http_protocol.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

            ap_die(eb->status, r);
            return AP_FILTER_ERROR;
        }
    }

    if (r->assbackwards) {
        r->sent_bodyct = 1;
        ap_remove_output_filter(f);
        return ap_pass_brigade(f->next, b);
    }

    /*
     * Now that we are ready to send a response, we need to combine the two
     * header field tables into a single table.  If we don't do this, our
     * later attempts to set or unset a given fieldname might be bypassed.
     */
    if (!apr_is_empty_table(r->err_headers_out)) {
        r->headers_out = apr_table_overlay(r->pool, r->err_headers_out,
                                           r->headers_out);
    }

    /*
     * Remove the 'Vary' header field if the client can't handle it.
     * Since this will have nasty effects on HTTP/1.1 caches, force
     * the response into HTTP/1.0 mode.
     *
     * Note: the force-response-1.0 should come before the call to
     *       basic_http_header_check()
     */
    if (apr_table_get(r->subprocess_env, "force-no-vary") != NULL) {
        apr_table_unset(r->headers_out, "Vary");
        r->proto_num = HTTP_VERSION(1,0);
        apr_table_set(r->subprocess_env, "force-response-1.0", "1");
    }
    else {
        fixup_vary(r);
    }

    /*
     * Now remove any ETag response header field if earlier processing
     * says so (such as a 'FileETag None' directive).
     */
    if (apr_table_get(r->notes, "no-etag") != NULL) {
        apr_table_unset(r->headers_out, "ETag");
    }

    /* determine the protocol and whether we should use keepalives. */
    basic_http_header_check(r, &protocol);
    ap_set_keepalive(r);

    if (r->chunked) {
        apr_table_mergen(r->headers_out, "Transfer-Encoding", "chunked");
        apr_table_unset(r->headers_out, "Content-Length");
    }

    apr_table_setn(r->headers_out, "Content-Type", 
                   ap_make_content_type(r, r->content_type));

    if (r->content_encoding) {
        apr_table_setn(r->headers_out, "Content-Encoding",
                       r->content_encoding);
    }

    if (!apr_is_empty_array(r->content_languages)) {
        int i;
        char **languages = (char **)(r->content_languages->elts);
        for (i = 0; i < r->content_languages->nelts; ++i) {
            apr_table_mergen(r->headers_out, "Content-Language", languages[i]);
        }
    }

    /*
     * Control cachability for non-cachable responses if not already set by
     * some other part of the server configuration.
     */
    if (r->no_cache && !apr_table_get(r->headers_out, "Expires")) {
        char *date = apr_palloc(r->pool, APR_RFC822_DATE_LEN);
        ap_recent_rfc822_date(date, r->request_time);
        apr_table_addn(r->headers_out, "Expires", date);
    }

    /* This is a hack, but I can't find anyway around it.  The idea is that
     * 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",
                     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);
}

/* 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 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.
 *
 *    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 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.
 *    This step also sends a 100 Continue response to HTTP/1.1 clients,
 *    so should not be called until the module is *definitely* ready to
 *    read content. (otherwise, the point of the 100 response is defeated).
 *    Never call this function more than once.
 *
 * 3. Finally, call 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.
 */

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) {
        int conversion_error = 0;
        char *endstr;

        errno = 0;
        r->remaining = strtol(lenp, &endstr, 10); /* depend on ANSI */

        /* See comments in ap_http_filter() */
        if (errno || (endstr && *endstr) || (r->remaining < 0)) {
            conversion_error = 1; 
        }

        if (conversion_error) {
            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;
}

/**
 * Parse a chunk extension, detect overflow.
 * There are two error cases:
 *  1) If the conversion would require too many bits, a -1 is returned.
 *  2) If the conversion used the correct number of bits, but an overflow
 *     caused only the sign bit to flip, then that negative number is
 *     returned.
 * In general, any negative number can be considered an overflow error.
 */
static long get_chunk_size(char *b)
{
    long chunksize = 0;
    size_t chunkbits = sizeof(long) * 8;

    /* Skip leading zeros */
    while (*b == '0') {
        ++b;
    }

    while (apr_isxdigit(*b) && (chunkbits > 0)) {
        int xvalue = 0;

        if (*b >= '0' && *b <= '9') {
            xvalue = *b - '0';
        }
        else if (*b >= 'A' && *b <= 'F') {
            xvalue = *b - 'A' + 0xa;
        }
        else if (*b >= 'a' && *b <= 'f') {
            xvalue = *b - 'a' + 0xa;
        }

        chunksize = (chunksize << 4) | xvalue;
        chunkbits -= 4;
        ++b;
    }
    if (apr_isxdigit(*b) && (chunkbits <= 0)) {
        /* overflow */
        return -1;
    }

    return chunksize;
}

/* 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;
}

/* In HTTP/1.1, any method can have a body.  However, most GET handlers
 * wouldn't know what