drivers/net/virtio/virtio_user/vhost_kernel_tap.c

   1 /* SPDX-License-Identifier: BSD-3-Clause
   2  * Copyright(c) 2016 Intel Corporation
   3  */
   4
   5 #include <unistd.h>
   6 #include <sys/types.h>
   7 #include <sys/stat.h>
   8 #include <fcntl.h>
   9 #include <net/if.h>
  10 #include <errno.h>
  11 #include <string.h>
  12 #include <limits.h>
  13
  14 #include "vhost_kernel_tap.h"
  15 #include "../virtio_logs.h"
  16
  17 int
  18 vhost_kernel_open_tap(char **p_ifname, int hdr_size, int req_mq)
  19 {
  20         unsigned int tap_features;
  21         int sndbuf = INT_MAX;
  22         struct ifreq ifr;
  23         int tapfd;
  24         unsigned int offload =
  25                         TUN_F_CSUM |
  26                         TUN_F_TSO4 |
  27                         TUN_F_TSO6 |
  28                         TUN_F_TSO_ECN |
  29                         TUN_F_UFO;
  30
  31         /* TODO:
  32          * 1. verify we can get/set vnet_hdr_len, tap_probe_vnet_hdr_len
  33          * 2. get number of memory regions from vhost module parameter
  34          * max_mem_regions, supported in newer version linux kernel
  35          */
  36         tapfd = open(PATH_NET_TUN, O_RDWR);
  37         if (tapfd < 0) {
  38                 PMD_DRV_LOG(ERR, "fail to open %s: %s",
  39                             PATH_NET_TUN, strerror(errno));
  40                 return -1;
  41         }
  42
  43         /* Construct ifr */
  44         memset(&ifr, 0, sizeof(ifr));
  45         ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  46
  47         if (ioctl(tapfd, TUNGETFEATURES, &tap_features) == -1) {
  48                 PMD_DRV_LOG(ERR, "TUNGETFEATURES failed: %s", strerror(errno));
  49                 goto error;
  50         }
  51         if (tap_features & IFF_ONE_QUEUE)
  52                 ifr.ifr_flags |= IFF_ONE_QUEUE;
  53
  54         /* Let tap instead of vhost-net handle vnet header, as the latter does
  55          * not support offloading. And in this case, we should not set feature
  56          * bit VHOST_NET_F_VIRTIO_NET_HDR.
  57          */
  58         if (tap_features & IFF_VNET_HDR) {
  59                 ifr.ifr_flags |= IFF_VNET_HDR;
  60         } else {
  61                 PMD_DRV_LOG(ERR, "TAP does not support IFF_VNET_HDR");
  62                 goto error;
  63         }
  64
  65         if (req_mq)
  66                 ifr.ifr_flags |= IFF_MULTI_QUEUE;
  67
  68         if (*p_ifname)
  69                 strncpy(ifr.ifr_name, *p_ifname, IFNAMSIZ - 1);
  70         else
  71                 strncpy(ifr.ifr_name, "tap%d", IFNAMSIZ - 1);
  72         if (ioctl(tapfd, TUNSETIFF, (void *)&ifr) == -1) {
  73                 PMD_DRV_LOG(ERR, "TUNSETIFF failed: %s", strerror(errno));
  74                 goto error;
  75         }
  76
  77         fcntl(tapfd, F_SETFL, O_NONBLOCK);
  78
  79         if (ioctl(tapfd, TUNSETVNETHDRSZ, &hdr_size) < 0) {
  80                 PMD_DRV_LOG(ERR, "TUNSETVNETHDRSZ failed: %s", strerror(errno));
  81                 goto error;
  82         }
  83
  84         if (ioctl(tapfd, TUNSETSNDBUF, &sndbuf) < 0) {
  85                 PMD_DRV_LOG(ERR, "TUNSETSNDBUF failed: %s", strerror(errno));
  86                 goto error;
  87         }
  88
  89         /* TODO: before set the offload capabilities, we'd better (1) check
  90          * negotiated features to see if necessary to offload; (2) query tap
  91          * to see if it supports the offload capabilities.
  92          */
  93         if (ioctl(tapfd, TUNSETOFFLOAD, offload) != 0)
  94                 PMD_DRV_LOG(ERR, "TUNSETOFFLOAD ioctl() failed: %s",
  95                            strerror(errno));
  96
  97         if (!(*p_ifname))
  98                 *p_ifname = strdup(ifr.ifr_name);
  99
 100         return tapfd;
 101 error:
 102         close(tapfd);
 103         return -1;
 104 }