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 #define bpf_printk(fmt, ...)                                    \
  26 ({                                                              \
  27                char ____fmt[] = fmt;                            \
  28                bpf_trace_printk(____fmt, sizeof(____fmt),       \
  29                                 ##__VA_ARGS__);                 \
  30 })
  31
  32 SEC("sockops")
  33 int bpf_bufs(struct bpf_sock_ops *skops)
  34 {
  35         int bufsize = 1500000;
  36         int rwnd_init = 40;
  37         int rv = 0;
  38         int op;
  39
  40         /* For testing purposes, only execute rest of BPF program
  41          * if neither port numberis 55601
  42          */
  43         if (bpf_ntohl(skops->remote_port) != 55601 &&
  44             skops->local_port != 55601) {
  45                 skops->reply = -1;
  46                 return 1;
  47         }
  48
  49         op = (int) skops->op;
  50
  51 #ifdef DEBUG
  52         bpf_printk("Returning %d\n", rv);
  53 #endif
  54
  55         /* Usually there would be a check to insure the hosts are far
  56          * from each other so it makes sense to increase buffer sizes
  57          */
  58         switch (op) {
  59         case BPF_SOCK_OPS_RWND_INIT:
  60                 rv = rwnd_init;
  61                 break;
  62         case BPF_SOCK_OPS_TCP_CONNECT_CB:
  63                 /* Set sndbuf and rcvbuf of active connections */
  64                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  65                                     sizeof(bufsize));
  66                 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  67                                      &bufsize, sizeof(bufsize));
  68                 break;
  69         case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  70                 /* Nothing to do */
  71                 break;
  72         case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  73                 /* Set sndbuf and rcvbuf of passive connections */
  74                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  75                                     sizeof(bufsize));
  76                 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  77                                      &bufsize, sizeof(bufsize));
  78                 break;
  79         default:
  80                 rv = -1;
  81         }
  82 #ifdef DEBUG
  83         bpf_printk("Returning %d\n", rv);
  84 #endif
  85         skops->reply = rv;
  86         return 1;
  87 }
  88 char _license[] SEC("license") = "GPL";