302 Backend

We currently have two 302 backend: 302-js and 302-go

302-js is deployed at https://mirrors.mirrorz.org or https://m.mirrorz.org in short. You may visit https://m.mirrorz.org/archlinux/. Note that only /${cname} from the frontend/monitor are valid pathnames. Currently this is deployed using Cloudflare Workers. Credentials are configured as environment variables.

302-go is deployed at https://mirrors.cernet.edu.cn and https://mirrors.cngi.edu.cn. They only redirect to educational mirror sites.

Currently redirecting is decided from information collected by the monitor. Two policies are discussed and implemented.

302-js: Newest

In 302-js, users are just redirected to a mirror site with the most up-to-date info; however, this may not offer enough bandwidth.

302-go: Nearest

In 302-go, users are redirected to a mirror site based on their IP, ISP, geolocation etc. Detailed concern is discussed below.

design concern

• user
  • AS: Interconnect within one AS is usually better than across AS
  • IP: From the perspective of CERNET/CERNET2 and universities, mirror sites can fine-tune based on IP range
  • GEO: As this project is limited to .edu.cn mirror sites, geographical proximity does not necessarily imply fast network connection.
  • advanced users may manually specify a preference list, e.g. tuna-ustccampus.mirrors.edu.cn
• mirror site
  • endpoint: multiple upstreams (CERNET, CMNET, etc), ipv4/ipv6 only endpoint, and default endpoint
  • range: users inside this range should better be redirected to this mirror site
  • public: private mirror has limited access range, IP/ASN not in its range should not be redirected there
• operator (not implemented)
  • load balance
  • speed testing from multiple AS
  • manually adjust redirection (enable/disable, probability, etc)

mirrorz.d.json

Any mirror site participating in 302 backend should provide this file. Mirror site uses this file to announce their capabilities and restrictions. It is worth noting this file has no conflict with mirrorz.json so a mirror site may integrate them together.

{
  "extension": "D",
  "endpoints": [
    {
      "label": "ustc",
      "public": true,
      "resolve": "mirrors.ustc.edu.cn",
      "filter": [ "V4", "V6", "SSL", "NOSSL" ],
      "range": []
    },
    {
      "label": "ustc6",
      "public": true,
      "resolve": "ipv6.mirrors.ustc.edu.cn",
      "filter": [ "V6", "SSL", "NOSSL" ],
      "range": []
    },
    {
      "label": "ustcchinanet",
      "public": true,
      "resolve": "chinanet.mirrors.ustc.edu.cn",
      "filter": [ "V4", "SSL", "NOSSL" ],
      "range": [
        "AS4134",
        "AS4809",
        "REGION:AH",
        "ISP:CHINANET"
      ]
    },
    {
      "label": "ustccampus",
      "public": false,
      "resolve": "10.0.0.1:8080/proxy",
      "filter": [ "V4", "NOSSL" ],
      "range": [
        "202.0.0.0/24",
        "2001:da8::/32"
      ]
    }
  ],
  "site": { "the same as mirrorz.json/site" },
  "mirrors": [ "the same as mirrorz.json/mirrors" ]
}

Spec

• An endpoint in endpoints
  • label: a unique identifier for this endpoint
  • resolve: a domain name or IP address. This is directly concatenated in the final URL so a subpath may also be provided (e.g. linux.xidian.edu.cn/mirrors and 10.0.0.1:8080/proxy).
    • It should not end with slash / as the request path /archlinux/iso will be directly concatenated to it.
  • public: the endpoint can be reached outside of its range. Usually false for campus-only mirrors.
  • filter: Each endpoint has many capabilities
    • SSL: HTTPS available
    • NOSSL: HTTP available
    • V4: IPv4 available (A record)
    • V6: IPv6 available (AAAA record)
  • range: when public, the endpoint prefers these ranges, other user may still use this endpoint; otherwise it only serves these CIDRs/ISPs (Note that GEO is not included)
    • COUNTRY: Must start with COUNTRY, then a colon, then ISO country code. Example: COUNTRY:CN or COUNTRY:US. Defaults to CN.
    • REGION: Must start with REGION, then a colon, then province name (GB/T 2260-2007). Example: REGION:BJ (Beijing) or REGION:SH (Shanghai). Defaults to BJ.
    • ISP: Must start with ISP, then a colon, then ISP name. Example: ISP:CERNET or ISP:CHINANET. Defaults to CERNET. All currently supported values are CERNET, CSTNET, CHINANET, UNICOM and CMCC.
    • ASN (deprecated): Must start with AS. Example: AS4538 and AS13335
    • CIDR: Example: 202.0.0.0/24 or 2001:da8::/32
• site/mirrors
  • This is used by mirrorz-monitor. Defined in mirrorz.json.

Note

On range when multiple endpoints

    {
      "label": "ustc",
      "public": true,
      "resolve": "mirrors.ustc.edu.cn",
      "filter": [ "V4", "V6", "SSL", "NOSSL" ],
      "range": [ " ISP:CMCC should not be included here as we already have a more specified endpoint. " ]
    },
    {
      "label": "ustccmcc",
      "public": true,
      "resolve": "cmcc.mirrors.ustc.edu.cn",
      "filter": [ "V4", "SSL", "NOSSL" ],
      "range": [ "ISP:CMCC" ]
    },

The first endpoint is the default endpoint. If all the endpoints have the same preference, we choose the first one.

Usually, the first endpoint is a generic endpoint (e.g. mirrors.xx.edu.cn). To make a preference difference, if further endpoint (e.g. mirrors4 or cmcc.mirrors) covers a more specfic range, the generic endpoint should not declare these ranges and the redirector should redirect the user to the more specific endpoint.

For example, if mirrors4 contains some CIDR in its range, e.g. 166.111.0.0, then we prefer mirrors4 over mirrors when there are requests from that CIDR.

Another example is that for CMCC users, we prefer cmcc.mirrors over mirrors.

If a user does not match any range or match exactly the same in mirrors and mirrors4, then we prefer mirrors, i.e. the default one.

On range when private endpoint

    {
      "label": "ustccampus",
      "public": false,
      "resolve": "10.0.0.1:8080",
      "filter": [ "V4", "NOSSL" ],
      "range": [ "202.0.0.0/24" ]
    },

Campus-only mirror site may use a private IP but declare a public range. For example, suppose USTC has a private IP range of 10.0.0.0/8, USTC mirror is located at 10.0.0.1:8080, and when one user inside USTC accesses mirrors.edu.cn, its IP is NATed into 202.0.0.0/24, then mirrors.edu.cn can resolve the request into ustccampus endpoint.

TODO

Advanced user can explicitly annouce their capability in their request like http://ssl.mirrors.edu.cn, then we must redirect it to a https site. Some interesting usage like https://sjtug-nossl-wsyu-ssl-ustc-tuna.mirrors.edu.cn, namely no preference (http and https both ok) for sjtug, use http endpoint for wsyu, and force ssl for ustc and tuna.

Advanced user can explicitly annouce their capability/preference in their request like 4.mirrors.edu.cn, then we must redirect it to a IPv4 only site. Those with resolve: "mirrors.example.com", filter: ["V4", "V6"] is not acceptable for 4.mirrors.edu.cn as the user client may resolve mirrors.example.com with AAAA first, but its IPv6 is broken (common case for most IPv6 enabled edge devices), we must return something like 4.mirrors.example.com. So for each mirror site, it should add some IPv4 only and IPv6 only endpoint like tuna4 and ustc4 for this special case.

Syntax sugar: By default we assume each endpoint has both http and https, hence resolve: "mirrors.example.com", filter:["NOSSL", "SSL"] is equivalent to resolve: "mirrors.example.com", filter:[]. If it has only one ability, like resolve: "mirrors.example.com", filter:["NOSSL"] then it can be rewritten into resolve:"http://mirrors.example.com", filter:[]. And to be more simple, resolve:"http://10.10.10.10", filter: [] can be rewritten into resolve: "10.10.10.10", filter: [] as IP endpoint usually does not have ssl enabled (if enabled, then explicitly use resolve:"101.6.6.6", filter: ["NOSSL", "SSL"]).

Syntar sugar: By default we assume each endpoint has both A and AAAA, hence resolve: "mirrors.example.com", filter:["V4", "V6"] is equivalent to resolve: "mirrors.example.com", filter:[]. To be more simple, resolve:"10.10.10.10", filter: [ "V4" ] can be rewritten into resolve: "10.10.10.10", filter: []. Note that resolve: "10.10.10.10", filter: ["V6"] is invalid and the "V6" filter will be ignored.

Partial capability: One endpoint with filter: [ "NOSSL", "SSL", "SSL:centos" ], namely force SSL for one cname called centos. If one user requests with http://mirrors.edu.cn/centos, this endpoint would not be redirected.