LXR linux/samples/bpf/tcp_basertt

   1/* Copyright (c) 2017 Facebook
   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 * BPF program to set base_rtt to 80us when host is running TCP-NV and
   8 * both hosts are in the same datacenter (as determined by IPv6 prefix).
   9 *
  10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  11 */
  12
  13#include <uapi/linux/bpf.h>
  14#include <uapi/linux/tcp.h>
  15#include <uapi/linux/if_ether.h>
  16#include <uapi/linux/if_packet.h>
  17#include <uapi/linux/ip.h>
  18#include <linux/socket.h>
  19#include <bpf/bpf_helpers.h>
  20#include <bpf/bpf_endian.h>
  21
  22#define DEBUG 1
  23
  24SEC("sockops")
  25int bpf_basertt(struct bpf_sock_ops *skops)
  26{
  27        char cong[20];
  28        char nv[] = "nv";
  29        int rv = 0, n;
  30        int op;
  31
  32        op = (int) skops->op;
  33
  34#ifdef DEBUG
  35        bpf_printk("BPF command: %d\n", op);
  36#endif
  37
  38        /* Check if both hosts are in the same datacenter. For this
  39         * example they are if the 1st 5.5 bytes in the IPv6 address
  40         * are the same.
  41         */
  42        if (skops->family == AF_INET6 &&
  43            skops->local_ip6[0] == skops->remote_ip6[0] &&
  44            (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  45            (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  46                switch (op) {
  47                case BPF_SOCK_OPS_BASE_RTT:
  48                        n = bpf_getsockopt(skops, SOL_TCP, TCP_CONGESTION,
  49                                           cong, sizeof(cong));
  50                        if (!n && !__builtin_memcmp(cong, nv, sizeof(nv)+1)) {
  51                                /* Set base_rtt to 80us */
  52                                rv = 80;
  53                        } else if (n) {
  54                                rv = n;
  55                        } else {
  56                                rv = -1;
  57                        }
  58                        break;
  59                default:
  60                        rv = -1;
  61                }
  62        } else {
  63                rv = -1;
  64        }
  65#ifdef DEBUG
  66        bpf_printk("Returning %d\n", rv);
  67#endif
  68        skops->reply = rv;
  69        return 1;
  70}
  71char _license[] SEC("license") = "GPL";
  72