samples/bpf/tcp_clamp_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  * Sample BPF program to set send and receive buffers to 150KB, sndcwnd clamp
   8  * to 100 packets and SYN and SYN_ACK RTOs to 10ms when both hosts are within
   9  * the same datacenter. For his example, we assume they are within the same
  10  * datacenter when the first 5.5 bytes of their IPv6 addresses are the same.
  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_clamp(struct bpf_sock_ops *skops)
  34 {
  35         int bufsize = 150000;
  36         int to_init = 10;
  37         int clamp = 100;
  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 && skops->local_port != 55601) {
  45                 skops->reply = -1;
  46                 return 0;
  47         }
  48
  49         op = (int) skops->op;
  50
  51 #ifdef DEBUG
  52         bpf_printk("BPF command: %d\n", op);
  53 #endif
  54
  55         /* Check that both hosts are within same datacenter. For this example
  56          * it is the case when the first 5.5 bytes of their IPv6 addresses are
  57          * the same.
  58          */
  59         if (skops->family == AF_INET6 &&
  60             skops->local_ip6[0] == skops->remote_ip6[0] &&
  61             (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  62             (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  63                 switch (op) {
  64                 case BPF_SOCK_OPS_TIMEOUT_INIT:
  65                         rv = to_init;
  66                         break;
  67                 case BPF_SOCK_OPS_TCP_CONNECT_CB:
  68                         /* Set sndbuf and rcvbuf of active connections */
  69                         rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
  70                                             &bufsize, sizeof(bufsize));
  71                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  72                                              SO_RCVBUF, &bufsize,
  73                                              sizeof(bufsize));
  74                         break;
  75                 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  76                         rv = bpf_setsockopt(skops, SOL_TCP,
  77                                             TCP_BPF_SNDCWND_CLAMP,
  78                                             &clamp, sizeof(clamp));
  79                         break;
  80                 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  81                         /* Set sndbuf and rcvbuf of passive connections */
  82                         rv = bpf_setsockopt(skops, SOL_TCP,
  83                                             TCP_BPF_SNDCWND_CLAMP,
  84                                             &clamp, sizeof(clamp));
  85                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  86                                              SO_SNDBUF, &bufsize,
  87                                              sizeof(bufsize));
  88                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  89                                              SO_RCVBUF, &bufsize,
  90                                              sizeof(bufsize));
  91                         break;
  92                 default:
  93                         rv = -1;
  94                 }
  95         } else {
  96                 rv = -1;
  97         }
  98 #ifdef DEBUG
  99         bpf_printk("Returning %d\n", rv);
 100 #endif
 101         skops->reply = rv;
 102         return 1;
 103 }
 104 char _license[] SEC("license") = "GPL";