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      1 /*
      2  * Copyright (C) 2019 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "common/libs/utils/network.h"
     18 
     19 #include <linux/if.h>
     20 #include <linux/if_tun.h>
     21 #include <string.h>
     22 
     23 #include "common/libs/glog/logging.h"
     24 
     25 namespace cvd {
     26 namespace {
     27 // This should be the size of virtio_net_hdr_v1, from linux/virtio_net.h, but
     28 // the version of that header that ships with android in Pie does not include
     29 // that struct (it was added in Q).
     30 // This is what that struct looks like:
     31 // struct virtio_net_hdr_v1 {
     32 // u8 flags;
     33 // u8 gso_type;
     34 // u16 hdr_len;
     35 // u16 gso_size;
     36 // u16 csum_start;
     37 // u16 csum_offset;
     38 // u16 num_buffers;
     39 // };
     40 static constexpr int SIZE_OF_VIRTIO_NET_HDR_V1 = 12;
     41 }  // namespace
     42 
     43 SharedFD OpenTapInterface(const std::string& interface_name) {
     44   constexpr auto TUNTAP_DEV = "/dev/net/tun";
     45 
     46   auto tap_fd = SharedFD::Open(TUNTAP_DEV, O_RDWR | O_NONBLOCK);
     47   if (!tap_fd->IsOpen()) {
     48     LOG(ERROR) << "Unable to open tun device: " << tap_fd->StrError();
     49     return tap_fd;
     50   }
     51 
     52   struct ifreq ifr;
     53   memset(&ifr, 0, sizeof(ifr));
     54   ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
     55   strncpy(ifr.ifr_name, interface_name.c_str(), IFNAMSIZ);
     56 
     57   int err = tap_fd->Ioctl(TUNSETIFF, &ifr);
     58   if (err < 0) {
     59     LOG(ERROR) << "Unable to connect to " << interface_name
     60                << " tap interface: " << tap_fd->StrError();
     61     tap_fd->Close();
     62     return cvd::SharedFD();
     63   }
     64 
     65   // The interface's configuration may have been modified or just not set
     66   // correctly on creation. While qemu checks this and enforces the right
     67   // configuration, crosvm does not, so it needs to be set before it's passed to
     68   // it.
     69   tap_fd->Ioctl(TUNSETOFFLOAD,
     70                 reinterpret_cast<void*>(TUN_F_CSUM | TUN_F_UFO | TUN_F_TSO4 |
     71                                         TUN_F_TSO6));
     72   int len = SIZE_OF_VIRTIO_NET_HDR_V1;
     73   tap_fd->Ioctl(TUNSETVNETHDRSZ, &len);
     74 
     75   return tap_fd;
     76 }
     77 }  // namespace cvd
     78