net_util: Introduce virtio-net control queue handling code

This code is ported from the net_util.rs in virtio-devices. The point
being to move it to the net_util crate so that it can later be reused
from vhost-user-net backend.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

net_util/src/ctrl_queue.rs

@@ -0,0 +1,140 @@
+// Copyright (c) 2021 Intel Corporation. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+use crate::Tap;
+use libc::c_uint;
+use virtio_bindings::bindings::virtio_net::{
+    VIRTIO_NET_CTRL_GUEST_OFFLOADS, VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, VIRTIO_NET_CTRL_MQ,
+    VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX, VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN,
+    VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, VIRTIO_NET_ERR, VIRTIO_NET_F_GUEST_CSUM,
+    VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
+    VIRTIO_NET_F_GUEST_UFO, VIRTIO_NET_OK,
+};
+use vm_memory::{ByteValued, Bytes, GuestMemoryError, GuestMemoryMmap};
+use vm_virtio::Queue;
+
+#[derive(Debug)]
+pub enum Error {
+    /// Read queue failed.
+    GuestMemory(GuestMemoryError),
+    /// No queue pairs number.
+    NoQueuePairsDescriptor,
+    /// No status descriptor
+    NoStatusDescriptor,
+}
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[repr(C, packed)]
+#[derive(Debug, Clone, Copy, Default)]
+pub struct ControlHeader {
+    pub class: u8,
+    pub cmd: u8,
+}
+
+unsafe impl ByteValued for ControlHeader {}
+
+pub struct CtrlQueue {
+    pub taps: Vec<Tap>,
+}
+
+impl CtrlQueue {
+    pub fn new(taps: Vec<Tap>) -> Self {
+        CtrlQueue { taps }
+    }
+
+    pub fn process(&mut self, mem: &GuestMemoryMmap, queue: &mut Queue) -> Result<bool> {
+        let mut used_desc_heads = Vec::new();
+        for avail_desc in queue.iter(&mem) {
+            let ctrl_hdr: ControlHeader =
+                mem.read_obj(avail_desc.addr).map_err(Error::GuestMemory)?;
+            let data_desc = avail_desc
+                .next_descriptor()
+                .ok_or(Error::NoQueuePairsDescriptor)?;
+            let status_desc = data_desc
+                .next_descriptor()
+                .ok_or(Error::NoStatusDescriptor)?;
+
+            let ok = match u32::from(ctrl_hdr.class) {
+                VIRTIO_NET_CTRL_MQ => {
+                    let queue_pairs = mem
+                        .read_obj::<u16>(data_desc.addr)
+                        .map_err(Error::GuestMemory)?;
+                    if u32::from(ctrl_hdr.cmd) != VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET {
+                        warn!("Unsupported command: {}", ctrl_hdr.cmd);
+                        false
+                    } else if (queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN as u16)
+                        || (queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX as u16)
+                    {
+                        warn!("Number of MQ pairs out of range: {}", queue_pairs);
+                        false
+                    } else {
+                        info!("Number of MQ pairs requested: {}", queue_pairs);
+                        true
+                    }
+                }
+                VIRTIO_NET_CTRL_GUEST_OFFLOADS => {
+                    let features = mem
+                        .read_obj::<u64>(data_desc.addr)
+                        .map_err(Error::GuestMemory)?;
+                    if u32::from(ctrl_hdr.cmd) != VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET {
+                        warn!("Unsupported command: {}", ctrl_hdr.cmd);
+                        false
+                    } else {
+                        let mut ok = true;
+                        for tap in self.taps.iter_mut() {
+                            info!("Reprogramming tap offload with features: {}", features);
+                            tap.set_offload(virtio_features_to_tap_offload(features))
+                                .map_err(|e| {
+                                    error!("Error programming tap offload: {:?}", e);
+                                    ok = false
+                                })
+                                .ok();
+                        }
+                        ok
+                    }
+                }
+                _ => {
+                    warn!("Unsupported command {:?}", ctrl_hdr);
+                    false
+                }
+            };
+
+            mem.write_obj(
+                if ok { VIRTIO_NET_OK } else { VIRTIO_NET_ERR } as u8,
+                status_desc.addr,
+            )
+            .map_err(Error::GuestMemory)?;
+            used_desc_heads.push((avail_desc.index, avail_desc.len));
+        }
+
+        for (desc_index, len) in used_desc_heads.iter() {
+            queue.add_used(&mem, *desc_index, *len);
+            queue.update_avail_event(&mem);
+        }
+
+        Ok(!used_desc_heads.is_empty())
+    }
+}
+
+pub fn virtio_features_to_tap_offload(features: u64) -> c_uint {
+    let mut tap_offloads: c_uint = 0;
+    if features & (1 << VIRTIO_NET_F_GUEST_CSUM) != 0 {
+        tap_offloads |= net_gen::TUN_F_CSUM;
+    }
+    if features & (1 << VIRTIO_NET_F_GUEST_TSO4) != 0 {
+        tap_offloads |= net_gen::TUN_F_TSO4;
+    }
+    if features & (1 << VIRTIO_NET_F_GUEST_TSO6) != 0 {
+        tap_offloads |= net_gen::TUN_F_TSO6;
+    }
+    if features & (1 << VIRTIO_NET_F_GUEST_ECN) != 0 {
+        tap_offloads |= net_gen::TUN_F_TSO_ECN;
+    }
+    if features & (1 << VIRTIO_NET_F_GUEST_UFO) != 0 {
+        tap_offloads |= net_gen::TUN_F_UFO;
+    }
+
+    tap_offloads
+}

net_util/src/lib.rs

@@ -13,6 +13,7 @@ extern crate lazy_static;
 #[macro_use]
 extern crate log;
 
+mod ctrl_queue;
 mod mac;
 mod open_tap;
 mod queue_pair;
@@ -22,6 +23,7 @@ use std::io::Error as IoError;
 use std::os::unix::io::{FromRawFd, RawFd};
 use std::{io, mem, net};
 
+pub use ctrl_queue::{CtrlQueue, Error as CtrlQueueError};
 pub use mac::{MacAddr, MAC_ADDR_LEN};
 pub use open_tap::{open_tap, Error as OpenTapError};
 pub use queue_pair::{NetCounters, NetQueuePair, NetQueuePairError, RxVirtio, TxVirtio};