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.TH PCAP 3PCAP "25 July 2018"

.SH NAME

pcap \- Packet Capture library

.SH SYNOPSIS

.nf

.ft B

#include <pcap/pcap.h>

.LP

.ft B

.ft

.fi

.SH 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''.

.SS 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

.BR pcap_create (),

set the appropriate options on the handle, and then activate it with

.BR pcap_activate ().

.PP

To obtain a list of devices that can be opened for a live capture, call

.BR pcap_findalldevs ();

to free the list returned by

.BR pcap_findalldevs (),

call

.BR pcap_freealldevs ().

.BR pcap_lookupdev ()

will return the first device on that list that is not a ``loopback``

network interface.

.PP

To open a handle for a ``savefile'' from which to read packets, given the

pathname of the ``savefile'', call

.BR pcap_open_offline ();

to set up a handle for a ``savefile'', given a

.B "FILE\ *"

referring to a file already opened for reading, call

.BR pcap_fopen_offline ().

.PP

In order to get a ``fake''

.B pcap_t

for use in routines that require a

.B pcap_t

as an argument, such as routines to open a ``savefile'' for writing and

to compile a filter expression, call

.BR pcap_open_dead ().

.PP

.BR pcap_create (),

.BR pcap_open_offline (),

.BR pcap_fopen_offline (),

and

.BR pcap_open_dead ()

return a pointer to a

.BR 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

.BR pcap_close ().

.PP

The options that can be set on a capture handle include

.IP "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

.IR snaplen ,

and

.I snaplen

is less

than the size of a packet that is captured, only the first

.I snaplen

bytes of that packet will be captured and provided as packet data.

.IP

A snapshot length of 65535 should be sufficient, on most if not all

networks, to capture all the data available from the packet.

.IP

The snapshot length is set with

.BR pcap_set_snaplen ().

.IP "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.

.IP

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.

.IP

Note that even if an application does not set promiscuous mode, the

adapter could well be in promiscuous mode for some other reason.

.IP

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.

.IP

Promiscuous mode is set with

.BR pcap_set_promisc ().

.IP "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.

.IP

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.

.IP

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.

.IP

Monitor mode is set with

.BR pcap_set_rfmon (),

and

.BR pcap_can_set_rfmon ()

can be used to determine whether an adapter can be put into monitor

mode.

.IP "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.

.IP

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.

.IP

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.

.IP

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.

.IP

.BR 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

.B 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.

.IP

The packet buffer timeout is set with

.BR pcap_set_timeout ().

.IP "immediate mode"

In immediate mode, packets are always delivered as soon as they arrive,

with no buffering.  Immediate mode is set with

.BR pcap_set_immediate_mode ().

.IP "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.

.IP

The buffer size is set with

.BR pcap_set_buffer_size ().

.IP "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

.BR pcap-tstamp (@MAN_MISC_INFO@)

for a list of time stamp types.

.IP

The time stamp type is set with

.BR pcap_set_tstamp_type ().

.PP

Reading packets from a network interface may require that you have

special privileges:

.TP

.B Under SunOS 3.x or 4.x with NIT or BPF:

You must have read access to

.I /dev/nit

or

.IR /dev/bpf* .

.TP

.B Under Solaris with DLPI:

You must have read/write access to the network pseudo device, e.g.

.IR /dev/le .

On at least some versions of Solaris, however, this is not sufficient to

allow

.I 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.

.IP

In newer versions of Solaris, you must have been given the

.B 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

.B defaultpriv

key with the

.B usermod (@MAN_ADMIN_COMMANDS@)

command.

.TP

.B Under HP-UX with DLPI:

You must be root or the application capturing packets must be installed

setuid to root.

.TP

.B Under IRIX with snoop:

You must be root or the application capturing packets must be installed

setuid to root.

.TP

.B 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

.B \-D

flag).

.TP

.B 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

.IR 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

.IR pfconfig ,

so

.I 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.

.TP

.B Under BSD (this includes macOS):

You must have read access to

.I /dev/bpf*

on systems that don't have a cloning BPF device, or to

.I /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.

.PP

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

.PP

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

.BR pcap_datalink ();

.I https://www.tcpdump.org/linktypes.html

lists the values it returns and describes the packet formats that

correspond to those values.

.PP

Do

.B NOT

assume that the packets for a given capture or ``savefile`` will have

any given link-layer header type, such as

.B DLT_EN10MB

for Ethernet.  For example, the "any" device on Linux will have a

link-layer header type of

.B 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

.B DLT_EN10MB

for Ethernet.

.PP

To obtain the

.B "FILE\ *"

corresponding to a

.B pcap_t

opened for a ``savefile'', call

.BR pcap_file ().

.TP

.B Routines

.RS

.TP

.BR pcap_create (3PCAP)

get a

.B pcap_t

for live capture

.TP

.BR pcap_activate (3PCAP)

activate a

.B pcap_t

for live capture

.TP

.BR pcap_findalldevs (3PCAP)

get a list of devices that can be opened for a live capture

.TP

.BR pcap_freealldevs (3PCAP)

free list of devices

.TP

.BR pcap_lookupdev (3PCAP)

get first non-loopback device on that list

.TP

.BR pcap_open_offline (3PCAP)

open a

.B pcap_t

for a ``savefile'', given a pathname

.TP

.BR pcap_open_offline_with_tstamp_precision (3PCAP)

open a

.B pcap_t

for a ``savefile'', given a pathname, and specify the precision to

provide for packet time stamps

.TP

.BR pcap_fopen_offline (3PCAP)

open a

.B pcap_t

for a ``savefile'', given a

.B "FILE\ *"

.TP

.BR pcap_fopen_offline_with_tstamp_precision (3PCAP)

open a

.B pcap_t

for a ``savefile'', given a

.BR "FILE\ *" ,

and specify the precision to provide for packet time stamps

.TP

.BR pcap_open_dead (3PCAP)

create a ``fake''

.B pcap_t

.TP

.BR pcap_close (3PCAP)

close a

.B pcap_t

.TP

.BR pcap_set_snaplen (3PCAP)

set the snapshot length for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_snapshot (3PCAP)

get the snapshot length for a

.B pcap_t

.TP

.BR pcap_set_promisc (3PCAP)

set promiscuous mode for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_set_protocol_linux (3PCAP)

set capture protocol for a not-yet-activated

.B pcap_t

for live capture (Linux only)

.TP

.BR pcap_set_rfmon (3PCAP)

set monitor mode for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_can_set_rfmon (3PCAP)

determine whether monitor mode can be set for a

.B pcap_t

for live capture

.TP

.BR pcap_set_timeout (3PCAP)

set packet buffer timeout for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_set_immediate_mode (3PCAP)

set immediate mode for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_set_buffer_size (3PCAP)

set buffer size for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_set_tstamp_type (3PCAP)

set time stamp type for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_list_tstamp_types (3PCAP)

get list of available time stamp types for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_free_tstamp_types (3PCAP)

free list of available time stamp types

.TP

.BR pcap_tstamp_type_val_to_name (3PCAP)

get name for a time stamp type

.TP

.BR pcap_tstamp_type_val_to_description (3PCAP)

get description for a time stamp type

.TP

.BR pcap_tstamp_type_name_to_val (3PCAP)

get time stamp type corresponding to a name

.TP

.BR pcap_set_tstamp_precision (3PCAP)

set time stamp precision for a not-yet-activated

.B pcap_t

for live capture

.TP

.BR pcap_get_tstamp_precision (3PCAP)

get the time stamp precision of a

.B pcap_t

for live capture

.TP

.BR pcap_datalink (3PCAP)

get link-layer header type for a

.B pcap_t

.TP

.BR pcap_file (3PCAP)

get the

.B "FILE\ *"

for a

.B pcap_t

opened for a ``savefile''

.TP

.BR pcap_is_swapped (3PCAP)

determine whether a ``savefile'' being read came from a machine with the

opposite byte order

.TP

.BR pcap_major_version (3PCAP)

.PD 0

.TP

.BR pcap_minor_version (3PCAP)

get the major and minor version of the file format version for a

``savefile''

.PD

.RE

.SS 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

.BR pcap_list_datalinks ()

on an activated

.B pcap_t

for the device.

To free a list of link-layer header types, call

.BR pcap_free_datalinks ().

To set the link-layer header type for a device, call

.BR 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.

.TP

.B Routines

.RS

.TP

.BR pcap_list_datalinks (3PCAP)

get a list of link-layer header types for a device

.TP

.BR pcap_free_datalinks (3PCAP)

free list of link-layer header types

.TP

.BR pcap_set_datalink (3PCAP)

set link-layer header type for a device

.TP

.BR pcap_datalink_val_to_name (3PCAP)

get name for a link-layer header type

.TP

.BR pcap_datalink_val_to_description (3PCAP)

get description for a link-layer header type

.TP

.BR pcap_datalink_name_to_val (3PCAP)

get link-layer header type corresponding to a name

.RE

.SS Reading packets

Packets are read with

.BR pcap_dispatch ()

or

.BR pcap_loop (),

which process one or more packets, calling a callback routine for each

packet, or with

.BR pcap_next ()

or

.BR pcap_next_ex (),

which return the next packet.

The callback for

.BR pcap_dispatch ()

and

.BR pcap_loop ()

is supplied a pointer to a

.IR "struct pcap_pkthdr" ,

which includes the following members:

.RS

.TP

.B ts

a

.I struct timeval

containing the time when the packet was captured

.TP

.B caplen

a

.I bpf_u_int32

giving the number of bytes of the packet that are available from the

capture

.TP

.B len

a

.I 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).

.RE

.PP

The callback is also supplied a

.I const u_char

pointer to the first

.B caplen

(as given in the

.I 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

.I snaplen

in your call to

.BR 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.

.PP

.BR pcap_next ()

is passed an argument that points to a

.I struct pcap_pkthdr

structure, and fills it in with the time stamp and length values for the

packet.  It returns a

.I const u_char

to the first

.B caplen

bytes of the packet on success, and NULL on error.

.PP

.BR pcap_next_ex ()

is passed two pointer arguments, one of which points to a

.IR struct pcap_pkthdr *

and one of which points to a

.IR "const u_char" *.

It sets the first pointer to point to a

.I struct pcap_pkthdr

structure with the time stamp and length values for the packet, and sets

the second pointer to point to the first

.B caplen

bytes of the packet.

.PP

To force the loop in

.BR pcap_dispatch ()

or

.BR pcap_loop ()

to terminate, call

.BR pcap_breakloop ().

.PP

By default, when reading packets from an interface opened for a live

capture,

.BR pcap_dispatch (),

.BR pcap_next (),

and

.BR pcap_next_ex ()

will, if no packets are currently available to be read, block waiting

for packets to become available.  On some, but

.I 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.

.PP

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

.BR pcap_setnonblock ()

to put a handle into non-blocking mode or to take it out of non-blocking

mode; call

.BR 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.

.PP

Non-blocking mode is often combined with routines such as

.BR select (2)

or

.BR 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

.BR 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.

.PP

Not all handles have such a descriptor available;

.BR pcap_get_selectable_fd ()

will return

.B PCAP_ERROR

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,

.BR pcap_get_required_select_timeout ()

will return a pointer to a

.B 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

.BR pcap_get_required_select_timeout ()

returns NULL, no such timeout is available, and those routines cannot be

used with the device.

.PP

In addition, for various

reasons, one or more of those routines will not work properly with the

descriptor; the documentation for

.BR pcap_get_selectable_fd ()

gives details.  Note that, just as an attempt to read packets from a

.B pcap_t

may not return any packets if the packet buffer timeout expires, a

.BR select (),

.BR 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.

.TP

.B Routines

.RS

.TP

.BR pcap_dispatch (3PCAP)

read a bufferful of packets from a

.B pcap_t

open for a live capture or the full set of packets from a

.B pcap_t

open for a ``savefile''

.TP

.BR pcap_loop (3PCAP)

read packets from a

.B pcap_t

until an interrupt or error occurs

.TP

.BR pcap_next (3PCAP)

read the next packet from a

.B pcap_t

without an indication whether an error occurred

.TP

.BR pcap_next_ex (3PCAP)

read the next packet from a

.B pcap_t

with an error indication on an error

.TP

.BR pcap_breakloop (3PCAP)

prematurely terminate the loop in

.BR pcap_dispatch ()

or

.BR pcap_loop ()

.TP

.BR pcap_setnonblock (3PCAP)

set or clear non-blocking mode on a

.B pcap_t

.TP

.BR pcap_getnonblock (3PCAP)

get the state of non-blocking mode for a

.B pcap_t

.TP

.BR pcap_get_selectable_fd (3PCAP)

attempt to get a descriptor for a

.B pcap_t

that can be used in calls such as

.BR select (2)

and

.BR poll (2)

.TP

.BR pcap_get_required_select_timeout (3PCAP)

if no descriptor usable with

.BR select (2)

and

.BR poll (2)

is available for the

.BR pcap_t ,

attempt to get a timeout usable with those routines

.RE

.SS 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.

.PP

A filter can be specified as a text string; the syntax and semantics of

the string are as described by

.BR pcap-filter (@MAN_MISC_INFO@).

A filter string is compiled into a program in a pseudo-machine-language

by

.BR pcap_compile ()

and the resulting program can be made a filter for a handle with

.BR pcap_setfilter ().

The result of

.BR pcap_compile ()

can be freed with a call to

.BR pcap_freecode ().

.BR pcap_compile ()

may require a network mask for certain expressions in the filter string;

.BR pcap_lookupnet ()

can be used to find the network address and network mask for a given

capture device.

.PP

A compiled filter can also be applied directly to a packet that has been

read using

.BR pcap_offline_filter ().

.TP

.B Routines

.RS

.TP

.BR pcap_compile (3PCAP)

compile filter expression to a pseudo-machine-language code program

.TP

.BR pcap_freecode (3PCAP)

free a filter program

.TP

.BR pcap_setfilter (3PCAP)

set filter for a

.B pcap_t

.TP

.BR pcap_lookupnet (3PCAP)

get network address and network mask for a capture device

.TP

.BR pcap_offline_filter (3PCAP)

apply a filter program to a packet

.RE

.SS 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

.BR pcap_setdirection ().

.TP

.BR Routines

.RS

.TP

.BR pcap_setdirection (3PCAP)

specify whether to capture incoming packets, outgoing packets, or both

.RE

.SS Capture statistics

To get statistics about packets received and dropped in a live capture,

call

.BR pcap_stats ().

.TP

.B Routines

.RS

.TP

.BR pcap_stats (3PCAP)

get capture statistics

.RE

.SS Opening a handle for writing captured packets

To open a ``savefile`` to which to write packets, given the pathname the

``savefile'' should have, call

.BR pcap_dump_open ().

To open a ``savefile`` to which to write packets, given the pathname the

``savefile'' should have, call

.BR pcap_dump_open ();

to set up a handle for a ``savefile'', given a

.B "FILE\ *"

referring to a file already opened for writing, call

.BR pcap_dump_fopen ().

They each return pointers to a

.BR 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

.BR pcap_dumper_t ,

call

.BR pcap_dump_close ().

.TP

.B Routines

.RS

.TP

.BR pcap_dump_open (3PCAP)

open a

.B pcap_dumper_t

for a ``savefile``, given a pathname

.TP

.BR pcap_dump_fopen (3PCAP)

open a

.B pcap_dumper_t

for a ``savefile``, given a

.B "FILE\ *"

.TP

.BR pcap_dump_close (3PCAP)

close a

.B pcap_dumper_t

.TP

.BR pcap_dump_file (3PCAP)

get the

.B "FILE\ *"

for a

.B pcap_dumper_t

opened for a ``savefile''

.RE

.SS Writing packets

To write a packet to a

.BR pcap_dumper_t ,

call

.BR pcap_dump ().

Packets written with

.BR pcap_dump ()

may be buffered, rather than being immediately written to the

``savefile''.  Closing the

.B 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

.BR pcap_dumper_t ,

and not yet written to the ``savefile'' because they're buffered by the

.BR pcap_dumper_t ,

to be written to the ``savefile'', without closing the

.BR pcap_dumper_t ,

call

.BR pcap_dump_flush ().

.TP

.B Routines

.RS

.TP

.BR pcap_dump (3PCAP)

write packet to a

.B pcap_dumper_t

.TP

.BR pcap_dump_flush (3PCAP)

flush buffered packets written to a