iphelper.hh

/*
 * IPHelper.hh - Provides several methods that can be used by elements to manage IP packets
 *
 * Romain Gaillard, Tom Barbette
 */
 
#ifndef MIDDLEBOX_IPHELPER_HH
#define MIDDLEBOX_IPHELPER_HH
 
#include <click/config.h>
#include <click/glue.hh>
#include <clicknet/tcp.h>
#include <clicknet/udp.h>
 
CLICK_DECLS
 
class IPHelper
{
public:
    inline uint16_t packetTotalLength(Packet* packet) const;
 
    inline uint16_t getIPHeaderOffset(Packet* packet) const;
 
    inline void setPacketTotalLength(WritablePacket* packet, unsigned length) const;
 
    inline uint32_t getDestinationAddress(Packet* packet) const;
 
    inline uint32_t getSourceAddress(Packet* packet) const;
 
    inline void computeIPChecksum(WritablePacket* packet) const;
 
 
    inline void rewrite_ipport(WritablePacket* p, IPAddress ip, uint16_t port,
                               const int shift, bool is_tcp);
};
 
inline uint16_t IPHelper::packetTotalLength(Packet *packet) const
{
    const click_ip *iph = packet->ip_header();
 
    return ntohs(iph->ip_len);
}
 
inline uint16_t IPHelper::getIPHeaderOffset(Packet *packet) const
{
    return (((const unsigned char *)packet->ip_header()) - packet->data());
}
 
inline void IPHelper::setPacketTotalLength(WritablePacket* packet, unsigned length) const
{
    click_ip *iph = packet->ip_header();
    iph->ip_len = htons(length);
}
 
 
inline void IPHelper::computeIPChecksum(WritablePacket *packet) const
{
    click_ip *iph = packet->ip_header();
 
    //unsigned plen = ntohs(iph->ip_len) - (iph->ip_hl << 2);
    unsigned hlen = iph->ip_hl << 2;
 
    iph->ip_sum = 0;
    iph->ip_sum = click_in_cksum((const unsigned char *)iph, hlen);
}
 
inline uint32_t IPHelper::getSourceAddress(Packet* packet) const
{
    const click_ip *iph = packet->ip_header();
 
    return *(const uint32_t*)&iph->ip_src;
}
 
inline uint32_t IPHelper::getDestinationAddress(Packet* packet) const
{
    const click_ip *iph = packet->ip_header();
 
    return *(const uint32_t*)&iph->ip_dst;
}
 
inline void
IPHelper::rewrite_ipport(WritablePacket* p, IPAddress ip, uint16_t port,
                            const int shift, bool is_tcp) {
    assert(p->network_header());
    assert(p->transport_header());
    uint32_t old_hw, t_old_hw;
    uint32_t new_hw, t_new_hw;
 
    uint16_t *xip = reinterpret_cast<uint16_t *>(&p->ip_header()->ip_src);
    old_hw = (uint32_t) xip[(shift * 2) + 0] + xip[(shift*2) + 1];
    t_old_hw = old_hw;
    old_hw += (old_hw >> 16);
 
    memcpy(&xip[shift*2], &ip, 4);
 
    new_hw = (uint32_t) xip[(shift*2) + 0] + xip[(shift*2) + 1];
    t_new_hw = new_hw;
    new_hw += (new_hw >> 16);
    click_ip *iph = p->ip_header();
    click_update_in_cksum(&iph->ip_sum, old_hw, new_hw);
 
    uint16_t *xport = reinterpret_cast<uint16_t *>(&p->tcp_header()->th_sport);
    t_old_hw += (uint32_t) xport[shift + 0];
    t_old_hw += (t_old_hw >> 16);
    xport[shift + 0] = port;
    t_new_hw += (uint32_t) xport[shift + 0];
    t_new_hw += (t_new_hw >> 16);
 
    if (is_tcp)
        click_update_in_cksum(&p->tcp_header()->th_sum, t_old_hw, t_new_hw);
    else
        click_update_in_cksum(&p->udp_header()->uh_sum, t_old_hw, t_new_hw);
}
 
CLICK_ENDDECLS
#endif