gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/runsc/sandbox/bpf/af_xdp.ebpf.c (about)

     1  // Copyright 2022 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // clang-format off
    16  // Contains types needed by later headers.
    17  #include <linux/types.h>
    18  // clang-format on
    19  #include <bpf/bpf_helpers.h>
    20  #include <linux/bpf.h>
    21  
    22  #define section(secname) __attribute__((section(secname), used))
    23  
    24  char __license[] section("license") = "Apache-2.0";
    25  
    26  // Note: bpf_helpers.h includes a struct definition for bpf_map_def in some, but
    27  // not all, environments. Define our own equivalent struct to avoid issues with
    28  // multiple declarations.
    29  struct gvisor_bpf_map_def {
    30    unsigned int type;
    31    unsigned int key_size;
    32    unsigned int value_size;
    33    unsigned int max_entries;
    34    unsigned int map_flags;
    35  };
    36  
    37  // A map of RX queue number to AF_XDP socket. We only ever use one key: 0.
    38  struct gvisor_bpf_map_def section("maps") sock_map = {
    39      .type = BPF_MAP_TYPE_XSKMAP,  // Note: "XSK" means AF_XDP socket.
    40      .key_size = sizeof(int),
    41      .value_size = sizeof(int),
    42      .max_entries = 1,
    43  };
    44  
    45  section("xdp") int xdp_prog(struct xdp_md *ctx) {
    46    // Lookup the socket for the current RX queue. Veth devices by default have
    47    // only one RX queue. If one is found, redirect the packet to that socket.
    48    // Otherwise pass it on to the kernel network stack.
    49    //
    50    // TODO: We can support multiple sockets with a fancier hash-based handoff.
    51    return bpf_redirect_map(&sock_map, ctx->rx_queue_index, XDP_PASS);
    52  }