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 07cc9b76252e76e21f284e05ac2e0644f0bcd42b..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)))
@@ -155,7 +156,28 @@ return TRUE;
 static void
 tfo_out_check(int sock)
 {
-# if defined(TCP_INFO) && defined(EXIM_HAVE_TCPI_UNACKED)
+# ifdef __FreeBSD__
+struct tcp_info tinfo;
+int val;
+socklen_t len = sizeof(val);
+
+/* The observability as of 12.1 is not useful as a client, only telling us that
+a TFO option was used on SYN.  It could have been a TFO-R, or ignored by the
+server. */
+
+/*
+if (tcp_out_fastopen == TFO_ATTEMPTED_NODATA || tcp_out_fastopen == TFO_ATTEMPTED_DATA)
+  if (getsockopt(sock, IPPROTO_TCP, TCP_FASTOPEN, &val, &len) == 0 && val != 0) {}
+*/
+switch (tcp_out_fastopen)
+  {
+  case TFO_ATTEMPTED_NODATA:   tcp_out_fastopen = TFO_USED_NODATA; break;
+  case TFO_ATTEMPTED_DATA:     tcp_out_fastopen = TFO_USED_DATA; break;
+  default: break; /* compiler quietening */
+  }
+
+# else /* Linux & Apple */
+#  if defined(TCP_INFO) && defined(EXIM_HAVE_TCPI_UNACKED)
 struct tcp_info tinfo;
 socklen_t len = sizeof(tinfo);
 
@@ -205,7 +227,8 @@ switch (tcp_out_fastopen)
 
   default: break; /* compiler quietening */
   }
-# endif
+#  endif
+# endif        /* Linux & Apple */
 }
 #endif
 
@@ -478,7 +501,7 @@ else
     rc = n;
     }
   else
-
+    {
     rc = send(outblock->cctx->sock, outblock->buffer, n,
 #ifdef MSG_MORE
              more ? MSG_MORE : 0
@@ -486,6 +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)