* [PATCH pve-container] fix #7571: emit mtu in ifupdown-based LXC guests
@ 2026-05-06 23:00 Ilan Karasik
2026-06-16 10:22 ` Fabian Grünbichler
0 siblings, 1 reply; 5+ messages in thread
From: Ilan Karasik @ 2026-05-06 23:00 UTC (permalink / raw)
To: pve-devel; +Cc: iamkarasik
From: iamkarasik <ilankarasik@gmail.com>
Signed-off-by: iamkarasik <ilankarasik@gmail.com>
---
src/PVE/LXC/Setup/Debian.pm | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/PVE/LXC/Setup/Debian.pm b/src/PVE/LXC/Setup/Debian.pm
index 837397b..bbf73d5 100644
--- a/src/PVE/LXC/Setup/Debian.pm
+++ b/src/PVE/LXC/Setup/Debian.pm
@@ -284,6 +284,7 @@ sub setup_network {
$net->{needsroute6} = 1;
}
}
+ $net->{mtu} = $d->{mtu} if defined($d->{mtu});
$networks->{ $d->{name} } = $net if keys %$net;
}
}
@@ -337,6 +338,7 @@ sub setup_network {
$interfaces .= "\tgateway $gw\n";
}
}
+ $interfaces .= "\tmtu $net->{mtu}\n" if defined($net->{mtu});
foreach my $attr (@{ $section->{attr} }) {
$interfaces .= "\t$attr\n";
}
@@ -450,6 +452,7 @@ sub setup_network {
|| $aname eq 'netmask'
|| $aname eq 'gateway'
|| $aname eq 'broadcast'
+ || $aname eq 'mtu'
) {
# skip
} else {
--
2.51.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH pve-container] fix #7571: emit mtu in ifupdown-based LXC guests
2026-05-06 23:00 [PATCH pve-container] fix #7571: emit mtu in ifupdown-based LXC guests Ilan Karasik
@ 2026-06-16 10:22 ` Fabian Grünbichler
2026-06-17 18:32 ` [PATCH v2] " Ilan Karasik
0 siblings, 1 reply; 5+ messages in thread
From: Fabian Grünbichler @ 2026-06-16 10:22 UTC (permalink / raw)
To: Ilan Karasik, pve-devel
Hi!
please see https://pve.proxmox.com/wiki/Developer_Documentation#Software_License_and_Copyright
for our CLA requirements, and send a signed copy as instructed there.
On May 7, 2026 1:00 am, Ilan Karasik wrote:
> From: iamkarasik <ilankarasik@gmail.com>
please add a short description of the commit/patch here, see our
developer documentation for details:
> Do not put in a literal description of the code diff, especially not
> for simpler changes. The commit message should not focus on the
> detailed what's done/changed but rather answer:
>
> Why this was done otherwise previously (or why this was missing
> until now).
>
> Why the new approach is better or necessary (e.g., a
> bug was found, requirements changed, a prerequisite was merged that
> enables this).
>
> What the resulting effect is for users or developers
> (if not already obvious from the subject line). If there should be
> no visible/semantic change then explicitly stating so can also be
> good for non-trivial changes.
Thanks!
>
> Signed-off-by: iamkarasik <ilankarasik@gmail.com>
> ---
> src/PVE/LXC/Setup/Debian.pm | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/src/PVE/LXC/Setup/Debian.pm b/src/PVE/LXC/Setup/Debian.pm
> index 837397b..bbf73d5 100644
> --- a/src/PVE/LXC/Setup/Debian.pm
> +++ b/src/PVE/LXC/Setup/Debian.pm
> @@ -284,6 +284,7 @@ sub setup_network {
> $net->{needsroute6} = 1;
> }
> }
> + $net->{mtu} = $d->{mtu} if defined($d->{mtu});
> $networks->{ $d->{name} } = $net if keys %$net;
> }
> }
> @@ -337,6 +338,7 @@ sub setup_network {
> $interfaces .= "\tgateway $gw\n";
> }
> }
> + $interfaces .= "\tmtu $net->{mtu}\n" if defined($net->{mtu});
> foreach my $attr (@{ $section->{attr} }) {
> $interfaces .= "\t$attr\n";
> }
> @@ -450,6 +452,7 @@ sub setup_network {
> || $aname eq 'netmask'
> || $aname eq 'gateway'
> || $aname eq 'broadcast'
> + || $aname eq 'mtu'
> ) {
> # skip
> } else {
> --
> 2.51.2
>
>
>
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] fix #7571: emit mtu in ifupdown-based LXC guests
2026-06-16 10:22 ` Fabian Grünbichler
@ 2026-06-17 18:32 ` Ilan Karasik
2026-09-07 14:04 ` Fabian Grünbichler
0 siblings, 1 reply; 5+ messages in thread
From: Ilan Karasik @ 2026-06-17 18:32 UTC (permalink / raw)
To: pve-devel; +Cc: Ilan Karasik
This fixes a bug where custom mtu settings applied to an LXC container
are silently ignored during network setup for Debian-based guests
using ifupdown.
Because the Proxmox network setup was failing to write the mtu value
to the guest's `/etc/network/interfaces` file, the container would
always default to an mtu of 1500.
This patch resolves the issue by writing the `mtu <value>` directive into the
guest's network configuration file at /etc/network/interfaces.
Signed-off-by: Ilan Karasik <ilankarasik@gmail.com>
---
src/PVE/LXC/Setup/Debian.pm | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/PVE/LXC/Setup/Debian.pm b/src/PVE/LXC/Setup/Debian.pm
index 837397b..bbf73d5 100644
--- a/src/PVE/LXC/Setup/Debian.pm
+++ b/src/PVE/LXC/Setup/Debian.pm
@@ -284,6 +284,7 @@ sub setup_network {
$net->{needsroute6} = 1;
}
}
+ $net->{mtu} = $d->{mtu} if defined($d->{mtu});
$networks->{ $d->{name} } = $net if keys %$net;
}
}
@@ -337,6 +338,7 @@ sub setup_network {
$interfaces .= "\tgateway $gw\n";
}
}
+ $interfaces .= "\tmtu $net->{mtu}\n" if defined($net->{mtu});
foreach my $attr (@{ $section->{attr} }) {
$interfaces .= "\t$attr\n";
}
@@ -450,6 +452,7 @@ sub setup_network {
|| $aname eq 'netmask'
|| $aname eq 'gateway'
|| $aname eq 'broadcast'
+ || $aname eq 'mtu'
) {
# skip
} else {
--
2.51.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] fix #7571: emit mtu in ifupdown-based LXC guests
2026-06-17 18:32 ` [PATCH v2] " Ilan Karasik
@ 2026-09-07 14:04 ` Fabian Grünbichler
2026-09-07 15:39 ` [PATCH v3] " Ilan Karasik
0 siblings, 1 reply; 5+ messages in thread
From: Fabian Grünbichler @ 2026-09-07 14:04 UTC (permalink / raw)
To: Ilan Karasik, pve-devel
On June 17, 2026 8:32 pm, Ilan Karasik wrote:
> This fixes a bug where custom mtu settings applied to an LXC container
> are silently ignored during network setup for Debian-based guests
> using ifupdown.
>
> Because the Proxmox network setup was failing to write the mtu value
> to the guest's `/etc/network/interfaces` file, the container would
> always default to an mtu of 1500.
>
> This patch resolves the issue by writing the `mtu <value>` directive into the
> guest's network configuration file at /etc/network/interfaces.
>
> Signed-off-by: Ilan Karasik <ilankarasik@gmail.com>
> ---
> src/PVE/LXC/Setup/Debian.pm | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/src/PVE/LXC/Setup/Debian.pm b/src/PVE/LXC/Setup/Debian.pm
> index 837397b..bbf73d5 100644
> --- a/src/PVE/LXC/Setup/Debian.pm
> +++ b/src/PVE/LXC/Setup/Debian.pm
> @@ -284,6 +284,7 @@ sub setup_network {
> $net->{needsroute6} = 1;
> }
> }
> + $net->{mtu} = $d->{mtu} if defined($d->{mtu});
> $networks->{ $d->{name} } = $net if keys %$net;
> }
> }
> @@ -337,6 +338,7 @@ sub setup_network {
> $interfaces .= "\tgateway $gw\n";
> }
> }
> + $interfaces .= "\tmtu $net->{mtu}\n" if defined($net->{mtu});
sorry for the long turnaround time!
should we also set this higher up in the dhcp/manual part?
> foreach my $attr (@{ $section->{attr} }) {
> $interfaces .= "\t$attr\n";
> }
> @@ -450,6 +452,7 @@ sub setup_network {
> || $aname eq 'netmask'
> || $aname eq 'gateway'
> || $aname eq 'broadcast'
> + || $aname eq 'mtu'
> ) {
> # skip
> } else {
> --
> 2.51.2
>
>
>
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v3] fix #7571: emit mtu in ifupdown-based LXC guests
2026-09-07 14:04 ` Fabian Grünbichler
@ 2026-09-07 15:39 ` Ilan Karasik
0 siblings, 0 replies; 5+ messages in thread
From: Ilan Karasik @ 2026-09-07 15:39 UTC (permalink / raw)
To: pve-devel; +Cc: iamkarasik
From: iamkarasik <ilankarasik@gmail.com>
This fixes a bug where custom mtu settings applied to an LXC container
are silently ignored during network setup for Debian-based guests
using ifupdown.
Because the Proxmox network setup was failing to write the mtu value
to the guest's `/etc/network/interfaces` file, the container would
always default to an mtu of 1500.
This patch resolves the issue by writing the `mtu <value>` directive into the
guest's network configuration file at /etc/network/interfaces. This
configuration applies to static, dhcp, and manual configurations.
Signed-off-by: Ilan Karasik <ilankarasik@gmail.com>
---
src/PVE/LXC/Setup/Debian.pm | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
diff --git a/src/PVE/LXC/Setup/Debian.pm b/src/PVE/LXC/Setup/Debian.pm
index 837397b..fd4a7d4 100644
--- a/src/PVE/LXC/Setup/Debian.pm
+++ b/src/PVE/LXC/Setup/Debian.pm
@@ -284,6 +284,7 @@ sub setup_network {
$net->{needsroute6} = 1;
}
}
+ $net->{mtu} = $d->{mtu} if defined($d->{mtu});
$networks->{ $d->{name} } = $net if keys %$net;
}
}
@@ -298,6 +299,7 @@ sub setup_network {
my $done_auto = {};
my $done_v4_hash = {};
my $done_v6_hash = {};
+ my $done_mtu_hash = {};
my ($os, $version) = ($conf->{ostype}, $self->{version});
my $print_section = sub {
@@ -317,7 +319,12 @@ sub setup_network {
if (!defined($net->{address})) {
# no address => no iface line
} elsif ($net->{address} =~ /^(dhcp|manual)$/) {
- $interfaces .= "iface $ifname inet $1\n\n";
+ $interfaces .= "iface $ifname inet $1\n";
+ if (defined($net->{mtu}) && !$done_mtu_hash->{$ifname}) {
+ $interfaces .= "\tmtu $net->{mtu}\n";
+ $done_mtu_hash->{$ifname} = 1;
+ }
+ $interfaces .= "\n";
} else {
$interfaces .= "iface $ifname inet static\n";
if (
@@ -329,6 +336,10 @@ sub setup_network {
$interfaces .= "\taddress $net->{address}\n" if defined($net->{address});
$interfaces .= "\tnetmask $net->{netmask}\n" if defined($net->{netmask});
}
+ if (defined($net->{mtu}) && !$done_mtu_hash->{$ifname}) {
+ $interfaces .= "\tmtu $net->{mtu}\n";
+ $done_mtu_hash->{$ifname} = 1;
+ }
remove_gateway_scripts($section->{attr});
if (defined(my $gw = $net->{gateway})) {
if ($net->{needsroute}) {
@@ -348,7 +359,12 @@ sub setup_network {
if (!defined($net->{address6})) {
# no address => no iface line
} elsif ($net->{address6} =~ /^(auto|dhcp|manual)$/) {
- $interfaces .= "iface $ifname inet6 $1\n\n";
+ $interfaces .= "iface $ifname inet6 $1\n";
+ if (defined($net->{mtu}) && !$done_mtu_hash->{$ifname}) {
+ $interfaces .= "\tmtu $net->{mtu}\n";
+ $done_mtu_hash->{$ifname} = 1;
+ }
+ $interfaces .= "\n";
} else {
$interfaces .= "iface $ifname inet6 static\n";
if (
@@ -360,6 +376,10 @@ sub setup_network {
$interfaces .= "\taddress $net->{address6}\n" if defined($net->{address6});
$interfaces .= "\tnetmask $net->{netmask6}\n" if defined($net->{netmask6});
}
+ if (defined($net->{mtu}) && !$done_mtu_hash->{$ifname}) {
+ $interfaces .= "\tmtu $net->{mtu}\n";
+ $done_mtu_hash->{$ifname} = 1;
+ }
remove_gateway_scripts($section->{attr});
if (defined(my $gw = $net->{gateway6})) {
if ($net->{needsroute6}) {
@@ -450,6 +470,7 @@ sub setup_network {
|| $aname eq 'netmask'
|| $aname eq 'gateway'
|| $aname eq 'broadcast'
+ || $aname eq 'mtu'
) {
# skip
} else {
--
2.51.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-09-08 7:47 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2026-05-06 23:00 [PATCH pve-container] fix #7571: emit mtu in ifupdown-based LXC guests Ilan Karasik
2026-06-16 10:22 ` Fabian Grünbichler
2026-06-17 18:32 ` [PATCH v2] " Ilan Karasik
2026-09-07 14:04 ` Fabian Grünbichler
2026-09-07 15:39 ` [PATCH v3] " Ilan Karasik
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