Mac OS X v10.5 and later: About Back to My Mac security
Back to My Mac is a feature in Mac OS X v10.5 and later that makes it easy to automatically connect to your other computers over the Internet. Once you've signed into MobileMe on your computer and enabled Back to My Mac, you may securely reach other computers via the Internet. The other computer(s) also must be signed into the same MobileMe account, be using Mac OS X v10.5 or later, and have Back to My Mac enabled on them. After completing a new installation of Mac OS X v10.5 or later, Back to My Mac is enabled by default, however, the computer cannot be reached until sharing services (such as File Sharing or Screen Sharing) have been enabled in Sharing preferences (in System Preferences). To ensure network connections between your computers are secure over the Internet, Back to My Mac uses a technology called IPSec to encrypt data. To provide secure and trusted authentication, Back to My Mac uses Kerberos with Digital Certificates. Kerberos provides an additional convenience; it eliminates the need for you to enter your username and password each time you wish to reach another computer in your Back to My Mac network. To learn more about Kerberos, see this article.
PCAP_GET_SELECTABLE_FD(3PCAP)PCAP_GET_SELECTABLE_FD(3PCAP)NAME
pcap_get_selectable_fd - get a file descriptor on which a select() can be done for a live capture
SYNOPSIS
#include <pcap/pcap.h>
int pcap_get_selectable_fd(pcap_t *p);
DESCRIPTION
pcap_get_selectable_fd() returns, on UNIX, a file descriptor number for a file descriptor on which one can do a select() or poll() to wait
for it to be possible to read packets without blocking, if such a descriptor exists, or -1, if no such descriptor exists. Some network
devices opened with pcap_create() and pcap_activate(), or with pcap_open_live(), do not support select() or poll() (for example, regular
network devices on FreeBSD 4.3 and 4.4, and Endace DAG devices), so -1 is returned for those devices.
Note that in:
FreeBSD prior to FreeBSD 4.6;
NetBSD prior to NetBSD 3.0;
OpenBSD prior to OpenBSD 2.4;
Mac OS X prior to Mac OS X 10.7;
select() and poll() do not work correctly on BPF devices; pcap_get_selectable_fd() will return a file descriptor on most of those versions
(the exceptions being FreeBSD 4.3 and 4.4), but a simple select() or poll() will not indicate that the descriptor is readable until a full
buffer's worth of packets is received, even if the read timeout expires before then. To work around this, an application that uses
select() or poll() to wait for packets to arrive must put the pcap_t in non-blocking mode, and must arrange that the select() or poll()
have a timeout less than or equal to the read timeout, and must try to read packets after that timeout expires, regardless of whether
select() or poll() indicated that the file descriptor for the pcap_t is ready to be read or not. (That workaround will not work in FreeBSD
4.3 and later; however, in FreeBSD 4.6 and later, select() and poll() work correctly on BPF devices, so the workaround isn't necessary,
although it does no harm.)
Note also that poll() doesn't work on character special files, including BPF devices, in Mac OS X 10.4 and 10.5, so, while select() can be
used on the descriptor returned by pcap_get_selectable_fd(), poll() cannot be used on it those versions of Mac OS X. Kqueues also don't
work on that descriptor. poll(), but not kqueues, work on that descriptor in Mac OS X releases prior to 10.4; poll() and kqueues work on
that descriptor in Mac OS X 10.6 and later.
pcap_get_selectable_fd() is not available on Windows.
RETURN VALUE
A selectable file descriptor is returned if one exists; otherwise, -1 is returned.
SEE ALSO pcap(3PCAP), select(2), poll(2)
5 April 2008 PCAP_GET_SELECTABLE_FD(3PCAP)
