LXR linux/samples/bpf/tcp_synrto

   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 SYN and SYN-ACK RTOs to 10ms when using IPv6 addresses
   8 * and the first 5.5 bytes of the IPv6 addresses are the same (in this example
   9 * that means both hosts are in the same datacenter).
  10 *
  11 * Use load_sock_ops to load this BPF program.
  12 */
  13
  14#include <uapi/linux/bpf.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_synrto(struct bpf_sock_ops *skops)
  33{
  34        int rv = -1;
  35        int op;
  36
  37        /* For testing purposes, only execute rest of BPF program
  38         * if neither port numberis 55601
  39         */
  40        if (bpf_ntohl(skops->remote_port) != 55601 &&
  41            skops->local_port != 55601)
  42                return -1;
  43
  44        op = (int) skops->op;
  45
  46#ifdef DEBUG
  47        bpf_printk("BPF command: %d\n", op);
  48#endif
  49
  50        /* Check for TIMEOUT_INIT operation and IPv6 addresses */
  51        if (op == BPF_SOCK_OPS_TIMEOUT_INIT &&
  52                skops->family == AF_INET6) {
  53
  54                /* If the first 5.5 bytes of the IPv6 address are the same
  55                 * then both hosts are in the same datacenter
  56                 * so use an RTO of 10ms
  57                 */
  58                if (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                        rv = 10;
  62        }
  63#ifdef DEBUG
  64        bpf_printk("Returning %d\n", rv);
  65#endif
  66        skops->reply = rv;
  67        return 1;
  68}
  69char _license[] SEC("license") = "GPL";
  70