struct sk_buff与socket
作者:gfree.wind@gmail.com
在Linux2.6中,struct sk_buf承担了socket的输入输出的传输缓存的任务。
首先,还是先看struct socket的定义
/**
* struct socket - general BSD socket
* @state: socket state (%SS_CONNECTED, etc)
* @type: socket type (%SOCK_STREAM, etc)
* @flags: socket flags (%SOCK_ASYNC_NOSPACE, etc)
* @ops: protocol specific socket operations
* @file: File back pointer for gc
* @sk: internal networking protocol agnostic socket representation
* @wq: wait queue for several uses
*/
struct socket {
socket_state state;
kmemcheck_bitfield_begin(type);
short type;
kmemcheck_bitfield_end(type);
unsigned long flags;
struct socket_wq *wq;
struct file *file;
struct sock *sk;
const struct proto_ops *ops;
}; |
代码中的注释对于每一个变量说的都很清楚——看到这里,我先感叹一下,linux2.6的结构体的注释比老版本要清楚的多。到目前为止,我所看到的关键的结构体,都有清晰的注释。我们可以看出struct socket中的sock变量,是socket变量的工作核心。
那么现在跳转到struct sock的定义处。由于struct sock的定义过长,所以只展示一部分。
struct sock {
/*
* Now struct inet_timewait_sock also uses sock_common, so please just
* don't add nothing before this first member (__sk_common) --acme
*/
struct sock_common __sk_common;
/* skip some codes */
int sk_rcvbuf; /* skip some codes */
int sk_sndbuf;
struct sk_buff_head sk_receive_queue;
struct sk_buff_head sk_write_queue;
}; |
其中,sk_rcvbuf和sk_sendbuf分别是接收和发送缓存的字节数。
而struct sk_buff_head的定义如下:
struct sk_buff_head {
/* These two members must be first. */
struct sk_buff *next;
struct sk_buff *prev;
__u32 qlen;
spinlock_t lock;
}; |
可以看出socket的接收和发送缓存是使用一个双链表将sk_buff组织起来的。
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