Lingering close changed to handle NGX_AGAIN. The "do { c->recv() } while (c->read->ready)" form used in the ngx_http_lingering_close_handler() is not really correct, as for example with SSL c->read->ready may be still set when returning NGX_AGAIN due to SSL_ERROR_WANT_WRITE. Therefore the above might be an infinite loop. This doesn't really matter in lingering close, as we shutdown write side of the socket anyway and also disable renegotiation (and even without shutdown and with renegotiation it requires using very large certificate chain and tuning socket buffers to trigger SSL_ERROR_WANT_WRITE). But for the sake of correctness added an NGX_AGAIN check.

--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -3311,6 +3311,10 @@ ngx_http_lingering_close_handler(ngx_eve
 
         ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0, "lingering read: %z", n);
 
+        if (n == NGX_AGAIN) {
+            break;
+        }
+
         if (n == NGX_ERROR || n == 0) {
             ngx_http_close_request(r, 0);
             return;