accf_data(9)

accf_data9

Buffer incoming connections until data arrives

Usage

options INET options ACCEPT_FILTER_DATA

In rc.conf(5): kld_list="accf_data"

Overview

This is a filter to be placed on a socket that will be using accept() to receive incoming connections.

It prevents the application from receiving the connected descriptor via accept() until data arrives on the connection.

The ACCEPT_FILTER_DATA kernel option is also a module that can be enabled at runtime via kldload(8) if the INET option has been compiled into the kernel.

Examples

Assuming ACCEPT_FILTER_DATA has been included in the kernel config file or the accf_data module has been loaded, this will enable the data accept filter on the socket sok.

	struct accept_filter_arg afa;
	bzero(&afa, sizeof(afa));
	strcpy(afa.af_name, "dataready");
	setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));

Releases

67 releases since FreeBSD 4.2-RELEASE; the text changed 40 times.

  1. 4.2
  2. 4.3
  3. 4.4–4.11
  4. 5.0
  5. 5.1–5.5
  6. 6.0–6.3
  7. 6.4
  8. 7.0
  9. 7.1
  10. 7.2
  11. 7.3
  12. 7.4
  13. 8.0
  14. 8.1
  15. 8.2
  16. 8.3
  17. 8.4
  18. 9.0
  19. 9.1
  20. 9.2
  21. 9.3
  22. 10.0
  23. 10.1
  24. 10.2
  25. 10.3
  26. 10.4
  27. 11.0
  28. 11.1
  29. 11.2
  30. 11.3
  31. 11.4
  32. 12.0
  33. 12.1
  34. 12.2
  35. 12.3
  36. 12.4
  37. 13.0–13.2
  38. 13.3–14.4
  39. 14.5
  40. 15.0
  41. 15.1–16.0

History

The accept filter mechanism and the accf_data filter were introduced in FreeBSD 4.0.

Authors

This manual page and the filter were written by Alfred Perlstein.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.