taglinefilesource code
send_tail120include/net/sock.hstruct sk_buff    * volatile send_tail;
send_tail687net/ipv4/af_inet.csk->send_tail = NULL;
send_tail1867net/ipv4/ip.csk->send_tail = skb;
send_tail1872net/ipv4/ip.csk->send_tail->link3 = skb;
send_tail1873net/ipv4/ip.csk->send_tail = skb;
send_tail2746net/ipv4/tcp.cnewsk->send_tail = NULL;
send_tail3214net/ipv4/tcp.csk->send_tail = NULL;
send_tail3251net/ipv4/tcp.csk->send_tail = skb;
send_tail3255net/ipv4/tcp.csk->send_tail->link3 = skb;
send_tail3256net/ipv4/tcp.csk->send_tail = skb;
send_tail3268net/ipv4/tcp.cif (sk->send_tail == NULL || sk->send_head == NULL) 
send_tail3271net/ipv4/tcp.csk->send_tail = NULL;
send_tail3462net/ipv4/tcp.csk->send_tail = NULL;