upstream commit

Keep track of the last time we actually heard from the
client and use this to also schedule a client_alive_check().  Prevents
activity on a forwarded port from indefinitely preventing the select timeout
so that client_alive_check() will eventually (although not optimally) be
called.

Analysis by willchan at google com via bz#2756, feedback & ok djm@

Upstream-ID: c08721e0bbda55c6d18e2760f3fe1b17fb71169e

1 files changed, 15 insertions, 3 deletions

diff --git a/serverloop.c b/serverloop.c
index b5eb3440a..4b8d5ba68 100644
--- a/serverloop.c
+++ b/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.193 2017/05/31 07:00:13 markus Exp $ */
+/* $OpenBSD: serverloop.c,v 1.194 2017/08/11 03:58:36 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -204,6 +204,7 @@ wait_until_can_do_something(int connection_in, int connection_out,
         int ret;
         time_t minwait_secs = 0;
         int client_alive_scheduled = 0;
+        static time_t last_client_time;
 
         /* Allocate and update select() masks for channel descriptors. */
         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
@@ -268,8 +269,19 @@ wait_until_can_do_something(int connection_in, int connection_out,
                 memset(*writesetp, 0, *nallocp);
                 if (errno != EINTR)
                         error("select: %.100s", strerror(errno));
-        } else if (ret == 0 && client_alive_scheduled)
-                client_alive_check();
+        } else if (client_alive_scheduled) {
+                time_t now = monotime();
+
+                if (ret == 0) { /* timeout */
+                        client_alive_check();
+                } else if (FD_ISSET(connection_in, *readsetp)) {
+                        last_client_time = now;
+                } else if (last_client_time != 0 && last_client_time +
+                    options.client_alive_interval < now) {
+                        client_alive_check();
+                        last_client_time = now;
+                }
+        }
 
         notify_done(*readsetp);
 }