使用skb_push()增加的长度大于headroom的值，怎么办？

panic ?

net/core/skbuff.c:

void skb_under_panic(struct sk_buff *skb, int sz, void *here)
{
        printk(KERN_EMERG "skb_under_panic: text:%p len:%d put:%d head:%p "
                          "data:%p tail:%#lx end:%#lx dev:%s\n",
               here, skb->len, sz, skb->head, skb->data,
               (unsigned long)skb->tail, (unsigned long)skb->end,
               skb->dev ? skb->dev->name : "<NULL>");
        BUG();
}

unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
{
        skb->data -= len;
        skb->len  += len;
        if (unlikely(skb->data<skb->head))
                skb_under_panic(skb, len, __builtin_return_address(0));
        return skb->data;
}

skb_realloc_headroom()?

skb_copy_expand()?

@孔建军 对，使用skb_push时，代码在BUG()处报错了……

@王介 多谢提示，有点思路了。

skb_realloc_headroom(skb, nhr) 将skb的包体重新分配到头部空隙为nhr字节的包缓冲上去

skb_cow(skb, headroom) 当包体的前部空隙小于headroom或者是克隆包时, 重建包缓冲并释放原包引用