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/*
* Copyright (C) 2014, 2015 Martine Lenders <mlenders@inf.fu-berlin.de>
* 2015 Freie Universitรคt Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup net_gnrc_pkt Packet
* @ingroup net_gnrc_pktbuf
* @brief Network packet abstraction type and helper functions
* @{
*
* @file
* @brief General definitions for network packets and their helper functions
*
* @author Martine Lenders <mlenders@inf.fu-berlin.de>
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*/
#ifndef GNRC_PKT_H_
#define GNRC_PKT_H_
#include <inttypes.h>
#include <stdlib.h>
#include "kernel_types.h"
#include "net/gnrc/nettype.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Type to represent parts (either headers or payload) of a packet,
* called snips.
* @details The idea behind the packet snips is that they either can represent
* protocol-specific headers or payload. A packet can be comprised of
* multiple pktsnip_t elements.
*
* Example:
*
* buffer
* +---------------------------+ +------+
* | size = 14 | data +-------------->| |
* | type = NETTYPE_ETHERNET |------+ +------+
* +---------------------------+ . .
* | next . .
* v +------+
* +---------------------------+ +----------->| |
* | size = 40 | data | | |
* | type = NETTYPE_IPV6 |---------+ +------+
* +---------------------------+ . .
* | next . .
* v +------+
* +---------------------------+ +-------->| |
* | size = 8 | data | +------+
* | type = NETTYPE_UDP |------------+ . .
* +---------------------------+ . .
* | next +------+
* v +----->| |
* +---------------------------+ | | |
* | size = 59 | data | . .
* | type = NETTYPE_UNDEF |---------------+ . .
* +---------------------------+ . .
*
* To keep data duplication as low as possible the order of the snips
* in a packet will be reversed depending on if you send the packet or if
* you received it. For sending the order is from (in the network stack) lowest
* protocol snip to the highest, for receiving the order is from highest
* snip to the lowest. This way, if a layer needs to duplicate the packet
* a tree is created rather than a duplication of the whole package.
*
* A very extreme example for this (we only expect one or two duplications at
* maximum per package) can be seen here:
*
* Sending Receiving
* ======= =========
*
* * Payload * L2 header
* ^ ^
* | |
* |\ |\
* | * L4 header 1 | * L2.5 header 1
* | * L3 header 1 | * L3 header 1
* | * netif header 1 | * L4 header 1
* * L4 header 2 | * Payload 1
* ^ * L3 header 2
* | ^
* |\ |
* | * L3 header 2 |\
* | * L2 header 2 | * L4 header 2
* * L2 header 3 | * Payload 2
* |\ * Payload 3
* | * L2 header 3
* * L2 header 4
*
* @note This type has no initializer on purpose. Please use @ref net_gnrc_pktbuf
* as factory.
*/
/* packed to be aligned correctly in the static packet buffer */
typedef struct gnrc_pktsnip {
/**
* @brief Counter of threads currently having control over this packet.
*
* @internal
*/
unsigned int users;
struct gnrc_pktsnip *next; /**< next snip in the packet */
void *data; /**< pointer to the data of the snip */
size_t size; /**< the length of the snip in byte */
gnrc_nettype_t type; /**< protocol of the packet snip */
#ifdef MODULE_GNRC_NETERR
kernel_pid_t err_sub; /**< subscriber to errors related to this
* packet snip */
#endif
} gnrc_pktsnip_t;
/**
* @brief Calculates length of a packet in byte.
*
* @param[in] pkt list of packet snips.
*
* @return length of the list of headers.
*/
static inline size_t gnrc_pkt_len(gnrc_pktsnip_t *pkt)
{
size_t len = 0;
while (pkt) {
len += pkt->size;
pkt = pkt->next;
}
return len;
}
/**
* @brief Calculates length of a packet in byte upto (including) a snip with the given type.
*
* @param[in] pkt list of packet snips.
* @param[in] type type of snip to stop calculation.
*
* @return length of the list of headers.
*/
static inline size_t gnrc_pkt_len_upto(gnrc_pktsnip_t *pkt, gnrc_nettype_t type)
{
size_t len = 0;
while (pkt) {
len += pkt->size;
if (pkt->type == type) {
break;
}
pkt = pkt->next;
}
return len;
}
/**
* @brief Count the numbers of snips in the given packet
*
* @param[in] pkt first snip in the packet
*
* @return number of snips in the given packet
*/
static inline size_t gnrc_pkt_count(const gnrc_pktsnip_t *pkt)
{
size_t count = 0;
while (pkt) {
++count;
pkt = pkt->next;
}
return count;
}
/**
* @brief Searches the packet for a packet snip of a specific type
*
* @param[in] pkt list of packet snips
* @param[in] type the type to search for
*
* @return the packet snip in @p pkt with @ref gnrc_nettype_t @p type
* @return NULL, if none of the snips in @p pkt is of @p type
*/
gnrc_pktsnip_t *gnrc_pktsnip_search_type(gnrc_pktsnip_t *pkt,
gnrc_nettype_t type);
#ifdef __cplusplus
}
#endif
#endif /* GNRC_PKT_H_ */
/** @} */
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