[PATCH proxmox-backup v2 1/1] fix #7329: api: avoid overwriting existing IPv6 config method

[Shan Shaji <s.shaji@proxmox.com>]

If the inet6 address family's cidr6/gatway6 values are not present, the
interface.method6 values is mutated with `NetworkConfigMethod::Manual`
even if the interface.method6 already has a value. For example, if
the config method is `auto` then it gets replaced by `Manual` config
method.

Later, when writing the config file to the interfaces.new file if the
config method is manual and if there are no IPv6 specific attributes
present, then the inet6 stanza gets skipped.

In order to fix the issue update the condition to only set the config
method to `::Manual` if there is no value present inside the `method6`
property of the interface object.

Fixes: https://bugzilla.proxmox.com/show_bug.cgi?id=7329
Signed-off-by: Shan Shaji <s.shaji@proxmox.com>
---

 **note**: This is a new patch. 
 
 src/api2/node/network.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/api2/node/network.rs b/src/api2/node/network.rs
index 4ee0231d..d0a04e59 100644
--- a/src/api2/node/network.rs
+++ b/src/api2/node/network.rs
@@ -782,7 +782,7 @@ pub fn update_interface(
 
     if interface.cidr6.is_some() || interface.gateway6.is_some() {
         interface.method6 = Some(NetworkConfigMethod::Static);
-    } else {
+    } else if interface.method6.is_none() {
         interface.method6 = Some(NetworkConfigMethod::Manual);
     }
 
-- 
2.47.3