/* Copyright (c) 2017 Facebook * * This program is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. * * BPF program to set initial receive window to 40 packets when using IPv6 * and the first 5.5 bytes of the IPv6 addresses are not the same (in this * example that means both hosts are not the same datacenter). * * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program. */ #include <uapi/linux/bpf.h> #include <uapi/linux/if_ether.h> #include <uapi/linux/if_packet.h> #include <uapi/linux/ip.h> #include <linux/socket.h> #include <bpf/bpf_helpers.h> #include <bpf/bpf_endian.h> #define DEBUG 1 SEC("sockops") int bpf_rwnd(struct bpf_sock_ops *skops) { int rv = -1; int op; /* For testing purposes, only execute rest of BPF program * if neither port numberis 55601 */ if (bpf_ntohl(skops->remote_port) != 55601 && skops->local_port != 55601) { skops->reply = -1; return 1; } op = (int) skops->op; #ifdef DEBUG bpf_printk("BPF command: %d\n", op); #endif /* Check for RWND_INIT operation and IPv6 addresses */ if (op == BPF_SOCK_OPS_RWND_INIT && skops->family == AF_INET6) { /* If the first 5.5 bytes of the IPv6 address are not the same * then both hosts are not in the same datacenter * so use a larger initial advertized window (40 packets) */ if (skops->local_ip6[0] != skops->remote_ip6[0] || (bpf_ntohl(skops->local_ip6[1]) & 0xfffff000) != (bpf_ntohl(skops->remote_ip6[1]) & 0xfffff000)) rv = 40; } #ifdef DEBUG bpf_printk("Returning %d\n", rv); #endif skops->reply = rv; return 1; } char _license[] SEC("license") = "GPL";