[PATCH proxmox] fix #7329: proxmox-network-api: add missing `Auto` network config method

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

when adding an iface object with network type as inet6 and the config
type as auto, the web UI was showing an error inside the "Network
interfaces" section. This was because the `NetworkParser` failed to
parse the auto method. Inorder to fix the issue, add new `Auto` variant
inside the `NetworkConfigMethod` enum and update the match clause to
handle `Auto` variant.

Signed-off-by: Shan Shaji <s.shaji@proxmox.com>
---

 Reference: https://manpages.debian.org/trixie/ifupdown/interfaces.5.en.html#INET6_ADDRESS_FAMILY

 proxmox-network-api/src/api_types.rs     |  2 ++
 proxmox-network-api/src/config/mod.rs    |  1 +
 proxmox-network-api/src/config/parser.rs | 43 ++++++++++++++++++++++++
 3 files changed, 46 insertions(+)

diff --git a/proxmox-network-api/src/api_types.rs b/proxmox-network-api/src/api_types.rs
index 4860a114..b86f8570 100644
--- a/proxmox-network-api/src/api_types.rs
+++ b/proxmox-network-api/src/api_types.rs
@@ -37,6 +37,8 @@ pub enum NetworkConfigMethod {
     DHCP,
     /// Define the loopback interface.
     Loopback,
+    /// Define interfaces with automatically assigned IPv6 addresses.
+    Auto,
 }
 
 #[api()]
diff --git a/proxmox-network-api/src/config/mod.rs b/proxmox-network-api/src/config/mod.rs
index 9b9f0d50..84fdff86 100644
--- a/proxmox-network-api/src/config/mod.rs
+++ b/proxmox-network-api/src/config/mod.rs
@@ -177,6 +177,7 @@ fn write_iface(iface: &Interface, w: &mut dyn Write) -> Result<(), Error> {
             NetworkConfigMethod::Loopback => "loopback",
             NetworkConfigMethod::Manual => "manual",
             NetworkConfigMethod::DHCP => "dhcp",
+            NetworkConfigMethod::Auto => "auto",
         }
     }
 
diff --git a/proxmox-network-api/src/config/parser.rs b/proxmox-network-api/src/config/parser.rs
index 8cbc6ac8..dafe19f8 100644
--- a/proxmox-network-api/src/config/parser.rs
+++ b/proxmox-network-api/src/config/parser.rs
@@ -461,6 +461,7 @@ impl<R: BufRead> NetworkParser<R> {
                 Token::Static => config_method = Some(NetworkConfigMethod::Static),
                 Token::Manual => config_method = Some(NetworkConfigMethod::Manual),
                 Token::DHCP => config_method = Some(NetworkConfigMethod::DHCP),
+                Token::Auto => config_method = Some(NetworkConfigMethod::Auto),
                 _ => bail!("unknown iface option {}", text),
             }
         }
@@ -742,6 +743,48 @@ mod test {
         Ok(())
     }
 
+    #[test]
+    fn test_network_config_parser_ipv6_variants() -> Result<(), Error> {
+        let input = "auto lo\n\
+                 iface lo inet6 loopback\n\
+                 \n\
+                 auto ens18\n\
+                 iface ens18 inet6 auto\n\
+                 \n\
+                 auto ens20\n\
+                 iface ens20 inet6 static\n\
+                 \taddress 2001:db8:a::1/64\n\
+                 \tgateway 2001:db8:a::fe\n\
+                 \n\
+                 auto ens21\n\
+                 iface ens21 inet6 dhcp\n";
+
+        let mut parser = NetworkParser::new(input.as_bytes());
+
+        let config = parser.parse_interfaces(None)?;
+
+        let output = String::try_from(config)?;
+
+        let expected = "auto lo\n\
+                    iface lo inet6 loopback\n\
+                    \n\
+                    auto ens18\n\
+                    iface ens18 inet6 auto\n\
+                    \n\
+                    auto ens20\n\
+                    iface ens20 inet6 static\n\
+                    \taddress 2001:db8:a::1/64\n\
+                    \tgateway 2001:db8:a::fe\n\
+                    \n\
+                    auto ens21\n\
+                    iface ens21 inet6 dhcp\n\
+                    \n";
+
+        assert_eq!(output, expected);
+
+        Ok(())
+    }
+
     #[test]
     fn test_network_config_parser_no_blank_2() -> Result<(), Error> {
         // Adapted from bug 2926
-- 
2.47.3