ip.h

Go to the documentation of this file.

/*
 * Copyright 2012,2013,2014 Didier Barvaux
 * Copyright 2007,2008 Thales Alenia Space
 * Copyright 2007,2009,2010,2013,2014 Viveris Technologies
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * @file   common/ip.h
 * @brief  IP-agnostic packet
 * @author Didier Barvaux <didier.barvaux@toulouse.viveris.com>
 */

#ifndef ROHC_COMMON_IP_H
#define ROHC_COMMON_IP_H

#include "protocols/ipv4.h"
#include "protocols/ipv6.h"

#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>


/** The selected IP header */
typedef enum
{
        ROHC_IP_HDR_NONE   = 0,  /**< No IP header selected */
        ROHC_IP_HDR_FIRST  = 1,  /**< The first IP header is selected */
        ROHC_IP_HDR_SECOND = 2,  /**< The second IP header is selected */
        /* max 2 IP headers handled at the moment */
} ip_header_pos_t;


/// IP version
typedef enum
{
        /// IP version 4
        IPV4 = 4,
        /// IP version 6
        IPV6 = 6,
        /// not IP
        IP_UNKNOWN = 0,
        /// IP version 4 (malformed)
        IPV4_MALFORMED = 1,
        /// IP version 6 (malformed)
        IPV6_MALFORMED = 2,
} ip_version;


/** A network header */
struct net_hdr
{
        uint8_t proto;  /**< The header protocol */
        uint8_t *data;  /**< The header data */
        size_t len;     /**< The header length (in bytes) */
};


/**
 * @brief Defines an IP-agnostic packet that can handle
 *        an IPv4 or IPv6 packet
 */
struct ip_packet
{
        /// The version of the IP packet
        ip_version version;

        /// The IP header
        union
        {
                /// The IPv4 header
                struct ipv4_hdr v4;
                /// The IPv6 header
                struct ipv6_hdr v6;
        } header;

        /// The whole IP data (header + payload) if not NULL
        const uint8_t *data;

        /// The length (in bytes) of the whole IP data (header + payload)
        size_t size;

        struct net_hdr nh;  /**< The next header (extension headers included) */
        struct net_hdr nl;  /**< The next layer (extension headers excluded) */
};


/*
 * Inline functions
 */

#ifndef __KERNEL__ /* already provided by Linux kernel */

static inline uint16_t swab16(const uint16_t value)
        __attribute__((warn_unused_result, const));

/**
 * @brief In-place change the byte order in a two-byte value.
 *
 * @param value The two-byte value to modify
 * @return      The same value with the byte order changed
 */
static inline uint16_t swab16(const uint16_t value)
{
        return ((value & 0x00ff) << 8) | ((value & 0xff00) >> 8);
}


#if defined(__i386__) || defined(__x86_64__)

static inline uint16_t ip_fast_csum(const uint8_t *iph,
                                    const size_t ihl)
        __attribute__((nonnull(1), warn_unused_result, pure));

/**
 * @brief This is a version of ip_compute_csum() optimized for IP headers,
 *        which always checksum on 4 octet boundaries.
 *
 * @author Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
 *         Arnt Gulbrandsen.
 *
 * @param iph The IPv4 header
 * @param ihl The length of the IPv4 header
 * @return    The IPv4 checksum
 */
static inline uint16_t ip_fast_csum(const uint8_t *iph,
                                    const size_t ihl)
{
        uint32_t __ihl = ihl;
        uint32_t sum;

        __asm__ __volatile__(
           " \n\
       movl (%1), %0      \n\
       subl $4, %2              \n\
       jbe 2f           \n\
       addl 4(%1), %0   \n\
       adcl 8(%1), %0   \n\
       adcl 12(%1), %0  \n\
1:     adcl 16(%1), %0  \n\
       lea 4(%1), %1    \n\
       decl %2          \n\
       jne 1b           \n\
       adcl $0, %0              \n\
       movl %0, %2              \n\
       shrl $16, %0     \n\
       addw %w2, %w0    \n\
       adcl $0, %0              \n\
       notl %0          \n\
2:     \n\
       "
           /* Since the input registers which are loaded with iph and ihl
              are modified, we must also specify them as outputs, or gcc
              will assume they contain their original values. */
                : "=r" (sum), "=r" (iph), "=r" (__ihl)
                : "1" (iph), "2" (__ihl)
                : "memory");

        return (uint16_t) (sum & 0xffff);
}


#else

static inline uint16_t from32to16(const uint32_t x)
        __attribute__((warn_unused_result, const));

static inline uint16_t from32to16(const uint32_t x)
{
        uint32_t y;
        /* add up 16-bit and 16-bit for 16+c bit */
        y = (x & 0xffff) + (x >> 16);
        /* add up carry.. */
        y = (y & 0xffff) + (y >> 16);
        return y;
}

static inline uint16_t ip_fast_csum(const uint8_t *const iph,
                                    const size_t ihl)
        __attribute__((nonnull(1), warn_unused_result, pure));

/**
 *  This is a version of ip_compute_csum() optimized for IP headers,
 *  which always checksum on 4 octet boundaries.
 */
static inline uint16_t ip_fast_csum(const uint8_t *const iph,
                                    const size_t ihl)
{
        const uint8_t *buff = iph;
        size_t len = ihl * 4;
        bool odd;
        size_t count;
        uint32_t result = 0;

        if(len == 0)
        {
                goto out;
        }
        odd = 1 & (uintptr_t) buff;
        if(odd)
        {
#ifdef __LITTLE_ENDIAN
                result = *buff;
#else
                result += (*buff << 8);
#endif
                len--;
                buff++;
        }
        count = len >> 1; /* nr of 16-bit words.. */
        if(count)
        {
                if(2 & (uintptr_t) buff)
                {
                        result += *(uint16_t *) buff;
                        count--;
                        len -= 2;
                        buff += 2;
                }
                count >>= 1; /* nr of 32-bit words.. */
                if(count)
                {
                        uint32_t carry = 0;
                        do
                        {
                                uint32_t word = *(uint32_t *) buff;
                                count--;
                                buff += sizeof(uint32_t);
                                result += carry;
                                result += word;
                                carry = (word > result);
                        }
                        while(count);
                        result += carry;
                        result = (result & 0xffff) + (result >> 16);
                }
                if(len & 2)
                {
                        result += *(uint16_t *) buff;
                        buff += 2;
                }
        }
        if(len & 1)
        {
#ifdef __LITTLE_ENDIAN
                result += *buff;
#else
                result += (*buff << 8);
#endif
        }
        result = from32to16(result);
        if(odd)
        {
                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
        }
out:
        return ~result;
}


#endif /* !__i386__ && !__x86_64__ */

#else /* !__KERNEL__ */
#  include <asm/checksum.h>
#endif /* __KERNEL__ */


/*
 * Function prototypes.
 */

/* Generic functions */

static inline
ip_version ip_get_version(const struct ip_packet *const ip)
        __attribute__((warn_unused_result, nonnull(1), pure));
uint8_t ip_get_protocol(const struct ip_packet *const ip)
        __attribute__((warn_unused_result, nonnull(1), pure));
unsigned int ip_get_tos(const struct ip_packet *const ip)
        __attribute__((warn_unused_result, nonnull(1), pure));
unsigned int ip_get_ttl(const struct ip_packet *const ip)
        __attribute__((warn_unused_result, nonnull(1), pure));

void ip_set_version(struct ip_packet *const ip, const ip_version value)
        __attribute__((nonnull(1)));
void ip_set_protocol(struct ip_packet *const ip, const uint8_t value)
        __attribute__((nonnull(1)));
void ip_set_tos(struct ip_packet *const ip, const uint8_t value)
        __attribute__((nonnull(1)));
void ip_set_ttl(struct ip_packet *const ip, const uint8_t value)
        __attribute__((nonnull(1)));
void ip_set_saddr(struct ip_packet *const ip, const uint8_t *value)
        __attribute__((nonnull(1, 2)));
void ip_set_daddr(struct ip_packet *const ip, const uint8_t *value)
        __attribute__((nonnull(1, 2)));

/**
 * @brief Get the IP version of an IP packet
 *
 * The function handles \ref ip_packet whose \ref ip_packet::version is
 * \ref IP_UNKNOWN.
 *
 * @param ip The IP packet to analyze
 * @return   The version of the IP packet
 */
static inline
ip_version ip_get_version(const struct ip_packet *const ip)
{
        return ip->version;
}

#endif