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PCAP(3PCAP)                                                  PCAP(3PCAP)

NAME         top

       pcap - Packet Capture library

SYNOPSIS         top

       #include <pcap/pcap.h>

DESCRIPTION         top

       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         top

       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 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         top

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

AUTHORS         top

       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         top

       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.

COLOPHON         top

       This page is part of the libpcap (packet capture library)
       project.  Information about the project can be found at 
       ⟨http://www.tcpdump.org/⟩.  If you have a bug report for this
       manual page, see ⟨http://www.tcpdump.org/#patches⟩.  This page
       was obtained from the project's upstream Git repository
       ⟨https://github.com/the-tcpdump-group/libpcap.git⟩ on 2020-12-18.
       (At that time, the date of the most recent commit that was found
       in the repository was 2020-12-15.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

                            9 September 2020                 PCAP(3PCAP)