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/bpf_helpers.h> 20 #include <bpf/bpf_endian.h> 21 22 #define DEBUG 1 23 24 SEC("sockops") 25 int bpf_cong(struct bpf_sock_ops *skops) 26 { 27 char cong[] = "dctcp"; 28 int rv = 0; 29 int op; 30 31 /* For testing purposes, only execute rest of BPF program 32 * if neither port numberis 55601 33 */ 34 if (bpf_ntohl(skops->remote_port) != 55601 && 35 skops->local_port != 55601) { 36 skops->reply = -1; 37 return 1; 38 } 39 40 op = (int) skops->op; 41 42 #ifdef DEBUG 43 bpf_printk("BPF command: %d\n", op); 44 #endif 45 46 /* Check if both hosts are in the same datacenter. For this 47 * example they are if the 1st 5.5 bytes in the IPv6 address 48 * are the same. 49 */ 50 if (skops->family == AF_INET6 && 51 skops->local_ip6[0] == skops->remote_ip6[0] && 52 (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) == 53 (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) { 54 switch (op) { 55 case BPF_SOCK_OPS_NEEDS_ECN: 56 rv = 1; 57 break; 58 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB: 59 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, 60 cong, sizeof(cong)); 61 break; 62 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB: 63 rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, 64 cong, sizeof(cong)); 65 break; 66 default: 67 rv = -1; 68 } 69 } else { 70 rv = -1; 71 } 72 #ifdef DEBUG 73 bpf_printk("Returning %d\n", rv); 74 #endif 75 skops->reply = rv; 76 return 1; 77 } 78 char _license[] SEC("license") = "GPL"; 79