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Posted to cvs@httpd.apache.org by jo...@apache.org on 2020/03/30 09:17:35 UTC
svn commit: r1875871 - /httpd/httpd/trunk/modules/ssl/ssl_engine_io.c
Author: jorton
Date: Mon Mar 30 09:17:35 2020
New Revision: 1875871
URL: http://svn.apache.org/viewvc?rev=1875871&view=rev
Log:
mod_ssl: Extend the coalescing filter to avoid sending HTTP response
headers in a separate TLS record to the response body in some cases.
* modules/ssl/ssl_engine_io.c:
Increase size of coalesce buffer to AP_IOBUFSIZE (8Kb).
(ssl_io_filter_coalesce): Try harder to fill the prefix which
gets coalesced, including a read&split of a morphing bucket type
Github: closes #106
Modified:
httpd/httpd/trunk/modules/ssl/ssl_engine_io.c
Modified: httpd/httpd/trunk/modules/ssl/ssl_engine_io.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/ssl/ssl_engine_io.c?rev=1875871&r1=1875870&r2=1875871&view=diff
==============================================================================
--- httpd/httpd/trunk/modules/ssl/ssl_engine_io.c (original)
+++ httpd/httpd/trunk/modules/ssl/ssl_engine_io.c Mon Mar 30 09:17:35 2020
@@ -1662,18 +1662,25 @@ static apr_status_t ssl_io_filter_input(
}
-/* ssl_io_filter_output() produces one SSL/TLS message per bucket
+/* ssl_io_filter_output() produces one SSL/TLS record per bucket
* passed down the output filter stack. This results in a high
- * overhead (network packets) for any output comprising many small
- * buckets. SSI page applied through the HTTP chunk filter, for
- * example, may produce many brigades containing small buckets -
- * [chunk-size CRLF] [chunk-data] [CRLF].
+ * overhead (more network packets & TLS processing) for any output
+ * comprising many small buckets. SSI output passed through the HTTP
+ * chunk filter, for example, may produce many brigades containing
+ * small buckets - [chunk-size CRLF] [chunk-data] [CRLF].
*
- * The coalescing filter merges many small buckets into larger buckets
- * where possible, allowing the SSL I/O output filter to handle them
- * more efficiently. */
+ * Sending HTTP response headers as a separate TLS record to the
+ * response body also reveals information to a network observer (the
+ * size of headers) which can be significant.
+ *
+ * The coalescing filter merges data buckets with the aim of producing
+ * fewer, larger TLS records - without copying/buffering all content
+ * and introducing unnecessary overhead.
+ *
+ * ### This buffering could be probably be done more comprehensively
+ * ### in ssl_io_filter_output itself. */
-#define COALESCE_BYTES (2048)
+#define COALESCE_BYTES (AP_IOBUFSIZE)
struct coalesce_ctx {
char buffer[COALESCE_BYTES];
@@ -1686,6 +1693,7 @@ static apr_status_t ssl_io_filter_coales
apr_bucket *e, *upto;
apr_size_t bytes = 0;
struct coalesce_ctx *ctx = f->ctx;
+ apr_size_t buffered = ctx ? ctx->bytes : 0; /* space used on entry */
unsigned count = 0;
/* The brigade consists of zero-or-more small data buckets which
@@ -1706,9 +1714,7 @@ static apr_status_t ssl_io_filter_coales
&& !APR_BUCKET_IS_METADATA(e)
&& e->length != (apr_size_t)-1
&& e->length < COALESCE_BYTES
- && (bytes + e->length) < COALESCE_BYTES
- && (ctx == NULL
- || bytes + ctx->bytes + e->length < COALESCE_BYTES);
+ && (buffered + bytes + e->length) < COALESCE_BYTES;
e = APR_BUCKET_NEXT(e)) {
/* don't count zero-length buckets */
if (e->length) {
@@ -1716,6 +1722,51 @@ static apr_status_t ssl_io_filter_coales
count++;
}
}
+
+ /* If there is room remaining and the next bucket is a data
+ * bucket, try to include it in the prefix to coalesce. For a
+ * typical [HEAP] [FILE] HTTP response brigade, this handles
+ * merging the headers and the start of the body into a single TLS
+ * record. */
+ if (bytes + buffered > 0
+ && bytes + buffered < COALESCE_BYTES
+ && e != APR_BRIGADE_SENTINEL(bb)
+ && !APR_BUCKET_IS_METADATA(e)) {
+ apr_status_t rv;
+
+ /* For an indeterminate length bucket (PIPE/CGI/...), try a
+ * non-blocking read to have it morph into a HEAP. If the
+ * read fails with EAGAIN, it is harmless to try a split
+ * anyway, split is ENOTIMPL for most PIPE-like buckets. */
+ if (e->length == (apr_size_t)-1) {
+ const char *discard;
+ apr_size_t ignore;
+
+ rv = apr_bucket_read(e, &discard, &ignore, APR_NONBLOCK_READ);
+ if (rv != APR_SUCCESS && !APR_STATUS_IS_EAGAIN(rv)) {
+ ap_log_cerror(APLOG_MARK, APLOG_ERR, rv, f->c, APLOGNO()
+ "coalesce failed to read from data bucket");
+ }
+ }
+
+ rv = apr_bucket_split(e, COALESCE_BYTES - (buffered + bytes));
+ if (rv == APR_SUCCESS) {
+ ap_log_cerror(APLOG_MARK, APLOG_TRACE4, 0, f->c,
+ "coalesce: adding %" APR_SIZE_T_FMT " bytes "
+ "from split bucket, adding %" APR_SIZE_T_FMT,
+ e->length, bytes + buffered);
+
+ count++;
+ bytes += e->length;
+ e = APR_BUCKET_NEXT(e);
+ }
+ else if (rv != APR_ENOTIMPL) {
+ ap_log_cerror(APLOG_MARK, APLOG_ERR, rv, f->c, APLOGNO()
+ "coalesce: failed to split data bucket");
+ return AP_FILTER_ERROR;
+ }
+ }
+
upto = e;
/* Coalesce the prefix, if: