inetsw table

Data struct.

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123 /* The inetsw table contains everything that inet_create needs to
124  * build a new socket.
125  */
126 static struct list_head inetsw[SOCK_MAX];
127 static DEFINE_SPINLOCK(inetsw_lock);

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socket

how to create a inet socket

Data Structure

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1019 static const struct net_proto_family inet_family_ops = {
1020         .family = PF_INET,
1021         .create = inet_create,
1022         .owner  = THIS_MODULE,
1023 };

call trace

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> inet_create
> > search the right inetsw array element with type/protocol
> > sock->ops = answer->ops;
> > k = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot);
> > sock_init_data(sock, sk);
> > init the sk

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socket

system call socket

Summary

System call socket will do two things:

  1. create a struct socket *sock.
    Mainly done by __sock_create, which alloc a struct socket *sock,
    then init it with the creating method of net_families[family].
  2. map the sock to a file descriptor by sock_map_fd.
    TODO…..

call trace:

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> socket
> > sock_create
> > > __sock_create
> > > > sock = sock_alloc();
> > > > sock->type = type;
> > > > rcu_read_lock();
> > > > pf = rcu_dereference(net_families[family]);
> > > > try_module_get(pf->owner))
> > > > rcu_read_unlock();
> > > > pf->create(net, sock, protocol, kern);
> > > > module_put(pf->owner)
> > socket_map_fd

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socket

socket net_proto_family

summary

Each family has a corresponding array element of struct net_proto_family,
which will be called in system call socket.

Data Structure

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181 struct net_proto_family {
182         int             family;
183         int             (*create)(struct net *net, struct socket *sock,
184                                   int protocol, int kern);
185         struct module   *owner;
186 };

The create is important, which is first and basic function during
system call socket.

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164 static DEFINE_SPINLOCK(net_family_lock);
165 static const struct net_proto_family __rcu *net_families[NPROTO] __read_mostly;

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git

how to update github page in multi pos

Requirement

I want to write blog with github page and octopress in the office
and in the home.

Steps

The github page has work well done with pc in the home.
Now setup the environment in office to write github page.
The github page repo:
https://github.com/martinbj2008/martinbj2008.github.io

the octopress is pushed to git repo as branch “source”

How to write blog and sync them to github while avoid conflict with home?

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route

IPv4 route fib tree rebalance

call trace

以插入一条新的路由为例。

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> fib_insert_node
> > trie_rebalance
> > > while loop
> > > > resize
> > > > tnode_put_child_reorg
> > > > tnode_free_flush

###trie_rebalance

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for_each_node(from current node tn to  fib_trie root)
	call resize()
	tnode_put_child_reorg

从当前节点开始一直到根节点，以当前节点作为一个子树，
反复调用resize, 并通过tnode_put_child_reorg
更新当前节点的父节点的统计信息。

注： resize可能会更改子树的根节点！

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IRQs

where softirq is invoked

##summary
softirq 真正干活的函数是__do_softirq。
linuxv3.11内核里能够执行__do_softirq,有如下调用,
这里指真正执行softirq的地方，不是触发(设置)softirq标志 !!!

  1. 每个硬中断退出的时。
  2. 当bh使能的时。
  3. 发送回环报文时。

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