沾包 nagle算法等

1.根據Nagle算法，什麼時候要發送包

內核代碼，Nagle算法下，當一個報文能夠被髮送時，下面這個函數返回0

Filename : \linux-3.4.4\net\ipv4\tcp_output.c
/* Return 0, if packet can be sent now without violation Nagle's rules:
         * 1. It is full sized.
         * 2. Or it contains FIN. (already checked by caller)
         * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
         * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
         *    With Minshall's modification: all sent small packets are ACKed.
         */
static inline int tcp_nagle_check(const struct tcp_sock *tp,
                                          const struct sk_buff *skb,
                                          unsigned mss_now, int nonagle)
{
    return skb->len < mss_now && ((nonagle & TCP_NAGLE_CORK) 
    || (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}

1.報文到達MSS

2.有FIN 

3.!TCP_CORK && TCP_NOREPLY

4.!TCP_CORK && All_ACKED

5.超時