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/bpf_helpers.h>
  21 #include <bpf/bpf_endian.h>
  22
  23 #define DEBUG 1
  24
  25 SEC("sockops")
  26 int bpf_clamp(struct bpf_sock_ops *skops)
  27 {
  28         int bufsize = 150000;
  29         int to_init = 10;
  30         int clamp = 100;
  31         int rv = 0;
  32         int op;
  33
  34         /* For testing purposes, only execute rest of BPF program
  35          * if neither port numberis 55601
  36          */
  37         if (bpf_ntohl(skops->remote_port) != 55601 && skops->local_port != 55601) {
  38                 skops->reply = -1;
  39                 return 0;
  40         }
  41
  42         op = (int) skops->op;
  43
  44 #ifdef DEBUG
  45         bpf_printk("BPF command: %d\n", op);
  46 #endif
  47
  48         /* Check that both hosts are within same datacenter. For this example
  49          * it is the case when the first 5.5 bytes of their IPv6 addresses are
  50          * the same.
  51          */
  52         if (skops->family == AF_INET6 &&
  53             skops->local_ip6[0] == skops->remote_ip6[0] &&
  54             (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  55             (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  56                 switch (op) {
  57                 case BPF_SOCK_OPS_TIMEOUT_INIT:
  58                         rv = to_init;
  59                         break;
  60                 case BPF_SOCK_OPS_TCP_CONNECT_CB:
  61                         /* Set sndbuf and rcvbuf of active connections */
  62                         rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
  63                                             &bufsize, sizeof(bufsize));
  64                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  65                                              SO_RCVBUF, &bufsize,
  66                                              sizeof(bufsize));
  67                         break;
  68                 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  69                         rv = bpf_setsockopt(skops, SOL_TCP,
  70                                             TCP_BPF_SNDCWND_CLAMP,
  71                                             &clamp, sizeof(clamp));
  72                         break;
  73                 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  74                         /* Set sndbuf and rcvbuf of passive connections */
  75                         rv = bpf_setsockopt(skops, SOL_TCP,
  76                                             TCP_BPF_SNDCWND_CLAMP,
  77                                             &clamp, sizeof(clamp));
  78                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  79                                              SO_SNDBUF, &bufsize,
  80                                              sizeof(bufsize));
  81                         rv += bpf_setsockopt(skops, SOL_SOCKET,
  82                                              SO_RCVBUF, &bufsize,
  83                                              sizeof(bufsize));
  84                         break;
  85                 default:
  86                         rv = -1;
  87                 }
  88         } else {
  89                 rv = -1;
  90         }
  91 #ifdef DEBUG
  92         bpf_printk("Returning %d\n", rv);
  93 #endif
  94         skops->reply = rv;
  95         return 1;
  96 }
  97 char _license[] SEC("license") = "GPL";