Portability	non-portable
Stability	experimental
Maintainer	bos@serpentine.com

Network.Pcap.Base

Contents

Types
Device opening
Filter handling
Device utilities
Interface control
Link layer utilities
Packet processing
Sending packets
Conversion
Miscellaneous

Description

The Network.Pcap.Base module is a low-level binding to all of the functions in libpcap. See http://www.tcpdump.org for more information.

Only a minimum of marshaling is done. For a higher-level interface that's more friendly, use the Network.Pcap module.

To convert captured packet data to a list, extract the length of the captured buffer from the packet header record and use peekArray to convert the captured data to a list. For illustration:

	import Network.Pcap.Base
	import Foreign.Marshal.Array (peekArray)

	main = do
        let printIt :: PktHdr -> Ptr Word8 -> IO ()
		printIt ph bytep = do
	          a <- peekArray (fromIntegral (hdrCaptureLength ph)) bytep 
	       	  print a

	    p <- openLive "em0" 100 True 10000
	    s <- withForeignPtr p $ \ptr -> do
	           dispatch ptr (-1) printIt
	    return ()

Note that the SockAddr exported here is not the SockAddr from Network.Socket. The SockAddr from Network.Socket corresponds to struct sockaddr_in in BSD terminology. The SockAddr record here is BSD's struct sockaddr. See W.R.Stevens, TCP Illustrated, volume 2, for further elucidation.

This binding should be portable across systems that can use the libpcap library from tcpdump.org. It will not work with Winpcap, a similar library for Windows, although adapting it should not prove difficult.

Synopsis

Types

data PcapTag Source

data PcapDumpTag Source

packet capture descriptor

type Pdump = ForeignPtr PcapDumpTag Source

dump file descriptor

type BpfProgram = ForeignPtr BpfProgramTag Source

Compiled Berkeley Packet Filter program

data BpfProgramTag Source

type Callback = PktHdr -> Ptr Word8 -> IO ()Source

the type of the callback function passed to dispatch or loop.

data Direction Source

The direction in which packets are to be captured. See setDirection.

Constructors

InOut	incoming and outgoing packets (the default
In	incoming packets
Out	outgoing packets

Instances

Eq Direction
Read Direction
Show Direction

data Link Source

Datalink types.

This covers all of the datalink types defined in bpf.h. Types defined on your system may vary.

Constructors

DLT_NULL	no link layer encapsulation
DLT_UNKNOWN Int	unknown encapsulation
DLT_EN10MB	10 Mbit per second (or faster) ethernet
DLT_EN3MB	original 3 Mbit per second ethernet
DLT_AX25	amateur radio AX.25
DLT_PRONET	Proteon ProNET Token Ring
DLT_CHAOS	Chaos
DLT_IEEE802	IEEE 802 networks
DLT_ARCNET	ARCNET
DLT_SLIP	Serial line IP
DLT_PPP	Point-to-point protocol
DLT_FDDI	FDDI
DLT_ATM_RFC1483	LLC SNAP encapsulated ATM
DLT_RAW	raw IP
DLT_SLIP_BSDOS	BSD OS serial line IP
DLT_PPP_BSDOS	BSD OS point-to-point protocol
DLT_ATM_CLIP	Linux classical IP over ATM
DLT_REDBACK_SMARTEDGE	Redback SmartEdge 400/800
DLT_PPP_SERIAL	PPP over serial with HDLC encapsulation
DLT_PPP_ETHER	PPP over ethernet
DLT_SYMANTEC_FIREWALL	Symantec Enterprise Firewall
DLT_C_HDLC	Cisco HDLC
DLT_IEEE802_11	IEEE 802.11 wireless
DLT_FRELAY	Frame Relay
DLT_LOOP	OpenBSD loopback device
DLT_ENC	Encapsulated packets for IPsec
DLT_LINUX_SLL	Linux cooked sockets
DLT_LTALK	Apple LocalTalk
DLT_ECONET	Acorn Econet
DLT_IPFILTER	OpenBSD's old ipfilter
DLT_PFLOG	OpenBSD's pflog
DLT_CISCO_IOS	Cisco IOS
DLT_PRISM_HEADER	Intersil Prism II wireless chips
DLT_AIRONET_HEADER	Aironet (Cisco) 802.11 wireless
DLT_HHDLC	Siemens HiPath HDLC
DLT_IP_OVER_FC	RFC 2625 IP-over-Fibre Channel
DLT_SUNATM	Full Frontal ATM on Solaris with SunATM
DLT_IEEE802_11_RADIO	11 plus a number of bits of link-layer information
DLT_ARCNET_LINUX	Linux ARCNET header
DLT_APPLE_IP_OVER_IEEE1394	Apple IP-over-IEEE 1394
DLT_MTP2_WITH_PHDR	SS7, C7 MTP2 with pseudo-header
DLT_MTP2	SS7, C7 Message Transfer Part 2 (MPT2)
DLT_MTP3	SS7, C7 Message Transfer Part 3 (MPT3)
DLT_SCCP	SS7, C7 SCCP
DLT_DOCSIS	DOCSIS MAC frame
DLT_LINUX_IRDA	Linux IrDA packet
DLT_USER0	Reserved for private use
DLT_USER1	Reserved for private use
DLT_USER2	Reserved for private use
DLT_USER3	Reserved for private use
DLT_USER4	Reserved for private use
DLT_USER5	Reserved for private use
DLT_USER6	Reserved for private use
DLT_USER7	Reserved for private use
DLT_USER8	Reserved for private use
DLT_USER9	Reserved for private use
DLT_USER10	Reserved for private use
DLT_USER11	Reserved for private use
DLT_USER12	Reserved for private use
DLT_USER13	Reserved for private use
DLT_USER14	Reserved for private use
DLT_USER15	Reserved for private use
DLT_PPP_PPPD	Outgoing packets for ppp daemon
DLT_GPRS_LLC	GPRS LLC
DLT_GPF_T	GPF-T (ITU-T G.7041/Y.1303)
DLT_GPF_F	GPF-F (ITU-T G.7041/Y.1303)
DLT_LINUX_LAPD	Raw LAPD for vISDN (not generic LAPD)
DLT_A429	ARINC 429
DLT_A653_ICM	ARINC 653 Interpartition Communication messages
DLT_USB	USB packet
DLT_BLUETOOTH_HCI_H4	Bluetooth HCI UART transport layer (part H:4)
DLT_MFR	Multi Link Frame Relay (FRF.16)
DLT_IEEE802_16_MAC_CPS	IEEE 802.16 MAC Common Part Sublayer
DLT_USB_LINUX	USB packets, beginning with a Linux USB header
DLT_CAN20B	Controller Area Network (CAN) v2.0B
DLT_IEEE802_15_4_LINUX	IEEE 802.15.4, with address fields padded
DLT_PPI	Per Packet Information encapsulated packets
DLT_IEEE802_16_MAC_CPS_RADIO	16 MAC Common Part Sublayer with radiotap radio header
DLT_IEEE802_15_4	IEEE 802.15.4, exactly as in the spec

Instances

Eq Link
Ord Link
Read Link
Show Link

data Interface Source

The interface structure.

Constructors

Interface
Fields ifName :: String the interface name ifDescription :: String interface description string (if any) ifAddresses :: [PcapAddr] address families supported by this interface ifFlags :: Word32

Instances

Eq Interface
Read Interface
Show Interface

data PcapAddr Source

The address structure.

Constructors

PcapAddr
Fields addrSA :: SockAddr interface address addrMask :: Maybe SockAddr network mask addrBcast :: Maybe SockAddr broadcast address addrPeer :: Maybe SockAddr address of peer, of a point-to-point link

Instances

Eq PcapAddr
Read PcapAddr
Show PcapAddr

data SockAddr Source

The socket address record. Note that this is not the same as SockAddr from Network.Socket. (That is a Haskell version of C's struct sockaddr_in. This is the real struct sockaddr from the BSD network stack.)

Constructors

SockAddr
Fields saFamily :: !Family an address family exported by Network.Socket saAddr :: !ByteString

Instances

Eq SockAddr
Read SockAddr
Show SockAddr

data Network Source

The network address record. Both the address and mask are in network byte order.

Constructors

Network
Fields netAddr :: !Word32 IPv4 network address netMask :: !Word32 IPv4 netmask

Instances

Eq Network
Read Network
Show Network

data PktHdr Source

Constructors

PktHdr
Fields hdrSeconds :: !Word32 timestamp (seconds) hdrUseconds :: !Word32 timestamp (microseconds) hdrCaptureLength :: !Word32 number of bytes present in capture hdrWireLength :: !Word32 number of bytes on the wire

Instances

Eq PktHdr
Show PktHdr

data Statistics Source

Constructors

Statistics
Fields statReceived :: !Word32 packets received statDropped :: !Word32 packets dropped by `libpcap` statIfaceDropped :: !Word32 packets dropped by the network interface

Instances

Eq Statistics
Show Statistics

Device opening

openOffline Source

Arguments

:: FilePath	filename
-> IO (ForeignPtr PcapTag)

openOffline opens a dump file for reading. The file format is the same as used by tcpdump and Wireshark. The string "-" is a synonym for stdin.

openLive Source

Arguments

:: String	device name
-> Int	snapshot length
-> Bool	set to promiscuous mode?
-> Int	timeout in milliseconds
-> IO (ForeignPtr PcapTag)

openLive is used to get a packet descriptor that can be used to look at packets on the network. The arguments are the device name, the snapshot legnth (in bytes), the promiscuity of the interface (True == promiscuous) and a timeout in milliseconds.

Using "any" as the device name will capture packets from all interfaces. On some systems, reading from the "any" device is incompatible with setting the interfaces into promiscuous mode. In that case, only packets whose link layer addresses match those of the interfaces are captured.

openDead Source

Arguments

:: Link	datalink type
-> Int	snapshot length
-> IO (ForeignPtr PcapTag)	packet capture descriptor

openDead is used to get a packet capture descriptor without opening a file or device. It is typically used to test packet filter compilation by setFilter. The arguments are the link type and the snapshot length.

openDump Source

Arguments

:: Ptr PcapTag	packet capture descriptor
-> FilePath	dump file name
-> IO Pdump	davefile descriptor

openDump opens a dump file for writing. This dump file is written to by the dump function. The arguments are a raw packet capture descriptor and the file name, with "-" as a synonym for stdout.

Filter handling

setFilter Source

Arguments

:: Ptr PcapTag	packet capture descriptor
-> String	filter string
-> Bool	optimize?
-> Word32	IPv4 network mask
-> IO ()

Set a filter on the specified packet capture descriptor. Valid filter strings are those accepted by tcpdump.

compileFilter Source

Arguments

:: Int	snapshot length
-> Link	datalink type
-> String	filter string
-> Bool	optimize?
-> Word32	IPv4 network mask
-> IO BpfProgram

Compile a filter for use by another program using the Berkeley Packet Filter library.

Device utilities

lookupDev :: IO String Source

lookupDev returns the name of a device suitable for use with openLive and lookupNet. If you only have one interface, it is the function of choice. If not, see findAllDevs.

findAllDevs :: IO [Interface]Source

findAllDevs returns a list of all the network devices that can be opened by openLive. It returns only those devices that the calling process has sufficient privileges to open, so it may not find every device on the system.

lookupNet Source

Arguments

:: String	device name
-> IO Network

Return the network address and mask for the specified interface name. Only valid for IPv4. For other protocols, use findAllDevs and search the Interface list for the associated network mask.

Interface control

setNonBlock :: Ptr PcapTag -> Bool -> IO ()Source

Set a packet capture descriptor into non-blocking mode if the second argument is True, otherwise put it in blocking mode. Note that the packet capture descriptor must have been obtaine from openLive.

getNonBlock :: Ptr PcapTag -> IO Bool Source

Return the blocking status of the packet capture descriptor. True indicates that the descriptor is non-blocking. Descriptors referring to dump files opened by openDump always return False.

setDirection :: Ptr PcapTag -> Direction -> IO ()Source

Specify the direction in which packets are to be captured. Complete functionality is not necessarily available on all platforms.

Link layer utilities

datalink :: Ptr PcapTag -> IO Link Source

Returns the datalink type associated with the given pcap descriptor.

setDatalink :: Ptr PcapTag -> Link -> IO ()Source

Sets the datalink type for a given pcap descriptor.

listDatalinks :: Ptr PcapTag -> IO [Link]Source

List all the datalink types supported by a pcap descriptor. Entries from the resulting list are valid arguments to setDatalink.

Packet processing

dispatch Source

Arguments

:: Ptr PcapTag	packet capture descriptor
-> Int	number of packets to process
-> Callback	packet processing function
-> IO Int	number of packets read

Collect and process packets. The arguments are the packet capture descriptor, the count and a callback function.

The count is the maximum number of packets to process before returning. A count of -1 means process all of the packets received in one buffer (if a live capture) or all of the packets in a dump file (if offline).

The callback function is passed two arguments, a packet header record and a pointer to the packet data (Ptr Word8). THe header record contains the number of bytes captured, whcih can be used to marshal the data into a list or array.

loop Source

Arguments

:: Ptr PcapTag	packet capture descriptor
-> Int	number of packet to read
-> Callback	packet processing function
-> IO Int	number of packets read

Similar to dispatch, but loop until the number of packets specified by the second argument are read. A negative value loops forever.

This function does not return when a live read tiemout occurs. Use dispatch instead if you wnat to specify a timeout.

next Source

Arguments

:: Ptr PcapTag	packet capture descriptor
-> IO (PktHdr, Ptr Word8)	packet header and data of the next packet

Read the next packet (equivalent to calling dispatch with a count of 1).

dump Source

Arguments

:: Ptr PcapDumpTag	dump file descriptor
-> Ptr PktHdr	packet header record
-> Ptr Word8	packet data
-> IO ()

Write the packet data given by the second and third arguments to a dump file opened by openDead. dump is designed so it can be easily used as a default callback function by dispatch or loop.

Sending packets

sendPacket Source

Arguments

:: Ptr PcapTag
-> Ptr Word8	packet data (including link-level header)
-> Int	packet size
-> IO ()

Send a raw packet through the network interface.

Conversion

toPktHdr :: Ptr PktHdr -> IO PktHdr Source

Miscellaneous

statistics :: Ptr PcapTag -> IO Statistics Source

Returns the number of packets received, the number of packets dropped by the packet filter and the number of packets dropped by the interface (before processing by the packet filter).

version :: Ptr PcapTag -> IO (Int, Int)Source

Version of the library. The returned pair consists of the major and minor version numbers.

isSwapped :: Ptr PcapTag -> IO Bool Source

isSwapped returns True if the current dump file uses a different byte order than the one native to the system.

snapshotLen :: Ptr PcapTag -> IO Int Source

The snapshot length that was used in the call to openLive.