[pve-devel] [PATCH pve-common 0/1] network: tap_plug: fix mtu bugs

[pve-devel] [PATCH pve-common 0/1] network: tap_plug: fix mtu bugs

[Alexandre Derumier]

a forum user have reported strange bug with ovs + mtu9000 when 
switching between 2 ovs bridge with different mtu. (1500 vs 9000)
https://forum.proxmox.com/threads/ovs-problem-with-mtu-9000-on-vms-assigned-to-vmbr0.105172/

I have found 2 bugs:

1) ovsint port mtu need to be set with ""ovs-vsctl set mtu-request"

(ip link set mtu 9000 don't seem to do nothing on ovs-int port, maybe this have change with last ovs version.)


fresh start of a vm 100 + firewall on ovs with mtu 9000:

153: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 9000 qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen 1000
    link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
154: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
155: fwln100o0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr100i0 state UNKNOWN group default qlen 1000


2) when switching between 2 bridges or ovs with differents mtu, mtu are not updated on existing interfaces (veth,tap, fwbr, fwnl)


vm start : vmbr0 mtu=1500 + firewall
-----------------------------
200: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen 1000
    link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
206: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
207: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr0 state UP group default qlen 1000
    link/ether 0a:2e:f5:f4:22:e3 brd ff:ff:ff:ff:ff:ff
208: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr100i0 state UP group default qlen 1000
    link/ether 96:0e:94:11:c1:45 brd ff:ff:ff:ff:ff:ff


switch to vmbr1 mtu=9000 + firewall
--------------------------------------

200: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen 1000
    link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
209: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
210: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue master vmbr3 state UP group default qlen 1000
    link/ether 0a:2e:f5:f4:22:e3 brd ff:ff:ff:ff:ff:ff
211: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue master fwbr100i0 state UP group default qlen 1000
    link/ether 96:0e:94:11:c1:45 brd ff:ff:ff:ff:ff:ff




Alexandre Derumier (1):
  network: tap_plug: fix mtu

 src/PVE/Network.pm | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

-- 
2.30.2

[pve-devel] [PATCH pve-common 1/1] network: tap_plug: fix mtu

[Alexandre Derumier]

- ovsint port mtu need to be set with ""ovs-vsctl set mtu-request"
- update mtu on already existing interfaces (fwbr,fwln,tap,veth)
  if existing tap|veth interface is replugged on a different mtu bridge
---
 src/PVE/Network.pm | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/PVE/Network.pm b/src/PVE/Network.pm
index d4d72d4..56ade27 100644
--- a/src/PVE/Network.pm
+++ b/src/PVE/Network.pm
@@ -211,6 +211,11 @@ sub disable_ipv6 {
 my $bridge_add_interface = sub {
     my ($bridge, $iface, $tag, $trunks) = @_;
 
+    my $bridgemtu = read_bridge_mtu($bridge);
+    eval {
+	PVE::Tools::run_command(['/sbin/ip', 'link', 'set', $iface, 'mtu', $bridgemtu]);
+    };
+
     # drop link local address (it can't be used when on a bridge anyway)
     disable_ipv6($iface);
     iface_set_master($iface, $bridge);
@@ -251,6 +256,9 @@ my $ovs_bridge_add_port = sub {
     push @$cmd, "trunks=". join(',', $trunks) if $trunks;
     push @$cmd, "vlan_mode=native-untagged" if $tag && $trunks;
 
+    my $bridgemtu = read_bridge_mtu($bridge);
+    push @$cmd, '--', 'set', 'Interface', $iface, "mtu_request=$bridgemtu";
+
     if ($internal) {
 	# second command
 	push @$cmd, '--', 'set', 'Interface', $iface, 'type=internal';
@@ -263,9 +271,12 @@ my $ovs_bridge_add_port = sub {
 };
 
 my $activate_interface = sub {
-    my ($iface) = @_;
+    my ($iface, $mtu) = @_;
+
+    my $cmd = ['/sbin/ip', 'link', 'set', $iface, 'up'];
+    push (@$cmd, ('mtu', $mtu)) if $mtu;
 
-    eval { run_command(['/sbin/ip', 'link', 'set', $iface, 'up']) };
+    eval { run_command($cmd) };
     die "can't activate interface '$iface' - $@\n" if $@;
 };
 
@@ -309,8 +320,8 @@ sub veth_create {
     # up vethpair
     disable_ipv6($veth);
     disable_ipv6($vethpeer);
-    &$activate_interface($veth);
-    &$activate_interface($vethpeer);
+    &$activate_interface($veth, $bridgemtu);
+    &$activate_interface($vethpeer, $bridgemtu);
 }
 
 sub veth_delete {
@@ -328,8 +339,10 @@ my $create_firewall_bridge_linux = sub {
     my ($vmid, $devid) = &$parse_tap_device_name($iface);
     my ($fwbr, $vethfw, $vethfwpeer) = &$compute_fwbr_names($vmid, $devid);
 
+    my $bridgemtu = read_bridge_mtu($bridge);
+
     &$cond_create_bridge($fwbr);
-    &$activate_interface($fwbr);
+    &$activate_interface($fwbr, $bridgemtu);
 
     copy_bridge_config($bridge, $fwbr);
     veth_create($vethfw, $vethfwpeer, $bridge);
@@ -349,15 +362,12 @@ my $create_firewall_bridge_ovs = sub {
     my $bridgemtu = read_bridge_mtu($bridge);
 
     &$cond_create_bridge($fwbr);
-    &$activate_interface($fwbr);
+    &$activate_interface($fwbr, $bridgemtu);
 
     &$bridge_add_interface($fwbr, $iface);
 
     &$ovs_bridge_add_port($bridge, $ovsintport, $tag, 1, $trunks);
-    &$activate_interface($ovsintport);
-
-    # set the same mtu for ovs int port
-    PVE::Tools::run_command(['/sbin/ip', 'link', 'set', $ovsintport, 'mtu', $bridgemtu]);
+    &$activate_interface($ovsintport, $bridgemtu);
 
     &$bridge_add_interface($fwbr, $ovsintport);
 };
-- 
2.30.2

Re: [pve-devel] [PATCH pve-common 0/1] network: tap_plug: fix mtu bugs

[DERUMIER, Alexandre]

Any comment about this patch ?

Forum user have tested it, and it's correctly fixing his mtu problem.

Le vendredi 18 février 2022 à 17:25 +0100, Alexandre Derumier a écrit :
> a forum user have reported strange bug with ovs + mtu9000 when 
> switching between 2 ovs bridge with different mtu. (1500 vs 9000)
> https://antiphishing.cetsi.fr/proxy/v3?i=cWdzUmRSM0ZiRHpoUDkxTSw3-
> 90dQgKDkqmWWemZ6js&r=WXNQOUY5VXRSNUlTdlVTThI4PzxOoz24vDyX_lRDxWFQYQjk
> Hq27xgjw3hQLoamBbuCSKIqia8FUio_zgv2Z4g&f=R0pWUVNEaUFuMTBCTlptbqOdxRIa
> EmX54Uku9_K8PFys74qKNMDYadHFvaTbTNhXBQ48X7FG7vbeJb39p0LVEQ&u=https%3A
> //forum.proxmox.com/threads/ovs-problem-with-mtu-9000-on-vms-
> assigned-to-vmbr0.105172/&k=8YLU
> 
> I have found 2 bugs:
> 
> 1) ovsint port mtu need to be set with ""ovs-vsctl set mtu-request"
> 
> (ip link set mtu 9000 don't seem to do nothing on ovs-int port, maybe
> this have change with last ovs version.)
> 
> 
> fresh start of a vm 100 + firewall on ovs with mtu 9000:
> 
> 153: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 9000
> qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen
> 1000
>     link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
> 154: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
>     link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
> 155: fwln100o0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> noqueue master fwbr100i0 state UNKNOWN group default qlen 1000
> 
> 
> 2) when switching between 2 bridges or ovs with differents mtu, mtu
> are not updated on existing interfaces (veth,tap, fwbr, fwnl)
> 
> 
> vm start : vmbr0 mtu=1500 + firewall
> -----------------------------
> 200: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500
> qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen
> 1000
>     link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
> 206: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
>     link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
> 207: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
> qdisc noqueue master vmbr0 state UP group default qlen 1000
>     link/ether 0a:2e:f5:f4:22:e3 brd ff:ff:ff:ff:ff:ff
> 208: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
> qdisc noqueue master fwbr100i0 state UP group default qlen 1000
>     link/ether 96:0e:94:11:c1:45 brd ff:ff:ff:ff:ff:ff
> 
> 
> switch to vmbr1 mtu=9000 + firewall
> --------------------------------------
> 
> 200: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500
> qdisc pfifo_fast master fwbr100i0 state UNKNOWN group default qlen
> 1000
>     link/ether 62:42:32:cc:a2:24 brd ff:ff:ff:ff:ff:ff
> 209: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
>     link/ether 46:f6:b7:95:23:86 brd ff:ff:ff:ff:ff:ff
> 210: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000
> qdisc noqueue master vmbr3 state UP group default qlen 1000
>     link/ether 0a:2e:f5:f4:22:e3 brd ff:ff:ff:ff:ff:ff
> 211: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000
> qdisc noqueue master fwbr100i0 state UP group default qlen 1000
>     link/ether 96:0e:94:11:c1:45 brd ff:ff:ff:ff:ff:ff
> 
> 
> 
> 
> Alexandre Derumier (1):
>   network: tap_plug: fix mtu
> 
>  src/PVE/Network.pm | 30 ++++++++++++++++++++----------
>  1 file changed, 20 insertions(+), 10 deletions(-)
>