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PCAP(3)			   Library Functions Manual		       PCAP(3)

NAME
       pcap - Packet Capture library

SYNOPSIS
       #include	<pcap/pcap.h>

DESCRIPTION
       The  Packet  Capture  library provides a	high level interface to	packet
       capture systems.	All packets on the network, even  those	 destined  for
       other  hosts,  are accessible through this mechanism.  It also supports
       saving captured packets to a ``savefile'', and reading packets  from  a
       ``savefile''.

   Opening a capture handle for	reading
       To  open	 a handle for a	live capture, given the	name of	the network or
       other interface on which	the capture should  be	done,  call  pcap_cre-
       ate(),  set the appropriate options on the handle, and then activate it
       with pcap_activate().

       To obtain a list	of devices that	can be opened for a live capture, call
       pcap_findalldevs();  to	free  the list returned	by pcap_findalldevs(),
       call pcap_freealldevs().	 pcap_lookupdev() will return the first	device
       on that list that is not	a ``loopback`` network interface.

       To  open	 a handle for a	``savefile'' from which	to read	packets, given
       the pathname of the ``savefile'', call pcap_open_offline(); to set up a
       handle  for  a ``savefile'', given a FILE * referring to	a file already
       opened for reading, call	pcap_fopen_offline().

       In order	to get a ``fake'' pcap_t for use in routines  that  require  a
       pcap_t  as  an  argument,  such	as routines to open a ``savefile'' for
       writing and to compile a	filter expression, call	pcap_open_dead().

       pcap_create(),	 pcap_open_offline(),	 pcap_fopen_offline(),	   and
       pcap_open_dead()	return a pointer to a pcap_t, which is the handle used
       for reading packets from	the capture stream or  the  ``savefile'',  and
       for  finding  out information about the capture stream or ``savefile''.
       To close	a handle, use pcap_close().

       The options that	can be set on a	capture	handle include

       snapshot	length
	      If, when capturing, you  capture	the  entire  contents  of  the
	      packet,  that  requires more CPU time to copy the	packet to your
	      application, more	disk and possibly network bandwidth  to	 write
	      the  packet  data	 to  a	file,  and more	disk space to save the
	      packet.  If you don't need the entire contents of	the  packet  -
	      for  example,  if	 you are only interested in the	TCP headers of
	      packets -	you can	set the	"snapshot length" for the  capture  to
	      an appropriate value.  If	the snapshot length is set to snaplen,
	      and snaplen is less than the size	of a packet that is  captured,
	      only the first snaplen bytes of that packet will be captured and
	      provided as packet data.

	      A	snapshot length	of 65535 should	be sufficient, on most if  not
	      all networks, to capture all the data available from the packet.

	      The snapshot length is set with pcap_set_snaplen().

       promiscuous mode
	      On  broadcast  LANs  such	 as  Ethernet,	if  the	 network isn't
	      switched,	or if the adapter is connected to a "mirror port" on a
	      switch to	which all packets passing through the switch are sent,
	      a	network	adapter	receives all packets  on  the  LAN,  including
	      unicast  or multicast packets not	sent to	a network address that
	      the network adapter isn't	configured to recognize.

	      Normally,	the adapter will discard those packets;	however,  many
	      network  adapters	support	"promiscuous mode", which is a mode in
	      which all	packets, even if they are not sent to an address  that
	      the  adapter recognizes, are provided to the host.  This is use-
	      ful for passively	capturing traffic between two  or  more	 other
	      hosts for	analysis.

	      Note  that even if an application	does not set promiscuous mode,
	      the adapter could	well be	in promiscuous	mode  for  some	 other
	      reason.

	      For  now,	 this doesn't work on the "any"	device;	if an argument
	      of "any" or NULL is supplied, the	setting	of promiscuous mode is
	      ignored.

	      Promiscuous mode is set with pcap_set_promisc().

       monitor mode
	      On IEEE 802.11 wireless LANs, even if an adapter is in promiscu-
	      ous mode,	it will	supply to the host only	frames for the network
	      with  which  it's	 associated.   It  might also supply only data
	      frames, not management or	control	frames,	and might not  provide
	      the  802.11  header or radio information pseudo-header for those
	      frames.

	      In "monitor mode", sometimes also	called "rfmon mode" (for  "Ra-
	      dio Frequency MONitor"), the adapter will	supply all frames that
	      it receives, with	802.11 headers,	and  might  supply  a  pseudo-
	      header with radio	information about the frame as well.

	      Note  that  in  monitor mode the adapter might disassociate from
	      the network with which it's associated, so that you will not  be
	      able to use any wireless networks	with that adapter.  This could
	      prevent accessing	files on a network server, or  resolving  host
	      names or network addresses, if you are capturing in monitor mode
	      and are not connected to another network with another adapter.

	      Monitor mode is set with pcap_set_rfmon(), and  pcap_can_set_rf-
	      mon()  can  be  used  to determine whether an adapter can	be put
	      into monitor mode.

       packet buffer timeout
	      If, when capturing, packets are delivered	as soon	 as  they  ar-
	      rive, the	application capturing the packets will be woken	up for
	      each packet as it	arrives, and might have	to make	 one  or  more
	      calls to the operating system to fetch each packet.

	      If,  instead,  packets are not delivered as soon as they arrive,
	      but are delivered	after a	short delay (called a  "packet	buffer
	      timeout"),  more	than  one packet can be	accumulated before the
	      packets are delivered, so	that a single wakeup would be done for
	      multiple	packets,  and  each set	of calls made to the operating
	      system would supply  multiple  packets,  rather  than  a	single
	      packet.  This reduces the	per-packet CPU overhead	if packets are
	      arriving at a high rate, increasing the number  of  packets  per
	      second that can be captured.

	      The  packet  buffer  timeout  is required	so that	an application
	      won't wait for the operating system's capture buffer to fill  up
	      before  packets  are  delivered; if packets are arriving slowly,
	      that wait	could take an arbitrarily long period of time.

	      Not all platforms	support	a packet buffer	timeout; on  platforms
	      that  don't, the packet buffer timeout is	ignored.  A zero value
	      for the timeout, on platforms that support a packet buffer time-
	      out,  will  cause	a read to wait forever to allow	enough packets
	      to arrive, with no timeout.  A negative value  is	 invalid;  the
	      result  of  setting  the	timeout	 to a negative value is	unpre-
	      dictable.

	      NOTE: the	packet buffer timeout cannot be	used  to  cause	 calls
	      that read	packets	to return within a limited period of time, be-
	      cause, on	some platforms,	the packet buffer timeout  isn't  sup-
	      ported,  and,  on	other platforms, the timer doesn't start until
	      at least one packet arrives.  This means that the	packet	buffer
	      timeout  should  NOT be used, for	example, in an interactive ap-
	      plication	to allow the packet capture loop to ``poll'' for  user
	      input  periodically, as there's no guarantee that	a call reading
	      packets will return after	the timeout expires even if no packets
	      have arrived.

	      The packet buffer	timeout	is set with pcap_set_timeout().

       immediate mode
	      In  immediate mode, packets are always delivered as soon as they
	      arrive,  with  no	 buffering.   Immediate	 mode  is   set	  with
	      pcap_set_immediate_mode().

       buffer size
	      Packets  that  arrive  for  a capture are	stored in a buffer, so
	      that they	do not have to be read by the application as  soon  as
	      they arrive.  On some platforms, the buffer's size can be	set; a
	      size that's too small could mean that, if	too many  packets  are
	      being  captured and the snapshot length doesn't limit the	amount
	      of data that's buffered, packets could be	dropped	if the	buffer
	      fills  up	before the application can read	packets	from it, while
	      a	size that's too	large could use	 more  non-pageable  operating
	      system  memory  than  is necessary to prevent packets from being
	      dropped.

	      The buffer size is set with pcap_set_buffer_size().

       timestamp type
	      On some platforms, the time stamp	given to packets on live  cap-
	      tures  can  come	from different sources that can	have different
	      resolutions or that can have different relationships to the time
	      values  for  the current time supplied by	routines on the	native
	      operating	system.	 See pcap-tstamp(7) for	a list of  time	 stamp
	      types.

	      The time stamp type is set with pcap_set_tstamp_type().

       Reading packets from a network interface	may require that you have spe-
       cial privileges:

       Under SunOS 3.x or 4.x with NIT or BPF:
	      You must have read access	to /dev/nit or /dev/bpf*.

       Under Solaris with DLPI:
	      You must have read/write access to the  network  pseudo  device,
	      e.g.   /dev/le.	On at least some versions of Solaris, however,
	      this is not sufficient to	allow tcpdump to capture in  promiscu-
	      ous mode;	on those versions of Solaris, you must be root,	or the
	      application capturing packets must be installed setuid to	 root,
	      in  order	 to  capture  in promiscuous mode.  Note that, on many
	      (perhaps all) interfaces,	if you don't  capture  in  promiscuous
	      mode,  you  will	not see	any outgoing packets, so a capture not
	      done in promiscuous mode may not be very useful.

	      In newer versions	of Solaris,  you  must	have  been  given  the
	      net_rawaccess  privilege;	 this is both necessary	and sufficient
	      to give you access to the	network	pseudo-device -	 there	is  no
	      need  to	change	the  privileges	on that	device.	 A user	can be
	      given that privilege by, for example, adding that	 privilege  to
	      the user's defaultpriv key with the usermod (8) command.

       Under HP-UX with	DLPI:
	      You  must	 be  root or the application capturing packets must be
	      installed	setuid to root.

       Under IRIX with snoop:
	      You must be root or the application capturing  packets  must  be
	      installed	setuid to root.

       Under Linux:
	      You  must	 be  root or the application capturing packets must be
	      installed	setuid to root (unless your distribution has a	kernel
	      that  supports  capability  bits such as CAP_NET_RAW and code to
	      allow those capability bits to be	given to  particular  accounts
	      and  to cause those bits to be set on a user's initial processes
	      when they	log in,	in which case you  must	 have  CAP_NET_RAW  in
	      order  to	capture	and CAP_NET_ADMIN to enumerate network devices
	      with, for	example, the -D	flag).

       Under ULTRIX and	Digital	UNIX/Tru64 UNIX:
	      Any user may capture network traffic.   However,	no  user  (not
	      even  the	 super-user) can capture in promiscuous	mode on	an in-
	      terface unless the super-user has	enabled	promiscuous-mode oper-
	      ation on that interface using pfconfig(8), and no	user (not even
	      the super-user) can capture unicast traffic received by or  sent
	      by the machine on	an interface unless the	super-user has enabled
	      copy-all-mode operation on that  interface  using	 pfconfig,  so
	      useful packet capture on an interface probably requires that ei-
	      ther promiscuous-mode or copy-all-mode operation,	or both	 modes
	      of operation, be enabled on that interface.

       Under BSD (this includes	macOS):
	      You  must	 have  read  access to /dev/bpf* on systems that don't
	      have a cloning BPF device, or to /dev/bpf	on  systems  that  do.
	      On  BSDs	with a devfs (this includes macOS), this might involve
	      more than	just having somebody with  super-user  access  setting
	      the  ownership  or permissions on	the BPF	devices	- it might in-
	      volve configuring	devfs to set the ownership or permissions  ev-
	      ery time the system is booted, if	the system even	supports that;
	      if it doesn't support that, you might have to  find  some	 other
	      way to make that happen at boot time.

       Reading a saved packet file doesn't require special privileges.

       The  packets  read from the handle may include a	``pseudo-header'' con-
       taining various forms of	packet	meta-data,  and	 probably  includes  a
       link-layer  header  whose contents can differ for different network in-
       terfaces.  To determine the format of the packets supplied by the  han-
       dle, call pcap_datalink(); https://www.tcpdump.org/linktypes.html lists
       the values it returns and describes the packet formats that  correspond
       to those	values.

       Do NOT assume that the packets for a given capture or ``savefile`` will
       have any	given link-layer header	type, such as DLT_EN10MB for Ethernet.
       For  example,  the  "any" device	on Linux will have a link-layer	header
       type of DLT_LINUX_SLL even if all devices on the	system at the time the
       "any"  device  is  opened  have	some  other  data  link	 type, such as
       DLT_EN10MB for Ethernet.

       To obtain the FILE * corresponding to a pcap_t  opened  for  a  ``save-
       file'', call pcap_file().

       Routines

	      pcap_create(3)
		     get a pcap_t for live capture

	      pcap_activate(3)
		     activate a	pcap_t for live	capture

	      pcap_findalldevs(3)
		     get  a list of devices that can be	opened for a live cap-
		     ture

	      pcap_freealldevs(3)
		     free list of devices

	      pcap_lookupdev(3)
		     get first non-loopback device on that list

	      pcap_open_offline(3)
		     open a pcap_t for a ``savefile'', given a pathname

	      pcap_open_offline_with_tstamp_precision(3)
		     open a pcap_t for a ``savefile'', given a	pathname,  and
		     specify the precision to provide for packet time stamps

	      pcap_fopen_offline(3)
		     open a pcap_t for a ``savefile'', given a FILE *

	      pcap_fopen_offline_with_tstamp_precision(3)
		     open  a  pcap_t  for  a ``savefile'', given a FILE	*, and
		     specify the precision to provide for packet time stamps

	      pcap_open_dead(3)
		     create a ``fake'' pcap_t

	      pcap_close(3)
		     close a pcap_t

	      pcap_set_snaplen(3)
		     set the snapshot length for  a  not-yet-activated	pcap_t
		     for live capture

	      pcap_snapshot(3)
		     get the snapshot length for a pcap_t

	      pcap_set_promisc(3)
		     set  promiscuous  mode for	a not-yet-activated pcap_t for
		     live capture

	      pcap_set_protocol_linux(3)
		     set capture protocol for a	not-yet-activated  pcap_t  for
		     live capture (Linux only)

	      pcap_set_rfmon(3)
		     set  monitor mode for a not-yet-activated pcap_t for live
		     capture

	      pcap_can_set_rfmon(3)
		     determine whether monitor mode can	be set	for  a	pcap_t
		     for live capture

	      pcap_set_timeout(3)
		     set  packet buffer	timeout	for a not-yet-activated	pcap_t
		     for live capture

	      pcap_set_immediate_mode(3)
		     set immediate mode	for  a	not-yet-activated  pcap_t  for
		     live capture

	      pcap_set_buffer_size(3)
		     set  buffer  size for a not-yet-activated pcap_t for live
		     capture

	      pcap_set_tstamp_type(3)
		     set time stamp type for a	not-yet-activated  pcap_t  for
		     live capture

	      pcap_list_tstamp_types(3)
		     get  list of available time stamp types for a not-yet-ac-
		     tivated pcap_t for	live capture

	      pcap_free_tstamp_types(3)
		     free list of available time stamp types

	      pcap_tstamp_type_val_to_name(3)
		     get name for a time stamp type

	      pcap_tstamp_type_val_to_description(3)
		     get description for a time	stamp type

	      pcap_tstamp_type_name_to_val(3)
		     get time stamp type corresponding to a name

	      pcap_set_tstamp_precision(3)
		     set time stamp precision for a  not-yet-activated	pcap_t
		     for live capture

	      pcap_get_tstamp_precision(3)
		     get the time stamp	precision of a pcap_t for live capture

	      pcap_datalink(3)
		     get link-layer header type	for a pcap_t

	      pcap_file(3)
		     get the FILE * for	a pcap_t opened	for a ``savefile''

	      pcap_is_swapped(3)
		     determine	whether	 a ``savefile''	being read came	from a
		     machine with the opposite byte order

	      pcap_major_version(3)
	      pcap_minor_version(3)
		     get the major and minor version of	the file  format  ver-
		     sion for a	``savefile''

   Selecting a link-layer header type for a live capture
       Some  devices may provide more than one link-layer header type.	To ob-
       tain a list of all link-layer header types provided by a	 device,  call
       pcap_list_datalinks() on	an activated pcap_t for	the device.  To	free a
       list of link-layer header types,	call  pcap_free_datalinks().   To  set
       the  link-layer	header	type  for  a device, call pcap_set_datalink().
       This should be done after the device has	been activated but before  any
       packets are read	and before any filters are compiled or installed.

       Routines

	      pcap_list_datalinks(3)
		     get a list	of link-layer header types for a device

	      pcap_free_datalinks(3)
		     free list of link-layer header types

	      pcap_set_datalink(3)
		     set link-layer header type	for a device

	      pcap_datalink_val_to_name(3)
		     get name for a link-layer header type

	      pcap_datalink_val_to_description(3)
		     get description for a link-layer header type

	      pcap_datalink_name_to_val(3)
		     get link-layer header type	corresponding to a name

   Reading packets
       Packets are read	with pcap_dispatch() or	pcap_loop(), which process one
       or more packets,	calling	a callback routine for each  packet,  or  with
       pcap_next() or pcap_next_ex(), which return the next packet.  The call-
       back for	pcap_dispatch()	and pcap_loop()	is supplied  a	pointer	 to  a
       struct pcap_pkthdr, which includes the following	members:

	      ts     a	struct timeval containing the time when	the packet was
		     captured

	      caplen a bpf_u_int32 giving the number of	bytes  of  the	packet
		     that are available	from the capture

	      len    a	bpf_u_int32  giving the	length of the packet, in bytes
		     (which might be more than the number of  bytes  available
		     from  the	capture, if the	length of the packet is	larger
		     than the maximum number of	bytes to capture).

       The callback is also supplied a	const  u_char  pointer	to  the	 first
       caplen  (as  given  in the struct pcap_pkthdr mentioned above) bytes of
       data from the packet.  This won't necessarily be	the entire packet;  to
       capture the entire packet, you will have	to provide a value for snaplen
       in your call to pcap_set_snaplen() that is sufficiently	large  to  get
       all  of	the  packet's  data - a	value of 65535 should be sufficient on
       most if not all networks).  When	reading	from a ``savefile'', the snap-
       shot  length  specified	when  the capture was performed	will limit the
       amount of packet	data available.

       pcap_next() is passed an	argument that points to	a  struct  pcap_pkthdr
       structure,  and	fills  it in with the time stamp and length values for
       the packet.  It returns a const u_char to the first caplen bytes	of the
       packet on success, and NULL on error.

       pcap_next_ex()  is passed two pointer arguments,	one of which points to
       a structpcap_pkthdr* and	one of which points to a  const	 u_char*.   It
       sets  the first pointer to point	to a struct pcap_pkthdr	structure with
       the time	stamp and length values	for the	packet,	and  sets  the	second
       pointer to point	to the first caplen bytes of the packet.

       To  force the loop in pcap_dispatch() or	pcap_loop() to terminate, call
       pcap_breakloop().

       By default, when	reading	packets	from an	interface opened  for  a  live
       capture,	 pcap_dispatch(),  pcap_next(),	and pcap_next_ex() will, if no
       packets are currently available to be read, block waiting  for  packets
       to become available.  On	some, but not all, platforms, if a packet buf-
       fer timeout was specified, the wait will	 terminate  after  the	packet
       buffer timeout expires; applications should be prepared for this, as it
       happens on some platforms, but should not rely on it, as	 it  does  not
       happen  on  other  platforms.   Note that the wait might, or might not,
       terminate even if no packets are	available; applications	should be pre-
       pared for this to happen, but must not rely on it happening.

       A  handle can be	put into ``non-blocking	mode'',	so that	those routines
       will, rather than blocking, return an indication	that  no  packets  are
       available  to  read.  Call pcap_setnonblock() to	put a handle into non-
       blocking	mode or	to take	it out of non-blocking mode; call pcap_getnon-
       block()	to  determine  whether a handle	is in non-blocking mode.  Note
       that non-blocking mode does not work correctly in Mac OS	X 10.6.

       Non-blocking mode is often combined with	routines such as select(2)  or
       poll(2) or other	routines a platform offers to wait for any of a	set of
       descriptors to be ready to read.	 To obtain, for	a handle, a descriptor
       that  can be used in those routines, call pcap_get_selectable_fd().  If
       the routine indicates that data is available to read on the descriptor,
       an attempt should be made to read from the device.

       Not   all  handles  have	 such  a  descriptor  available;  pcap_get_se-
       lectable_fd() will return PCAP_ERROR if no such	descriptor  is	avail-
       able.   If no such descriptor is	available, this	may be because the de-
       vice  must  be  polled  periodically  for  packets;   in	  that	 case,
       pcap_get_required_select_timeout()  will	 return	 a pointer to a	struct
       timeval whose value can be used as a timeout in those  routines.	  When
       the routine returns, an attmept should be made to read packets from the
       device.	If pcap_get_required_select_timeout() returns  NULL,  no  such
       timeout	is  available,	and those routines cannot be used with the de-
       vice.

       In addition, for	various	reasons, one or	more of	 those	routines  will
       not   work   properly   with  the  descriptor;  the  documentation  for
       pcap_get_selectable_fd()	gives details.	Note that, just	as an  attempt
       to  read	packets	from a pcap_t may not return any packets if the	packet
       buffer timeout expires, a select(), poll(), or other such call may,  if
       the  packet buffer timeout expires, indicate that a descriptor is ready
       to read even if there are no packets available to read.

       Routines

	      pcap_dispatch(3)
		     read a bufferful of packets from a	pcap_t open for	a live
		     capture or	the full set of	packets	from a pcap_t open for
		     a ``savefile''

	      pcap_loop(3)
		     read packets from a pcap_t	until an  interrupt  or	 error
		     occurs

	      pcap_next(3)
		     read  the next packet from	a pcap_t without an indication
		     whether an	error occurred

	      pcap_next_ex(3)
		     read the next packet from a pcap_t	with an	error  indica-
		     tion on an	error

	      pcap_breakloop(3)
		     prematurely  terminate  the  loop	in  pcap_dispatch() or
		     pcap_loop()

	      pcap_setnonblock(3)
		     set or clear non-blocking mode on a pcap_t

	      pcap_getnonblock(3)
		     get the state of non-blocking mode	for a pcap_t

	      pcap_get_selectable_fd(3)
		     attempt to	get a descriptor for a pcap_t that can be used
		     in	calls such as select(2)	and poll(2)

	      pcap_get_required_select_timeout(3)
		     if	 no  descriptor	 usable	 with select(2)	and poll(2) is
		     available for the pcap_t, attempt to get a	timeout	usable
		     with those	routines

   Filters
       In  order  to  cause  only  certain packets to be returned when reading
       packets,	a filter can be	set on a handle.  For a	live capture, the fil-
       tering  will be performed in kernel mode, if possible, to avoid copying
       ``uninteresting'' packets from the kernel to user mode.

       A filter	can be specified as a text string; the syntax and semantics of
       the string are as described by pcap-filter(7).  A filter	string is com-
       piled into a program in a pseudo-machine-language by pcap_compile() and
       the  resulting program can be made a filter for a handle	with pcap_set-
       filter().  The result of	pcap_compile() can be freed  with  a  call  to
       pcap_freecode().	 pcap_compile()	may require a network mask for certain
       expressions in the filter string; pcap_lookupnet() can be used to  find
       the network address and network mask for	a given	capture	device.

       A  compiled  filter  can	 also be applied directly to a packet that has
       been read using pcap_offline_filter().

       Routines

	      pcap_compile(3)
		     compile filter expression	to  a  pseudo-machine-language
		     code program

	      pcap_freecode(3)
		     free a filter program

	      pcap_setfilter(3)
		     set filter	for a pcap_t

	      pcap_lookupnet(3)
		     get network address and network mask for a	capture	device

	      pcap_offline_filter(3)
		     apply a filter program to a packet

   Incoming and	outgoing packets
       By  default,  libpcap  will attempt to capture both packets sent	by the
       machine and packets received by the machine.  To	limit it to  capturing
       only packets received by	the machine or,	if possible, only packets sent
       by the machine, call pcap_setdirection().

       Routines

	      pcap_setdirection(3)
		     specify whether to	 capture  incoming  packets,  outgoing
		     packets, or both

   Capture statistics
       To get statistics about packets received	and dropped in a live capture,
       call pcap_stats().

       Routines

	      pcap_stats(3)
		     get capture statistics

   Opening a handle for	writing	captured packets
       To open a ``savefile`` to which to write	packets,  given	 the  pathname
       the ``savefile''	should have, call pcap_dump_open().  To	open a ``save-
       file`` to which to write	packets, given the pathname  the  ``savefile''
       should  have,  call  pcap_dump_open(); to set up	a handle for a ``save-
       file'', given a FILE * referring	to a file already opened for  writing,
       call  pcap_dump_fopen().	 They each return pointers to a	pcap_dumper_t,
       which is	the handle used	for writing packets to the  ``savefile''.   If
       it  succeeds,  it  will	have  created the file if it doesn't exist and
       truncated the file if it	does exist.  To	close  a  pcap_dumper_t,  call
       pcap_dump_close().

       Routines

	      pcap_dump_open(3)
		     open a pcap_dumper_t for a	``savefile``, given a pathname

	      pcap_dump_fopen(3)
		     open a pcap_dumper_t for a	``savefile``, given a FILE *

	      pcap_dump_close(3)
		     close a pcap_dumper_t

	      pcap_dump_file(3)
		     get  the  FILE * for a pcap_dumper_t opened for a ``save-
		     file''

   Writing packets
       To write	a packet to a pcap_dumper_t, call pcap_dump().	Packets	 writ-
       ten  with  pcap_dump()  may  be buffered, rather	than being immediately
       written to the ``savefile''.  Closing the pcap_dumper_t will cause  all
       buffered-but-not-yet-written packets to be written to the ``savefile''.
       To force	all packets written to the pcap_dumper_t, and not yet  written
       to  the	``savefile'' because they're buffered by the pcap_dumper_t, to
       be written to the ``savefile'', without closing the pcap_dumper_t, call
       pcap_dump_flush().

       Routines

	      pcap_dump(3)
		     write packet to a pcap_dumper_t

	      pcap_dump_flush(3)
		     flush  buffered packets written to	a pcap_dumper_t	to the
		     ``savefile''

	      pcap_dump_ftell(3)
		     get current file position for a pcap_dumper_t

   Injecting packets
       If you have the required	privileges, you	can inject packets onto	a net-
       work  with  a  pcap_t  for  a  live  capture,  using  pcap_inject()  or
       pcap_sendpacket().  (The	two routines exist for compatibility with both
       OpenBSD and WinPcap; they perform the same function, but	have different
       return values.)

       Routines

	      pcap_inject(3)
	      pcap_sendpacket(3)
		     transmit a	packet

   Reporting errors
       Some routines return error or warning status codes; to convert them  to
       a string, use pcap_statustostr().

       Routines

	      pcap_statustostr(3)
		     get a string for an error or warning status code

   Getting library version information
       To  get	a  string  giving  version  information	 about	libpcap,  call
       pcap_lib_version().

       Routines

	      pcap_lib_version(3)
		     get library version string

BACKWARD COMPATIBILITY
       In versions of libpcap prior to 1.0, the	pcap.h header file was not  in
       a  pcap	directory on most platforms; if	you are	writing	an application
       that must work on versions of libpcap prior to 1.0,  include  <pcap.h>,
       which  will  include  <pcap/pcap.h>  for	 you,  rather  than  including
       <pcap/pcap.h>.

       pcap_create() and pcap_activate() were not  available  in  versions  of
       libpcap	prior to 1.0; if you are writing an application	that must work
       on versions of libpcap prior to 1.0, either use pcap_open_live()	to get
       a handle	for a live capture or, if you want to be able to use the addi-
       tional capabilities offered by using pcap_create() and pcap_activate(),
       use  an	autoconf(1) script or some other configuration script to check
       whether the libpcap 1.0 APIs are	available and use them	only  if  they
       are.

SEE ALSO
       autoconf(1),   tcpdump(1),  tcpslice(1),	 pcap-filter(7),  pfconfig(8),
       usermod(8)

AUTHORS
       The original authors of libpcap are:

       Van Jacobson, Craig Leres and  Steven  McCanne,	all  of	 the  Lawrence
       Berkeley	National Laboratory, University	of California, Berkeley, CA.

       The current version is available	from "The Tcpdump Group"'s Web site at

	      https://www.tcpdump.org/

BUGS
       To  report  a  security	issue  please  send an e-mail to security@tcp-
       dump.org.

       To report bugs and other	problems, contribute patches, request  a  fea-
       ture,  provide generic feedback etc please see the file CONTRIBUTING in
       the libpcap source tree root.

				 25 July 2018			       PCAP(3)

NAME | SYNOPSIS | DESCRIPTION | BACKWARD COMPATIBILITY | SEE ALSO | AUTHORS | BUGS

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