1*4882a593Smuzhiyun /* Copyright (c) 2017 Facebook 2*4882a593Smuzhiyun * 3*4882a593Smuzhiyun * This program is free software; you can redistribute it and/or 4*4882a593Smuzhiyun * modify it under the terms of version 2 of the GNU General Public 5*4882a593Smuzhiyun * License as published by the Free Software Foundation. 6*4882a593Smuzhiyun * 7*4882a593Smuzhiyun * BPF program to set initial receive window to 40 packets when using IPv6 8*4882a593Smuzhiyun * and the first 5.5 bytes of the IPv6 addresses are not the same (in this 9*4882a593Smuzhiyun * example that means both hosts are not the same datacenter). 10*4882a593Smuzhiyun * 11*4882a593Smuzhiyun * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program. 12*4882a593Smuzhiyun */ 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun #include <uapi/linux/bpf.h> 15*4882a593Smuzhiyun #include <uapi/linux/if_ether.h> 16*4882a593Smuzhiyun #include <uapi/linux/if_packet.h> 17*4882a593Smuzhiyun #include <uapi/linux/ip.h> 18*4882a593Smuzhiyun #include <linux/socket.h> 19*4882a593Smuzhiyun #include <bpf/bpf_helpers.h> 20*4882a593Smuzhiyun #include <bpf/bpf_endian.h> 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun #define DEBUG 1 23*4882a593Smuzhiyun 24*4882a593Smuzhiyun SEC("sockops") bpf_rwnd(struct bpf_sock_ops * skops)25*4882a593Smuzhiyunint bpf_rwnd(struct bpf_sock_ops *skops) 26*4882a593Smuzhiyun { 27*4882a593Smuzhiyun int rv = -1; 28*4882a593Smuzhiyun int op; 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun /* For testing purposes, only execute rest of BPF program 31*4882a593Smuzhiyun * if neither port numberis 55601 32*4882a593Smuzhiyun */ 33*4882a593Smuzhiyun if (bpf_ntohl(skops->remote_port) != 34*4882a593Smuzhiyun 55601 && skops->local_port != 55601) { 35*4882a593Smuzhiyun skops->reply = -1; 36*4882a593Smuzhiyun return 1; 37*4882a593Smuzhiyun } 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun op = (int) skops->op; 40*4882a593Smuzhiyun 41*4882a593Smuzhiyun #ifdef DEBUG 42*4882a593Smuzhiyun bpf_printk("BPF command: %d\n", op); 43*4882a593Smuzhiyun #endif 44*4882a593Smuzhiyun 45*4882a593Smuzhiyun /* Check for RWND_INIT operation and IPv6 addresses */ 46*4882a593Smuzhiyun if (op == BPF_SOCK_OPS_RWND_INIT && 47*4882a593Smuzhiyun skops->family == AF_INET6) { 48*4882a593Smuzhiyun 49*4882a593Smuzhiyun /* If the first 5.5 bytes of the IPv6 address are not the same 50*4882a593Smuzhiyun * then both hosts are not in the same datacenter 51*4882a593Smuzhiyun * so use a larger initial advertized window (40 packets) 52*4882a593Smuzhiyun */ 53*4882a593Smuzhiyun if (skops->local_ip6[0] != skops->remote_ip6[0] || 54*4882a593Smuzhiyun (bpf_ntohl(skops->local_ip6[1]) & 0xfffff000) != 55*4882a593Smuzhiyun (bpf_ntohl(skops->remote_ip6[1]) & 0xfffff000)) 56*4882a593Smuzhiyun rv = 40; 57*4882a593Smuzhiyun } 58*4882a593Smuzhiyun #ifdef DEBUG 59*4882a593Smuzhiyun bpf_printk("Returning %d\n", rv); 60*4882a593Smuzhiyun #endif 61*4882a593Smuzhiyun skops->reply = rv; 62*4882a593Smuzhiyun return 1; 63*4882a593Smuzhiyun } 64*4882a593Smuzhiyun char _license[] SEC("license") = "GPL"; 65