SSL: reworked posted next events.

Introduced in 9d2ad2fb4423 available bytes handling in SSL relied
on connection read handler being overwritten to set the ready flag
and the amount of available bytes.  This approach is, however, does
not work properly when connection read handler is changed, for example,
when switching to a next pipelined request, and can result in unexpected
connection timeouts, see here:

http://mailman.nginx.org/pipermail/nginx-devel/2019-December/012825.html

Fix is to introduce ngx_event_process_posted_next() instead, which
will set ready and available regardless of how event handler is set.

src/event/ngx_event.c

@@ -238,8 +238,6 @@ ngx_process_events_and_timers(ngx_cycle_t *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;
     }
 
@@ -263,6 +261,7 @@ ngx_process_events_and_timers(ngx_cycle_t *cycle)
     }
 
     ngx_event_process_posted(cycle, &ngx_posted_events);
+    ngx_event_process_posted_next(cycle, &ngx_posted_next_events);
 }
 
 

src/event/ngx_event_openssl.c

@@ -43,7 +43,6 @@ static ssize_t ngx_ssl_recv_early(ngx_connection_t *c, u_char *buf,
 #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);
@@ -2018,11 +2017,6 @@ ngx_ssl_recv(ngx_connection_t *c, u_char *buf, size_t size)
                         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);
                     }
 
@@ -2328,31 +2322,6 @@ 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.

src/event/ngx_event_openssl.h

@@ -86,7 +86,6 @@ 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;
 

src/event/ngx_event_posted.c

@@ -34,3 +34,29 @@ ngx_event_process_posted(ngx_cycle_t *cycle, ngx_queue_t *posted)
         ev->handler(ev);
     }
 }
+
+
+void
+ngx_event_process_posted_next(ngx_cycle_t *cycle, ngx_queue_t *posted)
+{
+    ngx_queue_t  *q;
+    ngx_event_t  *ev;
+
+    while (!ngx_queue_empty(posted)) {
+
+        q = ngx_queue_head(posted);
+        ev = ngx_queue_data(q, ngx_event_t, queue);
+
+        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
+                      "posted next event %p", ev);
+
+        ngx_delete_posted_event(ev);
+
+        if (!ev->ready) {
+            ev->ready = 1;
+            ev->available = -1;
+        }
+
+        ev->handler(ev);
+    }
+}

src/event/ngx_event_posted.h

@@ -39,6 +39,7 @@
 
 
 void ngx_event_process_posted(ngx_cycle_t *cycle, ngx_queue_t *posted);
+void ngx_event_process_posted_next(ngx_cycle_t *cycle, ngx_queue_t *posted);
 
 
 extern ngx_queue_t  ngx_posted_accept_events;