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Snow Leopard fixes poll() and kqueues to work on BPF devices (and ttys). 

Describe what happens with select() and poll() on Linux if the device on
which you're capturing goes away.
This commit is contained in:
Guy Harris 2009-10-11 22:44:39 -07:00
parent e6b89d9420
commit 0c8f81c821
1 changed files with 31 additions and 1 deletions
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32
pcap_get_selectable_fd.3pcap
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@ -104,6 +104,36 @@ can be used on the descriptor returned by
.B poll()
cannot be used on it those versions of Mac OS X. Kqueues also don't
work on that descriptor.
.BR poll() ,
but not kqueues, work on that descriptor in Mac OS X releases prior to
10.4;
.B poll()
and kqueues work on that descriptor in Mac OS X 10.6 and later.
.PP
On Linux, if the network interface on which you're capturing disappears
(e.g., if a USB interface is unplugged), select) will return an
indication that the descriptor has data available to read. If libpcap
is not using memory-mapped mode to capture, the attempt to read the next
packet will return an error; however, if it is using memory-mapped mode
to capture, which it will do if the kernel includes support for
memory-mapped mode, no packet or error will be returned if you have put
the
.B pcap_t
into non-blocking mode. You must use
.B poll()
in this case;
.B poll()
will return a
.B POLLERR
indication; a
.BR recv (2),
.BR recvfrom(2),
or
.BR recvmsg (2)
on the descriptor will return \-1 and set
.B errno
to
.B ENETDOWN.
.PP
.B pcap_get_selectable_fd()
is not available on Windows.
@ -111,4 +141,4 @@ is not available on Windows.
A selectable file descriptor is returned if one exists; otherwise, \-1
is returned.
.SH SEE ALSO
pcap(3PCAP), select(2), poll(2)
pcap(3PCAP), select(2), poll(2), recv(2)