device: add nm_device_get_ip_iface_from_platform()

We have a cached nm_device_get_ip_iface() property. However, the interface
name is not an ID for a link, meaning it can change any time.

Also, we already have the (ip) ifindex as proper identifier for the
platform link. We shouldn't use two redundant links.

Clearly, sometimes we need an ifname. For example for ethtool ioctl or
sysctl path names. For ethtool API, we resolve the actual name as late
as possible, and for sysctl API we prefer NMP_SYSCTL_PATHID_NETDIR*().
However, that is not always possible, for example for /proc/sys/net/ipv6/conf/.

Add a function that resolves the ifname by looking into the cache. This
of course is still racy, but it minimizes the time.

Also, we should less and less rely on the ifname, and resolve it as late
as possible. This patch adds a small wrapper going into that direction.

2 files changed, 13 insertions, 0 deletions

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index 8eed3abb04..11123fa19a 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -1480,6 +1480,18 @@ nm_device_get_ip_iface (NMDevice *self)
 	return priv->ip_iface ?: priv->iface;
 }
 
+const char *
+nm_device_get_ip_iface_from_platform (NMDevice *self)
+{
+	int ifindex;
+
+	ifindex = nm_device_get_ip_ifindex (self);
+	if (ifindex <= 0)
+		return NULL;
+
+	return nm_platform_link_get_name (nm_device_get_platform (self), ifindex);
+}
+
 int
 nm_device_get_ip_ifindex (const NMDevice *self)
 {
diff --git a/src/devices/nm-device.h b/src/devices/nm-device.h
index 83215256c9..4cf4e31b59 100644
--- a/src/devices/nm-device.h
+++ b/src/devices/nm-device.h
@@ -485,6 +485,7 @@ int             nm_device_get_ifindex           (NMDevice *dev);
 gboolean        nm_device_is_software           (NMDevice *dev);
 gboolean        nm_device_is_real               (NMDevice *dev);
 const char *    nm_device_get_ip_iface          (NMDevice *dev);
+const char *    nm_device_get_ip_iface_from_platform (NMDevice *dev);
 int             nm_device_get_ip_ifindex        (const NMDevice *dev);
 const char *    nm_device_get_driver            (NMDevice *dev);
 const char *    nm_device_get_driver_version    (NMDevice *dev);