with BSD 'route', save-and-restore IPv6 default routes

This should be a safer way to implement the desired behavior on *BSDs which do not
have a concept of routing metric. See discussion threads:

- https://gitlab.com/openconnect/vpnc-scripts/-/merge_requests/12#note_453784389
- https://gitlab.com/openconnect/vpnc-scripts/-/merge_requests/12#note_344089196

Signed-off-by: Daniel Lenski <dlenski@gmail.com>

diff --git a/vpnc-script b/vpnc-script
index 191bc00d4d39e5e9cd494980e145afdeccf59c82..b11cf73081640307cdc7217f2025d81190e70f16 100755 (executable)
--- a/vpnc-script
+++ b/vpnc-script
@@ -80,6 +80,7 @@ OS="`uname -s`"
 
 HOOKS_DIR=/etc/vpnc
 DEFAULT_ROUTE_FILE=/var/run/vpnc/defaultroute
+DEFAULT_ROUTE_FILE_IPV6=/var/run/vpnc/defaultroute_ipv6
 RESOLV_CONF_BACKUP=/var/run/vpnc/resolv.conf-backup
 SCRIPTNAME=`basename $0`
 
@@ -102,6 +103,7 @@ if [ "$OS" = "Linux" ]; then
        route_syntax_del="del"
        route_syntax_netmask="netmask"
        ifconfig_syntax_del="del"
+       netstat_syntax_ipv6="-6"
 else
        # iproute2 is Linux only; if `which ip` returns something on another OS, it's likely an unrelated tool
        # (see https://github.com/dlenski/openconnect/issues/132#issuecomment-470475009)
@@ -111,6 +113,7 @@ else
        route_syntax_del="delete"
        route_syntax_netmask="-netmask"
        ifconfig_syntax_del="delete"
+       netstat_syntax_ipv6="-f inet6"
 fi
 if [ "$OS" = "SunOS" ]; then
        route_syntax_interface="-interface"
@@ -471,12 +474,15 @@ else # use route command
        get_ipv6_default_gw() {
                # isn't -n supposed to give --numeric output?
                # apperently not...
-               netstat -r -n -f inet6 | awk '/^(default|::\/0)/ { print $2"%"$NF; }'
+               # FIXME: is there a better way to exclude loopback routes than filtering interface /^lo/?
+               netstat -r -n $netstat_syntax_ipv6 | awk '/^(default|::\/0)/ { if ($NF!~/^lo/) { print ($2~/^fe[89ab]/ ? $2"%"$NF : $2); } }'
        }
 
        set_ipv6_default_route() {
-               route add -inet6 ::/1 "$INTERNAL_IP6_ADDRESS" $route_syntax_interface
-               route add -inet6 8000::/1 "$INTERNAL_IP6_ADDRESS" $route_syntax_interface
+               DEFAULTGW="`get_ipv6_default_gw`"
+               echo "$DEFAULTGW" > "$DEFAULT_ROUTE_FILE_IPV6"
+               route $route_syntax_del -inet6 default $route_syntax_gw "$DEFAULTGW"
+               route add -inet6 default $route_syntax_gw "$INTERNAL_IP6_ADDRESS" $route_syntax_interface
        }
 
        set_ipv6_network_route() {
@@ -503,8 +509,11 @@ else # use route command
        }
 
        reset_ipv6_default_route() {
-               route $route_syntax_del -inet6 ::/1 "$INTERNAL_IP6_ADDRESS"
-               route $route_syntax_del -inet6 8000::/1 "$INTERNAL_IP6_ADDRESS"
+               if [ -s "$DEFAULT_ROUTE_FILE_IPV6" ]; then
+                       route $route_syntax_del -inet6 default $route_syntax_gw "`get_ipv6_default_gw`" $route_syntax_interface
+                       route add -inet6 default $route_syntax_gw `cat "$DEFAULT_ROUTE_FILE_IPV6"`
+                       rm -f -- "$DEFAULT_ROUTE_FILE_IPV6"
+               fi
                :
        }