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''.



Initializing

	pcap_init() initializes the library.  It takes an argument giving options; 
currently, the options are:


PCAP_CHAR_ENC_LOCAL
Treat  all  strings supplied as arguments, and return all strings to the caller, as
being in the local character encoding.


PCAP_CHAR_ENC_UTF_8
Treat all strings supplied as arguments, and return all strings to the  caller,  as
being in UTF-8.

On UNIX-like systems, the local character encoding is assumed to be UTF-8, so no character
encoding transformations are done.

On Windows, the local character encoding is the local ANSI code page.

If pcap_init() is called, the deprecated pcap_lookupdev()  routine  always  fails,  so  it
should  not  be  used,  and, on Windows, pcap_create() does not attempt to handle UTF-16LE
strings.

If pcap_init() is not called, strings are treated as being in the local ANSI code page  on
Windows,  pcap_lookupdev()  will  succeed  if  there  is a device on which to capture, and
pcap_create() makes an attempt to check whether the string passed  as  an  argument  is  a
UTF-16LE  string  -  note  that  this attempt is unsafe, as it may run past the end of the
string - to handle pcap_lookupdev() returning a UTF-16LE string. Programs that don't  call
pcap_init()  should,  on Windows, call pcap_wsockinit() to initialize Winsock; this is not
necessary if pcap_init() is called, as  pcap_init()  will  initialize  Winsock  itself  on
Windows.

Routines

pcap_init(3PCAP)
initialize the library



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_create(), set the appropriate options  on  the
handle,  and  then activate it with pcap_activate().  If pcap_activate() fails, the handle
should be closed with pcap_close().

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  useful  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 promiscuous  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 "Radio 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_rfmon() 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 arrive, 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 timeout, 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 unpredictable.

NOTE: the packet buffer timeout cannot be used to cause calls that read packets  to
return  within  a  limited  period  of time, because, on some platforms, the packet
buffer timeout isn't supported, 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 application 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 captures 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 special 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 promiscuous 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.

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 interface unless the super-user has enabled
promiscuous-mode operation 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 either 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  involve
configuring  devfs  to  set  the  ownership or permissions every 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'' containing various forms
of packet meta-data, and probably includes a link-layer header whose contents  can  differ
for  different network interfaces.  To determine the format of the packets supplied by the
handle, 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 or DLT_LINUX_SLL2 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  ``savefile'',  call
pcap_file().



Routines


pcap_create(3PCAP)
get a pcap_t for live capture


pcap_activate(3PCAP)
activate a pcap_t for live capture


pcap_findalldevs(3PCAP)
get a list of devices that can be opened for a live capture


pcap_freealldevs(3PCAP)
free list of devices


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


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


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


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


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


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


pcap_close(3PCAP)
close a pcap_t
 

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


pcap_snapshot(3PCAP)
get the snapshot length for a pcap_t


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


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


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


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


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


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


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


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


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


pcap_free_tstamp_types(3PCAP)
free list of available time stamp types


pcap_tstamp_type_val_to_name(3PCAP)
get name for a time stamp type


pcap_tstamp_type_val_to_description(3PCAP)
get description for a time stamp type


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


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


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


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

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


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


pcap_major_version(3PCAP)
pcap_minor_version(3PCAP)
get  the  major  and  minor  version  of  the  file  format  version  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 obtain 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(3PCAP)
get a list of link-layer header types for a device


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


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


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


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


pcap_datalink_name_to_val(3PCAP)
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 callback 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 snapshot 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 buffer 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 prepared 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_getnonblock() 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_selectable_fd() will return -1
if no such descriptor is available.  If no such  descriptor  is  available,  this  may  be
because   the   device   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 device.

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

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

pcap_next_ex(3PCAP)
read the next packet from a pcap_t with an error indication on an error

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

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

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

pcap_get_selectable_fd(3PCAP)
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(3PCAP)
attempt  to  get  a  timeout  required  for  using a pcap_t in calls such as
select(2) and poll(2)

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 filtering 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 compiled 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_setfilter().   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(3PCAP)
compile filter expression to a pseudo-machine-language code program

pcap_freecode(3PCAP)
free a filter program

pcap_setfilter(3PCAP)
set filter for a pcap_t

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

pcap_offline_filter(3PCAP)
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(3PCAP)
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(3PCAP)
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 ``savefile`` to  which  to  write  packets,
given the pathname the ``savefile'' should have, call pcap_dump_open(); to set up a handle
for a ``savefile'', 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(3PCAP)
open a pcap_dumper_t for a ``savefile``, given a pathname

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

pcap_dump_close(3PCAP)
close a pcap_dumper_t

pcap_dump_file(3PCAP)
get the FILE * for a pcap_dumper_t opened for a ``savefile''

Writing packets
To write a packet to a pcap_dumper_t, call pcap_dump().  Packets written 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(3PCAP)
write packet to a pcap_dumper_t

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

pcap_dump_ftell(3PCAP)
get current file position for a pcap_dumper_t

Injecting packets
If  you  have the required privileges, you can inject packets onto a network 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/Npcap; they perform the same function, but
have different return values.)

Routines

pcap_inject(3PCAP)
pcap_sendpacket(3PCAP)
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(3PCAP)
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(3PCAP)
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  ,  which will include  for you, rather than
including .

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 additional 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(8), 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@tcpdump.org.

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