taglinefilesource code
link346include/linux/skbuff.hstruct sk_buff    * volatile link3;  /* Link for IP protocol level buffer chains   */
link3549net/core/skbuff.cskb->link3 = NULL;
link3621net/core/skbuff.cn->link3=NULL;
link3367net/ipv4/af_inet.cskb2 = skb->link3;
link375net/ipv4/ip_output.cnewskb->link3=NULL;
link3438net/ipv4/ip_output.cif (skb->link3 != NULL)
link3441net/ipv4/ip_output.cskb->link3 = NULL;
link3450net/ipv4/ip_output.csk->send_tail->link3 = skb;
link3788net/ipv4/tcp.cskb = skb->link3;
link33495net/ipv4/tcp.cskb2 = skb->link3;
link33496net/ipv4/tcp.cskb->link3 = NULL;
link33522net/ipv4/tcp.csk->send_tail->link3 = skb;
link33525net/ipv4/tcp.cskb->link3 = NULL;
link33631net/ipv4/tcp.cif (sk->send_head->link3 &&
link33632net/ipv4/tcp.cafter(sk->send_head->h.seq, sk->send_head->link3->h.seq)) 
link33658net/ipv4/tcp.cif (sk->send_head->link3)  /* Any more queued retransmits? */
link33726net/ipv4/tcp.csk->send_head = oskb->link3;