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 initial receive window to 40 packets and send 8 * and receive buffers to 1.5MB. This would usually be done after 9 * doing appropriate checks that indicate the hosts are far enough 10 * away (i.e. large RTT). 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_bufs(struct bpf_sock_ops *skops) 27 { 28 int bufsize = 1500000; 29 int rwnd_init = 40; 30 int rv = 0; 31 int op; 32 33 /* For testing purposes, only execute rest of BPF program 34 * if neither port numberis 55601 35 */ 36 if (bpf_ntohl(skops->remote_port) != 55601 && 37 skops->local_port != 55601) { 38 skops->reply = -1; 39 return 1; 40 } 41 42 op = (int) skops->op; 43 44 #ifdef DEBUG 45 bpf_printk("Returning %d\n", rv); 46 #endif 47 48 /* Usually there would be a check to insure the hosts are far 49 * from each other so it makes sense to increase buffer sizes 50 */ 51 switch (op) { 52 case BPF_SOCK_OPS_RWND_INIT: 53 rv = rwnd_init; 54 break; 55 case BPF_SOCK_OPS_TCP_CONNECT_CB: 56 /* Set sndbuf and rcvbuf of active connections */ 57 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize, 58 sizeof(bufsize)); 59 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF, 60 &bufsize, sizeof(bufsize)); 61 break; 62 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB: 63 /* Nothing to do */ 64 break; 65 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB: 66 /* Set sndbuf and rcvbuf of passive connections */ 67 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize, 68 sizeof(bufsize)); 69 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF, 70 &bufsize, sizeof(bufsize)); 71 break; 72 default: 73 rv = -1; 74 } 75 #ifdef DEBUG 76 bpf_printk("Returning %d\n", rv); 77 #endif 78 skops->reply = rv; 79 return 1; 80 } 81 char _license[] SEC("license") = "GPL"; 82