kaodv-ipenc.c

aodv2003 在linux上的实现 很好

/*****************************************************************************
 *
 * Copyright (C) 2001 Uppsala University & Ericsson AB.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors: Erik Nordstr鰉, <[e-mail]>
 *
 *****************************************************************************/
#include <net/ip.h>
#include <linux/skbuff.h>
#include <linux/version.h>

#include "kaodv-ipenc.h"
#include "kaodv-expl.h" /* For print_ip() */

/* Simple function (based on R. Stevens) to calculate IP header checksum */
static u_int16_t ip_csum(unsigned short *buf, int nshorts)
{
    u_int32_t sum;
    
    for (sum = 0; nshorts > 0; nshorts--) {
        sum += *buf++;
    }
    
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    
    return ~sum;
}

struct sk_buff *ip_pkt_encapsulate(struct sk_buff *skb, __u32 dest)
{


    struct min_ipenc_hdr *ipe;    
    struct sk_buff *nskb;
    struct iphdr *iph;
    
    /* Allocate new data space at head */
    nskb = skb_copy_expand(skb, skb_headroom(skb),
			   skb_tailroom(skb) +
			   sizeof(struct min_ipenc_hdr), 
			   GFP_ATOMIC);

    if (nskb == NULL) {
	printk("Could not allocate new skb\n");
	kfree_skb(skb);
	return NULL;	
    }

    /* Set old owner */
    if (skb->sk != NULL)
	skb_set_owner_w(nskb, skb->sk);
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22))
    iph = skb->nh.iph;
#else
    iph = (struct iphdr *)skb->network_header;
#endif

    skb_put(nskb, sizeof(struct min_ipenc_hdr));
    
    /* Move the IP header */
    memcpy(nskb->data, skb->data, (iph->ihl << 2));
    /* Move the data */
    memcpy(nskb->data + (iph->ihl << 2) + sizeof(struct min_ipenc_hdr), 
	   skb->data + (iph->ihl << 2), skb->len - (iph->ihl << 2));
    
    kfree_skb(skb);
    skb = nskb;
    
    /* Update pointers */
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22))
    iph = skb->nh.iph = (struct iphdr *)skb->data;
#else
    iph = (struct iphdr *)skb->data;
    skb->network_header = skb->data;
#endif

    ipe = (struct min_ipenc_hdr *)(skb->data + (iph->ihl << 2));
    
    /* Save the old ip header information in the encapsulation header */
    ipe->protocol = iph->protocol;
    ipe->s = 0; /* No source address field in the encapsulation header */
    ipe->res = 0;
    ipe->check = 0;
    ipe->daddr = iph->daddr;

    /* Update the IP header */
    iph->daddr = dest;
    iph->protocol = IPPROTO_MIPE;
    iph->tot_len = htons(ntohs(iph->tot_len) + sizeof(struct min_ipenc_hdr));
    
    /* Recalculate checksums */
    ipe->check = ip_csum((unsigned short *)ipe, 4);

    ip_send_check(iph);

    if (iph->id == 0)
	ip_select_ident(iph, skb->dst, NULL);
        
    return skb;
}

struct sk_buff *ip_pkt_decapsulate(struct sk_buff *skb)
{
    struct min_ipenc_hdr *ipe;
    /* skb->nh.iph is probably not set yet */
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22))
    struct iphdr *iph = skb->nh.iph;
#else
    struct iphdr *iph = (struct iphdr *)skb->network_header; 
#endif

    ipe = (struct min_ipenc_hdr *)((char *)iph + (iph->ihl << 2));

    iph->protocol = ipe->protocol;
    iph->daddr = ipe->daddr;
    
    /* Shift the data to the left, overwriting the encap header */
    memmove(skb->data + (iph->ihl << 2), 
	    skb->data + (iph->ihl << 2) + sizeof(struct min_ipenc_hdr), 
	    skb->len - (iph->ihl << 2) - sizeof(struct min_ipenc_hdr));
    
    skb_trim(skb, skb->len - sizeof(struct min_ipenc_hdr));
    
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22))
    skb->nh.iph = iph = (struct iphdr *)skb->data;
#else
    iph = (struct iphdr *)skb->data;
    skb->network_header = skb->data;
#endif

    iph->tot_len = htons((ntohs(iph->tot_len) - sizeof(struct min_ipenc_hdr))); 
    ip_send_check(iph);
   
    return skb;
}