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电梯直达

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发表于 2015-04-23 22:58 |只看该作者 |倒序浏览

直接上代码了，代码比较老 2.6.20的
比如我要添加一个ip
ip add addr10.0.1.0/24 dev eth0
这会导致在LOCAL路由表中添加两个导出的广播地址
10.0.1.255/32
10.0.1.0/32（这个导出的广播地址有什么用，也就是下面标红处的代码，多谢）
void fib_add_ifaddr(struct in_ifaddr *ifa)
{
struct in_device *in_dev = ifa->ifa_dev;
struct net_device *dev = in_dev->dev;
struct in_ifaddr *prim = ifa;
__be32 mask = ifa->ifa_mask;
__be32 addr = ifa->ifa_local;
__be32 prefix = ifa->ifa_address&mask;

if (ifa->ifa_flags&IFA_F_SECONDARY) {
prim = inet_ifa_byprefix(in_dev, prefix, mask);
if (prim == NULL) {
printk(KERN_DEBUG "fib_add_ifaddr: bug: prim == NULL\n");
return;
}
}

fib_magic(RTM_NEWROUTE, RTN_LOCAL, addr, 32, prim);

if (!(dev->flags&IFF_UP))
return;

/* Add broadcast address, if it is explicitly assigned. */
if (ifa->ifa_broadcast && ifa->ifa_broadcast != htonl(0xFFFFFFFF))
fib_magic(RTM_NEWROUTE, RTN_BROADCAST, ifa->ifa_broadcast, 32, prim);

if (!ZERONET(prefix) && !(ifa->ifa_flags&IFA_F_SECONDARY) &&
(prefix != addr || ifa->ifa_prefixlen < 32)) {
fib_magic(RTM_NEWROUTE, dev->flags&IFF_LOOPBACK ? RTN_LOCAL :
RTN_UNICAST, prefix, ifa->ifa_prefixlen, prim);

/* Add network specific broadcasts, when it takes a sense */
if (ifa->ifa_prefixlen < 31) {
fib_magic(RTM_NEWROUTE, RTN_BROADCAST, prefix, 32, prim); fib_magic(RTM_NEWROUTE, RTN_BROADCAST, prefix|~mask, 32, prim);
}
}
}