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 congestion control to dctcp when both hosts are 8 * in the same datacenter (as deteremined by IPv6 prefix). 9 * 10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program. 11 */ 12 13 #include <uapi/linux/bpf.h> 14 #include <uapi/linux/tcp.h> 15 #include <uapi/linux/if_ether.h> 16 #include <uapi/linux/if_packet.h> 17 #include <uapi/linux/ip.h> 18 #include <linux/socket.h> 19 #include "bpf_helpers.h" 20 #include "bpf_endian.h" 21 22 #define DEBUG 1 23 24 #define bpf_printk(fmt, ...) \ 25 ({ \ 26 char ____fmt[] = fmt; \ 27 bpf_trace_printk(____fmt, sizeof(____fmt), \ 28 ##__VA_ARGS__); \ 29 }) 30 31 SEC("sockops") 32 int bpf_cong(struct bpf_sock_ops *skops) 33 { 34 char cong[] = "dctcp"; 35 int rv = 0; 36 int op; 37 38 /* For testing purposes, only execute rest of BPF program 39 * if neither port numberis 55601 40 */ 41 if (bpf_ntohl(skops->remote_port) != 55601 && 42 skops->local_port != 55601) { 43 skops->reply = -1; 44 return 1; 45 } 46 47 op = (int) skops->op; 48 49 #ifdef DEBUG 50 bpf_printk("BPF command: %d\n", op); 51 #endif 52 53 /* Check if both hosts are in the same datacenter. For this 54 * example they are if the 1st 5.5 bytes in the IPv6 address 55 * are the same. 56 */ 57 if (skops->family == AF_INET6 && 58 skops->local_ip6[0] == skops->remote_ip6[0] && 59 (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) == 60 (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) { 61 switch (op) { 62 case BPF_SOCK_OPS_NEEDS_ECN: 63 rv = 1; 64 break; 65 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB: 66 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, 67 cong, sizeof(cong)); 68 break; 69 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB: 70 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, 71 cong, sizeof(cong)); 72 break; 73 default: 74 rv = -1; 75 } 76 } else { 77 rv = -1; 78 } 79 #ifdef DEBUG 80 bpf_printk("Returning %d\n", rv); 81 #endif 82 skops->reply = rv; 83 return 1; 84 } 85 char _license[] SEC("license") = "GPL"; 86