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