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pool.go
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pool.go
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package fakeip
import (
"errors"
"net"
"sync"
"github.com/ClashrAuto/Clashr/common/cache"
)
// Pool is a implementation about fake ip generator without storage
type Pool struct {
max uint32
min uint32
gateway uint32
offset uint32
mux *sync.Mutex
cache *cache.LruCache
}
// Lookup return a fake ip with host
func (p *Pool) Lookup(host string) net.IP {
p.mux.Lock()
defer p.mux.Unlock()
if elm, exist := p.cache.Get(host); exist {
ip := elm.(net.IP)
// ensure ip --> host on head of linked list
n := ipToUint(ip.To4())
offset := n - p.min + 1
p.cache.Get(offset)
return ip
}
ip := p.get(host)
p.cache.Set(host, ip)
return ip
}
// LookBack return host with the fake ip
func (p *Pool) LookBack(ip net.IP) (string, bool) {
p.mux.Lock()
defer p.mux.Unlock()
if ip = ip.To4(); ip == nil {
return "", false
}
n := ipToUint(ip.To4())
offset := n - p.min + 1
if elm, exist := p.cache.Get(offset); exist {
host := elm.(string)
// ensure host --> ip on head of linked list
p.cache.Get(host)
return host, true
}
return "", false
}
// Gateway return gateway ip
func (p *Pool) Gateway() net.IP {
return uintToIP(p.gateway)
}
func (p *Pool) get(host string) net.IP {
current := p.offset
for {
p.offset = (p.offset + 1) % (p.max - p.min)
// Avoid infinite loops
if p.offset == current {
break
}
if !p.cache.Exist(p.offset) {
break
}
}
ip := uintToIP(p.min + p.offset - 1)
p.cache.Set(p.offset, host)
return ip
}
func ipToUint(ip net.IP) uint32 {
v := uint32(ip[0]) << 24
v += uint32(ip[1]) << 16
v += uint32(ip[2]) << 8
v += uint32(ip[3])
return v
}
func uintToIP(v uint32) net.IP {
return net.IPv4(byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
}
// New return Pool instance
func New(ipnet *net.IPNet, size int) (*Pool, error) {
min := ipToUint(ipnet.IP) + 2
ones, bits := ipnet.Mask.Size()
total := 1<<uint(bits-ones) - 2
if total <= 0 {
return nil, errors.New("ipnet don't have valid ip")
}
max := min + uint32(total) - 1
return &Pool{
min: min,
max: max,
gateway: min - 1,
mux: &sync.Mutex{},
cache: cache.NewLRUCache(cache.WithSize(size * 2)),
}, nil
}