kernel ipv4/ip_output.c

static inline int ip_finish_output2(struct sk_buff *skb){    struct dst_entry *dst = skb->dst;    struct rtable *rt = (struct rtable *)dst;    struct hh_cache *hh = dst->hh;    struct net_device *dev = dst->dev;    int hh_len = LL_RESERVED_SPACE(dev);    if (rt->rt_type == RTN_MULTICAST)        IP_INC_STATS(IPSTATS_MIB_OUTMCASTPKTS);    else if (rt->rt_type == RTN_BROADCAST)        IP_INC_STATS(IPSTATS_MIB_OUTBCASTPKTS);    /* Be paranoid, rather than too clever. */    if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {        struct sk_buff *skb2;        skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));        if (skb2 == NULL) {            kfree_skb(skb);            return -ENOMEM;        }        if (skb->sk)            skb_set_owner_w(skb2, skb->sk);        kfree_skb(skb);        skb = skb2;    }    if (hh) {        int hh_alen;        read_lock_bh(&hh->hh_lock);        hh_alen = HH_DATA_ALIGN(hh->hh_len);          memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);        read_unlock_bh(&hh->hh_lock);            skb_push(skb, hh->hh_len);        return hh->hh_output(skb);    } else if (dst->neighbour)        return dst->neighbour->output(skb);    if (net_ratelimit())        printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");    kfree_skb(skb);    return -EINVAL;}