taglinefilesource code
send_tail137include/net/sock.hstruct sk_buff    * volatile send_tail;
send_tail448net/ipv4/ip_output.csk->send_tail = skb;
send_tail453net/ipv4/ip_output.csk->send_tail->link3 = skb;
send_tail454net/ipv4/ip_output.csk->send_tail = skb;
send_tail393net/ipv4/tcp_input.cnewsk->send_tail = NULL;
send_tail534net/ipv4/tcp_input.csk->send_tail = NULL;
send_tail567net/ipv4/tcp_input.csk->send_tail = skb;
send_tail571net/ipv4/tcp_input.csk->send_tail->link3 = skb;
send_tail572net/ipv4/tcp_input.csk->send_tail = skb;
send_tail659net/ipv4/tcp_input.cif (sk->send_tail == NULL || sk->send_head == NULL) 
send_tail662net/ipv4/tcp_input.csk->send_tail = NULL;
send_tail820net/ipv4/tcp_input.csk->send_tail = NULL;