wireguard-control: break up large updates into multiple netlink messages

netlink-request/src/lib.rs

@@ -1,7 +1,7 @@
 #[cfg(target_os = "linux")]
 mod linux {
-
+    pub const MAX_NETLINK_BUFFER_LENGTH: usize = 4096;
-    const NETLINK_BUFFER_LENGTH: usize = 4096;
+    pub const MAX_GENL_PAYLOAD_LENGTH: usize = MAX_NETLINK_BUFFER_LENGTH - GENL_HDRLEN;
 
     use netlink_packet_core::{
         NetlinkDeserializable, NetlinkMessage, NetlinkPayload, NetlinkSerializable, NLM_F_ACK,
@@ -9,7 +9,7 @@ mod linux {
     };
     use netlink_packet_generic::{
         ctrl::{nlas::GenlCtrlAttrs, GenlCtrl, GenlCtrlCmd},
-        GenlFamily, GenlMessage,
+        GenlFamily, GenlMessage, constants::GENL_HDRLEN,
     };
     use netlink_packet_route::RtnlMessage;
     use netlink_sys::{constants::NETLINK_GENERIC, protocols::NETLINK_ROUTE, Socket};
@@ -82,16 +82,16 @@ mod linux {
     {
         let mut req = NetlinkMessage::from(message);
 
-        if req.buffer_len() > NETLINK_BUFFER_LENGTH {
+        if req.buffer_len() > MAX_NETLINK_BUFFER_LENGTH {
             return Err(io::Error::new(
                 io::ErrorKind::InvalidInput,
-                format!("Serialized netlink packet larger than maximum size {}", NETLINK_BUFFER_LENGTH),
+                format!("Serialized netlink packet larger than maximum size {}", MAX_NETLINK_BUFFER_LENGTH),
             ));
         }
 
         req.header.flags = flags.unwrap_or(NLM_F_REQUEST | NLM_F_ACK | NLM_F_EXCL | NLM_F_CREATE);
         req.finalize();
-        let mut buf = [0; NETLINK_BUFFER_LENGTH];
+        let mut buf = [0; MAX_NETLINK_BUFFER_LENGTH];
         req.serialize(&mut buf);
         let len = req.buffer_len();
 
@@ -133,4 +133,4 @@ mod linux {
 }
 
 #[cfg(target_os = "linux")]
-pub use linux::{netlink_request, netlink_request_genl, netlink_request_rtnl};
+pub use linux::{netlink_request, netlink_request_genl, netlink_request_rtnl, MAX_NETLINK_BUFFER_LENGTH, MAX_GENL_PAYLOAD_LENGTH};

wireguard-control/src/backends/kernel.rs

@@ -12,7 +12,7 @@ use netlink_packet_route::{
         self,
         nlas::{Info, InfoKind},
     },
-    LinkMessage, RtnlMessage,
+    LinkMessage, RtnlMessage, traits::Emitable,
 };
 use netlink_packet_wireguard::{
     self,
@@ -20,7 +20,7 @@ use netlink_packet_wireguard::{
     nlas::{WgAllowedIpAttrs, WgDeviceAttrs, WgPeerAttrs},
     Wireguard, WireguardCmd,
 };
-use netlink_request::{netlink_request_genl, netlink_request_rtnl};
+use netlink_request::{netlink_request_genl, netlink_request_rtnl, MAX_GENL_PAYLOAD_LENGTH};
 
 use std::{convert::TryFrom, io};
 
@@ -216,33 +216,105 @@ fn add_del(iface: &InterfaceName, add: bool) -> io::Result<()> {
 
 pub fn apply(builder: &DeviceUpdate, iface: &InterfaceName) -> io::Result<()> {
     add_del(iface, true)?;
-    let mut nlas = vec![WgDeviceAttrs::IfName(iface.as_str_lossy().to_string())];
+    let mut payload = ApplyPayload::new(iface);
     if let Some(Key(k)) = builder.private_key {
-        nlas.push(WgDeviceAttrs::PrivateKey(k));
+        payload.push(WgDeviceAttrs::PrivateKey(k));
     }
     if let Some(f) = builder.fwmark {
-        nlas.push(WgDeviceAttrs::Fwmark(f));
+        payload.push(WgDeviceAttrs::Fwmark(f));
     }
     if let Some(f) = builder.listen_port {
-        nlas.push(WgDeviceAttrs::ListenPort(f));
+        payload.push(WgDeviceAttrs::ListenPort(f));
     }
     if builder.replace_peers {
-        nlas.push(WgDeviceAttrs::Flags(WGDEVICE_F_REPLACE_PEERS));
+        payload.push(WgDeviceAttrs::Flags(WGDEVICE_F_REPLACE_PEERS));
     }
-    let peers: Vec<Vec<_>> = builder
+
-        .peers
+    builder.peers
         .iter()
-        .map(PeerConfigBuilder::to_attrs)
+        .for_each(|peer| {
-        .collect();
+            payload.push_peer(peer.to_attrs())
-    nlas.push(WgDeviceAttrs::Peers(peers));
-    let genlmsg: GenlMessage<Wireguard> = GenlMessage::from_payload(Wireguard {
-        cmd: WireguardCmd::SetDevice,
-        nlas,
         });
-    netlink_request_genl(genlmsg, Some(NLM_F_REQUEST | NLM_F_ACK))?;
+
+    for message in payload.finish() {
+        netlink_request_genl(message, Some(NLM_F_REQUEST | NLM_F_ACK))?;
+    }
     Ok(())
 }
 
+struct ApplyPayload {
+    iface: String,
+    nlas: Vec<WgDeviceAttrs>,
+    current_buffer_len: usize,
+    messages: Vec<GenlMessage<Wireguard>>,
+}
+
+impl ApplyPayload {
+    fn new(iface: &InterfaceName) -> Self {
+        Self {
+            iface: iface.as_str_lossy().to_string(),
+            nlas: vec![],
+            messages: vec![],
+            current_buffer_len: 0,
+        }
+    }
+
+    fn flush_nlas(&mut self) {
+        // cleanup: clear out any empty peer lists.
+        self.nlas.retain(|nla| !matches!(nla, WgDeviceAttrs::Peers(peers) if peers.len() == 0));
+
+        let name = WgDeviceAttrs::IfName(self.iface.clone());
+        self.current_buffer_len = name.buffer_len();
+
+        if !self.nlas.is_empty() {
+            self.messages.push(GenlMessage::from_payload(Wireguard {
+                cmd: WireguardCmd::SetDevice,
+                nlas: std::mem::replace(&mut self.nlas, vec![name]),
+            }));
+        }
+    }
+
+    /// Push a device attribute which will be optimally packed into 1 or more netlink messages
+    pub fn push(&mut self, nla: WgDeviceAttrs) {
+        let nla_buffer_len = nla.buffer_len();
+        if (self.current_buffer_len + nla_buffer_len) > MAX_GENL_PAYLOAD_LENGTH {
+            self.flush_nlas();
+        }
+        self.nlas.push(nla);
+        self.current_buffer_len += nla_buffer_len;
+    }
+
+    /// A helper function to assist in breaking up large peer lists across multiple netlink messages
+    pub fn push_peer(&mut self, peer: Vec<WgPeerAttrs>) {
+        const EMPTY_PEERS: WgDeviceAttrs = WgDeviceAttrs::Peers(vec![]);
+        let mut needs_peer_nla = !self.nlas.iter().any(|nla| matches!(nla, WgDeviceAttrs::Peers(_)));
+        let peer_buffer_len = peer.as_slice().buffer_len() + 4;
+        let additional_buffer_len = peer_buffer_len + if needs_peer_nla { EMPTY_PEERS.buffer_len() } else { 0 };
+        if (self.current_buffer_len + additional_buffer_len) > MAX_GENL_PAYLOAD_LENGTH {
+            self.flush_nlas();
+            needs_peer_nla = true;
+        }
+
+        if needs_peer_nla {
+            self.push(EMPTY_PEERS);
+        }
+        let peers_nla = self.nlas.iter_mut().find_map(|nla| {
+            match nla {
+                WgDeviceAttrs::Peers(peers) => Some(peers),
+                _ => None,
+            }
+        }).expect("WgDeviceAttrs::Peers missing from NLAs when it should exist.");
+
+        peers_nla.push(peer);
+        self.current_buffer_len += peer_buffer_len;
+    }
+
+    pub fn finish(mut self) -> Vec<GenlMessage<Wireguard>> {
+        self.flush_nlas();
+        self.messages
+    }
+}
+
 pub fn get_by_name(name: &InterfaceName) -> Result<Device, io::Error> {
     let genlmsg: GenlMessage<Wireguard> = GenlMessage::from_payload(Wireguard {
         cmd: WireguardCmd::GetDevice,
@@ -265,3 +337,57 @@ pub fn get_by_name(name: &InterfaceName) -> Result<Device, io::Error> {
 pub fn delete_interface(iface: &InterfaceName) -> io::Result<()> {
     add_del(iface, false)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use netlink_request::MAX_NETLINK_BUFFER_LENGTH;
+    use std::str::FromStr;
+
+    #[test]
+    fn test_simple_payload() {
+        let mut payload = ApplyPayload::new(&InterfaceName::from_str("wg0").unwrap());
+        payload.push(WgDeviceAttrs::PrivateKey([1u8; 32]));
+        payload.push(WgDeviceAttrs::Fwmark(111));
+        payload.push(WgDeviceAttrs::ListenPort(12345));
+        payload.push(WgDeviceAttrs::Flags(WGDEVICE_F_REPLACE_PEERS));
+        payload.push_peer(vec![
+            WgPeerAttrs::PublicKey([2u8; 32]),
+            WgPeerAttrs::PersistentKeepalive(25),
+            WgPeerAttrs::Endpoint("1.1.1.1:51820".parse().unwrap()),
+            WgPeerAttrs::AllowedIps(vec![vec![
+                WgAllowedIpAttrs::Family(AF_INET),
+                WgAllowedIpAttrs::IpAddr([10, 1, 1, 1].into()),
+                WgAllowedIpAttrs::Cidr(24)
+            ]]),
+        ]);
+        assert_eq!(payload.finish().len(), 1);
+    }
+
+    #[test]
+    fn test_massive_payload() {
+        let mut payload = ApplyPayload::new(&InterfaceName::from_str("wg0").unwrap());
+        payload.push(WgDeviceAttrs::PrivateKey([1u8; 32]));
+        payload.push(WgDeviceAttrs::Fwmark(111));
+        payload.push(WgDeviceAttrs::ListenPort(12345));
+        payload.push(WgDeviceAttrs::Flags(WGDEVICE_F_REPLACE_PEERS));
+        for _ in 0..10_000 {
+            payload.push_peer(vec![
+                WgPeerAttrs::PublicKey([2u8; 32]),
+                WgPeerAttrs::PersistentKeepalive(25),
+                WgPeerAttrs::Endpoint("1.1.1.1:51820".parse().unwrap()),
+                WgPeerAttrs::AllowedIps(vec![vec![
+                    WgAllowedIpAttrs::Family(AF_INET),
+                    WgAllowedIpAttrs::IpAddr([10, 1, 1, 1].into()),
+                    WgAllowedIpAttrs::Cidr(24)
+                ]]),
+            ]);
+        }
+
+        let messages = payload.finish();
+        assert!(messages.len() > 1);
+        for message in messages {
+            assert!(message.buffer_len() < MAX_NETLINK_BUFFER_LENGTH);
+        }
+    }
+}