netlink: Fix the issue of update_interface

When updating an interface, there's maybe an existed
interface whose name would be the same with the updated
required name, thus it would update failed with interface
name existed error. Thus we should rename the existed interface
with an temporary name and swap it with the previouse interface
name last.

Fixes: #6842

Signed-off-by: fupan <fupan.lfp@antgroup.com>

src/agent/src/netlink.rs

@@ -89,6 +89,27 @@ impl Handle {
                 .await?;
         }
 
+        // we need to update the link's interface name, thus we should rename the existed link whose name
+        // is the same with the link's request name, otherwise, it would update the link failed with the
+        // name conflicted.
+        let mut new_link = None;
+        if link.name() != iface.name {
+            if let Ok(link) = self.find_link(LinkFilter::Name(iface.name.as_str())).await {
+                // update the existing interface name with a temporary name, otherwise
+                // it would failed to udpate this interface with an existing name.
+                let mut request = self.handle.link().set(link.index());
+                request.message_mut().header = link.header.clone();
+
+                request
+                    .name(format!("{}_temp", link.name()))
+                    .up()
+                    .execute()
+                    .await?;
+
+                new_link = Some(link);
+            }
+        }
+
         // Update link
         let mut request = self.handle.link().set(link.index());
         request.message_mut().header = link.header.clone();
@@ -101,6 +122,14 @@ impl Handle {
             .execute()
             .await?;
 
+        // swap the updated iface's name.
+        if let Some(nlink) = new_link {
+            let mut request = self.handle.link().set(nlink.index());
+            request.message_mut().header = nlink.header.clone();
+
+            request.name(link.name()).up().execute().await?;
+        }
+
         Ok(())
     }