Performance: workaround Linux kernel bug

[exim.git] / src / src / smtp_out.c

diff --git a/src/src/smtp_out.c b/src/src/smtp_out.c
index 96ee152826ef504cbbf529cd35b3ae45afe1f388..86c3e412775cc53d3feed2f5112864257af69d13 100644 (file)
--- a/src/src/smtp_out.c
+++ b/src/src/smtp_out.c
@@ -3,6 +3,7 @@
 *************************************************/
 
 /* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* A number of functions for driving outgoing SMTP calls. */
@@ -63,8 +64,8 @@ if (is_tainted(expint))
   return FALSE;
   }
 
-while (isspace(*expint)) expint++;
-if (*expint == 0) return TRUE;
+Uskip_whitespace(&expint);
+if (!*expint) return TRUE;
 
 while ((iface = string_nextinlist(&expint, &sep, big_buffer,
           big_buffer_size)))
@@ -500,7 +501,7 @@ else
     rc = n;
     }
   else
-
+    {
     rc = send(outblock->cctx->sock, outblock->buffer, n,
 #ifdef MSG_MORE
              more ? MSG_MORE : 0
@@ -508,6 +509,17 @@ else
              0
 #endif
             );
+
+#if defined(__linux__)
+    /* This is a workaround for a current linux kernel bug: as of
+    5.6.8-200.fc31.x86_64  small (<MSS) writes get delayed by about 200ms,
+    This is despite NODELAY being active.
+    https://bugzilla.redhat.com/show_bug.cgi?id=1803806 */
+
+    if (!more)
+      setsockopt(outblock->cctx->sock, IPPROTO_TCP, TCP_CORK, &off, sizeof(off));
+#endif
+    }
   }
 
 if (rc <= 0)