Proxy Auto-Configuration (PAC) file

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代理自动配置(PAC)文件是一个 JavaScript 脚本,其核心是一个 JavaScript 函数,用来决定网页浏览请求(HTTP、HTTPS,和 FTP)应当直连目标地址,还是被转发给一个网页代理服务器并通过代理连接。PAC 文件中的核心 JavaScript 函数通常是这样定义的:

function FindProxyForURL(url, host){
    // ...
}        

ret = FindProxyForURL(url, host);

函数语法

function FindProxyForURL(url, host)

参数

url
要访问的 URL。类似 https:// 这样的 URL 中的路径和查询组件已被去除。在 Chrome 浏览器中, 你可以通过设置 PacHttpsUrlStrippingEnabledfalse 来禁止这种行为;在Firefox浏览器中对应的选项是network.proxy.autoconfig_url.include_path
host
The hostname extracted from the URL. This is only for convenience; it is the same string as between :// and the first : or / after that. The port number is not included in this parameter. It can be extracted from the URL when necessary.

Description

Returns a string describing the configuration. The format of this string is defined in return value format below.

Return value format

  • The JavaScript function returns a single string
  • If the string is null, no proxies should be used
  • The string can contain any number of the following building blocks, separated by a semicolon:
DIRECT
Connections should be made directly, without any proxies
PROXY host:port
The specified proxy should be used
SOCKS host:port
The specified SOCKS server should be used

Recent versions of Firefox support as well:

HTTP host:port
The specified proxy should be used
HTTPS host:port
The specified HTTPS proxy should be used
SOCKS4 host:port
SOCKS5 host:port
The specified SOCKS server (with the specified SOCK version) should be used

If there are multiple semicolon-separated settings, the left-most setting will be used, until Firefox fails to establish the connection to the proxy. In that case, the next value will be used, etc.

The browser will automatically retry a previously unresponsive proxy after 30 minutes. Additional attempts will continue beginning at one hour, always adding 30 minutes to the elapsed time between attempts.

If all proxies are down, and there was no DIRECT option specified, the browser will ask if proxies should be temporarily ignored, and direct connections attempted. After 20 minutes, the browser will ask if proxies should be retried, asking again after an additional 40 minutes. Queries will continue, always adding 20 minutes to the elapsed time between queries.

例子

PROXY w3proxy.netscape.com:8080; PROXY mozilla.netscape.com:8081
主代理是 w3proxy:8080;如果它出现故障,则使用 mozilla:8081 直到主代理恢复。
PROXY w3proxy.netscape.com:8080; PROXY mozilla.netscape.com:8081; DIRECT
Same as above, but if both proxies go down, automatically start making direct connections. (In the first example above, Netscape will ask user confirmation about making direct connections; in this case, there is no user intervention.)
PROXY w3proxy.netscape.com:8080; SOCKS socks:1080
如果主代理出现问题,则尝试使用 SOCKS 来链接。

The auto-config file should be saved to a file with a .pac filename extension:

proxy.pac

其 MIME 类型应被设置为:

application/x-ns-proxy-autoconfig

Next, you should configure your server to map the .pac filename extension to the MIME type.

Notes:

  • The JavaScript function should always be saved to a file by itself and not be embedded in HTML.
  • The examples at the end of this document are complete. There is no additional syntax needed to save it into a file and use it. (Of course, the JavaScripts must be edited to reflect your site's domain name and/or subnets.)

Predefined functions and environment

These functions can be used in building the PAC file:

Note: pactester (part of the pacparser package) was used to test the following syntax examples.

  • The PAC file is named proxy.pac
  • Command line: pactester -p ~/pacparser-master/tests/proxy.pac -u http://www.mozilla.org
    • This command passes the host parameter www.mozilla.org and the url parameter http://www.mozilla.org.

isPlainHostName()

语法

isPlainHostName(host)

参数

host
The hostname from the URL (excluding port number).

Description

True if and only if there is no domain name in the hostname (no dots).

例子

function FindProxyForURL(url, host) {
  if (!isPlainHostName(host))
    return host;
}

//returns "www.mozilla.org"
function FindProxyForURL(url, host) {
  if (isPlainHostName("www"))
    return "isPlainHostName is true";
  return "isPlainHostName is false";
}

//returns "isPlainHostName is true"

dnsDomainIs()

语法

dnsDomainIs(host, domain)

参数

host
Is the hostname from the URL.
domain
Is the domain name to test the hostname against.

Description

Returns true if and only if the domain of hostname matches.

例子

function FindProxyForURL(url, host) {
  if (dnsDomainIs("www.mozilla.org", ".mozilla.org"))
    return "dnsDomainIs is true";
  return "dnsDomainIs is false";
}

//returns "dnsDomainIs is true"
function FindProxyForURL(url, host) {
  if (dnsDomainIs("www", ".mozilla.org"))
    return "dnsDomainIs is true";
  return "dnsDomainIs is false";
}

//returns "dnsDomainIs is false"

localHostOrDomainIs()

语法

localHostOrDomainIs(host, hostdom)

参数

host
The hostname from the URL.
hostdom
Fully qualified hostname to match against.

Description

Is true if the hostname matches exactly the specified hostname, or if there is no domain name part in the hostname, but the unqualified hostname matches.

例子

function FindProxyForURL(url, host) {
  if (localHostOrDomainIs("www.mozilla.org", "www.mozilla.org"))
    return "localHostOrDomainIs is true (exact match)";
  return "localHostOrDomainIs is false";
}

//returns "localHostOrDomainIs is true (exact match)"
function FindProxyForURL(url, host) {
  if (localHostOrDomainIs("www", "www.mozilla.org"))
    return "localHostOrDomainIs is true (hostname match, domain not specified))";
  return "localHostOrDomainIs is false";
}

//returns "localHostOrDomainIs is true (hostname match, domain not specified))"
function FindProxyForURL(url, host) {
  if (localHostOrDomainIs("www.google.com", "www.mozilla.org"))
    return "localHostOrDomainIs is true";
  return "localHostOrDomainIs is false (domain name mismatch)";
} 

// returns "localHostOrDomainIs is false (domain name mismatch)"
function FindProxyForURL(url, host) {
  if (localHostOrDomainIs("home.mozilla.org", "www.mozilla.org"))
    return "localHostOrDomainIs is true";
  return "localHostOrDomainIs is false (domain name mismatch)"; 
}

// returns "localHostOrDomainIs is false (hostname mismatch)"

isResolvable()

语法

isResolvable(host)

参数

host
is the hostname from the URL.

Tries to resolve the hostname. Returns true if succeeds.

Examples:

function FindProxyForURL(url, host) {
  if (isResolvable("www.mozilla.org"))
    return "isResolvable is true";
  return "isResolvable is false";
}

// returns "isResolvable is true"

isInNet()

语法

isInNet(host, pattern, mask)

参数

host
a DNS hostname, or IP address. If a hostname is passed, it will be resolved into an IP address by this function.
pattern
an IP address pattern in the dot-separated format.
mask
mask for the IP address pattern informing which parts of the IP address should be matched against. 0 means ignore, 255 means match.

True if and only if the IP address of the host matches the specified IP address pattern.

Pattern and mask specification is done the same way as for SOCKS configuration.

例子:

function FindProxyForURL(url, host) {
// put in the address returned by dnsResolve (see next example)
  if (isInNet(host, "63.245.213.24", "255.255.255.255"))
    return "isInNet is true";
  return "isInNet is false";
}

// returns "isInNet is true"

dnsResolve()

dnsResolve(host)

参数

host
要解析的主机名。

将给定的 DNS 主机名解析为 IP 地址并返回为标准格式的 IP 地址字符串。

例子

function FindProxyForURL(url, host) {
  return dnsResolve("www.mozilla.org");
} 

//returns the string "104.16.41.2"

convert_addr()

语法

convert_addr(ipaddr)

参数

ipaddr
Any dotted address such as an IP address or mask.

Concatenates the four dot-separated bytes into one 4-byte word and converts it to decimal.

例子

function FindProxyForURL(url, host) {
  return convert_addr("104.16.41.2");
} 

//returns the decimal number 1745889538

myIpAddress()

语法

myIpAddress()

参数

(none)

返回当前 Firefox 所在设备的 IP 地址并返回为标准格式的 IP 地址字符串。

myIpAddress() returns the same IP address as the server address returned by nslookup localhost on a Linux machine. It does not return the public IP address.

例子

function FindProxyForURL(url, host) {
  return myIpAddress();
} 

//returns the string "127.0.1.1" if you were running Firefox on that localhost

dnsDomainLevels()

语法

dnsDomainLevels(host)

参数

host
is the hostname from the URL.

Returns the number (integer) of DNS domain levels (number of dots) in the hostname.

例子:

function FindProxyForURL(url, host) {
  return dnsDomainLevels("www");
}

//returns 0
function FindProxyForURL(url, host) {
  return dnsDomainLevels("mozilla.org");
}

//returns 1
function FindProxyForURL(url, host) {
  return dnsDomainLevels("www.mozilla.org");
}

//returns 2

shExpMatch()

语法

shExpMatch(str, shexp)

参数

str
is any string to compare (e.g. the URL, or the hostname).
shexp
is a shell expression to compare against.

Returns true if the string matches the specified shell expression.

Currently, the patterns are shell expressions, not regular expressions.

例子

function FindProxyForURL(url, host) {
  return shExpMatch("http://home.netscape.com/people/ari/index.html", "*/ari/*");
}

//returns true
function FindProxyForURL(url, host) {
  return shExpMatch("http://home.netscape.com/people/montulli/index.html", "*/ari/*");
}

//returns false

weekdayRange()

语法

weekdayRange(wd1, wd2, gmt)

Note: (Before Firefox 49) wd1 must be less than wd2 if you want the function to evaluate these parameters as a range. See the warning below.

参数

wd1 and wd2
One of the ordered weekday strings:
"SUN"|"MON"|"TUE"|"WED"|"THU"|"FRI"|"SAT"
gmt
Is either the string "GMT" or is left out.

Only the first parameter is mandatory. Either the second, the third, or both may be left out.

If only one parameter is present, the function returns a value of true on the weekday that the parameter represents. If the string "GMT" is specified as a second parameter, times are taken to be in GMT. Otherwise, they are assumed to be in the local timezone.

If both wd1 and wd1 are defined, the condition is true if the current weekday is in between those two ordered weekdays. Bounds are inclusive, but the bounds are ordered. If the "GMT" parameter is specified, times are taken to be in GMT. Otherwise, the local timezone is used.

The order of the days matter; Before Firefox 49, weekdayRange("SUN", "SAT") will always evaluate to true. Now weekdayRange("WED", "SUN") will only evaluate true if the current day is Wednesday or Sunday.

例子

function FindProxyForURL(url, host) {
  return weekdayRange("MON", "FRI");
}

//returns true Monday through Friday (local timezone)
function FindProxyForURL(url, host) {
  return weekdayRange("MON", "FRI", "GMT");
}

//returns true Monday through Friday (GMT timezone)
function FindProxyForURL(url, host) {
  return weekdayRange("SAT");
}

//returns true true on Saturdays local time
function FindProxyForURL(url, host) {
  return weekdayRange("SAT", "GMT");
}

//returns true on Saturdays GMT time
function FindProxyForURL(url, host) {
  return weekdayRange("FRI", "MON");
}

//returns true Friday and Monday only (note, order does matter!)

dateRange()

语法

dateRange(<day1>, <month1>, <year1>, <day2>, <month2>, <year2>, <gmt>)

Note: (Before Firefox 49) day1 must be less than day2, month1 must be less than month2, and year1 must be less than year2 if you want the function to evaluate these parameters as a range. See the warning below.

参数

day
Is the ordered day of the month between 1 and 31 (as an integer).
1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31
month
Is one of the ordered month strings below.
"JAN"|"FEB"|"MAR"|"APR"|"MAY"|"JUN"|"JUL"|"AUG"|"SEP"|"OCT"|"NOV"|"DEC"
year
Is the ordered full year integer number. For example, 2016 (not 16).
gmt
Is either the string "GMT", which makes time comparison occur in GMT timezone, or is left out. If left unspecified, times are taken to be in the local timezone.

If only a single value is specified (from each category: day, month, year), the function returns a true value only on days that match that specification. If both values are specified, the result is true between those times, including bounds, but the bounds are ordered.

The order of the days, months, and years matter; Before Firefox 49, dateRange("JAN", "DEC") will always evaluate to true. Now dateRange("DEC", "JAN") will only evaluate true if the current month is December or January.

例子

function FindProxyForURL(url, host) {
  return dateRange(1);
}

//returns true on the first day of each month, local timezone
function FindProxyForURL(url, host) {
  return dateRange(1, "GMT")
}

//returns true on the first day of each month, GMT timezone
function FindProxyForURL(url, host) {
  return dateRange(1, 15);
}

//returns true on the first half of each month
function FindProxyForURL(url, host) {
  return dateRange(24, "DEC");
}

//returns true on 24th of December each year
function FindProxyForURL(url, host) {
  return dateRange("JAN", "MAR");
}

//returns true on the first quarter of the year
function FindProxyForURL(url, host) {
  return dateRange(1, "JUN", 15, "AUG");
}

//returns true from June 1st until August 15th, each year (including June 1st and August 15th)
function FindProxyForURL(url, host) {
  return dateRange(1, "JUN", 1995, 15, "AUG", 1995);
}

//returns true from June 1st, 1995, until August 15th, same year
function FindProxyForURL(url, host) {
  return dateRange("OCT", 1995, "MAR", 1996);
}

//returns true from October 1995 until March 1996 (including the entire month of October 1995 and March 1996)
function FindProxyForURL(url, host) {
  return dateRange(1995);
}

//returns true during the entire year of 1995
function FindProxyForURL(url, host) {
  return dateRange(1995, 1997);
}

//returns true from beginning of year 1995 until the end of year 1997

timeRange()

语法

timeRange(<hour1>, <min1>, <sec1>, <hour2>, <min2>, <sec2>, <gmt>)

Note: (Before Firefox 49) the category hour1, min1, sec1 must be less than the category hour2, min2, sec2 if you want the function to evaluate these parameters as a range. See the warning below.

参数

hour
小时,区间为 0 到 23。(0 是午夜 0 点,1 是上午 1 点,11 是正午 12 点,23 是下午 11 点。)
min
分钟,区间为 0 到 59。
sec
 秒,区间为 0 到 59。
gmt
可以指定为字符串 "GMT" 代表使用 GMT 时区,或不指定(原文:not specified),即代表使用浏览器获取到的平台本地时间。

If only a single value is specified (from each category: hour, minute, second), the function returns a true value only at times that match that specification. If both values are specified, the result is true between those times, including bounds, but the bounds are ordered.

The order of the hour, minute, second matter; Before Firefox 49, timeRange(0, 23) will always evaluate to true. Now timeRange(23, 0) will only evaluate true if the current hour is 23:00 or midnight.

例子

function FindProxyForURL(url, host) {
  return timerange(12);
}

//returns true from noon to 1pm
function FindProxyForURL(url, host) {
  return timerange(12, 13);
}

//returns true from noon to 1pm
function FindProxyForURL(url, host) {
  return timerange(12, "GMT");
}

//true from noon to 1pm, in GMT timezone
function FindProxyForURL(url, host) {
  return timerange(9, 17);
}

//returns true from 9am to 5pm
function FindProxyForURL(url, host) {
  return timerange(8, 30, 17, 00);
}

//returns true from 8:30am to 5:00pm
function FindProxyForURL(url, host) {
  return timerange(0, 0, 0, 0, 0, 30);
}

//returns true between midnight and 30 seconds past midnight

例 1

对除本地主机以外的所有连接使用代理

Note: Since all of the examples that follow are very specific, they have not been tested.

All hosts which aren't fully qualified, or the ones that are in local domain, will be connected to directly. Everything else will go through w3proxy:8080. If the proxy goes down, connections become direct automatically:

function FindProxyForURL(url, host) {
  if (isPlainHostName(host) || dnsDomainIs(host, ".mozilla.org")) {
    return "DIRECT";
  } else {
    return "PROXY w3proxy.mozilla.org:8080; DIRECT";
  }
}

Note: This is the simplest and most efficient autoconfig file for cases where there's only one proxy.

例 2

和例 1 一样,但是 use proxy for local servers which are outside the firewall

If there are hosts (such as the main Web server) that belong to the local domain but are outside the firewall and are only reachable through the proxy server, those exceptions can be handled using the localHostOrDomainIs() function:

function FindProxyForURL(url, host) {
  if ((isPlainHostName(host) ||
      dnsDomainIs(host, ".mozilla.org")) &&
      !localHostOrDomainIs(host, "www.mozilla.org") &&
      !localHostOrDoaminIs(host, "merchant.mozilla.org")) {
        return "DIRECT";
  } else {
    return "PROXY w3proxy.mozilla.org:8080; DIRECT";
  }
}

The above example will use the proxy for everything except local hosts in the mozilla.org domain, with the further exception that hosts www.mozilla.org and merchant.mozilla.org will go through the proxy.

Note the order of the above exceptions for efficiency: localHostOrDomainIs() functions only get executed for URLs that are in local domain, not for every URL. Be careful to note the parentheses around the or expression before the and expression to achieve the above-mentioned efficient behaviour.

例 3

如果无法解析域名,则使用代理

This example will work in an environment where the internal DNS server is set up so that it can only resolve internal host names, and the goal is to use a proxy only for hosts that aren't resolvable:

function FindProxyForURL(url, host) {
  if (isResolvable(host))
    return "DIRECT";
  else
    return "PROXY proxy.mydomain.com:8080";
}

The above requires consulting the DNS every time; it can be grouped intelligently with other rules so that DNS is consulted only if other rules do not yield a result:

function FindProxyForURL(url, host) {
  if (isPlainHostName(host) ||
      dnsDomainIs(host, ".mydomain.com") ||
      isResolvable(host)) {
    return "DIRECT";
  } else {
    return "PROXY proxy.mydomain.com:8080";
  }
}

例 4

基于网域(Subnet)的选择方案

In this example all of the hosts in a given subnet are connected-to directly, others are connected through the proxy:

function FindProxyForURL(url, host) {
  if (isInNet(host, "198.95.0.0", "255.255.0.0"))
    return "DIRECT";
  else
    return "PROXY proxy.mydomain.com:8080";
}

Again, use of the DNS server in the above can be minimized by adding redundant rules in the beginning:

function FindProxyForURL(url, host) {
  if (isPlainHostName(host) ||
      dnsDomainIs(host, ".mydomain.com") ||
      isInNet(host, "198.95.0.0", "255.255.0.0")) {
    return "DIRECT";
  } else {
    return "PROXY proxy.mydomain.com:8080";
  }
}

例 5

负载均衡 / 基于 URL 模式(pattern)的路由规划

This example is more sophisticated. There are four (4) proxy servers; one of them is a hot stand-by for all of the other ones, so if any of the remaining three goes down the fourth one will take over. Furthermore, the three remaining proxy servers share the load based on URL patterns, which makes their caching more effective (there is only one copy of any document on the three servers -- as opposed to one copy on each of them). The load is distributed like this:

Proxy 用途
#1 .com 域名
#2 .edu 域名
#3 所有其他域名
#4 备用(原文:hot stand-by,活跃备用、热备用)

All local accesses are desired to be direct. All proxy servers run on the port 8080 (they don't need to). Note how strings can be concatenated with the + operator in JavaScript.

function FindProxyForURL(url, host) {
  if (isPlainHostName(host) || dnsDomainIs(host, ".mydomain.com"))
      return "DIRECT";
  else if (shExpMatch(host, "*.com"))
      return "PROXY proxy1.mydomain.com:8080; " +
             "PROXY proxy4.mydomain.com:8080";
  else if (shExpMatch(host, "*.edu"))
      return "PROXY proxy2.mydomain.com:8080; " +
             "PROXY proxy4.mydomain.com:8080";
  else
      return "PROXY proxy3.mydomain.com:8080; " +
             "PROXY proxy4.mydomain.com:8080";
}

例 6

为特定协议设置代理

Most of the standard JavaScript functionality is available for use in the FindProxyForURL() function. As an example, to set different proxies based on the protocol the substring() function can be used:

function FindProxyForURL(url, host) {
  if (url.substring(0, 5) == "http:") {
    return "PROXY http-proxy.mydomain.com:8080";
  }
  else if (url.substring(0, 4) == "ftp:") {
    return "PROXY ftp-proxy.mydomain.com:8080";
  }
  else if (url.substring(0, 7) == "gopher:") {
    return "PROXY gopher-proxy.mydomain.com:8080";
  }
  else if (url.substring(0, 6) == "https:" ||
           url.substring(0, 6) == "snews:") {
    return "PROXY security-proxy.mydomain.com:8080";
  } else {
    return "DIRECT";
  }
}

Note: The same can be accomplished using the shExpMatch() function described earlier.

For example:

// ...
if (shExpMatch(url, "http:*")) {
  return "PROXY http-proxy.mydomain.com:8080";
}
// ...

The autoconfig file can be output by a CGI script. This is useful, for example, when making the autoconfig file act differently based on the client IP address (the REMOTE_ADDR environment variable in CGI).

Use of isInNet(), isResolvable() and dnsResolve() functions should be carefully considered, as they require the DNS server to be consulted. All the other autoconfig-related functions are mere string-matching functions that don't require the use of a DNS server. If a proxy is used, the proxy will perform its DNS lookup which would double the impact on the DNS server. Most of the time these functions are not necessary to achieve the desired result.

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