LXR linux/samples/bpf/tcp_clamp

   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 * Sample BPF program to set send and receive buffers to 150KB, sndcwnd clamp
   8 * to 100 packets and SYN and SYN_ACK RTOs to 10ms when both hosts are within
   9 * the same datacenter. For his example, we assume they are within the same
  10 * datacenter when the first 5.5 bytes of their IPv6 addresses are the same.
  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_clamp(struct bpf_sock_ops *skops)
  34{
  35        int bufsize = 150000;
  36        int to_init = 10;
  37        int clamp = 100;
  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 && skops->local_port != 55601) {
  45                skops->reply = -1;
  46                return 0;
  47        }
  48
  49        op = (int) skops->op;
  50
  51#ifdef DEBUG
  52        bpf_printk("BPF command: %d\n", op);
  53#endif
  54
  55        /* Check that both hosts are within same datacenter. For this example
  56         * it is the case when the first 5.5 bytes of their IPv6 addresses are
  57         * the same.
  58         */
  59        if (skops->family == AF_INET6 &&
  60            skops->local_ip6[0] == skops->remote_ip6[0] &&
  61            (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  62            (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  63                switch (op) {
  64                case BPF_SOCK_OPS_TIMEOUT_INIT:
  65                        rv = to_init;
  66                        break;
  67                case BPF_SOCK_OPS_TCP_CONNECT_CB:
  68                        /* Set sndbuf and rcvbuf of active connections */
  69                        rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
  70                                            &bufsize, sizeof(bufsize));
  71                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  72                                             SO_RCVBUF, &bufsize,
  73                                             sizeof(bufsize));
  74                        break;
  75                case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  76                        rv = bpf_setsockopt(skops, SOL_TCP,
  77                                            TCP_BPF_SNDCWND_CLAMP,
  78                                            &clamp, sizeof(clamp));
  79                        break;
  80                case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  81                        /* Set sndbuf and rcvbuf of passive connections */
  82                        rv = bpf_setsockopt(skops, SOL_TCP,
  83                                            TCP_BPF_SNDCWND_CLAMP,
  84                                            &clamp, sizeof(clamp));
  85                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  86                                             SO_SNDBUF, &bufsize,
  87                                             sizeof(bufsize));
  88                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  89                                             SO_RCVBUF, &bufsize,
  90                                             sizeof(bufsize));
  91                        break;
  92                default:
  93                        rv = -1;
  94                }
  95        } else {
  96                rv = -1;
  97        }
  98#ifdef DEBUG
  99        bpf_printk("Returning %d\n", rv);
 100#endif
 101        skops->reply = rv;
 102        return 1;
 103}
 104char _license[] SEC("license") = "GPL";
 105