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 load_sock_ops 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_helpers.h"
  21#include "bpf_endian.h"
  22
  23#define DEBUG 1
  24
  25#define bpf_printk(fmt, ...)                                    \
  26({                                                              \
  27               char ____fmt[] = fmt;                            \
  28               bpf_trace_printk(____fmt, sizeof(____fmt),       \
  29                                ##__VA_ARGS__);                 \
  30})
  31
  32SEC("sockops")
  33int bpf_iw(struct bpf_sock_ops *skops)
  34{
  35        int bufsize = 1500000;
  36        int rwnd_init = 40;
  37        int iw = 40;
  38        int rv = 0;
  39        int op;
  40
  41        /* For testing purposes, only execute rest of BPF program
  42         * if neither port numberis 55601
  43         */
  44        if (bpf_ntohl(skops->remote_port) != 55601 &&
  45            skops->local_port != 55601) {
  46                skops->reply = -1;
  47                return 1;
  48        }
  49
  50        op = (int) skops->op;
  51
  52#ifdef DEBUG
  53        bpf_printk("BPF command: %d\n", op);
  54#endif
  55
  56        /* Usually there would be a check to insure the hosts are far
  57         * from each other so it makes sense to increase buffer sizes
  58         */
  59        switch (op) {
  60        case BPF_SOCK_OPS_RWND_INIT:
  61                rv = rwnd_init;
  62                break;
  63        case BPF_SOCK_OPS_TCP_CONNECT_CB:
  64                /* Set sndbuf and rcvbuf of active connections */
  65                rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  66                                    sizeof(bufsize));
  67                rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  68                                     &bufsize, sizeof(bufsize));
  69                break;
  70        case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  71                rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
  72                                    sizeof(iw));
  73                break;
  74        case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  75                /* Set sndbuf and rcvbuf of passive connections */
  76                rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  77                                    sizeof(bufsize));
  78                rv +=  bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  79                                      &bufsize, sizeof(bufsize));
  80                break;
  81        default:
  82                rv = -1;
  83        }
  84#ifdef DEBUG
  85        bpf_printk("Returning %d\n", rv);
  86#endif
  87        skops->reply = rv;
  88        return 1;
  89}
  90char _license[] SEC("license") = "GPL";
  91