[pve-devel] [PATCH manager] status/metrics: make MTU configurable

[Fabian Grünbichler]

since some users don't even have a full 1500 (and some systems might
have links with bigger MTU and not require as much fragmentation).

Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
---
As reported in
https://forum.proxmox.com/threads/error-message-too-long-in-external-metric.64642/

tested by configuring various values and looking at tcpdump output

 PVE/Status/Graphite.pm |  1 +
 PVE/Status/InfluxDB.pm |  1 +
 PVE/Status/Plugin.pm   | 13 ++++++++++++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/PVE/Status/Graphite.pm b/PVE/Status/Graphite.pm
index 41839a43..1b196c24 100644
--- a/PVE/Status/Graphite.pm
+++ b/PVE/Status/Graphite.pm
@@ -50,6 +50,7 @@ sub options {
     return {
 	server => {},
 	port => { optional => 1 },
+	mtu => { optional => 1 },
 	proto => { optional => 1 },
 	timeout => { optional => 1 },
 	path => { optional => 1 },
diff --git a/PVE/Status/InfluxDB.pm b/PVE/Status/InfluxDB.pm
index c7bc15a9..589a4936 100644
--- a/PVE/Status/InfluxDB.pm
+++ b/PVE/Status/InfluxDB.pm
@@ -28,6 +28,7 @@ sub options {
     return {
 	server => {},
 	port => {},
+	mtu => { optional => 1 },
 	disable => { optional => 1 },
    };
 }
diff --git a/PVE/Status/Plugin.pm b/PVE/Status/Plugin.pm
index d6fba529..7b27d8fc 100644
--- a/PVE/Status/Plugin.pm
+++ b/PVE/Status/Plugin.pm
@@ -33,6 +33,14 @@ my $defaultData = {
 	    type => 'integer',
 	    description => "server network port",
 	},
+	mtu => {
+	    type => 'integer',
+	    description => "MTU for metrics transmission over UDP",
+	    default => 1500,
+	    min => 512,
+	    maximum => 64*1024,
+	    optional => 1,
+	},
     },
 };
 
@@ -69,7 +77,10 @@ sub _disconnect {
 # UDP cannot do more than 64k at once. Overwrite for different protocol limits.
 sub _send_batch_size {
     my ($class, $cfg) = @_;
-    return 1450; # assume 1500 MTU, empty IPv6 UDP packet needs 48 bytes overhead
+
+    # default to 1500 MTU, empty IPv6 UDP packet needs 48 bytes overhead 
+    my $mtu = $cfg->{mtu} // 1500;
+    return $mtu - 50;
 }
 
 # call with the smalles $data chunks possible
-- 
2.20.1