samples/bpf/tcp_iw_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 congestion window and initial receive
   8  * window to 40 packets and send and receive buffers to 1.5MB. This
   9  * would usually be done after doing appropriate checks that indicate
  10  * the hosts are far enough away (i.e. large RTT).
  11  *
  12  * Use load_sock_ops 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_iw(struct bpf_sock_ops *skops)
  34 {
  35         int bufsize = 1500000;
  36         int rwnd_init = 40;
  37         int iw = 40;
  38         int rv = 0;
  39         int op;
  40
  41         /* For testing purposes, only execute rest of BPF program
  42          * if neither port numberis 55601
  43          */
  44         if (bpf_ntohl(skops->remote_port) != 55601 &&
  45             skops->local_port != 55601) {
  46                 skops->reply = -1;
  47                 return 1;
  48         }
  49
  50         op = (int) skops->op;
  51
  52 #ifdef DEBUG
  53         bpf_printk("BPF command: %d\n", op);
  54 #endif
  55
  56         /* Usually there would be a check to insure the hosts are far
  57          * from each other so it makes sense to increase buffer sizes
  58          */
  59         switch (op) {
  60         case BPF_SOCK_OPS_RWND_INIT:
  61                 rv = rwnd_init;
  62                 break;
  63         case BPF_SOCK_OPS_TCP_CONNECT_CB:
  64                 /* Set sndbuf and rcvbuf of active connections */
  65                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  66                                     sizeof(bufsize));
  67                 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  68                                      &bufsize, sizeof(bufsize));
  69                 break;
  70         case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  71                 rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
  72                                     sizeof(iw));
  73                 break;
  74         case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  75                 /* Set sndbuf and rcvbuf of passive connections */
  76                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  77                                     sizeof(bufsize));
  78                 rv +=  bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  79                                       &bufsize, sizeof(bufsize));
  80                 break;
  81         default:
  82                 rv = -1;
  83         }
  84 #ifdef DEBUG
  85         bpf_printk("Returning %d\n", rv);
  86 #endif
  87         skops->reply = rv;
  88         return 1;
  89 }
  90 char _license[] SEC("license") = "GPL";