tcp_synrto_kern.c 1.7 KB

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  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 SYN and SYN-ACK RTOs to 10ms when using IPv6 addresses
  8. * and the first 5.5 bytes of the IPv6 addresses are the same (in this example
  9. * that means both hosts are in the same datacenter).
  10. *
  11. * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  12. */
  13. #include <uapi/linux/bpf.h>
  14. #include <uapi/linux/if_ether.h>
  15. #include <uapi/linux/if_packet.h>
  16. #include <uapi/linux/ip.h>
  17. #include <linux/socket.h>
  18. #include <bpf/bpf_helpers.h>
  19. #include <bpf/bpf_endian.h>
  20. #define DEBUG 1
  21. SEC("sockops")
  22. int bpf_synrto(struct bpf_sock_ops *skops)
  23. {
  24. int rv = -1;
  25. int op;
  26. /* For testing purposes, only execute rest of BPF program
  27. * if neither port numberis 55601
  28. */
  29. if (bpf_ntohl(skops->remote_port) != 55601 &&
  30. skops->local_port != 55601) {
  31. skops->reply = -1;
  32. return 1;
  33. }
  34. op = (int) skops->op;
  35. #ifdef DEBUG
  36. bpf_printk("BPF command: %d\n", op);
  37. #endif
  38. /* Check for TIMEOUT_INIT operation and IPv6 addresses */
  39. if (op == BPF_SOCK_OPS_TIMEOUT_INIT &&
  40. skops->family == AF_INET6) {
  41. /* If the first 5.5 bytes of the IPv6 address are the same
  42. * then both hosts are in the same datacenter
  43. * so use an RTO of 10ms
  44. */
  45. if (skops->local_ip6[0] == skops->remote_ip6[0] &&
  46. (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  47. (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000))
  48. rv = 10;
  49. }
  50. #ifdef DEBUG
  51. bpf_printk("Returning %d\n", rv);
  52. #endif
  53. skops->reply = rv;
  54. return 1;
  55. }
  56. char _license[] SEC("license") = "GPL";