details: https://hg.nginx.org/nginx/rev/9d2ad2fb4423
branches:
changeset: 7584:9d2ad2fb4423
user: Maxim Dounin <mdounin@mdounin.ru>
date: Thu Oct 17 16:02:24 2019 +0300
description:
SSL: available bytes handling (ticket #1431).

Added code to track number of bytes available in the socket.
This makes it possible to avoid looping for a long time while
working with fast enough peer when data are added to the socket buffer
faster than we are able to read and process data.

When kernel does not provide number of bytes available, it is
retrieved using ioctl(FIONREAD) as long as a buffer is filled by
SSL_read().

It is assumed that number of bytes returned by SSL_read() is close
to the number of bytes read from the socket, as we do not use
SSL compression. But even if it is not true for some reason, this
is not important, as we post an additional reading event anyway.

Note that data can be buffered at SSL layer, and it is not possible
to simply stop reading at some point and wait till the event will
be reported by the kernel again. This can be only done when there
are no data in SSL buffers, and there is no good way to find out if
it's the case.

Instead of trying to figure out if SSL buffers are empty, this patch
introduces events posted for the next event loop iteration - such
events will be processed only on the next event loop iteration,
after going into the kernel and retrieving additional events. This
seems to be simple and reliable approach.

diffstat:

src/event/ngx_event.c | 7 ++++
src/event/ngx_event_openssl.c | 68 +++++++++++++++++++++++++++++++++++++++++++
src/event/ngx_event_openssl.h | 1 +
src/event/ngx_event_posted.c | 1 +
src/event/ngx_event_posted.h | 1 +
5 files changed, 78 insertions(+), 0 deletions(-)

diffs (149 lines):

diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -237,6 +237,12 @@ ngx_process_events_and_timers(ngx_cycle_
}
}

+ if (!ngx_queue_empty(&ngx_posted_next_events)) {
+ ngx_queue_add(&ngx_posted_events, &ngx_posted_next_events);
+ ngx_queue_init(&ngx_posted_next_events);
+ timer = 0;
+ }
+
delta = ngx_current_msec;

(void) ngx_process_events(cycle, timer, flags);
@@ -639,6 +645,7 @@ ngx_event_process_init(ngx_cycle_t *cycl
#endif

ngx_queue_init(&ngx_posted_accept_events);
+ ngx_queue_init(&ngx_posted_next_events);
ngx_queue_init(&ngx_posted_events);

if (ngx_event_timer_init(cycle->log) == NGX_ERROR) {
diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -43,6 +43,7 @@ static ssize_t ngx_ssl_recv_early(ngx_co
#endif
static ngx_int_t ngx_ssl_handle_recv(ngx_connection_t *c, int n);
static void ngx_ssl_write_handler(ngx_event_t *wev);
+static void ngx_ssl_next_read_handler(ngx_event_t *rev);
#ifdef SSL_READ_EARLY_DATA_SUCCESS
static ssize_t ngx_ssl_write_early(ngx_connection_t *c, u_char *data,
size_t size);
@@ -2003,6 +2004,48 @@ ngx_ssl_recv(ngx_connection_t *c, u_char

if (size == 0) {
c->read->ready = 1;
+
+ if (c->read->available >= 0) {
+ c->read->available -= bytes;
+
+ /*
+ * there can be data buffered at SSL layer,
+ * so we post an event to continue reading on the next
+ * iteration of the event loop
+ */
+
+ if (c->read->available < 0) {
+ c->read->available = 0;
+ c->read->ready = 0;
+
+ if (c->ssl->next_read_handler == NULL) {
+ c->ssl->next_read_handler = c->read->handler;
+ c->read->handler = ngx_ssl_next_read_handler;
+ }
+
+ ngx_post_event(c->read, &ngx_posted_next_events);
+ }
+
+ ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+ "SSL_read: avail:%d", c->read->available);
+
+ } else {
+
+#if (NGX_HAVE_FIONREAD)
+
+ if (ngx_socket_nread(c->fd, &c->read->available) == -1) {
+ c->read->error = 1;
+ ngx_connection_error(c, ngx_socket_errno,
+ ngx_socket_nread_n " failed");
+ return NGX_ERROR;
+ }
+
+ ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+ "SSL_read: avail:%d", c->read->available);
+
+#endif
+ }
+
return bytes;
}

@@ -2285,6 +2328,31 @@ ngx_ssl_write_handler(ngx_event_t *wev)
}


+static void
+ngx_ssl_next_read_handler(ngx_event_t *rev)
+{
+ ngx_connection_t *c;
+
+ c = rev->data;
+
+ ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0, "SSL next read handler");
+
+ rev->handler = c->ssl->next_read_handler;
+ c->ssl->next_read_handler = NULL;
+
+ if (!rev->ready) {
+ rev->ready = 1;
+ rev->available = -1;
+ }
+
+ if (rev->posted) {
+ ngx_delete_posted_event(rev);
+ }
+
+ rev->handler(rev);
+}
+
+
/*
* OpenSSL has no SSL_writev() so we copy several bufs into our 16K buffer
* before the SSL_write() call to decrease a SSL overhead.
diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -86,6 +86,7 @@ struct ngx_ssl_connection_s {

ngx_event_handler_pt saved_read_handler;
ngx_event_handler_pt saved_write_handler;
+ ngx_event_handler_pt next_read_handler;

u_char early_buf;

diff --git a/src/event/ngx_event_posted.c b/src/event/ngx_event_posted.c
--- a/src/event/ngx_event_posted.c
+++ b/src/event/ngx_event_posted.c
@@ -11,6 +11,7 @@


ngx_queue_t ngx_posted_accept_events;
+ngx_queue_t ngx_posted_next_events;
ngx_queue_t ngx_posted_events;


diff --git a/src/event/ngx_event_posted.h b/src/event/ngx_event_posted.h
--- a/src/event/ngx_event_posted.h
+++ b/src/event/ngx_event_posted.h
@@ -42,6 +42,7 @@ void ngx_event_process_posted(ngx_cycle_


extern ngx_queue_t ngx_posted_accept_events;
+extern ngx_queue_t ngx_posted_next_events;
extern ngx_queue_t ngx_posted_events;


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