Merge pull request #470 from Luap99/macvlan-rename

macvlan: fix name collision on hostns

src/network/macvlan.rs

@@ -2,6 +2,7 @@ use std::{collections::HashMap, net::IpAddr, os::unix::prelude::RawFd};
 
 use log::debug;
 use netlink_packet_route::nlas::link::{InfoData, InfoKind, InfoMacVlan, Nla};
+use rand::distributions::{Alphanumeric, DistString};
 
 use crate::{
     dns::aardvark::AardvarkEntry,
@@ -165,7 +166,48 @@ fn setup(
     opts.info_data = Some(InfoData::MacVlan(vec![InfoMacVlan::Mode(
         data.macvlan_mode,
     )]));
-    host.create_link(opts).wrap("create macvlan interface")?;
+    let mut result = host.create_link(opts.clone());
+    // Sigh, the kernel creates the interface first in the hostns before moving it into the netns.
+    // Therefore it can fail with EEXIST if the name is already used on the host. Create the link
+    // with tmp name, then rename it in the netns.
+    // If you change the iterations here make sure to match the number in early return case below as well.
+    for i in 0..3 {
+        match result {
+            // no error we can break
+            Ok(_) => break,
+
+            Err(err) => match err {
+                NetavarkError::Netlink(ref e) if -e.code == libc::EEXIST => {
+                    let random = Alphanumeric.sample_string(&mut rand::thread_rng(), 10);
+                    let tmp_name = "mv-".to_string() + &random;
+                    let mut opts = opts.clone();
+                    opts.name = tmp_name.clone();
+                    result = host.create_link(opts);
+                    if let Err(ref e) = result {
+                        // if last element return directly
+                        if i == 2 {
+                            return Err(NetavarkError::msg(format!(
+                                "create macvlan interface: {}",
+                                e
+                            )));
+                        }
+                        // retry, error could EEXIST again because we pick a random name
+                        continue;
+                    }
+                    let link = netns
+                        .get_link(netlink::LinkID::Name(tmp_name))
+                        .wrap("get tmp macvlan interface")?;
+                    netns
+                        .set_link_name(link.header.index, if_name.to_string())
+                        .wrap("rename tmp macvlan interface")?;
+
+                    // successful run, break out of loop
+                    break;
+                }
+                err => return Err(err).wrap("create macvlan interface")?,
+            },
+        }
+    }
 
     exec_netns!(hostns_fd, netns_fd, res, { disable_ipv6_autoconf(if_name) });
     res?; // return autoconf sysctl error

src/network/netlink.rs

@@ -23,8 +23,9 @@ pub struct Socket {
     buffer: [u8; 8192],
 }
 
+#[derive(Clone)]
 pub struct CreateLinkOptions {
-    name: String,
+    pub name: String,
     kind: InfoKind,
     pub info_data: Option<InfoData>,
     pub mtu: u32,
@@ -130,6 +131,16 @@ impl Socket {
         Ok(())
     }
 
+    pub fn set_link_name(&mut self, id: u32, name: String) -> NetavarkResult<()> {
+        let mut msg = LinkMessage::default();
+        msg.header.index = id;
+        msg.nlas.push(Nla::IfName(name));
+        let result = self.make_netlink_request(RtnlMessage::SetLink(msg), NLM_F_ACK)?;
+        expect_netlink_result!(result, 0);
+
+        Ok(())
+    }
+
     pub fn del_link(&mut self, id: LinkID) -> NetavarkResult<()> {
         let mut msg = LinkMessage::default();
 

test/300-macvlan.bats

@@ -236,3 +236,50 @@ EOF
    assert_json "$link_info" ".[].address" "=="  "$mac" "MAC matches container mac"
    assert_json "$link_info" '.[].flags[] | select(.=="UP")' "=="  "UP" "Container interface is up"
 }
+
+
+@test "macvlan same interface name on host" {
+
+           read -r -d '\0' config <<EOF
+{
+   "container_id": "someID",
+   "container_name": "someName",
+   "networks": {
+      "podman": {
+         "static_ips": [
+            "10.88.0.2"
+         ],
+         "interface_name": "eth0"
+      }
+   },
+   "network_info": {
+      "podman": {
+         "name": "podman",
+         "id": "2f259bab93aaaaa2542ba43ef33eb990d0999ee1b9924b557b7be53c0b7a1bb9",
+         "driver": "macvlan",
+         "network_interface": "eth0",
+         "subnets": [
+            {
+               "subnet": "10.88.0.0/16",
+               "gateway": "10.88.0.1"
+            }
+         ],
+         "ipv6_enabled": false,
+         "internal": false,
+         "dns_enabled": false,
+         "ipam_options": {
+            "driver": "host-local"
+         }
+      }
+   }
+}\0
+EOF
+
+   run_in_host_netns ip link add eth0 type dummy
+
+   run_netavark setup $(get_container_netns_path) <<<"$config"
+
+   run_in_container_netns ip link show eth0
+
+   run_netavark teardown $(get_container_netns_path) <<<"$config"
+}