taglinefilesource code
send_tail121include/net/sock.hstruct sk_buff    * volatile send_tail;
send_tail688net/ipv4/af_inet.csk->send_tail = NULL;
send_tail2471net/ipv4/ip.csk->send_tail = skb;
send_tail2476net/ipv4/ip.csk->send_tail->link3 = skb;
send_tail2477net/ipv4/ip.csk->send_tail = skb;
send_tail2951net/ipv4/tcp.cnewsk->send_tail = NULL;
send_tail3419net/ipv4/tcp.csk->send_tail = NULL;
send_tail3456net/ipv4/tcp.csk->send_tail = skb;
send_tail3460net/ipv4/tcp.csk->send_tail->link3 = skb;
send_tail3461net/ipv4/tcp.csk->send_tail = skb;
send_tail3473net/ipv4/tcp.cif (sk->send_tail == NULL || sk->send_head == NULL) 
send_tail3476net/ipv4/tcp.csk->send_tail = NULL;
send_tail3667net/ipv4/tcp.csk->send_tail = NULL;