From: Mike Brady <mikebrady@eircom.net>
Date: Wed, 14 Nov 2018 12:25:56 +0000 (+0000)
Subject: Check timer values a bit more carefully and ignore crazy values.
X-Git-Tag: 3.3RC0~177
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29a37f44b9fbdfd2e8ba26c5cee1e02ddb292649;p=thirdparty%2Fshairport-sync.git

Check timer values a bit more carefully and ignore crazy values.
---

diff --git a/rtp.c b/rtp.c
index 35b2a2bc..4d13199c 100644
--- a/rtp.c
+++ b/rtp.c
@@ -621,9 +621,14 @@ void *rtp_timing_receiver(void *arg) {
 
             distant_transmit_time = (uint64_t)nctohl(&packet[24]) << 32;
             distant_transmit_time += nctohl(&packet[28]);
-
-            uint64_t remote_processing_time = distant_transmit_time - distant_receive_time;
-
+            
+            uint64_t remote_processing_time = 0;
+            
+            if (distant_transmit_time >= distant_receive_time)
+            	remote_processing_time = distant_transmit_time - distant_receive_time;
+            else {
+            	debug(1, "Yikes: distant_transmit_time is before distant_receive_time; remote processing time set to zero.");
+            }
             // debug(1,"Return trip time: %" PRIu64 " uS, remote processing time: %" PRIu64 "
             // uS.",(return_time*1000000)>>32,(remote_processing_time*1000000)>>32);
 
@@ -632,10 +637,10 @@ void *rtp_timing_receiver(void *arg) {
             // remove the remote processing time from the record of the return time, as long at the
             // processing time looks sensible.
 
-            if ((remote_processing_time > 0) && (remote_processing_time < return_time))
+            if (remote_processing_time < return_time)
               return_time -= remote_processing_time;
             else
-              debug(1, "Non-sensical remote processing time -- ignored.");
+              debug(1, "Remote processing time greater than return time -- ignored.");
 
             int cc;
             for (cc = time_ping_history - 1; cc > 0; cc--) {