LXR linux/samples/bpf/tcp_cong

   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 congestion control to dctcp when both hosts are
   8 * in the same datacenter (as deteremined by IPv6 prefix).
   9 *
  10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  11 */
  12
  13#include <uapi/linux/bpf.h>
  14#include <uapi/linux/tcp.h>
  15#include <uapi/linux/if_ether.h>
  16#include <uapi/linux/if_packet.h>
  17#include <uapi/linux/ip.h>
  18#include <linux/socket.h>
  19#include "bpf_helpers.h"
  20#include "bpf_endian.h"
  21
  22#define DEBUG 1
  23
  24#define bpf_printk(fmt, ...)                                    \
  25({                                                              \
  26               char ____fmt[] = fmt;                            \
  27               bpf_trace_printk(____fmt, sizeof(____fmt),       \
  28                                ##__VA_ARGS__);                 \
  29})
  30
  31SEC("sockops")
  32int bpf_cong(struct bpf_sock_ops *skops)
  33{
  34        char cong[] = "dctcp";
  35        int rv = 0;
  36        int op;
  37
  38        /* For testing purposes, only execute rest of BPF program
  39         * if neither port numberis 55601
  40         */
  41        if (bpf_ntohl(skops->remote_port) != 55601 &&
  42            skops->local_port != 55601) {
  43                skops->reply = -1;
  44                return 1;
  45        }
  46
  47        op = (int) skops->op;
  48
  49#ifdef DEBUG
  50        bpf_printk("BPF command: %d\n", op);
  51#endif
  52
  53        /* Check if both hosts are in the same datacenter. For this
  54         * example they are if the 1st 5.5 bytes in the IPv6 address
  55         * are 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_NEEDS_ECN:
  63                        rv = 1;
  64                        break;
  65                case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  66                        rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
  67                                            cong, sizeof(cong));
  68                        break;
  69                case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  70                        rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
  71                                            cong, sizeof(cong));
  72                        break;
  73                default:
  74                        rv = -1;
  75                }
  76        } else {
  77                rv = -1;
  78        }
  79#ifdef DEBUG
  80        bpf_printk("Returning %d\n", rv);
  81#endif
  82        skops->reply = rv;
  83        return 1;
  84}
  85char _license[] SEC("license") = "GPL";
  86