net_util, virtio-devices, vhost_user_net: Relocate code for opening TAP

By moving the code for opening the TAP device into a shared location we
are starting to remove the requirement for the vhost-user-net backend to
depend on the virtio-devices crate which in of itself depends on many
other crates that are not necessary for the backend to function.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

Cargo.lock

@@ -638,6 +638,7 @@ dependencies = [
  "rand 0.7.3",
  "serde",
  "serde_json",
+ "virtio-bindings",
  "vmm-sys-util",
 ]
 

net_util/Cargo.toml

@@ -5,12 +5,12 @@ authors = ["The Chromium OS Authors"]
 
 [dependencies]
 libc = "0.2.72"
+net_gen = { path = "../net_gen" }
 rand = "0.7.3"
 serde = "1.0.114"
+virtio-bindings = "0.1.0"
 vmm-sys-util = ">=0.3.1"
 
-net_gen = { path = "../net_gen" }
-
 [dev-dependencies]
 lazy_static = "1.3.0"
 pnet = "0.26.0"

net_util/src/lib.rs

@@ -11,13 +11,14 @@
 #[macro_use]
 extern crate lazy_static;
 extern crate libc;
+extern crate net_gen;
 extern crate rand;
 extern crate serde;
-
-extern crate net_gen;
+extern crate virtio_bindings;
 extern crate vmm_sys_util;
 
 mod mac;
+mod open_tap;
 mod tap;
 
 use std::io::Error as IoError;
@@ -26,6 +27,7 @@ use std::net;
 use std::os::unix::io::FromRawFd;
 
 pub use mac::{MacAddr, MAC_ADDR_LEN};
+pub use open_tap::{open_tap, Error as OpenTapError};
 pub use tap::{Error as TapError, Tap};
 
 #[derive(Debug)]

net_util/src/open_tap.rs

@@ -0,0 +1,124 @@
+// Copyright (c) 2020 Intel Corporation. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+use super::TapError;
+use super::{MacAddr, Tap};
+use std::net::Ipv4Addr;
+use std::path::Path;
+use std::{fs, io};
+use virtio_bindings::bindings::virtio_net::virtio_net_hdr_v1;
+
+#[derive(Debug)]
+pub enum Error {
+    /// Failed to convert an hexadecimal string into an integer.
+    ConvertHexStringToInt(std::num::ParseIntError),
+    /// Error related to the multiqueue support.
+    MultiQueueSupport(String),
+    /// Failed to read the TAP flags from sysfs.
+    ReadSysfsTunFlags(io::Error),
+    /// Open tap device failed.
+    TapOpen(TapError),
+    /// Setting tap IP failed.
+    TapSetIp(TapError),
+    /// Setting tap netmask failed.
+    TapSetNetmask(TapError),
+    /// Setting MAC address failed
+    TapSetMac(TapError),
+    /// Getting MAC address failed
+    TapGetMac(TapError),
+    /// Setting tap interface offload flags failed.
+    TapSetOffload(TapError),
+    /// Setting vnet header size failed.
+    TapSetVnetHdrSize(TapError),
+    /// Enabling tap interface failed.
+    TapEnable(TapError),
+}
+
+type Result<T> = std::result::Result<T, Error>;
+
+fn vnet_hdr_len() -> usize {
+    std::mem::size_of::<virtio_net_hdr_v1>()
+}
+
+fn check_mq_support(if_name: &Option<&str>, queue_pairs: usize) -> Result<()> {
+    if let Some(tap_name) = if_name {
+        let mq = queue_pairs > 1;
+        let path = format!("/sys/class/net/{}/tun_flags", tap_name);
+        // interface does not exist, check is not required
+        if !Path::new(&path).exists() {
+            return Ok(());
+        }
+        let tun_flags_str = fs::read_to_string(path).map_err(Error::ReadSysfsTunFlags)?;
+        let tun_flags = u32::from_str_radix(tun_flags_str.trim().trim_start_matches("0x"), 16)
+            .map_err(Error::ConvertHexStringToInt)?;
+        if (tun_flags & net_gen::IFF_MULTI_QUEUE != 0) && !mq {
+            return Err(Error::MultiQueueSupport(String::from(
+                "TAP interface supports MQ while device does not",
+            )));
+        } else if (tun_flags & net_gen::IFF_MULTI_QUEUE == 0) && mq {
+            return Err(Error::MultiQueueSupport(String::from(
+                "Device supports MQ while TAP interface does not",
+            )));
+        }
+    }
+    Ok(())
+}
+
+/// Create a new virtio network device with the given IP address and
+/// netmask.
+pub fn open_tap(
+    if_name: Option<&str>,
+    ip_addr: Option<Ipv4Addr>,
+    netmask: Option<Ipv4Addr>,
+    host_mac: &mut Option<MacAddr>,
+    num_rx_q: usize,
+) -> Result<Vec<Tap>> {
+    let mut taps: Vec<Tap> = Vec::new();
+    let mut ifname: String = String::new();
+    let vnet_hdr_size = vnet_hdr_len() as i32;
+    let flag = net_gen::TUN_F_CSUM | net_gen::TUN_F_UFO | net_gen::TUN_F_TSO4 | net_gen::TUN_F_TSO6;
+
+    // In case the tap interface already exists, check if the number of
+    // queues is appropriate. The tap might not support multiqueue while
+    // the number of queues indicates the user expects multiple queues, or
+    // on the contrary, the tap might support multiqueue while the number
+    // of queues indicates the user doesn't expect multiple queues.
+    check_mq_support(&if_name, num_rx_q)?;
+
+    for i in 0..num_rx_q {
+        let tap: Tap;
+        if i == 0 {
+            tap = match if_name {
+                Some(name) => Tap::open_named(name, num_rx_q).map_err(Error::TapOpen)?,
+                None => Tap::new(num_rx_q).map_err(Error::TapOpen)?,
+            };
+            if let Some(ip) = ip_addr {
+                tap.set_ip_addr(ip).map_err(Error::TapSetIp)?;
+            }
+            if let Some(mask) = netmask {
+                tap.set_netmask(mask).map_err(Error::TapSetNetmask)?;
+            }
+            if let Some(mac) = host_mac {
+                tap.set_mac_addr(*mac).map_err(Error::TapSetMac)?
+            } else {
+                *host_mac = Some(tap.get_mac_addr().map_err(Error::TapGetMac)?)
+            }
+            tap.enable().map_err(Error::TapEnable)?;
+            tap.set_offload(flag).map_err(Error::TapSetOffload)?;
+
+            tap.set_vnet_hdr_size(vnet_hdr_size)
+                .map_err(Error::TapSetVnetHdrSize)?;
+
+            ifname = String::from_utf8(tap.get_if_name()).unwrap();
+        } else {
+            tap = Tap::open_named(ifname.as_str(), num_rx_q).map_err(Error::TapOpen)?;
+            tap.set_offload(flag).map_err(Error::TapSetOffload)?;
+
+            tap.set_vnet_hdr_size(vnet_hdr_size)
+                .map_err(Error::TapSetVnetHdrSize)?;
+        }
+        taps.push(tap);
+    }
+    Ok(taps)
+}

vhost_user_net/src/lib.rs

@@ -14,7 +14,7 @@ extern crate virtio_devices;
 
 use libc::{self, EFD_NONBLOCK};
 use log::*;
-use net_util::{MacAddr, Tap};
+use net_util::{open_tap, MacAddr, OpenTapError, Tap};
 use option_parser::{OptionParser, OptionParserError};
 use std::fmt;
 use std::io::{self};
@@ -28,7 +28,7 @@ use vhost_rs::vhost_user::{Error as VhostUserError, Listener};
 use vhost_user_backend::{VhostUserBackend, VhostUserDaemon, Vring, VringWorker};
 use virtio_bindings::bindings::virtio_net::*;
 use virtio_bindings::bindings::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
-use virtio_devices::net_util::{open_tap, RxVirtio, TxVirtio};
+use virtio_devices::net_util::{RxVirtio, TxVirtio};
 use virtio_devices::{NetCounters, NetQueuePair};
 use vm_memory::{GuestMemoryAtomic, GuestMemoryMmap};
 use vmm_sys_util::eventfd::EventFd;
@@ -66,7 +66,7 @@ pub enum Error {
     /// No memory configured.
     NoMemoryConfigured,
     /// Open tap device failed.
-    OpenTap(virtio_devices::net_util::Error),
+    OpenTap(OpenTapError),
     /// No socket provided
     SocketParameterMissing,
     /// Underlying QueuePair error

virtio-devices/src/net.rs

@@ -6,9 +6,9 @@
 // found in the THIRD-PARTY file.
 
 use super::net_util::{
-    build_net_config_space, build_net_config_space_with_mq, open_tap, register_listener,
-    unregister_listener, CtrlVirtio, NetCtrlEpollHandler, RxVirtio, TxVirtio, VirtioNetConfig,
-    KILL_EVENT, NET_EVENTS_COUNT, PAUSE_EVENT, RX_QUEUE_EVENT, RX_TAP_EVENT, TX_QUEUE_EVENT,
+    build_net_config_space, build_net_config_space_with_mq, register_listener, unregister_listener,
+    CtrlVirtio, NetCtrlEpollHandler, RxVirtio, TxVirtio, VirtioNetConfig, KILL_EVENT,
+    NET_EVENTS_COUNT, PAUSE_EVENT, RX_QUEUE_EVENT, RX_TAP_EVENT, TX_QUEUE_EVENT,
 };
 use super::Error as DeviceError;
 use super::{
@@ -18,6 +18,7 @@ use crate::VirtioInterrupt;
 use anyhow::anyhow;
 use libc::EAGAIN;
 use libc::EFD_NONBLOCK;
+use net_util::{open_tap, OpenTapError};
 use net_util::{MacAddr, Tap};
 use std::cmp;
 use std::collections::HashMap;
@@ -44,7 +45,7 @@ use vmm_sys_util::eventfd::EventFd;
 #[derive(Debug)]
 pub enum Error {
     /// Failed to open taps.
-    OpenTap(super::net_util::Error),
+    OpenTap(OpenTapError),
 }
 
 pub type Result<T> = result::Result<T, Error>;

virtio-devices/src/net_util.rs

@@ -4,17 +4,14 @@
 
 use super::Error as DeviceError;
 use super::{DescriptorChain, DeviceEventT, Queue};
-use net_util::{MacAddr, Tap, TapError};
+use net_util::{MacAddr, Tap};
 use serde::ser::{Serialize, SerializeStruct, Serializer};
 use std::cmp;
-use std::fs;
 use std::fs::File;
 use std::io::{self, Write};
 use std::mem;
-use std::net::Ipv4Addr;
 use std::num::Wrapping;
 use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
-use std::path::Path;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 use std::thread;
@@ -94,8 +91,6 @@ unsafe impl ByteValued for VirtioNetConfig {}
 
 #[derive(Debug)]
 pub enum Error {
-    /// Failed to convert an hexadecimal string into an integer.
-    ConvertHexStringToInt(std::num::ParseIntError),
     /// Read process MQ.
     FailedProcessMQ,
     /// Read queue failed.
@@ -108,30 +103,10 @@ pub enum Error {
     InvalidDesc,
     /// Invalid queue pairs number
     InvalidQueuePairsNum,
-    /// Error related to the multiqueue support.
-    MultiQueueSupport(String),
     /// No memory passed in.
     NoMemory,
     /// No ueue pairs nummber.
     NoQueuePairsNum,
-    /// Failed to read the TAP flags from sysfs.
-    ReadSysfsTunFlags(io::Error),
-    /// Open tap device failed.
-    TapOpen(TapError),
-    /// Setting tap IP failed.
-    TapSetIp(TapError),
-    /// Setting tap netmask failed.
-    TapSetNetmask(TapError),
-    /// Setting MAC address failed
-    TapSetMac(TapError),
-    /// Getting MAC address failed
-    TapGetMac(TapError),
-    /// Setting tap interface offload flags failed.
-    TapSetOffload(TapError),
-    /// Setting vnet header size failed.
-    TapSetVnetHdrSize(TapError),
-    /// Enabling tap interface failed.
-    TapEnable(TapError),
 }
 
 pub struct CtrlVirtio {
@@ -538,85 +513,3 @@ pub fn build_net_config_space_with_mq(
 fn vnet_hdr_len() -> usize {
     mem::size_of::<virtio_net_hdr_v1>()
 }
-
-fn check_mq_support(if_name: &Option<&str>, queue_pairs: usize) -> Result<()> {
-    if let Some(tap_name) = if_name {
-        let mq = queue_pairs > 1;
-        let path = format!("/sys/class/net/{}/tun_flags", tap_name);
-        // interface does not exist, check is not required
-        if !Path::new(&path).exists() {
-            return Ok(());
-        }
-        let tun_flags_str = fs::read_to_string(path).map_err(Error::ReadSysfsTunFlags)?;
-        let tun_flags = u32::from_str_radix(tun_flags_str.trim().trim_start_matches("0x"), 16)
-            .map_err(Error::ConvertHexStringToInt)?;
-        if (tun_flags & net_gen::IFF_MULTI_QUEUE != 0) && !mq {
-            return Err(Error::MultiQueueSupport(String::from(
-                "TAP interface supports MQ while device does not",
-            )));
-        } else if (tun_flags & net_gen::IFF_MULTI_QUEUE == 0) && mq {
-            return Err(Error::MultiQueueSupport(String::from(
-                "Device supports MQ while TAP interface does not",
-            )));
-        }
-    }
-    Ok(())
-}
-
-/// Create a new virtio network device with the given IP address and
-/// netmask.
-pub fn open_tap(
-    if_name: Option<&str>,
-    ip_addr: Option<Ipv4Addr>,
-    netmask: Option<Ipv4Addr>,
-    host_mac: &mut Option<MacAddr>,
-    num_rx_q: usize,
-) -> Result<Vec<Tap>> {
-    let mut taps: Vec<Tap> = Vec::new();
-    let mut ifname: String = String::new();
-    let vnet_hdr_size = vnet_hdr_len() as i32;
-    let flag = net_gen::TUN_F_CSUM | net_gen::TUN_F_UFO | net_gen::TUN_F_TSO4 | net_gen::TUN_F_TSO6;
-
-    // In case the tap interface already exists, check if the number of
-    // queues is appropriate. The tap might not support multiqueue while
-    // the number of queues indicates the user expects multiple queues, or
-    // on the contrary, the tap might support multiqueue while the number
-    // of queues indicates the user doesn't expect multiple queues.
-    check_mq_support(&if_name, num_rx_q)?;
-
-    for i in 0..num_rx_q {
-        let tap: Tap;
-        if i == 0 {
-            tap = match if_name {
-                Some(name) => Tap::open_named(name, num_rx_q).map_err(Error::TapOpen)?,
-                None => Tap::new(num_rx_q).map_err(Error::TapOpen)?,
-            };
-            if let Some(ip) = ip_addr {
-                tap.set_ip_addr(ip).map_err(Error::TapSetIp)?;
-            }
-            if let Some(mask) = netmask {
-                tap.set_netmask(mask).map_err(Error::TapSetNetmask)?;
-            }
-            if let Some(mac) = host_mac {
-                tap.set_mac_addr(*mac).map_err(Error::TapSetMac)?
-            } else {
-                *host_mac = Some(tap.get_mac_addr().map_err(Error::TapGetMac)?)
-            }
-            tap.enable().map_err(Error::TapEnable)?;
-            tap.set_offload(flag).map_err(Error::TapSetOffload)?;
-
-            tap.set_vnet_hdr_size(vnet_hdr_size)
-                .map_err(Error::TapSetVnetHdrSize)?;
-
-            ifname = String::from_utf8(tap.get_if_name()).unwrap();
-        } else {
-            tap = Tap::open_named(ifname.as_str(), num_rx_q).map_err(Error::TapOpen)?;
-            tap.set_offload(flag).map_err(Error::TapSetOffload)?;
-
-            tap.set_vnet_hdr_size(vnet_hdr_size)
-                .map_err(Error::TapSetVnetHdrSize)?;
-        }
-        taps.push(tap);
-    }
-    Ok(taps)
-}