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Note that the read timeout in "pcap_open_live()" does *NOT* guarantee 

that "pcap_dispatch()" will always return within that many milliseconds;
some platforms don't support a read timeout, meaning the read timeout
argument is ignored, and, on other platforms (SunOS 5.x and possibly
SunOS 4.x and 3.x), the timer starts when the first packet arrives, so
the timeout doesn't expire until at least one packet arrives.
This commit is contained in:
guy 2000-12-28 01:58:05 +00:00
parent 042a2010bb
commit 70121e5b65
1 changed files with 20 additions and 4 deletions
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24
pcap.3
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@ -1,4 +1,4 @@
.\" @(#) $Header: /tcpdump/master/libpcap/Attic/pcap.3,v 1.14 2000-12-12 09:31:45 guy Exp $
.\" @(#) $Header: /tcpdump/master/libpcap/Attic/pcap.3,v 1.15 2000-12-28 01:58:05 guy Exp $
.\"
.\" Copyright (c) 1994, 1996, 1997
.\" The Regents of the University of California. All rights reserved.
@ -124,7 +124,12 @@ specifies if the interface is to be put into promiscuous mode.
(Note that even if this parameter is false, the interface
could well be in promiscuous mode for some other reason.)
.I to_ms
specifies the read timeout in milliseconds.
specifies the read timeout in milliseconds. The read timeout is used to
arrange that the read not necessarily return immediately when a packet
is seen, but that it wait for some amount of time to allow more packets
to arrive and to read multiple packets from the OS kernel in one
operation. Not all platforms support a read timeout; on platforms that
don't, the read timeout is ignored.
.I ebuf
is used to return error text and is only set when
.B pcap_open_live()
@ -209,8 +214,19 @@ of -1 processes all the packets received in one buffer. A
.I cnt
of 0 processes all packets until an error occurs,
.B EOF
is reached, or the read times out (when doing live reads and a non-zero
read timeout is specified).
is reached, or, on some platforms, the read times out (when doing live
reads and a non-zero read timeout is specified).
.B pcap_dispatch()
will not necessarily return when the read times out; on some platforms,
the read timeout isn't supported, and, on other platforms, the timer
doesn't start until at least one packet arrives. This means that the
read timeout should
.B NOT
be used in, for example, an interactive application, to allow the packet
capture loop to ``poll'' for user input periodically, as there's no
guarantee that
.B pcap_dispatch()
will return after the timeout expires.
.I callback
specifies a routine to be called with three arguments:
a