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"; 105