From a222f7e0554fe8057a6d9c6749acbd066798fa9d Mon Sep 17 00:00:00 2001

From: Thomas Haller <thaller@redhat.com>

Date: Tue, 13 Jun 2017 12:26:51 +0200

Subject: [PATCH 1/1] device: don't set MTU of device unless explicitly

 configured

Since commit 2b51d3967 "device: merge branch 'th/device-mtu-bgo777251'",

we always set the MTU for certain device types during activation. Even

if the MTU is neither specified via the connection nor other means, like

DHCP.

Revert that change. On activation, if nothing explicitly configures the

MTU, leave it unchanged. This is like what we do with ethernet's

cloned-mac-address, which has a default value "preserve".

So, as last resort the default value for MTU is now 0 (don't change),

instead of depending on the device type.

Note that you also can override the default value in global

configuration via NetworkManager.conf.

This behavior makes sense, because whenever NM actively resets the MTU,

it remembers the previous value and restores it when deactivating

the connection. That wasn't implemented before 2b51d3967, and the

MTU would depend on which connection was previously active. That

is no longer an issue as the MTU gets reset when deactivating.

https://bugzilla.redhat.com/show_bug.cgi?id=1460760

(cherry picked from commit 4ca3002b86948847711cd5b1937008baef3c30da)

(cherry picked from commit 588841f2e086774420a7ff4452d87e45ffae578a)

---

 man/NetworkManager.conf.xml        | 2 +-

 src/devices/nm-device-infiniband.c | 2 +-

 src/devices/nm-device-ip-tunnel.c  | 2 +-

 src/devices/nm-device-private.h    | 4 ----

 src/devices/nm-device-vlan.c       | 2 +-

 src/devices/nm-device.c            | 2 +-

 src/devices/wifi/nm-device-wifi.c  | 2 +-

 7 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/man/NetworkManager.conf.xml b/man/NetworkManager.conf.xml

index 5e76c0ace..71c62cc15 100644

--- a/man/NetworkManager.conf.xml

+++ b/man/NetworkManager.conf.xml

@@ -655,7 +655,7 @@ ipv6.ip6-privacy=0

         </varlistentry>

         <varlistentry>

           <term><varname>ethernet.mtu</varname></term>

-          <listitem><para>If configured explicitly to 0, the MTU is not reconfigured during device activation unless it is required due to IPv6 constraints. If left unspecified, a DHCP/IPv6 SLAAC provided value is used or a default of 1500.</para></listitem>

+          <listitem><para>If configured explicitly to 0, the MTU is not reconfigured during device activation unless it is required due to IPv6 constraints. If left unspecified, a DHCP/IPv6 SLAAC provided value is used or the MTU is not reconfigured during activation.</para></listitem>

         </varlistentry>

         <varlistentry>

           <term><varname>ethernet.wake-on-lan</varname></term>

diff --git a/src/devices/nm-device-infiniband.c b/src/devices/nm-device-infiniband.c

index f7875d099..7e0412703 100644

--- a/src/devices/nm-device-infiniband.c

+++ b/src/devices/nm-device-infiniband.c

@@ -139,7 +139,7 @@ get_configured_mtu (NMDevice *device, gboolean *out_is_user_config)

 		}

 	}

 	*out_is_user_config = (mtu != 0);

-	return mtu ?: NM_DEVICE_DEFAULT_MTU_INFINIBAND;

+	return mtu;

 }

 static gboolean

diff --git a/src/devices/nm-device-ip-tunnel.c b/src/devices/nm-device-ip-tunnel.c

index 53b7cf4e5..2f505ef4c 100644

--- a/src/devices/nm-device-ip-tunnel.c

+++ b/src/devices/nm-device-ip-tunnel.c

@@ -767,7 +767,7 @@ get_configured_mtu (NMDevice *self, gboolean *out_is_user_config)

 		}

 	}

 	*out_is_user_config = (mtu != 0);

-	return mtu ?: NM_DEVICE_DEFAULT_MTU_WIRED;

+	return mtu;

 }

 static NMDeviceCapabilities

diff --git a/src/devices/nm-device-private.h b/src/devices/nm-device-private.h

index a4067f9c2..9eccafdc6 100644

--- a/src/devices/nm-device-private.h

+++ b/src/devices/nm-device-private.h

@@ -116,10 +116,6 @@ gboolean nm_device_ipv6_sysctl_set (NMDevice *self, const char *property, const

 /*****************************************************************************/

-#define NM_DEVICE_DEFAULT_MTU_WIRED          ((guint32) 1500)

-#define NM_DEVICE_DEFAULT_MTU_WIRELESS       ((guint32) 1500)

-#define NM_DEVICE_DEFAULT_MTU_INFINIBAND     ((guint32) 0)

-

 gint64 nm_device_get_configured_mtu_from_connection_default (NMDevice *self,

                                                              const char *property_name);

diff --git a/src/devices/nm-device-vlan.c b/src/devices/nm-device-vlan.c

index 06db64465..a74da8f22 100644

--- a/src/devices/nm-device-vlan.c

+++ b/src/devices/nm-device-vlan.c

@@ -586,7 +586,7 @@ get_configured_mtu (NMDevice *self, gboolean *out_is_user_config)

 	if (ifindex > 0)

 		mtu = nm_platform_link_get_mtu (nm_device_get_platform (NM_DEVICE (self)), ifindex);

-	return mtu ?: NM_DEVICE_DEFAULT_MTU_WIRED;

+	return mtu;

 }

 /*****************************************************************************/

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c

index e60995d57..e37b24bff 100644

--- a/src/devices/nm-device.c

+++ b/src/devices/nm-device.c

@@ -7150,7 +7150,7 @@ nm_device_get_configured_mtu_for_wired (NMDevice *self, gboolean *out_is_user_co

 	}

 	*out_is_user_config = FALSE;

-	return NM_DEVICE_DEFAULT_MTU_WIRED;

+	return 0;

 }

 /*****************************************************************************/

diff --git a/src/devices/wifi/nm-device-wifi.c b/src/devices/wifi/nm-device-wifi.c

index 7359be96e..20692ed9e 100644

--- a/src/devices/wifi/nm-device-wifi.c

+++ b/src/devices/wifi/nm-device-wifi.c

@@ -2742,7 +2742,7 @@ get_configured_mtu (NMDevice *device, gboolean *out_is_user_config)

 		}

 	}

 	*out_is_user_config = (mtu != 0);

-	return mtu ?: NM_DEVICE_DEFAULT_MTU_WIRELESS;

+	return mtu;

 }

 static gboolean

-- 

2.13.0