Linux内核源代码解析之TCP面向字节流

本文原创为freas_1990，转载请标明出处：http://blog.csdn.net/freas_1990/article/details/11264237

大家都知道TCP是面向stream，而UDP是面向datagram的。

那，到底什么是stream呢？

我们来看一下以下代码

/* Now we need to check if we have a half built packet. */if ((skb = tcp_dequeue_partial(sk)) != NULL) {        int hdrlen;         /* IP header + TCP header */hdrlen = ((unsigned long)skb->h.th - (unsigned long)skb->data)         + sizeof(struct tcphdr);/* Add more stuff to the end of skb->len */if (!(flags & MSG_OOB)) {copy = min(sk->mss - (skb->len - hdrlen), len);/* FIXME: this is really a bug. */if (copy <= 0) {  printk("TCP: **bug**: \"copy\" <= 0!!\n");  copy = 0;}  memcpy_fromfs(skb->data + skb->len, from, copy);skb->len += copy;from += copy;copied += copy;len -= copy;sk->write_seq += copy;      }if ((skb->len - hdrlen) >= sk->mss ||    (flags & MSG_OOB) ||    !sk->packets_out)tcp_send_skb(sk, skb);elsetcp_enqueue_partial(skb, sk);continue;}

明白了吧？