taglinefilesource code
link346include/linux/skbuff.hstruct sk_buff    * volatile link3;  /* Link for IP protocol level buffer chains   */
link3541net/core/skbuff.cskb->link3 = NULL;
link3612net/core/skbuff.cn->link3=NULL;
link3353net/ipv4/af_inet.cskb2 = skb->link3;
link32315net/ipv4/ip.cnewskb->link3=NULL;
link32464net/ipv4/ip.cif (skb->link3 != NULL)
link32467net/ipv4/ip.cskb->link3 = NULL;
link32476net/ipv4/ip.csk->send_tail->link3 = skb;
link3771net/ipv4/tcp.cskb = skb->link3;
link33433net/ipv4/tcp.cskb2 = skb->link3;
link33434net/ipv4/tcp.cskb->link3 = NULL;
link33460net/ipv4/tcp.csk->send_tail->link3 = skb;
link33463net/ipv4/tcp.cskb->link3 = NULL;
link33569net/ipv4/tcp.cif (sk->send_head->link3 &&
link33570net/ipv4/tcp.cafter(sk->send_head->h.seq, sk->send_head->link3->h.seq)) 
link33596net/ipv4/tcp.cif (sk->send_head->link3)  /* Any more queued retransmits? */
link33664net/ipv4/tcp.csk->send_head = oskb->link3;