samples/bpf/tcp_bufs_kern.c

   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 initial receive window to 40 packets and send
   8  * and receive buffers to 1.5MB. This would usually be done after
   9  * doing appropriate checks that indicate the hosts are far enough
  10  * away (i.e. large RTT).
  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_helpers.h"
  21 #include "bpf_endian.h"
  22
  23 #define DEBUG 1
  24
  25 SEC("sockops")
  26 int bpf_bufs(struct bpf_sock_ops *skops)
  27 {
  28         int bufsize = 1500000;
  29         int rwnd_init = 40;
  30         int rv = 0;
  31         int op;
  32
  33         /* For testing purposes, only execute rest of BPF program
  34          * if neither port numberis 55601
  35          */
  36         if (bpf_ntohl(skops->remote_port) != 55601 &&
  37             skops->local_port != 55601) {
  38                 skops->reply = -1;
  39                 return 1;
  40         }
  41
  42         op = (int) skops->op;
  43
  44 #ifdef DEBUG
  45         bpf_printk("Returning %d\n", rv);
  46 #endif
  47
  48         /* Usually there would be a check to insure the hosts are far
  49          * from each other so it makes sense to increase buffer sizes
  50          */
  51         switch (op) {
  52         case BPF_SOCK_OPS_RWND_INIT:
  53                 rv = rwnd_init;
  54                 break;
  55         case BPF_SOCK_OPS_TCP_CONNECT_CB:
  56                 /* Set sndbuf and rcvbuf of active connections */
  57                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  58                                     sizeof(bufsize));
  59                 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  60                                      &bufsize, sizeof(bufsize));
  61                 break;
  62         case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  63                 /* Nothing to do */
  64                 break;
  65         case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  66                 /* Set sndbuf and rcvbuf of passive connections */
  67                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  68                                     sizeof(bufsize));
  69                 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  70                                      &bufsize, sizeof(bufsize));
  71                 break;
  72         default:
  73                 rv = -1;
  74         }
  75 #ifdef DEBUG
  76         bpf_printk("Returning %d\n", rv);
  77 #endif
  78         skops->reply = rv;
  79         return 1;
  80 }
  81 char _license[] SEC("license") = "GPL";