Reimplement content length filter to fix problem where all output from (8166cfbe) · Commits · CYBER - Cyber Security / TS 103 523 MSP / TLMSP / TLMSP Apache Httpd

CHANGES

+6 −0

Original line number	Diff line number	Diff line
		Changes with Apache 2.0.20-dev
		*) Fix problem in content-length filter where the filter would
		buffer all the output from a CGI before sending any bytes
		down the filter stack to the network. This problem would cause
		significant memory consumption if the CGIs generated
		lots of bytes. [Bill Stoddard]

		*) Get non-blocking CGI pipe reads working with the bucket brigades.
		[Bill Stoddard]

server/protocol.c

+98 −58

Original line number	Diff line number	Diff line
		@@ -853,40 +853,83 @@ AP_CORE_DECLARE_NONSTD(apr_status_t) ap_content_length_filter(ap_filter_t *f,
		struct content_length_ctx *ctx;
		apr_status_t rv;
		apr_bucket *e;
		int send_it = 0;
		int eos = 0, flush = 0, partial_send_okay = 0;
		apr_bucket_brigade more, split;
		apr_read_type_e eblock = APR_NONBLOCK_READ;

		ctx = f->ctx;
		if (!ctx) { /* first time through */
		f->ctx = ctx = apr_pcalloc(r->pool, sizeof(struct content_length_ctx));
		ctx->compute_len = 1; /* Assume we will compute the length */
		}

		/* Humm, is this check the best it can be?
		* - protocol >= HTTP/1.1 implies support for chunking
		* - non-keepalive implies the end of byte stream will be signaled
		* by a connection close
		* In both cases, we can send bytes to the client w/o needing to
		* compute content-length.
		* Todo:
		* We should be able to force connection close from this filter
		* when we see we are buffering too much.
		*/
		if ((r->proto_num >= HTTP_VERSION(1,1)) \|\|
		(!f->r->connection->keepalive)) {
		partial_send_okay = 1;
		}

		more = b;
		while (more) {
		b = more;
		more = NULL;
		split = NULL;
		flush = 0;

		APR_BRIGADE_FOREACH(e, b) {
		const char *ignored;
		apr_size_t len;

		if (APR_BUCKET_IS_EOS(e) \|\| APR_BUCKET_IS_FLUSH(e)) {
		send_it = 1;
		/* If we've accumulated more than 4xAP_MIN_BYTES_TO_WRITE and
		* the client supports chunked encoding, send what we have
		* and come back for more.
		*/
		if ((ctx->curr_len > 4*AP_MIN_BYTES_TO_WRITE) && partial_send_okay) {
		split = b;
		more = apr_brigade_split(b, e);
		break;
		}
		len = 0;
		if (APR_BUCKET_IS_EOS(e)) {
		eos = 1;
		}
		else if (APR_BUCKET_IS_FLUSH(e)) {
		if (partial_send_okay) {
		split = b;
		more = apr_brigade_split(b, e);
		/* Remove the flush bucket from brigade 'more' */
		APR_BUCKET_REMOVE(e);
		flush = 1;
		break;
		}
		}
		if (e->length == -1) { /* if length unknown */
		rv = apr_bucket_read(e, &ignored, &len, APR_NONBLOCK_READ);
		if (rv == APR_EAGAIN) {
		/* If the protocol level implies support for chunked encoding,
		* flush the filter chain to the network then do a blocking
		* read. This is replicating the behaviour of ap_send_fb
		* in Apache 1.3.
		rv = apr_bucket_read(e, &ignored, &len, eblock);
		if (rv == APR_SUCCESS) {
		/* Attempt a nonblocking read next time through */
		eblock = APR_NONBLOCK_READ;
		}
		else if (rv == APR_EAGAIN) {
		/* Make the next read blocking. If the client supports chunked
		* encoding, flush the filter stack to the network.
		*/
		if (r->proto_num >= HTTP_VERSION(1,1)) {
		apr_bucket_brigade *split;
		split = apr_brigade_split(b, e);
		rv = ap_fflush(f, b);
		if (rv != APR_SUCCESS)
		return rv;
		b = split;
		ctx->curr_len = 0;
		eblock = APR_BLOCK_READ;
		if (partial_send_okay) {
		split = b;
		more = apr_brigade_split(b, e);
		flush = 1;
		break;
		}
		rv = apr_bucket_read(e, &ignored, &len, APR_BLOCK_READ);
		}
		if (rv != APR_SUCCESS) {
		else {
		ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, "ap_content_length_filter: "
		"apr_bucket_read() failed");
		return rv;
		@@ -899,39 +942,36 @@ AP_CORE_DECLARE_NONSTD(apr_status_t) ap_content_length_filter(ap_filter_t *f,
		r->bytes_sent += len;
		}

		if ((ctx->curr_len < AP_MIN_BYTES_TO_WRITE) && !send_it) {
		return ap_save_brigade(f, &ctx->saved, &b, (r->main) ? r->main->pool : r->pool);
		if (split) {
		ctx->compute_len = 0; /* Ooops, can't compute the length now */
		ctx->curr_len = 0;
		if (ctx->saved) {
		APR_BRIGADE_CONCAT(ctx->saved, split);
		apr_brigade_destroy(split);
		split = ctx->saved;
		ctx->saved = NULL;
		}

		/* We will compute a content length if:
		* The protocol is < 1.1
		* and We can not chunk
		* and this is a keepalive request.
		* or We already have all the data
		* This is a bit confusing, because we will always buffer up
		* to AP_MIN_BYTES_TO_WRITE, so if we get all the data while
		* we are buffering that much data, we set the c-l.
		*/
		if ((r->proto_num < HTTP_VERSION(1,1)
		&& (!ap_find_last_token(f->r->pool,
		apr_table_get(r->headers_out,
		"Transfer-Encoding"),
		"chunked")
		&& (f->r->connection->keepalive)))
		\|\| (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(b)))) {
		ctx->compute_len = 1;
		if (flush) {
		rv = ap_fflush(f->next, split);
		}
		else {
		ctx->compute_len = 0;
		rv = ap_pass_brigade(f->next, split);
		}
		if (rv != APR_SUCCESS)
		return rv;
		}
		}

		if ((ctx->curr_len < AP_MIN_BYTES_TO_WRITE) && !eos) {
		return ap_save_brigade(f, &ctx->saved, &b, (r->main) ? r->main->pool : r->pool);
		}

		if (ctx->compute_len) {
		/* save the brigade; we can't pass any data to the next
		* filter until we have the entire content length
		*/
		if (!send_it) {
		ap_save_brigade(f, &ctx->saved, &b, r->pool);
		return APR_SUCCESS;
		if (!eos) {
		return ap_save_brigade(f, &ctx->saved, &b, r->pool);
		}
		ap_set_content_length(r, r->bytes_sent);
		}

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