Respect the new behavior of TCP_DEFER_ACCEPT.

In Linux 2.6.32, TCP_DEFER_ACCEPT was changed to accept connections
after the deferring period is finished without any data available.
(Reading from the socket returns EAGAIN in this case.)

Since in nginx TCP_DEFER_ACCEPT is set to "post_accept_timeout", we
do not need to wait longer if deferred accept returns with no data.
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 68cb345..ea05305 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -416,6 +416,20 @@
 
     if (n == NGX_AGAIN) {
 
+#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)
+        if (c->listening->deferred_accept
+#if (NGX_HTTP_SSL)
+            && c->ssl == NULL
+#endif
+            )
+        {
+            ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                          "client timed out in deferred accept");
+            ngx_http_close_connection(c);
+            return;
+        }
+#endif
+
         if (!rev->timer_set) {
             ngx_add_timer(rev, c->listening->post_accept_timeout);
         }
@@ -617,6 +631,15 @@
     if (n == -1) {
         if (err == NGX_EAGAIN) {
 
+#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)
+            if (c->listening->deferred_accept) {
+                ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                              "client timed out in deferred accept");
+                ngx_http_close_connection(c);
+                return;
+            }
+#endif
+
             if (!rev->timer_set) {
                 ngx_add_timer(rev, c->listening->post_accept_timeout);
             }