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 "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_clamp(struct bpf_sock_ops *skops)
  27{
  28        int bufsize = 150000;
  29        int to_init = 10;
  30        int clamp = 100;
  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 && skops->local_port != 55601) {
  38                skops->reply = -1;
  39                return 0;
  40        }
  41
  42        op = (int) skops->op;
  43
  44#ifdef DEBUG
  45        bpf_printk("BPF command: %d\n", op);
  46#endif
  47
  48        /* Check that both hosts are within same datacenter. For this example
  49         * it is the case when the first 5.5 bytes of their IPv6 addresses are
  50         * the same.
  51         */
  52        if (skops->family == AF_INET6 &&
  53            skops->local_ip6[0] == skops->remote_ip6[0] &&
  54            (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  55            (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  56                switch (op) {
  57                case BPF_SOCK_OPS_TIMEOUT_INIT:
  58                        rv = to_init;
  59                        break;
  60                case BPF_SOCK_OPS_TCP_CONNECT_CB:
  61                        /* Set sndbuf and rcvbuf of active connections */
  62                        rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
  63                                            &bufsize, sizeof(bufsize));
  64                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  65                                             SO_RCVBUF, &bufsize,
  66                                             sizeof(bufsize));
  67                        break;
  68                case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  69                        rv = bpf_setsockopt(skops, SOL_TCP,
  70                                            TCP_BPF_SNDCWND_CLAMP,
  71                                            &clamp, sizeof(clamp));
  72                        break;
  73                case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  74                        /* Set sndbuf and rcvbuf of passive connections */
  75                        rv = bpf_setsockopt(skops, SOL_TCP,
  76                                            TCP_BPF_SNDCWND_CLAMP,
  77                                            &clamp, sizeof(clamp));
  78                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  79                                             SO_SNDBUF, &bufsize,
  80                                             sizeof(bufsize));
  81                        rv += bpf_setsockopt(skops, SOL_SOCKET,
  82                                             SO_RCVBUF, &bufsize,
  83                                             sizeof(bufsize));
  84                        break;
  85                default:
  86                        rv = -1;
  87                }
  88        } else {
  89                rv = -1;
  90        }
  91#ifdef DEBUG
  92        bpf_printk("Returning %d\n", rv);
  93#endif
  94        skops->reply = rv;
  95        return 1;
  96}
  97char _license[] SEC("license") = "GPL";
  98