LXR linux/samples/bpf/tcp_iw

   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 initial congestion window and initial receive
   8 * window to 40 packets and send and receive buffers to 1.5MB. This
   9 * would usually be done after doing appropriate checks that indicate
  10 * the hosts are far enough away (i.e. large RTT).
  11 *
  12 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  13 */
  14
  15#include <uapi/linux/bpf.h>
  16#include <uapi/linux/if_ether.h>
  17#include <uapi/linux/if_packet.h>
  18#include <uapi/linux/ip.h>
  19#include <linux/socket.h>
  20#include <bpf/bpf_helpers.h>
  21#include <bpf/bpf_endian.h>
  22
  23#define DEBUG 1
  24
  25SEC("sockops")
  26int bpf_iw(struct bpf_sock_ops *skops)
  27{
  28        int bufsize = 1500000;
  29        int rwnd_init = 40;
  30        int iw = 40;
  31        int rv = 0;
  32        int op;
  33
  34        /* For testing purposes, only execute rest of BPF program
  35         * if neither port numberis 55601
  36         */
  37        if (bpf_ntohl(skops->remote_port) != 55601 &&
  38            skops->local_port != 55601) {
  39                skops->reply = -1;
  40                return 1;
  41        }
  42
  43        op = (int) skops->op;
  44
  45#ifdef DEBUG
  46        bpf_printk("BPF command: %d\n", op);
  47#endif
  48
  49        /* Usually there would be a check to insure the hosts are far
  50         * from each other so it makes sense to increase buffer sizes
  51         */
  52        switch (op) {
  53        case BPF_SOCK_OPS_RWND_INIT:
  54                rv = rwnd_init;
  55                break;
  56        case BPF_SOCK_OPS_TCP_CONNECT_CB:
  57                /* Set sndbuf and rcvbuf of active connections */
  58                rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  59                                    sizeof(bufsize));
  60                rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  61                                     &bufsize, sizeof(bufsize));
  62                break;
  63        case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  64                rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
  65                                    sizeof(iw));
  66                break;
  67        case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  68                /* Set sndbuf and rcvbuf of passive connections */
  69                rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  70                                    sizeof(bufsize));
  71                rv +=  bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  72                                      &bufsize, sizeof(bufsize));
  73                break;
  74        default:
  75                rv = -1;
  76        }
  77#ifdef DEBUG
  78        bpf_printk("Returning %d\n", rv);
  79#endif
  80        skops->reply = rv;
  81        return 1;
  82}
  83char _license[] SEC("license") = "GPL";
  84