[pve-devel] [PATCH pve-common 1/2] network: add support for disabling bridge learning on tap|veth|fwln ports

[Alexandre Derumier]

Currently, if bridge receive an unknown dest mac (network bug/attack/..),
we are flooding packets to all bridge ports.

This can waste cpu time, even more with firewall enabled.
Also, if firewall is used with reject action, the src mac of RST
packet is the original unknown dest mac.
(This can block the server at Hetzner for example)

So, we can disable learning && unicast_flood on tap|veth|fwln port interface.
Then mac address need to be add statically in bridge fdb.

Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 src/PVE/Network.pm | 60 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 6 deletions(-)

diff --git a/src/PVE/Network.pm b/src/PVE/Network.pm
index 15838a0..2d99af0 100644
--- a/src/PVE/Network.pm
+++ b/src/PVE/Network.pm
@@ -207,6 +207,14 @@ sub disable_ipv6 {
     close($fh);
 }
 
+my $bridge_disable_interface_learning = sub {
+    my ($iface) = @_;
+
+    PVE::ProcFSTools::write_proc_entry("/sys/class/net/$iface/brport/unicast_flood", "0");
+    PVE::ProcFSTools::write_proc_entry("/sys/class/net/$iface/brport/learning", "0");
+
+};
+
 my $bridge_add_interface = sub {
     my ($bridge, $iface, $tag, $trunks) = @_;
 
@@ -268,6 +276,43 @@ my $activate_interface = sub {
     die "can't activate interface '$iface' - $@\n" if $@;
 };
 
+sub add_bridge_fdb {
+    my ($iface, $mac) = @_;
+
+    my $learning = PVE::Tools::file_read_firstline("/sys/class/net/$iface/brport/learning");
+    return if $learning;
+
+    my ($vmid, $devid) = &$parse_tap_device_name($iface, 1);
+    return if !defined($vmid);
+
+    PVE::Tools::run_command(['/sbin/bridge', 'fdb', 'append', $mac, 'dev', $iface, 'master', 'static']);
+
+    my ($fwbr, $vethfw, $vethfwpeer, $ovsintport) = &$compute_fwbr_names($vmid, $devid);
+
+    if (-d "/sys/class/net/$vethfwpeer") {
+	PVE::Tools::run_command(['/sbin/bridge', 'fdb', 'append', $mac, 'dev', $vethfwpeer, 'master', 'static']);
+    }
+
+}
+
+sub del_bridge_fdb {
+    my ($iface, $mac) = @_;
+
+    my $learning = PVE::Tools::file_read_firstline("/sys/class/net/$iface/brport/learning");
+    return if $learning;
+
+    my ($vmid, $devid) = &$parse_tap_device_name($iface, 1);
+    return if !defined($vmid);
+
+    PVE::Tools::run_command(['/sbin/bridge', 'fdb', 'del', $mac, 'dev', $iface, 'master', 'static']);
+
+    my ($fwbr, $vethfw, $vethfwpeer, $ovsintport) = &$compute_fwbr_names($vmid, $devid);
+
+    if (-d "/sys/class/net/$vethfwpeer") {
+	PVE::Tools::run_command(['/sbin/bridge', 'fdb', 'del', $mac, 'dev', $vethfwpeer, 'master', 'static']);
+    }
+}
+
 sub tap_create {
     my ($iface, $bridge) = @_;
 
@@ -322,7 +367,7 @@ sub veth_delete {
 }
 
 my $create_firewall_bridge_linux = sub {
-    my ($iface, $bridge, $tag, $trunks) = @_;
+    my ($iface, $bridge, $tag, $trunks, $disablelearning) = @_;
 
     my ($vmid, $devid) = &$parse_tap_device_name($iface);
     my ($fwbr, $vethfw, $vethfwpeer) = &$compute_fwbr_names($vmid, $devid);
@@ -333,14 +378,15 @@ my $create_firewall_bridge_linux = sub {
     copy_bridge_config($bridge, $fwbr);
     veth_create($vethfw, $vethfwpeer, $bridge);
 
-    &$bridge_add_interface($fwbr, $vethfw);
     &$bridge_add_interface($bridge, $vethfwpeer, $tag, $trunks);
+    &$bridge_disable_interface_learning($vethfwpeer) if $disablelearning;
+    &$bridge_add_interface($fwbr, $vethfw);
 
     &$bridge_add_interface($fwbr, $iface);
 };
 
 my $create_firewall_bridge_ovs = sub {
-    my ($iface, $bridge, $tag, $trunks) = @_;
+    my ($iface, $bridge, $tag, $trunks, $disablelearning) = @_;
 
     my ($vmid, $devid) = &$parse_tap_device_name($iface);
     my ($fwbr, undef, undef, $ovsintport) = &$compute_fwbr_names($vmid, $devid);
@@ -359,6 +405,7 @@ my $create_firewall_bridge_ovs = sub {
     PVE::Tools::run_command(['/sbin/ip', 'link', 'set', $ovsintport, 'mtu', $bridgemtu]);
 
     &$bridge_add_interface($fwbr, $ovsintport);
+    &$bridge_disable_interface_learning($ovsintport) if $disablelearning;
 };
 
 my $cleanup_firewall_bridge = sub {
@@ -383,7 +430,7 @@ my $cleanup_firewall_bridge = sub {
 };
 
 sub tap_plug {
-    my ($iface, $bridge, $tag, $firewall, $trunks, $rate) = @_;
+    my ($iface, $bridge, $tag, $firewall, $trunks, $rate, $disablelearning) = @_;
 
     #cleanup old port config from any openvswitch bridge
     eval {run_command("/usr/bin/ovs-vsctl del-port $iface", outfunc => sub {}, errfunc => sub {}) };
@@ -402,16 +449,17 @@ sub tap_plug {
 	}
 
 	if ($firewall) {
-	    &$create_firewall_bridge_linux($iface, $bridge, $tag, $trunks);
+	    &$create_firewall_bridge_linux($iface, $bridge, $tag, $trunks, $disablelearning);
 	} else {
 	    &$bridge_add_interface($bridge, $iface, $tag, $trunks);
 	}
+	&$bridge_disable_interface_learning($iface) if $disablelearning;
 
     } else {
 	&$cleanup_firewall_bridge($iface); # remove stale devices
 
 	if ($firewall) {
-	    &$create_firewall_bridge_ovs($iface, $bridge, $tag, $trunks);
+	    &$create_firewall_bridge_ovs($iface, $bridge, $tag, $trunks, $disablelearning);
 	} else {
 	    &$ovs_bridge_add_port($bridge, $iface, $tag, undef, $trunks);
 	}
-- 
2.30.2