From 00825afd79a45977698e25f31db65fc60d96628f Mon Sep 17 00:00:00 2001
From: zsdc <taras@vyos.io>
Date: Mon, 4 May 2020 16:24:57 +0300
Subject: VTI: T1291: Fix for invlid VTI interface down state

In case when between hosts exists two IPSec tunnels for VTI (for example, when both sides act as connection initiators), the older unused/replaced tunnel may switch VTI interface to the "down" state even if a newer IPSec connection is still in-use. Depending on other IPSec settings, this leads to a situation when VTI interfaces continuously flapping or stuck in a "down" state.
This fix is an adaptation of PR from @m-asama for the current code base. It adding new dependency from actual SA state of IPSec connection, and do not allow to switch down a VTI interface if at least one of child connections is active or try to change the state of a VTI interface to the same, as already active.
---
 scripts/vti-up-down          |  7 +++----
 scripts/vyatta-vti-config.pl | 22 ++++++++++++++++++----
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/scripts/vti-up-down b/scripts/vti-up-down
index 08e31c0..4672076 100755
--- a/scripts/vti-up-down
+++ b/scripts/vti-up-down
@@ -5,15 +5,14 @@
 source /etc/default/vyatta
 source /etc/default/locale
 case "$PLUTO_VERB" in
-route-client | up-client | up-host)
+up-client | up-host)
 /bin/ip route delete default table 220
-/opt/vyatta/sbin/vyatta-vti-config.pl --updown --intf=$1 --action=up
+/opt/vyatta/sbin/vyatta-vti-config.pl --updown --intf=$1 --conn=$PLUTO_CONNECTION --action=up > /dev/null 2>&1 &
     ;;
 down-client | down-host)
-/opt/vyatta/sbin/vyatta-vti-config.pl --updown --intf=$1 --action=down 
+/opt/vyatta/sbin/vyatta-vti-config.pl --updown --intf=$1 --conn=$PLUTO_CONNECTION --action=down > /dev/null 2>&1 &
     ;;
 *)
     ;;
 esac
 exit 0
-
diff --git a/scripts/vyatta-vti-config.pl b/scripts/vyatta-vti-config.pl
index 0886202..0318b22 100755
--- a/scripts/vyatta-vti-config.pl
+++ b/scripts/vyatta-vti-config.pl
@@ -45,29 +45,35 @@ my $gencmds = "";
 my $result = 0;
 my $updown="";
 my $intfName="";
+my $conn_name="";
 my $action="";
 my $checkref="";
 
 GetOptions(
     "updown" => \$updown,
     "intf=s"   => \$intfName,
+    "conn=s"   => \$conn_name,
     "action=s" => \$action,
     "checkref" => \$checkref,
 );
 
 #
-# --updown intfName --action=[up|down]
+# --updown --intf=vtiX --conn=peer-X.X.X.X-tunnel-vti --action=[up|down]
 #
 if ($updown ne '') {
     if (!(defined $intfName) || $intfName eq '') {
         # invalid
         exit -1;
     }
+    if (!(defined $conn_name) || $conn_name eq '' || $conn_name !~ m/^peer-[a-zA-Z0-9_.:-]+-tunnel-vti$/) {
+        # invalid
+        exit -1;
+    }
     if (!(defined $action) || $action eq '') {
         # invalid
         exit -1;
     }
-    vti_handle_updown($intfName, $action);
+    vti_handle_updown($intfName, $conn_name, $action);
     exit 0;
 }
 
@@ -230,7 +236,7 @@ exit $result;
 # Handle VTI tunnel state based on input from strongswan and configuration.
 #
 sub vti_handle_updown {
-    my ($intfName, $action) = @_;
+    my ($intfName, $conn_name, $action) = @_;
     my $vcIntf = new Vyatta::Config();
     $vcIntf->setLevel('interfaces');
     my $disabled = $vcIntf->existsOrig("vti $intfName disabled");
@@ -254,7 +260,15 @@ sub vti_handle_updown {
                     }
                 }
             }
-            system("sudo /sbin/ip link set $intfName $action\n");
+            # check if child SA is in ISTALLED state (connection already fully established)
+            # we are inverting exit code to convert 0 value to True in Perl
+            my $child_sa_installed = !system("sudo swanctl -l -r -i $conn_name | grep -s -q state=INSTALLED");
+            # change interface state only if one of these is true:
+            # - VTI interface is in UP state, no active child SA was found, and event is down-client or down-host
+            # - VTI interface is in DOWN state, active child SA was found, and event is up-client or up-host
+            if (($state && !$child_sa_installed && ($action eq "down")) || (!$state && $child_sa_installed && ($action eq "up"))) {
+                system("sudo /sbin/ip link set $intfName $action\n");
+            }
         }
     }
 }
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