[datadog] runtime-rs: store netkit mode from InfoData and use it for L3 detection

Signed-off-by: Mateo Lelong <mateo.lelong@datadoghq.com>

Author: TheRayquaza

src/runtime-rs/crates/resource/src/network/network_with_netns.rs

@@ -314,10 +314,22 @@ async fn create_endpoint(
                 Arc::new(ret)
             }
             "netkit" => {
-                // L3 mode netkit devices have no MAC address and are not supported.
-                if attrs.hardware_addr.is_empty() {
+                let is_l3 = link
+                    .as_any()
+                    .downcast_ref::<link::Netkit>()
+                    .and_then(|n| n.mode)
+                    .map_or_else(
+                        || {
+                            attrs.hardware_addr.is_empty()
+                            // L3 devices have no MAC address, so check for all-zero.
+                            // https://github.com/torvalds/linux/blob/master/drivers/net/netkit.c
+                                || attrs.hardware_addr.iter().all(|&b| b == 0)
+                        },
+                        |m| m == netlink_packet_route::link::NetkitMode::L3,
+                    );
+                if is_l3 {
                     return Err(anyhow!(
-                        "netkit device {} has no MAC address (L3 mode not supported - use L2 mode or veth)",
+                        "netkit device {} is in L3 mode (not supported - use L2 mode or veth)",
                         attrs.name
                     ));
                 }

src/runtime-rs/crates/resource/src/network/utils/link/manager.rs

@@ -5,7 +5,7 @@
 //
 
 use netlink_packet_route::link::{
-    InfoBridge, InfoData, InfoKind, LinkAttribute, LinkInfo, LinkMessage,
+    InfoBridge, InfoData, InfoKind, InfoNetkit, LinkAttribute, LinkInfo, LinkMessage, NetkitMode,
 };
 
 use super::{Link, LinkAttrs};
@@ -150,8 +150,8 @@ fn link_info(mut infos: Vec<LinkInfo>) -> Box<dyn Link> {
                 InfoData::Bridge(ibs) => {
                     link = Some(Box::new(parse_bridge(ibs)));
                 }
-                InfoData::Netkit(_) => {
-                    link = Some(Box::new(Netkit::default()));
+                InfoData::Netkit(nks) => {
+                    link = Some(Box::new(parse_netkit(nks)));
                 }
                 _ => {
                     link = Some(Box::new(Device::default()));
@@ -173,6 +173,17 @@ fn link_info(mut infos: Vec<LinkInfo>) -> Box<dyn Link> {
     link.unwrap()
 }
 
+fn parse_netkit(infos: Vec<InfoNetkit>) -> Netkit {
+    let mut netkit = Netkit::default();
+    for info in infos {
+        if let InfoNetkit::Mode(mode) = info {
+            netkit.mode = Some(mode);
+            break;
+        }
+    }
+    netkit
+}
+
 fn parse_bridge(mut ibs: Vec<InfoBridge>) -> Bridge {
     let mut bridge = Bridge::default();
     while let Some(ib) = ibs.pop() {
@@ -204,6 +215,9 @@ macro_rules! impl_network_dev {
             fn r#type(&self) -> &'static str {
                 $r_type
             }
+            fn as_any(&self) -> &dyn std::any::Any {
+                self
+            }
         }
     };
 }
@@ -222,7 +236,13 @@ macro_rules! define_and_impl_network_dev {
 define_and_impl_network_dev!("device", Device);
 define_and_impl_network_dev!("tuntap", Tuntap);
 define_and_impl_network_dev!("veth", Veth);
-define_and_impl_network_dev!("netkit", Netkit);
+#[derive(Debug, PartialEq, Eq, Clone, Default)]
+pub struct Netkit {
+    attrs: Option<LinkAttrs>,
+    pub mode: Option<NetkitMode>,
+}
+
+impl_network_dev!("netkit", Netkit);
 define_and_impl_network_dev!("ipvlan", IpVlan);
 define_and_impl_network_dev!("macvlan", MacVlan);
 define_and_impl_network_dev!("vlan", Vlan);

src/runtime-rs/crates/resource/src/network/utils/link/mod.rs

@@ -10,7 +10,7 @@ mod driver_info;
 pub use driver_info::get_driver_info;
 mod macros;
 mod manager;
-pub use manager::get_link_from_message;
+pub use manager::{get_link_from_message, Netkit};
 
 use std::os::unix::io::RawFd;
 
@@ -145,4 +145,5 @@ pub trait Link: Send + Sync {
     fn attrs(&self) -> &LinkAttrs;
     fn set_attrs(&mut self, attr: LinkAttrs);
     fn r#type(&self) -> &str;
+    fn as_any(&self) -> &dyn std::any::Any;
 }