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author | delphij <delphij@FreeBSD.org> | 2012-05-14 09:32:10 +0000 |
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committer | delphij <delphij@FreeBSD.org> | 2012-05-14 09:32:10 +0000 |
commit | b6e0e7f97f5c44a9fcb7365163dec3180f258cec (patch) | |
tree | 040e480164b9989cf6547bcb0e316a28285e998e /contrib/libpcap/pcap-tstamp.manmisc | |
parent | a3451bb93bbf335a8f6b5feb9b80b256b0e304fe (diff) | |
download | FreeBSD-src-b6e0e7f97f5c44a9fcb7365163dec3180f258cec.zip FreeBSD-src-b6e0e7f97f5c44a9fcb7365163dec3180f258cec.tar.gz |
Add 3 missing files that was generated but not included with the initial
commit.
Reported by: buganini via IRC
MFC after: 2 weeks
Diffstat (limited to 'contrib/libpcap/pcap-tstamp.manmisc')
-rw-r--r-- | contrib/libpcap/pcap-tstamp.manmisc | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/contrib/libpcap/pcap-tstamp.manmisc b/contrib/libpcap/pcap-tstamp.manmisc new file mode 100644 index 0000000..d66a397 --- /dev/null +++ b/contrib/libpcap/pcap-tstamp.manmisc @@ -0,0 +1,132 @@ +.\" +.\" Copyright (c) 1987, 1988, 1989, 1990, 1991, 1992, 1994, 1995, 1996, 1997 +.\" The Regents of the University of California. All rights reserved. +.\" 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-TSTAMP 7 "22 August 2010" +.SH NAME +pcap-tstamp \- packet time stamps in libpcap +.SH DESCRIPTION +When capturing traffic, each packet is given a time stamp representing, +for incoming packets, the arrival time of the packet and, for outgoing +packets, the transmission time of the packet. This time is an +approximation of the arrival or transmission time. If it is supplied by +the operating system running on the host on which the capture is being +done, there are several reasons why it might not precisely represent the +arrival or transmission time: +.IP +if the time stamp is applied to the packet when the networking stack +receives the packet, the networking stack might not see the packet until +an interrupt is delivered for the packet or a timer event causes the +networking device driver to poll for packets, and the time stamp might +not be applied until the packet has had some processing done by other +code in the networking stack, so there might be a significant delay +between the time when the last bit of the packet is received by the +capture device and when the networking stack time-stamps the packet; +.IP +the timer used to generate the time stamps might have low resolution, +for example, it might be a timer updated once per host operating system +timer tick, with the host operating system timer ticking once every few +milliseconds; +.IP +a high-resolution timer might use a counter that runs at a rate +dependent on the processor clock speed, and that clock speed might be +adjusted upwards or downwards over time and the timer might not be able +to compensate for all those adjustments; +.IP +the host operating system's clock might be adjusted over time to match a +time standard to which the host is being synchronized, which might be +done by temporarily slowing down or speeding up the clock or by making a +single adjustment; +.IP +different CPU cores on a multi-core or multi-processor system might be +running at different speeds, or might not have time counters all +synchronized, so packets time-stamped by different cores might not have +consistent time stamps. +.LP +In addition, packets time-stamped by different cores might be +time-stamped in one order and added to the queue of packets for libpcap +to read in another order, so time stamps might not be monotonically +increasing. +.LP +Some capture devices on some platforms can provide time stamps for +packets; those time stamps are usually high-resolution time stamps, and +are usually applied to the packet when the first or last bit of the +packet arrives, and are thus more accurate than time stamps provided by +the host operating system. Those time stamps might not, however, be +synchronized with the host operating system's clock, so that, for +example, the time stamp of a packet might not correspond to the time +stamp of an event on the host triggered by the arrival of that packet. +.LP +Depending on the capture device and the software on the host, libpcap +might allow different types of time stamp to be used. The +.BR pcap_list_tstamp_types (3PCAP) +routine provides, for a packet capture handle created by +.BR pcap_create (3PCAP) +but not yet activated by +.BR pcap_activate (3PCAP), +a list of time stamp types supported by the capture device for that +handle. +The list might be empty, in which case no choice of time stamp type is +offered for that capture device. If the list is not empty, the +.BR pcap_set_tstamp_type (3PCAP) +routine can be used after a +.B pcap_create() +call and before a +.B pcap_activate() +call to specify the type of time stamp to be used on the device. +The time stamp types are listed here; the first value is the #define to +use in code, the second value is the value returned by +.B pcap_tstamp_type_val_to_name() +and accepted by +.BR pcap_tstamp_name_to_val() . +.RS 5 +.TP 5 +.BR PCAP_TSTAMP_HOST " - " host +Time stamp provided by the host on which the capture is being done. The +precision of this time stamp is unspecified; it might or might not be +synchronized with the host operating system's clock. +.TP 5 +.BR PCAP_TSTAMP_HOST_LOWPREC " - " host_lowprec +Time stamp provided by the host on which the capture is being done. +This is a low-precision time stamp, synchronized with the host operating +system's clock. +.TP 5 +.BR PCAP_TSTAMP_HOST_HIPREC " - " host_hiprec +Time stamp provided by the host on which the capture is being done. +This is a high-precision time stamp; it might or might not be +synchronized with the host operating system's clock. It might be more +expensive to fetch than +.BR PCAP_TSTAMP_HOST_LOWPREC . +.TP 5 +.BR PCAP_TSTAMP_ADAPTER " - " adapter +Time stamp provided by the network adapter on which the capture is being +done. This is a high-precision time stamp, synchronized with the host +operating system's clock. +.TP 5 +.BR PCAP_TSTAMP_ADAPTER_UNSYNCED " - " adapter_unsynced +Time stamp provided by the network adapter on which the capture is being +done. This is a high-precision time stamp; it is not synchronized with +the host operating system's clock. +.RE +.SH SEE ALSO +pcap_set_tstamp_type(3PCAP), +pcap_list_tstamp_types(3PCAP), +pcap_tstamp_type_val_to_name(3PCAP), +pcap_tstamp_name_to_val(3PCAP) |