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分类： LINUX
2007-10-25 18:39:27
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前面已经分析了，将接口添进网桥时，用户空间调用ioctl(br_socket_fd, SIOCBRADDIF, &ifr)
注意到在void br_dev_setup(struct net_device *dev)中已经对dev->do_ioctl进行了赋值，即：
dev->do_ioctl = br_dev_ioctl
进行ioctl进行访问的时候，进入到br_dev_ioctl: (net/brige/br_ioctl.c)
int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
struct net_bridge *br = netdev_priv(dev);
switch(cmd) {
case SIOCDEVPRIVATE:
return old_dev_ioctl(dev, rq, cmd);
//添加一个接口
case SIOCBRADDIF:
//删除一个接口
case SIOCBRDELIF:
return add_del_if(br, rq->ifr_ifindex, cmd == SIOCBRADDIF);
}
pr_debug("Bridge does not support ioctl 0x%x\n", cmd);
return -EOPNOTSUPP;
}
我们在用户空间使用的标志是SIOCBRADDIF。所以流程进入add_del_if()
static int add_del_if(struct net_bridge *br, int ifindex, int isadd)
{
struct net_device *dev;
int ret;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
dev = dev_get_by_index(ifindex);
if (dev == NULL)
return -EINVAL;
if (isadd)
ret = br_add_if(br, dev);
else
ret = br_del_if(br, dev);
dev_put(dev);
return ret;
}
因为cmd == SIOCBRADDIF为真，所以调用br_add_if():
int br_add_if(struct net_bridge *br, struct net_device *dev) (net/brige/br_if.c))
{
struct net_bridge_port *p;
int err = 0;
//回环。或者非以及网接口
if (dev->flags & IFF_LOOPBACK || dev->type != ARPHRD_ETHER)
return -EINVAL;
//构造数据包函数为网桥类型
if (dev->hard_start_xmit == br_dev_xmit)
return -ELOOP;
//此接口已经存在于网桥
if (dev->br_port != NULL)
return -EBUSY;
//为dev 创建网桥接口.dev->br_port。指向所属网桥端口
//dev->br_port->br：指向它所属的网桥
//为该接口创建net_bridge_port
if (IS_ERR(p = new_nbp(br, dev, br_initial_port_cost(dev))))
return PTR_ERR(p);
//更新port->MAC对应表
if ((err = br_fdb_insert(br, p, dev->dev_addr, 1)))
destroy_nbp(p);
else if ((err = br_sysfs_addif(p)))
del_nbp(p);
else {
//设置接口为混杂模式
dev_set_promiscuity(dev, 1);
//将p->list更新至br->port_list中
list_add_rcu(&p->list, &br->port_list);
spin_lock_bh(&br->lock);
br_stp_recalculate_bridge_id(br);
if ((br->dev->flags & IFF_UP)
&& (dev->flags & IFF_UP) && netif_carrier_ok(dev))
br_stp_enable_port(p);
spin_unlock_bh(&br->lock);
dev_set_mtu(br->dev, br_min_mtu(br));
}
return err;
}
为接口创建net_bridge_port的函数为new_nbp。这个函数比较简单：
static struct net_bridge_port *new_nbp(struct net_bridge *br,
struct net_device *dev,
unsigned long cost)
{
int index;
struct net_bridge_port *p;
index = find_portno(br);
if (index < 0)
return ERR_PTR(index);
p = kmalloc(sizeof(*p), GFP_KERNEL);
if (p == NULL)
return ERR_PTR(-ENOMEM);
memset(p, 0, sizeof(*p));
p->br = br;
dev_hold(dev);
p->dev = dev;
p->path_cost = cost;
p->priority = 0x8000 >> BR_PORT_BITS;
dev->br_port = p;
p->port_no = index;
br_init_port(p);
p->state = BR_STATE_DISABLED;
kobject_init(&p->kobj);
return p;
}
之后，把要加入的接口对应的mac与接口作为本机静态项加入到prot—mac对应表。这是在br_fdb_insert()中实现的
int br_fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
const unsigned char *addr, int is_local)
{
int ret;
spin_lock_bh(&br->hash_lock);
ret = fdb_insert(br, source, addr, is_local);
spin_unlock_bh(&br->hash_lock);
return ret;
}
操作存在异步性，在插入之前加锁。具体的插入在fdb_insert中实现
static int fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
const unsigned char *addr, int is_local)
{
struct hlist_node *h;
struct net_bridge_fdb_entry *fdb;
int hash = br_mac_hash(addr);
//判断是否为有效的mac 地址
if (!is_valid_ether_addr(addr))
return -EADDRNOTAVAIL;
hlist_for_each_entry(fdb, h, &br->hash[hash], hlist) {
//如果表中已经包含了此项
if (!memcmp(fdb->addr.addr, addr, ETH_ALEN)) {
//如果为本机MAC
/* attempt to update an entry for a local interface */
if (fdb->is_local) {
/* it is okay to have multiple ports with same
* address, just don't allow to be spoofed.
*/
if (is_local)
return 0;
if (net_ratelimit())
printk(KERN_WARNING "%s: received packet with "
" own address as source address\n",
source->dev->name);
return -EEXIST;
}
//如果添加的是本机IP
if (is_local) {
printk(KERN_WARNING "%s adding interface with same address "
"as a received packet\n",
source->dev->name);
goto update;
}
//如果添加的是静态MAC
//则不更新相关的信息
if (fdb->is_static)
return 0;
/* move to end of age list */
list_del(&fdb->u.age_list);
goto update;
}
}
fdb = kmem_cache_alloc(br_fdb_cache, GFP_ATOMIC);
if (!fdb)
return ENOMEM;
memcpy(fdb->addr.addr, addr, ETH_ALEN);
atomic_set(&fdb->use_count, 1);
hlist_add_head_rcu(&fdb->hlist, &br->hash[hash]);
if (!timer_pending(&br->gc_timer)) {
br->gc_timer.expires = jiffies + hold_time(br);
add_timer(&br->gc_timer);
}
update:
fdb->dst = source;
fdb->is_local = is_local;
fdb->is_static = is_local;
fdb->ageing_timer = jiffies;
if (!is_local)
list_add_tail(&fdb->u.age_list, &br->age_list);
return 0;
}
此函数先判断要插入项是否存在，若是已存在，且不为静态项，具更新对应项。若不存在该项，则分配一个net_bridge_fdb_entry，插入到CAM表
先来分析一下net_bridge_port的结构：
struct net_bridge_port
{
//当前端口所在的briage
struct net_bridge *br;
//此端口对应的物理端口
struct net_device *dev;
//同一桥内的端口链表？
struct list_head list;
/* STP */
u8 priority;
u8 state;
u16 port_no;
unsigned char topology_change_ack;
unsigned char config_pending;
port_id port_id;
port_id designated_port;
bridge_id designated_root;
bridge_id designated_bridge;
u32 path_cost;
u32 designated_cost;
struct timer_list forward_delay_timer;
struct timer_list hold_timer;
struct timer_list message_age_timer;
struct kobject kobj;
struct rcu_head rcu;
};
对应的net_bridge_fdb_entry结构：
//CAM表中对应的数据结构
struct net_bridge_fdb_entry
{
//用于CAM表连接的链表指针
struct hlist_node hlist;
//此项对应的物理出口
struct net_bridge_port *dst;
union {
struct list_head age_list;
struct rcu_head rcu;
} u;
//此项的当前的引用计数
atomic_t use_count;
//超时时间
unsigned long ageing_timer;
//MAC地址
mac_addr addr;
//是否为主机地址
unsigned char is_local;
//是否为静态地址
unsigned char is_static;
};
struct net_bridge_port
{
//当前端口所在的briage
struct net_bridge *br;
//此端口对应的物理端口
struct net_device *dev;
//同一桥内的端口链表？
struct list_head list;
/* STP */
u8 priority;
u8 state;
u16 port_no;
unsigned char topology_change_ack;
unsigned char config_pending;
port_id port_id;
port_id designated_port;
bridge_id designated_root;
bridge_id designated_bridge;
u32 path_cost;
u32 designated_cost;
struct timer_list forward_delay_timer;
struct timer_list hold_timer;
struct timer_list message_age_timer;
struct kobject kobj;
struct rcu_head rcu;
};
桥模块中的结构太多，一一总结下，免的下次看
