global var and structure:
static DEFINE_PER_NET(struct hlist_head *, xfrm_state_byspi);
static struct xfrm_policy_afinfo *xfrm_policy_afinfo[NPROTO];
xfrm_policy_afinfo 定义一个大的数组，每一个元素对应一个地址族，如ipv4（AF_INET），ipv6(AF_INET6).
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| struct xfrm_policy_afinfo {
unsigned short family;
rwlock_t lock;
struct xfrm_type_map *type_map;
struct dst_ops *dst_ops;
void (*garbage_collect)(net_t net);
int (*dst_lookup)(struct xfrm_dst **dst, struct flowi *fl);
int (*get_saddr)(net_t net, xfrm_address_t *saddr, xfrm_address_t *daddr);
struct dst_entry *(*find_bundle)(struct flowi *fl, struct xfrm_policy *policy);
int (*bundle_create)(struct xfrm_policy *policy,
struct xfrm_state **xfrm,
int nx,
struct flowi *fl,
struct dst_entry **dst_p);
void (*decode_session)(struct sk_buff *skb,
struct flowi *fl);
};
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在struct xfrm_policy_afinfo中有一个元素
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| struct xfrm_type_map *type_map;
struct xfrm_type_map {
rwlock_t lock;
struct xfrm_type *map[256];
};
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map 也是一个指针数组，其每个元素对应一个应用层的协议如 ESP(IPPROTO_ESP), AH, UDP(IPPROTO_UDP),TCP等。
两个相关的注册函数：
关于xfrm_policy_afinfo
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| int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)；
static void __init xfrm4_policy_init(void)
{
xfrm_policy_register_afinfo(&xfrm4_policy_afinfo);
}
static void __init xfrm6_policy_init(void)
{
xfrm_policy_register_afinfo(&xfrm6_policy_afinfo);
}
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| int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
{
int err = 0;
if (unlikely(afinfo == NULL))
return -EINVAL;
if (unlikely(afinfo->family >= NPROTO))
return -EAFNOSUPPORT;
write_lock(&xfrm_policy_afinfo_lock);
if (unlikely(xfrm_policy_afinfo[afinfo->family] != NULL))
err = -ENOBUFS;
else {
struct dst_ops *dst_ops = afinfo->dst_ops;
if (likely(dst_ops->kmem_cachep == NULL))
dst_ops->kmem_cachep = xfrm_dst_cache;
if (likely(dst_ops->check == NULL))
dst_ops->check = xfrm_dst_check;
if (likely(dst_ops->negative_advice == NULL))
dst_ops->negative_advice = xfrm_negative_advice;
if (likely(dst_ops->link_failure == NULL))
dst_ops->link_failure = xfrm_link_failure;
if (likely(afinfo->garbage_collect == NULL))
afinfo->garbage_collect = __xfrm_garbage_collect;
xfrm_policy_afinfo[afinfo->family] = afinfo;
}
write_unlock(&xfrm_policy_afinfo_lock);
return err;
}
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| int xfrm_register_type(struct xfrm_type *type, unsigned short family)
{
struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
struct xfrm_type_map *typemap;
int err = 0;
if (unlikely(afinfo == NULL))
return -EAFNOSUPPORT;
typemap = afinfo->type_map;
write_lock(&typemap->lock);
if (likely(typemap->map[type->proto] == NULL))
typemap->map[type->proto] = type;
else
err = -EEXIST;
write_unlock(&typemap->lock);
xfrm_policy_put_afinfo(afinfo);
return err;
}
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