| Lawrence Brakmo | c400296 | 2017-06-30 20:02:45 -0700 | [diff] [blame] | 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 when using IPv6 |
| 8 | * and the first 5.5 bytes of the IPv6 addresses are not the same (in this |
| 9 | * example that means both hosts are not the same datacenter). |
| 10 | * |
| 11 | * Use load_sock_ops to load this BPF program. |
| 12 | */ |
| 13 | |
| 14 | #include <uapi/linux/bpf.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" |
| 21 | |
| 22 | #define DEBUG 1 |
| 23 | |
| 24 | #define bpf_printk(fmt, ...) \ |
| 25 | ({ \ |
| 26 | char ____fmt[] = fmt; \ |
| 27 | bpf_trace_printk(____fmt, sizeof(____fmt), \ |
| 28 | ##__VA_ARGS__); \ |
| 29 | }) |
| 30 | |
| 31 | SEC("sockops") |
| 32 | int bpf_rwnd(struct bpf_sock_ops *skops) |
| 33 | { |
| 34 | int rv = -1; |
| 35 | int op; |
| 36 | |
| 37 | /* For testing purposes, only execute rest of BPF program |
| 38 | * if neither port numberis 55601 |
| 39 | */ |
| 40 | if (bpf_ntohl(skops->remote_port) != |
| 41 | 55601 && skops->local_port != 55601) |
| 42 | return -1; |
| 43 | |
| 44 | op = (int) skops->op; |
| 45 | |
| 46 | #ifdef DEBUG |
| 47 | bpf_printk("BPF command: %d\n", op); |
| 48 | #endif |
| 49 | |
| 50 | /* Check for RWND_INIT operation and IPv6 addresses */ |
| 51 | if (op == BPF_SOCK_OPS_RWND_INIT && |
| 52 | skops->family == AF_INET6) { |
| 53 | |
| 54 | /* If the first 5.5 bytes of the IPv6 address are not the same |
| 55 | * then both hosts are not in the same datacenter |
| 56 | * so use a larger initial advertized window (40 packets) |
| 57 | */ |
| 58 | if (skops->local_ip6[0] != skops->remote_ip6[0] || |
| 59 | (bpf_ntohl(skops->local_ip6[1]) & 0xfffff000) != |
| 60 | (bpf_ntohl(skops->remote_ip6[1]) & 0xfffff000)) |
| 61 | rv = 40; |
| 62 | } |
| 63 | #ifdef DEBUG |
| 64 | bpf_printk("Returning %d\n", rv); |
| 65 | #endif |
| 66 | skops->reply = rv; |
| 67 | return 1; |
| 68 | } |
| 69 | char _license[] SEC("license") = "GPL"; |