标签：linux route policy routing fib 负载均衡
上篇我们讲到了，如何匹配策略，得到一个路由表，其实在 rib_rule 里，存的是该策略所使用的路由表的索引，这里顺便解释一下 FIB (Forward Infomation Base), 即转发信息数据库，即相当于路由表。子网掩码长度相同的路由项，由 fn_zone 表示，并进行散列。想想现在进行到哪里了，确定了路由表，然后开始从子网掩码最长的子网匹配，确定目标主机与哪个子网匹配，所以根据目标主机的 IP 与此时的掩码长度可以得到与它匹配的子网。看代码：
static int
fn_hash_lookup(struct fib_table *tb, const struct flowi *flp, struct fib_result *res)
{
int err;
struct fn_zone *fz;
struct fn_hash *t = (struct fn_hash*)tb->tb_data;
read_lock(&fib_hash_lock);
for (fz = t->fn_zone_list; fz; fz = fz->fz_next) {
struct hlist_head *head;
struct hlist_node *node;
struct fib_node *f;
__be32 k = fz_key(flp->fl4_dst, fz);
head = &fz->fz_hash[fn_hash(k, fz)];
hlist_for_each_entry(f, node, head, fn_hash) {
if (f->fn_key != k)
continue;
err = fib_semantic_match(&f->fn_alias,
flp, res,
f->fn_key, fz->fz_mask,
fz->fz_order);
if (err <= 0)
goto out;
}
}
err = 1;
out:
read_unlock(&fib_hash_lock);
return err;
}int fib_semantic_match(struct list_head *head, const struct flowi *flp,
struct fib_result *res, __be32 zone, __be32 mask,
int prefixlen)
{
struct fib_alias *fa;
int nh_sel = 0;
list_for_each_entry_rcu(fa, head, fa_list) {
int err;
if (fa->fa_tos &&
fa->fa_tos != flp->fl4_tos)
continue;
if (fa->fa_scope < flp->fl4_scope)
continue;
fa->fa_state |= FA_S_ACCESSED;
err = fib_props[fa->fa_type].error;
if (err == 0) {
struct fib_info *fi = fa->fa_info;
if (fi->fib_flags & RTNH_F_DEAD)
continue;
switch (fa->fa_type) {
case RTN_UNICAST:
case RTN_LOCAL:
case RTN_BROADCAST:
case RTN_ANYCAST:
case RTN_MULTICAST:
for_nexthops(fi) {
if (nh->nh_flags&RTNH_F_DEAD)
continue;
if (!flp->oif || flp->oif == nh->nh_oif)
break;
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
if (nhsel < fi->fib_nhs) {
nh_sel = nhsel;
goto out_fill_res;
}
#else
if (nhsel < 1) {
goto out_fill_res;
}
#endif
endfor_nexthops(fi);
continue;
default:
printk(KERN_WARNING "fib_semantic_match bad type %#x\n",
fa->fa_type);
return -EINVAL;
}
}
return err;
}
return 1;
out_fill_res:
res->prefixlen = prefixlen;
res->nh_sel = nh_sel;
res->type = fa->fa_type;
res->scope = fa->fa_scope;
res->fi = fa->fa_info;
atomic_inc(&res->fi->fib_clntref);
return 0;
}
u32 tos = RT_FL_TOS(oldflp);
struct flowi fl = { .nl_u = { .ip4_u =
{ .daddr = oldflp->fl4_dst,
.saddr = oldflp->fl4_src,
.tos = tos & IPTOS_RT_MASK,
.scope = ((tos & RTO_ONLINK) ?
RT_SCOPE_LINK :
RT_SCOPE_UNIVERSE),
} },
.mark = oldflp->mark,
.iif = net->loopback_dev->ifindex,
.oif = oldflp->oif };标签：linux route policy routing fib 负载均衡
原文地址：http://blog.csdn.net/henzox/article/details/43566787
