《教你修改以及重构skb》在2.6.30上的实现

上次看了ubuntuer兄写的，受益匪浅，真是经典之作。
但ubuntuer兄的代码是基于2.6.18的，比较旧。今天经过摸索，我终于让其可以在2.6.30上运行了，代码如下：
skb_DIY.c

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
 
MODULE_LICENSE("GPL");
MODULE_AUTHOR("[e-mail]");

#define    ETH     "eth0"
#define    SIP     "192.168.238.180"
#define    DIP     "192.168.1.101"
#define    SPORT   39804
#define    DPORT   80

unsigned char   SMAC[ETH_ALEN] = {0x00,0x0C,0x29,0x4F,0xDE,0xAC};
unsigned char   DMAC[ETH_ALEN] = {0x00,0x50,0x56,0xFA,0x70,0x2A};

int cp_dev_xmit_tcp (char * eth, u_char * smac, u_char * dmac,
             u_char * pkt, int pkt_len,
             u_long sip, u_long dip,
             u_short sport, u_short dport, u_long seq, u_long ack_seq, u_char psh, u_char fin)
{
    struct sk_buff * skb = NULL;
    struct net_device * dev = NULL;
    struct ethhdr * ethdr = NULL;
    struct iphdr * iph = NULL;
    struct tcphdr * tcph = NULL;
    u_char * pdata = NULL;
    int nret = 1;
    if (NULL == smac || NULL == dmac) goto out;
    dev = dev_get_by_name(&init_net, eth);
    if (NULL == dev)
        goto out;
    skb = alloc_skb (pkt_len + sizeof (struct iphdr) + sizeof (struct tcphdr) + LL_RESERVED_SPACE (dev), GFP_ATOMIC);
    /* 
    LL_RESERVED_SPACE(dev) = 16
    alloc_skb返回以后，skb->head = skb_data = skb->tail =  alloc_skb分配的内存区首地址,skb->len = 0;
    skb->end = skb->tail + size;
         注：我的机子是32位x86机器，所以没有定义NET_SKBUFF_DATA_USES_OFFSET，因而，
     skb->tail,skb->mac_header,skb->network_header,skb->transport_header这几个成员都是指针
    */
      if (NULL == skb)
            goto out;
    skb_reserve (skb, LL_RESERVED_SPACE (dev));//add data and tail
    skb->dev = dev;
    skb->pkt_type = PACKET_OTHERHOST;
    skb->protocol = __constant_htons(ETH_P_IP);
    skb->ip_summed = CHECKSUM_NONE;
    skb->priority = 0;
    //skb->nh.iph = (struct iphdr*)skb_put(skb, sizeof (struct iphdr));
    //skb->h.th = (struct tcphdr*)skb_put(skb, sizeof (struct tcphdr));
    skb_set_network_header(skb, 0);    //skb->network_header = skb->data + 0;
    skb_put(skb, sizeof (struct iphdr)); //add tail and len
    skb_set_transport_header(skb, sizeof (struct iphdr));//skb->transport_header = skb->data + sizeof (struct iphdr)
    skb_put(skb, sizeof (struct tcphdr));   
    pdata = skb_put (skb, pkt_len);
      {
            if (NULL != pkt)
                 memcpy (pdata, pkt, pkt_len);
      }

    {
        tcph = tcp_hdr(skb);
        memset (tcph, 0, sizeof (struct tcphdr));
        tcph->source = sport;
        tcph->dest = dport;
        tcph->seq = seq;
        tcph->ack_seq = ack_seq;
        tcph->doff = 5;
        tcph->psh = psh;
        tcph->fin = fin;
        tcph->syn = 1;
        tcph->ack = 0;
        tcph->window = __constant_htons (5840);
        skb->csum = 0;
        tcph->check = 0;
    }

    {
        iph = ip_hdr(skb);
        iph->version = 4;
        iph->ihl = sizeof(struct iphdr)>>2;
        iph->frag_off = 0;
        iph->protocol = IPPROTO_TCP;
        iph->tos = 0;
        iph->daddr = dip;
        iph->saddr = sip;
        iph->ttl = 0x40;
        iph->tot_len = __constant_htons(skb->len);
        iph->check = 0;
    }
      skb->csum = skb_checksum (skb, iph->ihl*4, skb->len - iph->ihl * 4, 0);
    tcph->check = csum_tcpudp_magic (sip, dip, skb->len - iph->ihl * 4, IPPROTO_TCP, skb->csum);
    {
        ethdr = (struct ethhdr*)skb_push (skb, 14);//reduce data and add len
        memcpy (ethdr->h_dest, dmac, ETH_ALEN);
        memcpy (ethdr->h_source, smac, ETH_ALEN);
        ethdr->h_proto = __constant_htons (ETH_P_IP);
    }
     if (0 > dev_queue_xmit(skb)) goto out;
    nret = 0;
out:
    if (0 != nret && NULL != skb)
    {
        dev_put (dev);
        kfree_skb (skb);
    }
      return (nret);
}

static int __init init(void)
{
    printk("%s\n","insmod skb_diy module\n");
        cp_dev_xmit_tcp (ETH, SMAC, DMAC,NULL, 0,
                    in_aton(SIP),in_aton(DIP),
                    htons(SPORT),htons(DPORT),
                    0, 0, 0, 0);
    return 0;
}

static void __exit fini(void)
{
    printk("%s\n","remove skb_diy module.\n");
}

module_init(init);
module_exit(fini);


Makefile:

PWD:=$(shell pwd)
KERNEL_SRC = /lib/modules/`uname -r`/build
obj-m:=skb_DIY.o
skb_DIY-objs:=skb.o
all:
    make -C $(KERNEL_SRC) M=$(PWD) modules
clean:
    rm -f *.o
    rm -f *.ko
    rm -f .*.cmd
    rm -rf .tmp_versions
    rm -f *.mod.c
    rm -f *.symvers
    rm -f *.order