LXR linux/samples/bpf/xdp_redirect_map

   1/* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
   2 *
   3 * This program is free software; you can redistribute it and/or
   4 * modify it under the terms of version 2 of the GNU General Public
   5 * License as published by the Free Software Foundation.
   6 *
   7 * This program is distributed in the hope that it will be useful, but
   8 * WITHOUT ANY WARRANTY; without even the implied warranty of
   9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10 * General Public License for more details.
  11 */
  12#define KBUILD_MODNAME "foo"
  13#include <uapi/linux/bpf.h>
  14#include <linux/in.h>
  15#include <linux/if_ether.h>
  16#include <linux/if_packet.h>
  17#include <linux/if_vlan.h>
  18#include <linux/ip.h>
  19#include <linux/ipv6.h>
  20#include <bpf/bpf_helpers.h>
  21
  22/* The 2nd xdp prog on egress does not support skb mode, so we define two
  23 * maps, tx_port_general and tx_port_native.
  24 */
  25struct {
  26        __uint(type, BPF_MAP_TYPE_DEVMAP);
  27        __uint(key_size, sizeof(int));
  28        __uint(value_size, sizeof(int));
  29        __uint(max_entries, 100);
  30} tx_port_general SEC(".maps");
  31
  32struct {
  33        __uint(type, BPF_MAP_TYPE_DEVMAP);
  34        __uint(key_size, sizeof(int));
  35        __uint(value_size, sizeof(struct bpf_devmap_val));
  36        __uint(max_entries, 100);
  37} tx_port_native SEC(".maps");
  38
  39/* Count RX packets, as XDP bpf_prog doesn't get direct TX-success
  40 * feedback.  Redirect TX errors can be caught via a tracepoint.
  41 */
  42struct {
  43        __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
  44        __type(key, u32);
  45        __type(value, long);
  46        __uint(max_entries, 1);
  47} rxcnt SEC(".maps");
  48
  49/* map to store egress interface mac address */
  50struct {
  51        __uint(type, BPF_MAP_TYPE_ARRAY);
  52        __type(key, u32);
  53        __type(value, __be64);
  54        __uint(max_entries, 1);
  55} tx_mac SEC(".maps");
  56
  57static void swap_src_dst_mac(void *data)
  58{
  59        unsigned short *p = data;
  60        unsigned short dst[3];
  61
  62        dst[0] = p[0];
  63        dst[1] = p[1];
  64        dst[2] = p[2];
  65        p[0] = p[3];
  66        p[1] = p[4];
  67        p[2] = p[5];
  68        p[3] = dst[0];
  69        p[4] = dst[1];
  70        p[5] = dst[2];
  71}
  72
  73static __always_inline int xdp_redirect_map(struct xdp_md *ctx, void *redirect_map)
  74{
  75        void *data_end = (void *)(long)ctx->data_end;
  76        void *data = (void *)(long)ctx->data;
  77        struct ethhdr *eth = data;
  78        int rc = XDP_DROP;
  79        long *value;
  80        u32 key = 0;
  81        u64 nh_off;
  82        int vport;
  83
  84        nh_off = sizeof(*eth);
  85        if (data + nh_off > data_end)
  86                return rc;
  87
  88        /* constant virtual port */
  89        vport = 0;
  90
  91        /* count packet in global counter */
  92        value = bpf_map_lookup_elem(&rxcnt, &key);
  93        if (value)
  94                *value += 1;
  95
  96        swap_src_dst_mac(data);
  97
  98        /* send packet out physical port */
  99        return bpf_redirect_map(redirect_map, vport, 0);
 100}
 101
 102SEC("xdp_redirect_general")
 103int xdp_redirect_map_general(struct xdp_md *ctx)
 104{
 105        return xdp_redirect_map(ctx, &tx_port_general);
 106}
 107
 108SEC("xdp_redirect_native")
 109int xdp_redirect_map_native(struct xdp_md *ctx)
 110{
 111        return xdp_redirect_map(ctx, &tx_port_native);
 112}
 113
 114SEC("xdp_devmap/map_prog")
 115int xdp_redirect_map_egress(struct xdp_md *ctx)
 116{
 117        void *data_end = (void *)(long)ctx->data_end;
 118        void *data = (void *)(long)ctx->data;
 119        struct ethhdr *eth = data;
 120        __be64 *mac;
 121        u32 key = 0;
 122        u64 nh_off;
 123
 124        nh_off = sizeof(*eth);
 125        if (data + nh_off > data_end)
 126                return XDP_DROP;
 127
 128        mac = bpf_map_lookup_elem(&tx_mac, &key);
 129        if (mac)
 130                __builtin_memcpy(eth->h_source, mac, ETH_ALEN);
 131
 132        return XDP_PASS;
 133}
 134
 135/* Redirect require an XDP bpf_prog loaded on the TX device */
 136SEC("xdp_redirect_dummy")
 137int xdp_redirect_dummy_prog(struct xdp_md *ctx)
 138{
 139        return XDP_PASS;
 140}
 141
 142char _license[] SEC("license") = "GPL";
 143