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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package proxy

import (
        "net"
        "strings"
)

// A PerHost directs connections to a default Dailer unless the hostname
// requested matches one of a number of exceptions.
type PerHost struct {
        def, bypass Dialer

        bypassNetworks []*net.IPNet
        bypassIPs      []net.IP
        bypassZones    []string
        bypassHosts    []string
}

// NewPerHost returns a PerHost Dialer that directs connections to either
// defaultDialer or bypass, depending on whether the connection matches one of
// the configured rules.
func NewPerHost(defaultDialer, bypass Dialer) *PerHost {
        return &PerHost{
                def:    defaultDialer,
                bypass: bypass,
        }
}

// Dial connects to the address addr on the network net through either
// defaultDialer or bypass.
func (p *PerHost) Dial(network, addr string) (c net.Conn, err error) {
        host, _, err := net.SplitHostPort(addr)
        if err != nil {
                return nil, err
        }

        return p.dialerForRequest(host).Dial(network, addr)
}

func (p *PerHost) dialerForRequest(host string) Dialer {
        if ip := net.ParseIP(host); ip != nil {
                for _, net := range p.bypassNetworks {
                        if net.Contains(ip) {
                                return p.bypass
                        }
                }
                for _, bypassIP := range p.bypassIPs {
                        if bypassIP.Equal(ip) {
                                return p.bypass
                        }
                }
                return p.def
        }

        for _, zone := range p.bypassZones {
                if strings.HasSuffix(host, zone) {
                        return p.bypass
                }
                if host == zone[1:] {
                        // For a zone "example.com", we match "example.com"
                        // too.
                        return p.bypass
                }
        }
        for _, bypassHost := range p.bypassHosts {
                if bypassHost == host {
                        return p.bypass
                }
        }
        return p.def
}

// AddFromString parses a string that contains comma-separated values
// specifing hosts that should use the bypass proxy. Each value is either an
// IP address, a CIDR range, a zone (*.example.com) or a hostname
// (localhost). A best effort is made to parse the string and errors are
// ignored.
func (p *PerHost) AddFromString(s string) {
        hosts := strings.Split(s, ",")
        for _, host := range hosts {
                host = strings.TrimSpace(host)
                if len(host) == 0 {
                        continue
                }
                if strings.Contains(host, "/") {
                        // We assume that it's a CIDR address like 127.0.0.0/8
                        if _, net, err := net.ParseCIDR(host); err == nil {
                                p.AddNetwork(net)
                        }
                        continue
                }
                if ip := net.ParseIP(host); ip != nil {
                        p.AddIP(ip)
                        continue
                }
                if strings.HasPrefix(host, "*.") {
                        p.AddZone(host[1:])
                        continue
                }
                p.AddHost(host)
        }
}

// AddIP specifies an IP address that will use the bypass proxy. Note that
// this will only take effect if a literal IP address is dialed. A connection
// to a named host will never match an IP.
func (p *PerHost) AddIP(ip net.IP) {
        p.bypassIPs = append(p.bypassIPs, ip)
}

// AddIP specifies an IP range that will use the bypass proxy. Note that this
// will only take effect if a literal IP address is dialed. A connection to a
// named host will never match.
func (p *PerHost) AddNetwork(net *net.IPNet) {
        p.bypassNetworks = append(p.bypassNetworks, net)
}

// AddZone specifies a DNS suffix that will use the bypass proxy. A zone of
// "example.com" matches "example.com" and all of its subdomains.
func (p *PerHost) AddZone(zone string) {
        if strings.HasSuffix(zone, ".") {
                zone = zone[:len(zone)-1]
        }
        if !strings.HasPrefix(zone, ".") {
                zone = "." + zone
        }
        p.bypassZones = append(p.bypassZones, zone)
}

// AddHost specifies a hostname that will use the bypass proxy.
func (p *PerHost) AddHost(host string) {
        if strings.HasSuffix(host, ".") {
                host = host[:len(host)-1]
        }
        p.bypassHosts = append(p.bypassHosts, host)
}