common/libs/utils/network.cpp

/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "common/libs/utils/network.h"

#include <linux/if.h>
#include <linux/if_tun.h>
#include <string.h>

#include <android-base/strings.h>
#include "common/libs/glog/logging.h"

#include "common/libs/utils/environment.h"
#include "common/libs/utils/subprocess.h"

namespace cvd {
namespace {

static std::string DefaultHostArtifactsPath(const std::string& file_name) {
  return (cvd::StringFromEnv("ANDROID_HOST_OUT",
                             cvd::StringFromEnv("HOME", ".")) +
          "/") +
         file_name;
}

// This should be the size of virtio_net_hdr_v1, from linux/virtio_net.h, but
// the version of that header that ships with android in Pie does not include
// that struct (it was added in Q).
// This is what that struct looks like:
// struct virtio_net_hdr_v1 {
// u8 flags;
// u8 gso_type;
// u16 hdr_len;
// u16 gso_size;
// u16 csum_start;
// u16 csum_offset;
// u16 num_buffers;
// };
static constexpr int SIZE_OF_VIRTIO_NET_HDR_V1 = 12;
}  // namespace

SharedFD OpenTapInterface(const std::string& interface_name) {
  constexpr auto TUNTAP_DEV = "/dev/net/tun";

  auto tap_fd = SharedFD::Open(TUNTAP_DEV, O_RDWR | O_NONBLOCK);
  if (!tap_fd->IsOpen()) {
    LOG(ERROR) << "Unable to open tun device: " << tap_fd->StrError();
    return tap_fd;
  }

  if (cvd::HostArch() == "aarch64") {
    auto tapsetiff_path = DefaultHostArtifactsPath("bin/tapsetiff");
    cvd::Command cmd(tapsetiff_path);
    cmd.AddParameter(tap_fd);
    cmd.AddParameter(interface_name.c_str());
    int ret = cmd.Start().Wait();
    if (ret != 0) {
      LOG(ERROR) << "Unable to run tapsetiff.py. Exited with status " << ret;
      tap_fd->Close();
      return cvd::SharedFD();
    }
  } else {
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
    strncpy(ifr.ifr_name, interface_name.c_str(), IFNAMSIZ);

    int err = tap_fd->Ioctl(TUNSETIFF, &ifr);
    if (err < 0) {
      LOG(ERROR) << "Unable to connect to " << interface_name
                 << " tap interface: " << tap_fd->StrError();
      tap_fd->Close();
      return cvd::SharedFD();
    }

    // The interface's configuration may have been modified or just not set
    // correctly on creation. While qemu checks this and enforces the right
    // configuration, crosvm does not, so it needs to be set before it's passed to
    // it.
    tap_fd->Ioctl(TUNSETOFFLOAD,
                  reinterpret_cast<void*>(TUN_F_CSUM | TUN_F_UFO | TUN_F_TSO4 |
                                        TUN_F_TSO6));
    int len = SIZE_OF_VIRTIO_NET_HDR_V1;
    tap_fd->Ioctl(TUNSETVNETHDRSZ, &len);
  }

  return tap_fd;
}

std::set<std::string> TapInterfacesInUse() {
  Command cmd("/bin/bash");
  cmd.AddParameter("-c");
  cmd.AddParameter("egrep -h -e \"^iff:.*\" /proc/*/fdinfo/*");
  std::string stdin, stdout, stderr;
  RunWithManagedStdio(std::move(cmd), &stdin, &stdout, &stderr);
  auto lines = android::base::Split(stdout, "\n");
  std::set<std::string> tap_interfaces;
  for (const auto& line : lines) {
    if (line == "") {
      continue;
    }
    if (!android::base::StartsWith(line, "iff:\t")) {
      LOG(ERROR) << "Unexpected line \"" << line << "\"";
      continue;
    }
    tap_interfaces.insert(line.substr(std::string("iff:\t").size()));
  }
  return tap_interfaces;
}
}  // namespace cvd