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"; 98