Packet Class Reference

Inheritance diagram for Packet:

Detailed Description

A network packet.

Click's Packet class represents network packets within a router. Packet objects are passed from Element to Element via the Element::push() and Element::pull() functions. The vast majority of elements handle packets.

A packet consists of a data buffer, which stores the actual packet wire data, and a set of annotations, which store extra information calculated about the packet, such as the destination address to be used for routing. Every Packet object has different annotations, but a data buffer may be shared among multiple Packet objects, saving memory and speeding up packet copies. (See Packet::clone.) As a result a Packet's data buffer is not writable. To write into a packet, turn it into a nonshared WritablePacket first, using uniqueify(), push(), or put().

Data Buffer

A packet's data buffer is a single flat array of bytes. The buffer may be larger than the actual packet data, leaving unused spaces called headroom and tailroom before and after the data proper. Prepending headers or appending data to a packet can be quite efficient if there is enough headroom or tailroom.

The relationships among a Packet object's data buffer variables is shown here:

                     data()               end_data()
                        |                      |
       |<- headroom() ->|<----- length() ----->|<- tailroom() ->|
       |                v                      v                |
       +================+======================+================+
       |XXXXXXXXXXXXXXXX|   PACKET CONTENTS    |XXXXXXXXXXXXXXXX|
       +================+======================+================+
       ^                                                        ^
       |<------------------ buffer_length() ------------------->|
       |                                                        |
    buffer()                                               end_buffer()

Most code that manipulates packets is interested only in data() and length().

To create a Packet, call one of the make() functions. To destroy a Packet, call kill(). To clone a Packet, which creates a new Packet object that shares this packet's data, call clone(). To uniqueify a Packet, which unshares the packet data if necessary, call uniqueify(). To allocate extra space for headers or trailers, call push() and put(). To remove headers or trailers, call pull() and take().

                data()                          end_data()
                   |                                |
           push()  |  pull()                take()  |  put()
          <======= | =======>              <======= | =======>
                   v                                v                 
       +===========+================================+===========+
       |XXXXXXXXXXX|        PACKET CONTENTS         |XXXXXXXXXXX|
       +===========+================================+===========+

Packet objects are implemented in different ways in different drivers. The userlevel driver has its own C++ implementation. In the linuxmodule driver, however, Packet is an overlay on Linux's native sk_buff object: the Packet methods access underlying sk_buff data directly, with no overhead. (For example, Packet::data() returns the sk_buff's data field.)

Annotations

Annotations are extra information about a packet above and beyond the packet data. Packet supports several specific annotations, plus a user annotation area available for arbitrary use by elements.

Header pointers: Each packet has three header pointers, designed to point to the packet's MAC header, network header, and transport header, respectively. Convenience functions like ip_header() access these pointers cast to common header types. The header pointers are kept up to date when operations like push() or uniqueify() change the packet's data buffer. Header pointers can be null, and they can even point to memory outside the current packet data bounds. For example, a MAC header pointer will remain set even after pull() is used to shift the packet data past the MAC header. As a result, functions like mac_header_offset() can return negative numbers.
Timestamp: A timestamp associated with the packet. Most packet sources timestamp packets when they enter the router; other elements examine or modify the timestamp.
Device: A pointer to the device on which the packet arrived. Only meaningful in the linuxmodule driver, but provided in every driver.
Packet type: A small integer indicating whether the packet is meant for this host, broadcast, multicast, or some other purpose. Several elements manipulate this annotation; in linuxmodule, setting the annotation is required for the host network stack to process incoming packets correctly.
Performance counter (linuxmodule only): A 64-bit integer intended to hold a performance counter value. Used by SetCycleCount and others.
Next and previous packet: Pointers provided to allow elements to chain packets into a doubly linked list.
Annotations: Each packet has anno_size bytes available for annotations. Elements agree to use portions of the annotation area to communicate per-packet information. Macros in the <click/packet_anno.hh> header file define the annotations used by Click's current elements. One common annotation is the network address annotation -- see Packet::dst_ip_anno(). Routing elements, such as RadixIPLookup, set the address annotation to indicate the desired next hop; ARPQuerier uses this annotation to query the next hop's MAC.

New packets start wth all annotations set to zero or null. Cloning a packet copies its annotations.

Data

enum { default_headroom = 28, min_buffer_length = 64 }

static WritablePacket * make (uint32_t headroom, const void *data, uint32_t length, uint32_t tailroom)

Create and return a new packet.

static WritablePacket * make (const void *data, uint32_t length)

Create and return a new packet.

static WritablePacket * make (uint32_t length)

Create and return a new packet.

static Packet * make (struct sk_buff *skb)

Change an sk_buff into a Packet (linuxmodule).

static WritablePacket * make (unsigned char *data, uint32_t length, void(*destructor)(unsigned char *, size_t))

Create and return a new packet (userlevel).

void kill ()

Delete this packet.

bool shared () const

Test whether this packet's data is shared.

Packet * clone ()

Create a clone of this packet.

WritablePacket * uniqueify ()

Return an unshared packet containing this packet's data.

const unsigned char * data () const

Return the packet's data pointer.

const unsigned char * end_data () const

Return the packet's end data pointer.

uint32_t length () const

Return the packet's length.

uint32_t headroom () const

Return the packet's headroom.

uint32_t tailroom () const

Return the packet's tailroom.

const unsigned char * buffer () const

Return a pointer to the packet's data buffer.

const unsigned char * end_buffer () const

Return the packet's end data buffer pointer.

uint32_t buffer_length () const

Return the packet's buffer length.

sk_buff * skb ()

sk_buff * skb () const

WritablePacket * push (uint32_t len)

Add space for a header before the packet.

WritablePacket * push_mac_header (uint32_t len)

Add space for a MAC header before the packet.

Packet * nonunique_push (uint32_t len)

Add space for a header before the packet.

void pull (uint32_t len)

Remove a header from the front of the packet.

WritablePacket * put (uint32_t len)

Add space for data after the packet.

Packet * nonunique_put (uint32_t len)

Add space for data after the packet.

void take (uint32_t len)

Remove space from the end of the packet.

Packet * shift_data (int offset, bool free_on_failure=true)

Shift packet data within the data buffer.

void shrink_data (const unsigned char *data, uint32_t length)

Shrink the packet's data.

void change_headroom_and_length (uint32_t headroom, uint32_t length)

Shift the packet's data view to a different part of its buffer.

Annotations

enum { anno_size = 48 }

enum PacketType {
HOST = 0, BROADCAST = 1, MULTICAST = 2, OTHERHOST = 3,
OUTGOING = 4, LOOPBACK = 5, FASTROUTE = 6
}

Values for packet_type_anno(). Must agree with Linux's PACKET_ constants in <linux/if_packet.h>. More...

enum { dst_ip_anno_offset = 0, dst_ip_anno_size = 4, dst_ip6_anno_offset = 0, dst_ip6_anno_size = 16 }

const Timestamp & timestamp_anno () const

Return the timestamp annotation.

Timestamp & timestamp_anno ()

void set_timestamp_anno (const Timestamp &t)

Set the timestamp annotation.

net_device * device_anno () const

Return the device annotation.

void set_device_anno (net_device *dev)

Set the device annotation.

PacketType packet_type_anno () const

Return the packet type annotation.

void set_packet_type_anno (PacketType t)

Set the packet type annotation.

Packet * next () const

Return the next packet annotation.

Packet *& next ()

void set_next (Packet *p)

Set the next packet annotation.

Packet * prev () const

Return the previous packet annotation.

Packet *& prev ()

void set_prev (Packet *p)

Set the previous packet annotation.

IPAddress dst_ip_anno () const

Return the destination IPv4 address annotation.

void set_dst_ip_anno (IPAddress addr)

Set the destination IPv4 address annotation.

void * anno ()

Return a pointer to the annotation area.

const void * anno () const

uint8_t * anno_u8 ()

Return a pointer to the annotation area as uint8_ts.

const uint8_t * anno_u8 () const

overload

uint32_t * anno_u32 ()

Return a pointer to the annotation area as uint32_ts.

const uint32_t * anno_u32 () const

overload

uint8_t anno_u8 (int i) const

Return annotation byte at offset i.

void set_anno_u8 (int i, uint8_t v)

Set annotation byte at offset i.

uint16_t anno_u16 (int i) const

Return 16-bit annotation at offset i.

void set_anno_u16 (int i, uint16_t v)

Set 16-bit annotation at offset i.

int16_t anno_s16 (int i) const

Return 16-bit annotation at offset i.

void set_anno_s16 (int i, int16_t v)

Set 16-bit annotation at offset i.

uint32_t anno_u32 (int i) const

Return 32-bit annotation at offset i.

void set_anno_u32 (int i, uint32_t v)

Set 32-bit annotation at offset i.

int32_t anno_s32 (int i) const

Return 32-bit annotation at offset i.

void set_anno_s32 (int i, int32_t v)

Set 32-bit annotation at offset i.

uint64_t anno_u64 (int i) const

Return 64-bit annotation at offset i.

void set_anno_u64 (int i, uint64_t v)

Set 64-bit annotation at offset i.

void clear_annotations (bool all=true)

Clear all packet annotations.

void copy_annotations (const Packet *)

Copy most packet annotations from p.

Header Pointers

bool has_mac_header () const

Return true iff the packet's MAC header pointer is set.

const unsigned char * mac_header () const

Return the packet's MAC header pointer.

int mac_header_offset () const

Return the offset from the packet data to the MAC header.

uint32_t mac_header_length () const

Return the MAC header length.

int mac_length () const

Return the packet's length starting from its MAC header pointer.

void set_mac_header (const unsigned char *p)

Set the MAC header pointer.

void set_mac_header (const unsigned char *p, uint32_t len)

Set the MAC and network header pointers.

void clear_mac_header ()

Unset the MAC header pointer.

bool has_network_header () const

Return true iff the packet's network header pointer is set.

const unsigned char * network_header () const

Return the packet's network header pointer.

int network_header_offset () const

Return the offset from the packet data to the network header.

uint32_t network_header_length () const

Return the network header length.

int network_length () const

Return the packet's length starting from its network header pointer.

void set_network_header (const unsigned char *p, uint32_t len)

Set the network and transport header pointers.

void set_network_header_length (uint32_t len)

Set the network header length.

void clear_network_header ()

Unset the network header pointer.

bool has_transport_header () const

Return true iff the packet's network header pointer is set.

const unsigned char * transport_header () const

Return the packet's transport header pointer.

int transport_header_offset () const

Return the offset from the packet data to the transport header.

int transport_length () const

Return the packet's length starting from its transport header pointer.

void clear_transport_header ()

Unset the transport header pointer.

const click_ether * ether_header () const

Return the packet's MAC header pointer as Ethernet.

void set_ether_header (const click_ether *ethh)

Set the MAC header pointer to an Ethernet header.

const click_ip * ip_header () const

Return the packet's network header pointer as IPv4.

int ip_header_offset () const

Return the offset from the packet data to the IP header.

uint32_t ip_header_length () const

Return the IP header length.

void set_ip_header (const click_ip *iph, uint32_t len)

Set the network header pointer to an IPv4 header.

const click_ip6 * ip6_header () const

Return the packet's network header pointer as IPv6.

int ip6_header_offset () const

Return the offset from the packet data to the IPv6 header.

uint32_t ip6_header_length () const

Return the IPv6 header length.

void set_ip6_header (const click_ip6 *ip6h)

Set the network header pointer to an IPv6 header.

void set_ip6_header (const click_ip6 *ip6h, uint32_t len)

Set the network header pointer to an IPv6 header.

const click_icmp * icmp_header () const

Return the packet's transport header pointer as ICMP.

const click_tcp * tcp_header () const

Return the packet's transport header pointer as TCP.

const click_udp * udp_header () const

Return the packet's transport header pointer as UDP.

Member Enumeration Documentation

anonymous enum

Enumerator:

default_headroom	Default packet headroom() for Packet::make(). 4-byte aligned.
min_buffer_length	Minimum buffer_length() for Packet::make()

anonymous enum

Enumerator:

anno_size

Size of annotation area.

enum Packet::PacketType

Values for packet_type_anno(). Must agree with Linux's PACKET_ constants in <linux/if_packet.h>.

Enumerator:

HOST	Packet was sent to this host.
BROADCAST	Packet was sent to a link-level multicast address.
MULTICAST	Packet was sent to a link-level multicast address.
OTHERHOST	Packet was sent to a different host, but received anyway. The receiving device is probably in promiscuous mode.
OUTGOING	Packet was generated by this host and is being sent elsewhere.

Member Function Documentation

WritablePacket * Packet::make	(	uint32_t	headroom,
		const void *	data,
		uint32_t	length,
		uint32_t	tailroom
	)			`[static]`

Create and return a new packet.

Parameters:

	headroom	headroom in new packet
	data	data to be copied into the new packet
	length	length of packet
	tailroom	tailroom in new packet

Returns:: new packet, or null if no packet could be created

The data is copied into the new packet. If data is null, the packet's data is left uninitialized. The resulting packet's buffer_length() will be at least min_buffer_length ; if headroom + length + tailroom would be less, then tailroom is increased to make the total min_buffer_length .

The new packet's annotations are cleared and its header pointers are null.

WritablePacket * Packet::make	(	const void *	data,
		uint32_t	length
	)			`[inline, static]`

Create and return a new packet.

Parameters:

	data	data to be copied into the new packet
	length	length of packet

Returns:: new packet, or null if no packet could be created

The data is copied into the new packet. If data is null, the packet's data is left uninitialized. The new packet's headroom equals default_headroom , its tailroom is 0.

The returned packet's annotations are cleared and its header pointers are null.

WritablePacket * Packet::make ( uint32_t length ) [inline, static]

Create and return a new packet.

Parameters:

length

length of packet

Returns:: new packet, or null if no packet could be created

The packet's data is left uninitialized. The new packet's headroom equals default_headroom , its tailroom is 0.

The returned packet's annotations are cleared and its header pointers are null.

Packet * Packet::make ( struct sk_buff * skb ) [inline, static]

Change an sk_buff into a Packet (linuxmodule).

Parameters:

skb

input sk_buff

Returns:: the packet

In the Linux kernel module, Packet objects are sk_buff objects. This function simply changes an sk_buff into a Packet by claiming its skb argument. If skb->users is 1, then skb is orphaned by skb_orphan(skb) and returned. If it is larger than 1, then skb is cloned and the clone is returned. (sk_buffs used for Click Packet objects must have skb->users == 1.) Null might be returned if there's no memory for the clone.

The returned packet's annotations and header pointers are not cleared: they have the same values they did in the sk_buff. If the packet came from Linux, then the header pointers and shared annotations (timestamp, packet type, next/prev packet) might have valid values, but the Click annotations (address, user) likely do not. Use clear_annotations() to clear them.

WritablePacket * Packet::make	(	unsigned char *	data,
		uint32_t	length,
		void()(unsigned char , size_t)	destructor
	)			`[static]`

Create and return a new packet (userlevel).

Parameters:

	data	data used in the new packet
	length	length of packet
	destructor	destructor function

Returns:: new packet, or null if no packet could be created

The packet's data pointer becomes the data: the data is not copied into the new packet, rather the packet owns the data pointer. When the packet's data is eventually destroyed, either because the packet is deleted or because of something like a push() or full(), the destructor will be called with arguments destructor(data, length). (If destructor is null, the packet data will be freed by delete[] data.) The packet has zero headroom and tailroom.

The returned packet's annotations are cleared and its header pointers are null.

void Packet::kill ( ) [inline]

Delete this packet.

The packet header (including annotations) is destroyed and its memory returned to the system. The packet's data is also freed if this is the last clone.

bool Packet::shared ( ) const [inline]

Test whether this packet's data is shared.

Returns true iff the packet's data is shared. If shared() is false, then the result of uniqueify() will equal this.

Packet * Packet::clone ( )

Create a clone of this packet.

Returns:: the cloned packet

The returned clone has independent annotations, initially copied from this packet, but shares this packet's data. shared() returns true for both the packet and its clone. Returns null if there's no memory for the clone.

WritablePacket * Packet::uniqueify ( ) [inline]

Return an unshared packet containing this packet's data.

Returns:: the unshared packet, which is writable

The returned packet's data is unshared with any other packet, so it's safe to write the data. If shared() is false, this operation simply returns the input packet. If shared() is true, uniqueify() makes a copy of the data. The input packet is freed if the copy fails.

The returned WritablePacket pointer may not equal the input Packet pointer, so do not use the input pointer after the uniqueify() call.

The input packet's headroom and tailroom areas are copied in addition to its true contents. The header annotations are shifted to point into the new packet data if necessary.

uniqueify() is usually used like this:

 WritablePacket *q = p->uniqueify();
 if (!q)
     return 0;
 // p must not be used here.

const unsigned char * Packet::data ( ) const [inline]

Return the packet's data pointer.

This is the pointer to the first byte of packet data.

Reimplemented in WritablePacket.

const unsigned char * Packet::end_data ( ) const [inline]

Return the packet's end data pointer.

The result points at the byte following the packet data.

Invariant:: end_data() == data() + length()

Reimplemented in WritablePacket.

uint32_t Packet::length ( ) const [inline]

Return the packet's length.

uint32_t Packet::headroom ( ) const [inline]

Return the packet's headroom.

The headroom is the amount of space available in the current packet buffer before data(). A push() operation is cheap if the packet's unshared and the length pushed is less than headroom().

uint32_t Packet::tailroom ( ) const [inline]

Return the packet's tailroom.

The tailroom is the amount of space available in the current packet buffer following end_data(). A put() operation is cheap if the packet's unshared and the length put is less than tailroom().

const unsigned char * Packet::buffer ( ) const [inline]

Return a pointer to the packet's data buffer.

The result points at the packet's headroom, not its data.

Invariant:: buffer() == data() - headroom()

Reimplemented in WritablePacket.

const unsigned char * Packet::end_buffer ( ) const [inline]

Return the packet's end data buffer pointer.

The result points past the packet's tailroom.

Invariant:: end_buffer() == end_data() + tailroom()

Reimplemented in WritablePacket.

uint32_t Packet::buffer_length ( ) const [inline]

Return the packet's buffer length.

Invariant:: buffer_length() == headroom() + length() + tailroom()
buffer() + buffer_length() == end_buffer()

WritablePacket * Packet::push ( uint32_t len ) [inline]

Add space for a header before the packet.

Parameters:

len

amount of space to add

Returns:: packet with added header space, or null on failure

Returns a packet with an additional len bytes of uninitialized space before the current packet's data(). A copy of the packet data is made if there isn't enough headroom() in the current packet, or if the current packet is shared(). If no copy is made, this operation is quite efficient.

If a data copy would be required, but the copy fails because of lack of memory, then the current packet is freed.

push() is usually used like this:

 WritablePacket *q = p->push(14);
 if (!q)
     return 0;
 // p must not be used here.

Postcondition:: new length() == old length() + len (if no failure)

See also:: nonunique_push, push_mac_header, pull

WritablePacket * Packet::push_mac_header ( uint32_t len ) [inline]

Add space for a MAC header before the packet.

Parameters:

len

amount of space to add and length of MAC header

Returns:: packet with added header space, or null on failure

Combines the action of push() and set_mac_header(). len bytes are pushed for a MAC header, and on success, the packet's returned MAC and network header pointers are set as by set_mac_header(data(), len).

See also:: push

Packet * Packet::nonunique_push ( uint32_t len ) [inline]

Add space for a header before the packet.

Parameters:

len

amount of space to add

Returns:: packet with added header space, or null on failure

This is a variant of push(). Returns a packet with an additional len bytes of uninitialized space before the current packet's data(). A copy of the packet data is made if there isn't enough headroom() in the current packet. However, no copy is made if the current packet is shared; and if no copy is made, this operation is quite efficient.

If a data copy would be required, but the copy fails because of lack of memory, then the current packet is freed.

Note:: Unlike push(), nonunique_push() returns a Packet object, which has non-writable data.

See also:: push

void Packet::pull ( uint32_t len ) [inline]

Remove a header from the front of the packet.

Parameters:

len

amount of space to remove

Removes len bytes from the initial part of the packet, usually corresponding to some network header (for example, pull(14) removes an Ethernet header). This operation is efficient: it just bumps a pointer.

It is an error to attempt to pull more than length() bytes.

Postcondition:: new data() == old data() + len
new length() == old length() - len

See also:: push

WritablePacket * Packet::put ( uint32_t len ) [inline]

Add space for data after the packet.

Parameters:

len

amount of space to add

Returns:: packet with added trailer space, or null on failure

Returns a packet with an additional len bytes of uninitialized space after the current packet's data (starting at end_data()). A copy of the packet data is made if there isn't enough tailroom() in the current packet, or if the current packet is shared(). If no copy is made, this operation is quite efficient.

If a data copy would be required, but the copy fails because of lack of memory, then the current packet is freed.

put() is usually used like this:

 WritablePacket *q = p->put(100);
 if (!q)
     return 0;
 // p must not be used here.

Postcondition:: new length() == old length() + len (if no failure)

See also:: nonunique_put, take

Packet * Packet::nonunique_put ( uint32_t len ) [inline]

Add space for data after the packet.

Parameters:

len

amount of space to add

Returns:: packet with added trailer space, or null on failure

This is a variant of put(). Returns a packet with an additional len bytes of uninitialized space after the current packet's data (starting at end_data()). A copy of the packet data is made if there isn't enough tailroom() in the current packet. However, no copy is made if the current packet is shared; and if no copy is made, this operation is quite efficient.

If a data copy would be required, but the copy fails because of lack of memory, then the current packet is freed.

See also:: put

void Packet::take ( uint32_t len ) [inline]

Remove space from the end of the packet.

Parameters:

len

amount of space to remove

Removes len bytes from the end of the packet. This operation is efficient: it just bumps a pointer.

It is an error to attempt to pull more than length() bytes.

Postcondition:

new data() == old data()

new end_data() == old end_data() - len

new length() == old length() - len

See also:: push

Packet * Packet::shift_data	(	int	offset,
		bool	free_on_failure = `true`
	)

Shift packet data within the data buffer.

Parameters:

	offset	amount to shift packet data
	free_on_failure	if true, then delete the input packet on failure

Returns:: a packet with shifted data, or null on failure

Useful to align packet data. For example, if the packet's embedded IP header is located at pointer value 0x8CCA03, then shift_data(1) or shift_data(-3) will both align the header on a 4-byte boundary.

If the packet is shared() or there isn't enough headroom or tailroom for the operation, the packet is passed to uniqueify() first. This can fail if there isn't enough memory. If it fails, shift_data returns null, and if free_on_failure is true (the default), the input packet is freed.

The packet's mac_header, network_header, and transport_header areas are preserved, even if they lie within the headroom. Any headroom outside these regions may be overwritten, as may any tailroom.

Postcondition:: new data() == old data() + offset (if no copy is made)
new buffer() == old buffer() (if no copy is made)

void Packet::shrink_data	(	const unsigned char *	data,
		uint32_t	length
	)			`[inline]`

Shrink the packet's data.

Parameters:

	data	new data pointer
	length	new length

Warning:: This function is useful only in special contexts.

Note:: Only available at user level

User-level programs that read packet logs commonly read a large chunk of data (32 kB or more) into a base Packet object. The log reader then works over the data buffer and, for each packet contained therein, outputs a clone that shares memory with the base packet. This is space- and time-efficient, but the generated packets have gigantic headroom and tailroom. Uniqueifying a generated packet will wastefully copy this headroom and tailroom as well. The shrink_data function addresses this problem.

shrink_data() removes all of a packet's headroom and tailroom. The resulting packet has data() equal to data, length() equal to length, and headroom() and tailroom() equal to zero.

Precondition:: The packet must be a clone() of another existing packet.
data >= data(), data <= end_data(), data + length >= data(), and data + length <= end_data()

See also:: change_headroom_and_length

void Packet::change_headroom_and_length	(	uint32_t	headroom,
		uint32_t	length
	)			`[inline]`

Shift the packet's data view to a different part of its buffer.

Parameters:

	headroom	new headroom
	length	new length

Warning:: This function is useful only in special contexts.

Note:: Only available at user level

Shifts the packet's data() pointer to a different part of the packet's data buffer. The buffer pointer itself is not changed, and the packet's contents are not affected (except by the new view).

Precondition:: headroom + length <= buffer_length()

Postcondition:

new buffer() == old buffer()

new end_buffer() == old end_buffer()

new headroom() == headroom

new length() == length

See also:: shrink_data

bool Packet::has_mac_header ( ) const [inline]

Return true iff the packet's MAC header pointer is set.

See also:: set_mac_header, clear_mac_header

const unsigned char * Packet::mac_header ( ) const [inline]

Return the packet's MAC header pointer.

Warning:: Not useful if !has_mac_header().

See also:: ether_header, set_mac_header, clear_mac_header, mac_header_length, mac_length

Reimplemented in WritablePacket.

int Packet::mac_header_offset ( ) const [inline]

Return the offset from the packet data to the MAC header.

Returns:: mac_header() - data()

Warning:: Not useful if !has_mac_header().

uint32_t Packet::mac_header_length ( ) const [inline]

Return the MAC header length.

Returns:: network_header() - mac_header()

This equals the offset from the MAC header pointer to the network header pointer.

Warning:: Not useful if !has_mac_header() or !has_network_header().

int Packet::mac_length ( ) const [inline]

Return the packet's length starting from its MAC header pointer.

Invariant:: mac_length() == end_data() - mac_header()

Warning:: Not useful if !has_mac_header().

void Packet::set_mac_header ( const unsigned char * p ) [inline]

Set the MAC header pointer.

Parameters:

new header pointer

void Packet::set_mac_header	(	const unsigned char *	p,
		uint32_t	len
	)			`[inline]`

Set the MAC and network header pointers.

Parameters:

	p	new MAC header pointer
	len	new MAC header length

Postcondition:: mac_header() == p and network_header() == p + len

void Packet::clear_mac_header ( ) [inline]

Unset the MAC header pointer.

Postcondition:: has_mac_header() == false Does not affect the network or transport header pointers.

bool Packet::has_network_header ( ) const [inline]

Return true iff the packet's network header pointer is set.

See also:: set_network_header, clear_network_header

const unsigned char * Packet::network_header ( ) const [inline]

Return the packet's network header pointer.

Warning:: Not useful if !has_network_header().

See also:: ip_header, ip6_header, set_network_header, clear_network_header, network_header_length, network_length

Reimplemented in WritablePacket.

int Packet::network_header_offset ( ) const [inline]

Return the offset from the packet data to the network header.

Returns:: network_header() - data()

Warning:: Not useful if !has_network_header().

uint32_t Packet::network_header_length ( ) const [inline]

Return the network header length.

Returns:: transport_header() - network_header()

This equals the offset from the network header pointer to the transport header pointer.

Warning:: Not useful if !has_network_header() or !has_transport_header().

int Packet::network_length ( ) const [inline]

Return the packet's length starting from its network header pointer.

Invariant:: network_length() == end_data() - network_header()

Warning:: Not useful if !has_network_header().

void Packet::set_network_header	(	const unsigned char *	p,
		uint32_t	len
	)			`[inline]`

Set the network and transport header pointers.

Parameters:

	p	new network header pointer
	len	new network header length

Postcondition:: network_header() == p and transport_header() == p + len

void Packet::set_network_header_length ( uint32_t len ) [inline]

Set the network header length.

Parameters:

len

new network header length

Setting the network header length really just sets the transport header pointer.

Postcondition:: transport_header() == network_header() + len

void Packet::clear_network_header ( ) [inline]

Unset the network header pointer.

Postcondition:: has_network_header() == false Does not affect the MAC or transport header pointers.

bool Packet::has_transport_header ( ) const [inline]

Return true iff the packet's network header pointer is set.

See also:: set_network_header, clear_transport_header

const unsigned char * Packet::transport_header ( ) const [inline]

Return the packet's transport header pointer.

Warning:: Not useful if !has_transport_header().

See also:: tcp_header, udp_header, icmp_header, set_transport_header, clear_transport_header, transport_length

Reimplemented in WritablePacket.

int Packet::transport_header_offset ( ) const [inline]

Return the offset from the packet data to the transport header.

Returns:: transport_header() - data()

Warning:: Not useful if !has_transport_header().

int Packet::transport_length ( ) const [inline]

Return the packet's length starting from its transport header pointer.

Invariant:: transport_length() == end_data() - transport_header()

Warning:: Not useful if !has_transport_header().

void Packet::clear_transport_header ( ) [inline]

Unset the transport header pointer.

Postcondition:: has_transport_header() == false Does not affect the MAC or network header pointers.

const click_ether * Packet::ether_header ( )


Data
enum	{ default_headroom = 28, min_buffer_length = 64 }
static WritablePacket *	make (uint32_t headroom, const void *data, uint32_t length, uint32_t tailroom)
	Create and return a new packet.
static WritablePacket *	make (const void *data, uint32_t length)
	Create and return a new packet.
static WritablePacket *	make (uint32_t length)
	Create and return a new packet.
static Packet *	make (struct sk_buff *skb)
	Change an sk_buff into a Packet (linuxmodule).
static WritablePacket *	make (unsigned char data, uint32_t length, void(destructor)(unsigned char *, size_t))
	Create and return a new packet (userlevel).
void	kill ()
	Delete this packet.
bool	shared () const
	Test whether this packet's data is shared.
Packet *	clone ()
	Create a clone of this packet.
WritablePacket *	uniqueify ()
	Return an unshared packet containing this packet's data.
const unsigned char *	data () const
	Return the packet's data pointer.
const unsigned char *	end_data () const
	Return the packet's end data pointer.
uint32_t	length () const
	Return the packet's length.
uint32_t	headroom () const
	Return the packet's headroom.
uint32_t	tailroom () const
	Return the packet's tailroom.
const unsigned char *	buffer () const
	Return a pointer to the packet's data buffer.
const unsigned char *	end_buffer () const
	Return the packet's end data buffer pointer.
uint32_t	buffer_length () const
	Return the packet's buffer length.
sk_buff *	skb ()
sk_buff *	skb () const
WritablePacket *	push (uint32_t len)
	Add space for a header before the packet.
WritablePacket *	push_mac_header (uint32_t len)
	Add space for a MAC header before the packet.
Packet *	nonunique_push (uint32_t len)
	Add space for a header before the packet.
void	pull (uint32_t len)
	Remove a header from the front of the packet.
WritablePacket *	put (uint32_t len)
	Add space for data after the packet.
Packet *	nonunique_put (uint32_t len)
	Add space for data after the packet.
void	take (uint32_t len)
	Remove space from the end of the packet.
Packet *	shift_data (int offset, bool free_on_failure=true)
	Shift packet data within the data buffer.
void	shrink_data (const unsigned char *data, uint32_t length)
	Shrink the packet's data.
void	change_headroom_and_length (uint32_t headroom, uint32_t length)
	Shift the packet's data view to a different part of its buffer.
Annotations
enum	{ anno_size = 48 }
enum	PacketType { HOST = 0, BROADCAST = 1, MULTICAST = 2, OTHERHOST = 3, OUTGOING = 4, LOOPBACK = 5, FASTROUTE = 6 }
	Values for packet_type_anno(). Must agree with Linux's PACKET_ constants in <linux/if_packet.h>. More...
enum	{ dst_ip_anno_offset = 0, dst_ip_anno_size = 4, dst_ip6_anno_offset = 0, dst_ip6_anno_size = 16 }
const Timestamp &	timestamp_anno () const
	Return the timestamp annotation.
Timestamp &	timestamp_anno ()
void	set_timestamp_anno (const Timestamp &t)
	Set the timestamp annotation.
net_device *	device_anno () const
	Return the device annotation.
void	set_device_anno (net_device *dev)
	Set the device annotation.
PacketType	packet_type_anno () const
	Return the packet type annotation.
void	set_packet_type_anno (PacketType t)
	Set the packet type annotation.
Packet *	next () const
	Return the next packet annotation.
Packet *&	next ()
void	set_next (Packet *p)
	Set the next packet annotation.
Packet *	prev () const
	Return the previous packet annotation.
Packet *&	prev ()
void	set_prev (Packet *p)
	Set the previous packet annotation.
IPAddress	dst_ip_anno () const
	Return the destination IPv4 address annotation.
void	set_dst_ip_anno (IPAddress addr)
	Set the destination IPv4 address annotation.
void *	anno ()
	Return a pointer to the annotation area.
const void *	anno () const
uint8_t *	anno_u8 ()
	Return a pointer to the annotation area as uint8_ts.
const uint8_t *	anno_u8 () const
	overload
uint32_t *	anno_u32 ()
	Return a pointer to the annotation area as uint32_ts.
const uint32_t *	anno_u32 () const
	overload
uint8_t	anno_u8 (int i) const
	Return annotation byte at offset i.
void	set_anno_u8 (int i, uint8_t v)
	Set annotation byte at offset i.
uint16_t	anno_u16 (int i) const
	Return 16-bit annotation at offset i.
void	set_anno_u16 (int i, uint16_t v)
	Set 16-bit annotation at offset i.
int16_t	anno_s16 (int i) const
	Return 16-bit annotation at offset i.
void	set_anno_s16 (int i, int16_t v)
	Set 16-bit annotation at offset i.
uint32_t	anno_u32 (int i) const
	Return 32-bit annotation at offset i.
void	set_anno_u32 (int i, uint32_t v)
	Set 32-bit annotation at offset i.
int32_t	anno_s32 (int i) const
	Return 32-bit annotation at offset i.
void	set_anno_s32 (int i, int32_t v)
	Set 32-bit annotation at offset i.
uint64_t	anno_u64 (int i) const
	Return 64-bit annotation at offset i.
void	set_anno_u64 (int i, uint64_t v)
	Set 64-bit annotation at offset i.
void	clear_annotations (bool all=true)
	Clear all packet annotations.
void	copy_annotations (const Packet *)
	Copy most packet annotations from p.
Header Pointers
bool	has_mac_header () const
	Return true iff the packet's MAC header pointer is set.
const unsigned char *	mac_header () const
	Return the packet's MAC header pointer.
int	mac_header_offset () const
	Return the offset from the packet data to the MAC header.
uint32_t	mac_header_length () const
	Return the MAC header length.
int	mac_length () const
	Return the packet's length starting from its MAC header pointer.
void	set_mac_header (const unsigned char *p)
	Set the MAC header pointer.
void	set_mac_header (const unsigned char *p, uint32_t len)
	Set the MAC and network header pointers.
void	clear_mac_header ()
	Unset the MAC header pointer.
bool	has_network_header () const
	Return true iff the packet's network header pointer is set.
const unsigned char *	network_header () const
	Return the packet's network header pointer.
int	network_header_offset () const
	Return the offset from the packet data to the network header.
uint32_t	network_header_length () const
	Return the network header length.
int	network_length () const
	Return the packet's length starting from its network header pointer.
void	set_network_header (const unsigned char *p, uint32_t len)
	Set the network and transport header pointers.
void	set_network_header_length (uint32_t len)
	Set the network header length.
void	clear_network_header ()
	Unset the network header pointer.
bool	has_transport_header () const
	Return true iff the packet's network header pointer is set.
const unsigned char *	transport_header () const
	Return the packet's transport header pointer.
int	transport_header_offset () const
	Return the offset from the packet data to the transport header.
int	transport_length () const
	Return the packet's length starting from its transport header pointer.
void	clear_transport_header ()
	Unset the transport header pointer.
const click_ether *	ether_header () const
	Return the packet's MAC header pointer as Ethernet.
void	set_ether_header (const click_ether *ethh)
	Set the MAC header pointer to an Ethernet header.
const click_ip *	ip_header () const
	Return the packet's network header pointer as IPv4.
int	ip_header_offset () const
	Return the offset from the packet data to the IP header.
uint32_t	ip_header_length () const
	Return the IP header length.
void	set_ip_header (const click_ip *iph, uint32_t len)
	Set the network header pointer to an IPv4 header.
const click_ip6 *	ip6_header () const
	Return the packet's network header pointer as IPv6.
int	ip6_header_offset () const
	Return the offset from the packet data to the IPv6 header.
uint32_t	ip6_header_length () const
	Return the IPv6 header length.
void	set_ip6_header (const click_ip6 *ip6h)
	Set the network header pointer to an IPv6 header.
void	set_ip6_header (const click_ip6 *ip6h, uint32_t len)
	Set the network header pointer to an IPv6 header.
const click_icmp *	icmp_header () const
	Return the packet's transport header pointer as ICMP.
const click_tcp *	tcp_header () const
	Return the packet's transport header pointer as TCP.
const click_udp *	udp_header () const
	Return the packet's transport header pointer as UDP.