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                 return -1;
  47
  48         op = (int) skops->op;
  49
  50 #ifdef DEBUG
  51         bpf_printk("BPF command: %d\n", op);
  52 #endif
  53
  54         /* Usually there would be a check to insure the hosts are far
  55          * from each other so it makes sense to increase buffer sizes
  56          */
  57         switch (op) {
  58         case BPF_SOCK_OPS_RWND_INIT:
  59                 rv = rwnd_init;
  60                 break;
  61         case BPF_SOCK_OPS_TCP_CONNECT_CB:
  62                 /* Set sndbuf and rcvbuf of active connections */
  63                 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
  64                                     sizeof(bufsize));
  65                 rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
  66                                              &bufsize, sizeof(bufsize));
  67                 break;
  68         case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  69                 rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
  70                                     sizeof(iw));
  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 = rv*100 + 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";