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。

        vec_next->iov_base = CRLF;
        vec_next->iov_len = sizeof(CRLF) - 1;
        vec_next++;
        t_elt++;
    } while (t_elt < t_end);

#if APR_CHARSET_EBCDIC
    {
        apr_size_t len;
        char *tmp = apr_pstrcatv(r->pool, vec, vec_next - vec, &len);
        ap_xlate_proto_to_ascii(tmp, len);
        return apr_brigade_write(h->bb, NULL, NULL, tmp, len);
    }
#else
    return apr_brigade_writev(h->bb, NULL, NULL, vec, vec_next - vec);
#endif
}

/*
 * Determine the protocol to use for the response. Potentially downgrade
 * to HTTP/1.0 in some situations and/or turn off keepalives.
 *
 * also prepare r->status_line.
 */
static void basic_http_header_check(request_rec *r,
                                    const char **protocol)
{
    if (r->assbackwards) {
        /* no such thing as a response protocol */
        return;
    }

    if (!r->status_line) {
        r->status_line = status_lines[ap_index_of_response(r->status)];
    }

    /* Note that we must downgrade before checking for force responses. */
    if (r->proto_num > HTTP_VERSION(1,0)
        && apr_table_get(r->subprocess_env, "downgrade-1.0")) {
        r->proto_num = HTTP_VERSION(1,0);
    }

    /* kludge around broken browsers when indicated by force-response-1.0
     */
    if (r->proto_num == HTTP_VERSION(1,0)
        && apr_table_get(r->subprocess_env, "force-response-1.0")) {
        *protocol = "HTTP/1.0";
        r->connection->keepalive = AP_CONN_CLOSE;
    }
    else {
        *protocol = AP_SERVER_PROTOCOL;
    }

}

/* fill "bb" with a barebones/initial HTTP response header */
static void basic_http_header(request_rec *r, apr_bucket_brigade *bb,
                              const char *protocol)
{
    char *date;
    const char *server;
    header_struct h;
    struct iovec vec[4];

    if (r->assbackwards) {
        /* there are no headers to send */
        return;
    }

    /* Output the HTTP/1.x Status-Line and the Date and Server fields */

    vec[0].iov_base = (void *)protocol;
    vec[0].iov_len  = strlen(protocol);
    vec[1].iov_base = (void *)" ";
    vec[1].iov_len  = sizeof(" ") - 1;
    vec[2].iov_base = (void *)(r->status_line);
    vec[2].iov_len  = strlen(r->status_line);
    vec[3].iov_base = (void *)CRLF;
    vec[3].iov_len  = sizeof(CRLF) - 1;
#if APR_CHARSET_EBCDIC
    {
        char *tmp;
        apr_size_t len;
        tmp = apr_pstrcatv(r->pool, vec, 4, &len);
        ap_xlate_proto_to_ascii(tmp, len);
        apr_brigade_write(bb, NULL, NULL, tmp, len);
    }
#else
    apr_brigade_writev(bb, NULL, NULL, vec, 4);
#endif

    date = apr_palloc(r->pool, APR_RFC822_DATE_LEN);
    ap_recent_rfc822_date(date, r->request_time);

    h.pool = r->pool;
    h.bb = bb;
    form_header_field(&h, "Date", date);

    /* keep the set-by-proxy server header, otherwise
     * generate a new server header */
    if (r->proxyreq != PROXYREQ_NONE) {
        server = apr_table_get(r->headers_out, "Server");
        if (server) {
            form_header_field(&h, "Server", server);
        }
    }
    else {
        form_header_field(&h, "Server", ap_get_server_version());
    }

    /* unset so we don't send them again */
    apr_table_unset(r->headers_out, "Date");        /* Avoid bogosity */
    apr_table_unset(r->headers_out, "Server");
}

AP_DECLARE(void) ap_basic_http_header(request_rec *r, apr_bucket_brigade *bb)
{
    const char *protocol;

    basic_http_header_check(r, &protocol);
    basic_http_header(r, bb, protocol);
}

/* Navigator versions 2.x, 3.x and 4.0 betas up to and including 4.0b2
 * have a header parsing bug.  If the terminating \r\n occur starting
 * at offset 256, 257 or 258 of output then it will not properly parse
 * the headers.  Curiously it doesn't exhibit this problem at 512, 513.
 * We are guessing that this is because their initial read of a new request
 * uses a 256 byte buffer, and subsequent reads use a larger buffer.
 * So the problem might exist at different offsets as well.
 *
 * This should also work on keepalive connections assuming they use the
 * same small buffer for the first read of each new request.
 *
 * At any rate, we check the bytes written so far and, if we are about to
 * tickle the bug, we instead insert a bogus padding header.  Since the bug
 * manifests as a broken image in Navigator, users blame the server.  :(
 * It is more expensive to check the User-Agent than it is to just add the
 * bytes, so we haven't used the BrowserMatch feature here.
 */
static void terminate_header(apr_bucket_brigade *bb)
{
    char tmp[] = "X-Pad: avoid browser bug" CRLF;
    char crlf[] = CRLF;
    apr_off_t len;
    apr_size_t buflen;

    (void) apr_brigade_length(bb, 1, &len);

    if (len >= 255 && len <= 257) {
        buflen = strlen(tmp);
        ap_xlate_proto_to_ascii(tmp, buflen);
        apr_brigade_write(bb, NULL, NULL, tmp, buflen);
    }
    buflen = strlen(crlf);
    ap_xlate_proto_to_ascii(crlf, buflen);
    apr_brigade_write(bb, NULL, NULL, crlf, buflen);
}

/* Build the Allow field-value from the request handler method mask.
 * Note that we always allow TRACE, since it is handled below.
 */
static char *make_allow(request_rec *r)
{
    char *list;
    apr_int64_t mask;
    apr_array_header_t *allow = apr_array_make(r->pool, 10, sizeof(char *));
    apr_hash_index_t *hi = apr_hash_first(r->pool, methods_registry);

    mask = r->allowed_methods->method_mask;

    for (; hi; hi = apr_hash_next(hi)) {
        const void *key;
        void *val;

        apr_hash_this(hi, &key, NULL, &val);
        if ((mask & (AP_METHOD_BIT << *(int *)val)) != 0) {
            *(const char **)apr_array_push(allow) = key;

            /* the M_GET method actually refers to two methods */
            if (*(int *)val == M_GET)
                *(const char **)apr_array_push(allow) = "HEAD";
        }
    }

    /* TRACE is always allowed */
    *(const char **)apr_array_push(allow) = "TRACE";

    list = apr_array_pstrcat(r->pool, allow, ',');

    /* ### this is rather annoying. we should enforce registration of
       ### these methods */
    if ((mask & (AP_METHOD_BIT << M_INVALID))
        && (r->allowed_methods->method_list != NULL)
        && (r->allowed_methods->method_list->nelts != 0)) {
        int i;
        char **xmethod = (char **) r->allowed_methods->method_list->elts;

        /*
         * Append all of the elements of r->allowed_methods->method_list
         */
        for (i = 0; i < r->allowed_methods->method_list->nelts; ++i) {
            list = apr_pstrcat(r->pool, list, ",", xmethod[i], NULL);
        }
    }

    return list;
}

AP_DECLARE_NONSTD(int) ap_send_http_trace(request_rec *r)
{
    int rv;
    apr_bucket_brigade *b;
    header_struct h;

    if (r->method_number != M_TRACE) {
        return DECLINED;
    }

    /* Get the original request */
    while (r->prev) {
        r = r->prev;
    }

    if ((rv = ap_setup_client_block(r, REQUEST_NO_BODY))) {
        return rv;
    }

    ap_set_content_type(r, "message/http");

    /* Now we recreate the request, and echo it back */

    b = apr_brigade_create(r->pool, r->connection->bucket_alloc);
    apr_brigade_putstrs(b, NULL, NULL, r->the_request, CRLF, NULL);
    h.pool = r->pool;
    h.bb = b;
    apr_table_do((int (*) (void *, const char *, const char *))
                 form_header_field, (void *) &h, r->headers_in, NULL);
    apr_brigade_puts(b, NULL, NULL, CRLF);
    ap_pass_brigade(r->output_filters, b);

    return DONE;
}

AP_DECLARE(int) ap_send_http_options(request_rec *r)
{
    if (r->assbackwards) {
        return DECLINED;
    }

    apr_table_setn(r->headers_out, "Allow", make_allow(r));

    /* the request finalization will send an EOS, which will flush all
     * the headers out (including the Allow header)
     */

    return OK;
}

/* This routine is called by apr_table_do and merges all instances of
 * the passed field values into a single array that will be further
 * processed by some later routine.  Originally intended to help split
 * and recombine multiple Vary fields, though it is generic to any field
 * consisting of comma/space-separated tokens.
 */
static int uniq_field_values(void *d, const char *key, const char *val)
{
    apr_array_header_t *values;
    char *start;
    char *e;
    char **strpp;
    int  i;

    values = (apr_array_header_t *)d;

    e = apr_pstrdup(values->pool, val);

    do {
        /* Find a non-empty fieldname */

        while (*e == ',' || apr_isspace(*e)) {
            ++e;
        }
        if (*e == '\0') {
            break;
        }
        start = e;
        while (*e != '\0' && *e != ',' && !apr_isspace(*e)) {
            ++e;
        }
        if (*e != '\0') {
            *e++ = '\0';
        }

        /* Now add it to values if it isn't already represented.
         * Could be replaced by a ap_array_strcasecmp() if we had one.
         */
        for (i = 0, strpp = (char **) values->elts; i < values->nelts;
             ++i, ++strpp) {
            if (*strpp && strcasecmp(*strpp, start) == 0) {
                break;
            }
        }
        if (i == values->nelts) {  /* if not found */
            *(char **)apr_array_push(values) = start;
        }
    } while (*e != '\0');

    return 1;
}

/*
 * Since some clients choke violently on multiple Vary fields, or
 * Vary fields with duplicate tokens, combine any multiples and remove
 * any duplicates.
 */
static void fixup_vary(request_rec *r)
{
    apr_array_header_t *varies;

    varies = apr_array_make(r->pool, 5, sizeof(char *));

    /* Extract all Vary fields from the headers_out, separate each into
     * its comma-separated fieldname values, and then add them to varies
     * if not already present in the array.
     */
    apr_table_do((int (*)(void *, const char *, const char *))uniq_field_values,
                 (void *) varies, r->headers_out, "Vary", NULL);

    /* If we found any, replace old Vary fields with unique-ified value */

    if (varies->nelts > 0) {
        apr_table_setn(r->headers_out, "Vary",
                       apr_array_pstrcat(r->pool, varies, ','));
    }
}

AP_DECLARE(void) ap_set_content_type(request_rec *r, const char *ct)
{
    if (!ct) {
        r->content_type = NULL;
    }
    else if (!r->content_type || strcmp(r->content_type, ct)) {
        r->content_type = ct;

        /* Insert filters requested by the AddOutputFiltersByType 
         * configuration directive. Content-type filters must be 
         * inserted after the content handlers have run because 
         * only then, do we reliably know the content-type.
         */
        ap_add_output_filters_by_type(r);
    }
}

typedef struct header_filter_ctx {
    int headers_sent;
} header_filter_ctx;

AP_CORE_DECLARE_NONSTD(apr_status_t) ap_http_header_filter(ap_filter_t *f,
                                                           apr_bucket_brigade *b)
{
    request_rec *r = f->r;
    conn_rec *c = r->connection;
    const char *clheader;
    const char *protocol;
    apr_bucket *e;
    apr_bucket_brigade *b2;
    header_struct h;
    header_filter_ctx *ctx = f->ctx;

    AP_DEBUG_ASSERT(!r->main);

    if (r->header_only) {
        if (!ctx) {
            ctx = f->ctx = apr_pcalloc(r->pool, sizeof(header_filter_ctx));
        }
        else if (ctx->headers_sent) {
            apr_brigade_destroy(b);
            return OK;
        }
    }

    APR_BRIGADE_FOREACH(e, b) {
        if (e->type == &ap_bucket_type_error) {
            ap_bucket_error *eb = e->data;