1 /* Copyright (c) 2017 Facebook
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.
7 * BPF program to set base_rtt to 80us when host is running TCP-NV and
8 * both hosts are in the same datacenter (as determined by IPv6 prefix).
10 * Use load_sock_ops to load this BPF program.
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"
24 #define bpf_printk(fmt, ...) \
26 char ____fmt[] = fmt; \
27 bpf_trace_printk(____fmt, sizeof(____fmt), \
32 int bpf_basertt(struct bpf_sock_ops *skops)
42 bpf_printk("BPF command: %d\n", op);
45 /* Check if both hosts are in the same datacenter. For this
46 * example they are if the 1st 5.5 bytes in the IPv6 address
49 if (skops->family == AF_INET6 &&
50 skops->local_ip6[0] == skops->remote_ip6[0] &&
51 (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
52 (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
54 case BPF_SOCK_OPS_BASE_RTT:
55 n = bpf_getsockopt(skops, SOL_TCP, TCP_CONGESTION,
57 if (!n && !__builtin_memcmp(cong, nv, sizeof(nv)+1)) {
58 /* Set base_rtt to 80us */
73 bpf_printk("Returning %d\n", rv);
78 char _license[] SEC("license") = "GPL";