR_BLOCK_READ);
            if (rv != APR_SUCCESS) {
                apr_brigade_destroy(bb);
                return HTTP_BAD_REQUEST;
            }
        }
        apr_brigade_cleanup(bb);
    } while (!seen_eos);

    return OK;
}

/* Here we deal with getting the request message body from the client.
 * Whether or not the request contains a body is signaled by the presence
 * of a non-zero Content-Length or by a Transfer-Encoding: chunked.
 *
 * Note that this is more complicated than it was in Apache 1.1 and prior
 * versions, because chunked support means that the module does less.
 *
 * The proper procedure is this:
 *
 * 1. Call ap_setup_client_block() near the beginning of the request
 *    handler. This will set up all the necessary properties, and will
 *    return either OK, or an error code. If the latter, the module should
 *    return that error code. The second parameter selects the policy to
 *    apply if the request message indicates a body, and how a chunked
 *    transfer-coding should be interpreted. Choose one of
 *
 *    REQUEST_NO_BODY          Send 413 error if message has any body
 *    REQUEST_CHUNKED_ERROR    Send 411 error if body without Content-Length
 *    REQUEST_CHUNKED_DECHUNK  If chunked, remove the chunks for me.
 *    REQUEST_CHUNKED_PASS     If chunked, pass the chunk headers with body.
 *
 *    In order to use the last two options, the caller MUST provide a buffer
 *    large enough to hold a chunk-size line, including any extensions.
 *
 * 2. When you are ready to read a body (if any), call ap_should_client_block().
 *    This will tell the module whether or not to read input. If it is 0,
 *    the module should assume that there is no message body to read.
 *
 * 3. Finally, call ap_get_client_block in a loop. Pass it a buffer and its size.
 *    It will put data into the buffer (not necessarily a full buffer), and
 *    return the length of the input block. When it is done reading, it will
 *    return 0 if EOF, or -1 if there was an error.
 *    If an error occurs on input, we force an end to keepalive.
 *
 *    This step also sends a 100 Continue response to HTTP/1.1 clients if appropriate.
 */

AP_DECLARE(int) ap_setup_client_block(request_rec *r, int read_policy)
{
    const char *tenc = apr_table_get(r->headers_in, "Transfer-Encoding");
    const char *lenp = apr_table_get(r->headers_in, "Content-Length");

    r->read_body = read_policy;
    r->read_chunked = 0;
    r->remaining = 0;

    if (tenc) {
        if (strcasecmp(tenc, "chunked")) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                          "Unknown Transfer-Encoding %s", tenc);
            return HTTP_NOT_IMPLEMENTED;
        }
        if (r->read_body == REQUEST_CHUNKED_ERROR) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                          "chunked Transfer-Encoding forbidden: %s", r->uri);
            return (lenp) ? HTTP_BAD_REQUEST : HTTP_LENGTH_REQUIRED;
        }

        r->read_chunked = 1;
    }
    else if (lenp) {
        char *endstr;

        if (apr_strtoff(&r->remaining, lenp, &endstr, 10)
            || *endstr || r->remaining < 0) {
            r->remaining = 0;
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                          "Invalid Content-Length");
            return HTTP_BAD_REQUEST;
        }
    }

    if ((r->read_body == REQUEST_NO_BODY)
        && (r->read_chunked || (r->remaining > 0))) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                      "%s with body is not allowed for %s", r->method, r->uri);
        return HTTP_REQUEST_ENTITY_TOO_LARGE;
    }

#ifdef AP_DEBUG
    {
        /* Make sure ap_getline() didn't leave any droppings. */
        core_request_config *req_cfg =
            (core_request_config *)ap_get_module_config(r->request_config,
                                                        &core_module);
        AP_DEBUG_ASSERT(APR_BRIGADE_EMPTY(req_cfg->bb));
    }
#endif

    return OK;
}

AP_DECLARE(int) ap_should_client_block(request_rec *r)
{
    /* First check if we have already read the request body */

    if (r->read_length || (!r->read_chunked && (r->remaining <= 0))) {
        return 0;
    }

    return 1;
}

/* get_client_block is called in a loop to get the request message body.
 * This is quite simple if the client includes a content-length
 * (the normal case), but gets messy if the body is chunked. Note that
 * r->remaining is used to maintain state across calls and that
 * r->read_length is the total number of bytes given to the caller
 * across all invocations.  It is messy because we have to be careful not
 * to read past the data provided by the client, since these reads block.
 * Returns 0 on End-of-body, -1 on error or premature chunk end.
 *
 */
AP_DECLARE(long) ap_get_client_block(request_rec *r, char *buffer,
                                     apr_size_t bufsiz)
{
    apr_status_t rv;
    apr_bucket_brigade *bb;

    if (r->remaining < 0 || (!r->read_chunked && r->remaining == 0)) {
        return 0;
    }

    bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);
    if (bb == NULL) {
        r->connection->keepalive = AP_CONN_CLOSE;
        return -1;
    }

    rv = ap_get_brigade(r->input_filters, bb, AP_MODE_READBYTES,
                        APR_BLOCK_READ, bufsiz);

    /* We lose the failure code here.  This is why ap_get_client_block should
     * not be used.
     */
    if (rv != APR_SUCCESS) {
        /* if we actually fail here, we want to just return and
         * stop trying to read data from the client.
         */
        r->connection->keepalive = AP_CONN_CLOSE;
        apr_brigade_destroy(bb);
        return -1;
    }

    /* If this fails, it means that a filter is written incorrectly and that
     * it needs to learn how to properly handle APR_BLOCK_READ requests by
     * returning data when requested.
     */
    AP_DEBUG_ASSERT(!APR_BRIGADE_EMPTY(bb));

    /* Check to see if EOS in the brigade.
     *
     * If so, we have to leave a nugget for the *next* ap_get_client_block
     * call to return 0.
     */
    if (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(bb))) {
        if (r->read_chunked) {
            r->remaining = -1;
        }
        else {
            r->remaining = 0;
        }
    }

    rv = apr_brigade_flatten(bb, buffer, &bufsiz);
    if (rv != APR_SUCCESS) {
        apr_brigade_destroy(bb);
        return -1;
    }

    /* XXX yank me? */
    r->read_length += bufsiz;

    apr_brigade_destroy(bb);
    return bufsiz;
}

/* Context struct for ap_http_outerror_filter */
typedef struct {
    int seen_eoc;
} outerror_filter_ctx_t;

/* Filter to handle any error buckets on output */
apr_status_t ap_http_outerror_filter(ap_filter_t *f,
                                     apr_bucket_brigade *b)
{
    request_rec *r = f->r;
    outerror_filter_ctx_t *ctx = (outerror_filter_ctx_t *)(f->ctx);
    apr_bucket *e;

    /* Create context if none is present */
    if (!ctx) {
        ctx = apr_pcalloc(r->pool, sizeof(outerror_filter_ctx_t));
        f->ctx = ctx;
    }
    for (e = APR_BRIGADE_FIRST(b);
         e != APR_BRIGADE_SENTINEL(b);
         e = APR_BUCKET_NEXT(e))
    {
        if (AP_BUCKET_IS_ERROR(e)) {
            /*
             * Start of error handling state tree. Just one condition
             * right now :)
             */
            if (((ap_bucket_error *)(e->data))->status == HTTP_BAD_GATEWAY) {
                /* stream aborted and we have not ended it yet */
                r->connection->keepalive = AP_CONN_CLOSE;
            }
            continue;
        }
        /* Detect EOC buckets and memorize this in the context. */
        if (AP_BUCKET_IS_EOC(e)) {
            ctx->seen_eoc = 1;
        }
    }
    /*
     * Remove all data buckets that are in a brigade after an EOC bucket
     * was seen, as an EOC bucket tells us that no (further) resource
     * and protocol data should go out to the client. OTOH meta buckets
     * are still welcome as they might trigger needed actions down in
     * the chain (e.g. in network filters like SSL).
     * Remark 1: It is needed to dump ALL data buckets in the brigade
     *           since an filter in between might have inserted data
     *           buckets BEFORE the EOC bucket sent by the original
     *           sender and we do NOT want this data to be sent.
     * Remark 2: Dumping all data buckets here does not necessarily mean
     *           that no further data is send to the client as:
     *           1. Network filters like SSL can still be triggered via
     *              meta buckets to talk with the client e.g. for a
     *              clean shutdown.
     *           2. There could be still data that was buffered before
     *              down in the chain that gets flushed by a FLUSH or an
     *              EOS bucket.
     */
    if (ctx->seen_eoc) {
        for (e = APR_BRIGADE_FIRST(b);
             e != APR_BRIGADE_SENTINEL(b);
             e = APR_BUCKET_NEXT(e))
        {
            if (!APR_BUCKET_IS_METADATA(e)) {
                APR_BUCKET_REMOVE(e);
            }
        }
    }

    return ap_pass_brigade(f->next,  b);
}