# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1619036699 -10800
# Node ID 2851e4c7de030d4f7efc9fe4f7a3e1107c0d1a43
# Parent  c40f7a65c506649b3ac1a46c61a302aca390c43f
Mail: fixed reading with fully filled buffer (ticket #2159).

With SMTP pipelining, ngx_mail_read_command() can be called with s->buffer
without any space available, to parse additional commands received to the
buffer on previous calls.  Previously, this resulted in recv() being called
with zero length, resulting in zero being returned, which was interpreted
as a connection close by the client, so nginx silently closed connection.

Fix is to avoid calling c->recv() if there is no free space in the buffer,
but continue parsing of the already received commands.

diff --git a/src/mail/ngx_mail_handler.c b/src/mail/ngx_mail_handler.c
--- a/src/mail/ngx_mail_handler.c
+++ b/src/mail/ngx_mail_handler.c
@@ -833,20 +833,23 @@ ngx_mail_read_command(ngx_mail_session_t
     ngx_str_t                  l;
     ngx_mail_core_srv_conf_t  *cscf;
 
-    n = c->recv(c, s->buffer->last, s->buffer->end - s->buffer->last);
+    if (s->buffer->last < s->buffer->end) {
+
+        n = c->recv(c, s->buffer->last, s->buffer->end - s->buffer->last);
 
-    if (n == NGX_ERROR || n == 0) {
-        ngx_mail_close_connection(c);
-        return NGX_ERROR;
-    }
+        if (n == NGX_ERROR || n == 0) {
+            ngx_mail_close_connection(c);
+            return NGX_ERROR;
+        }
 
-    if (n > 0) {
-        s->buffer->last += n;
-    }
+        if (n > 0) {
+            s->buffer->last += n;
+        }
 
-    if (n == NGX_AGAIN) {
-        if (s->buffer->pos == s->buffer->last) {
-            return NGX_AGAIN;
+        if (n == NGX_AGAIN) {
+            if (s->buffer->pos == s->buffer->last) {
+                return NGX_AGAIN;
+            }
         }
     }