Add some "what if it's an earlier release" information.

Expand the BACKWARD COMPATIBILITY section to either say "sorry, you
can't get that with earlier releases of libpcap" or "if you need this,
here's what you'd have to do".

1 files changed, 95 insertions, 0 deletions

diff --git a/pcap_set_immediate_mode.3pcap.in b/pcap_set_immediate_mode.3pcap.in
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+.\"
+.\" Copyright (c) 1994, 1996, 1997
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that: (1) source code distributions
+.\" retain the above copyright notice and this paragraph in its entirety, (2)
+.\" distributions including binary code include the above copyright notice and
+.\" this paragraph in its entirety in the documentation or other materials
+.\" provided with the distribution, and (3) all advertising materials mentioning
+.\" features or use of this software display the following acknowledgement:
+.\" ``This product includes software developed by the University of California,
+.\" Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
+.\" the University nor the names of its contributors may be used to endorse
+.\" or promote products derived from this software without specific prior
+.\" written permission.
+.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+.\"
+.TH PCAP_SET_IMMEDIATE_MODE 3PCAP "22 August 2018"
+.SH NAME
+pcap_set_immediate_mode \- set immediate mode for a not-yet-activated capture
+handle
+.SH SYNOPSIS
+.nf
+.ft B
+#include <pcap/pcap.h>
+.LP
+.ft B
+int pcap_set_immediate_mode(pcap_t *p, int immediate_mode);
+.ft
+.fi
+.SH DESCRIPTION
+.B pcap_set_immediate_mode()
+sets whether immediate mode should be set on a capture handle when
+the handle is activated.  In immediate mode, packets are always
+delivered as soon as they arrive, with no buffering.
+If
+.I immediate_mode
+is non-zero, immediate mode will be set, otherwise it will not be set.
+.SH RETURN VALUE
+.B pcap_set_immediate_mode()
+returns 0 on success or
+.B PCAP_ERROR_ACTIVATED
+if called on a capture handle that has been activated.
+.SH BACKWARD COMPATIBILITY
+.PP
+This function became available in libpcap release 1.5.0.  In previous
+releases, if immediate delivery of packets is required:
+.IP
+on FreeBSD, NetBSD, OpenBSD, DragonFly BSD, macOS, and Solaris 11,
+immediate mode must be turned on with a
+.B BIOCIMMEDIATE
+.BR ioctl (2),
+as documented in
+.BR bpf(@MAN_DEVICES@) ,
+on the descriptor returned by
+.B pcap_fileno(3PCAP),
+after
+.BR pcap_activate(3PCAP)
+is called;
+.IP
+on Solaris 10 and earlier versions of Solaris, immediate mode must be
+turned on by using a read timeout of 0 when opening the device (this
+will not provide immediate delivery of packets on other platforms, so
+don't assume it's sufficient);
+.IP
+on Digital UNIX/Tru64 UNIX, immediate mode must be turned on by doing a
+.B BIOCMBIC
+.BR ioctl ,
+as documented in
+.BR packetfilter(7) ,
+to clear the
+.B ENBATCH
+flag on the descriptor returned by
+.B pcap_fileno(3PCAP),
+after
+.BR pcap_activate(3PCAP)
+is called;
+.IP
+on Windows, immediate mode must be turned on by calling
+.B pcap_setmintocopy()
+with a size of 0.
+.PP
+On Linux, with previous releases of libpcap, capture devices are always
+in immediate mode; however, in 1.5.0 and later, they are, by default,
+.B not
+in immediate mode, so if
+.B pcap_set_immediate_mode()
+is available, it should be used.
+.PP
+On other platforms, capture devices are always in immediate mode.
+.SH SEE ALSO
+pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP)