draft-ietf-httpbis-proxy-status-01.txt   draft-ietf-httpbis-proxy-status-02.txt 
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track P. Sikora Intended status: Standards Track P. Sikora
Expires: September 2, 2020 Google Expires: February 12, 2021 Google
March 1, 2020 August 11, 2020
The Proxy-Status HTTP Response Header Field The Proxy-Status HTTP Response Header Field
draft-ietf-httpbis-proxy-status-01 draft-ietf-httpbis-proxy-status-02
Abstract Abstract
This document defines the Proxy-Status HTTP header field to convey This document defines the Proxy-Status HTTP field to convey the
the details of intermediary handling of responses, including details of intermediary handling of responses, including generated
generated errors. errors.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ [1]. https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].
Working Group information can be found at https://httpwg.org/ [2]; Working Group information can be found at https://httpwg.org/ [2];
skipping to change at page 1, line 45 skipping to change at page 1, line 45
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 2, 2020. This Internet-Draft will expire on February 12, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. The Proxy-Status HTTP Header Field . . . . . . . . . . . . . 4 2. The Proxy-Status HTTP Field . . . . . . . . . . . . . . . . . 4
2.1. Proxy-Status Parameters . . . . . . . . . . . . . . . . . 5 2.1. Proxy-Status Parameters . . . . . . . . . . . . . . . . . 5
2.1.1. origin . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.1. next-hop . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2. fwd-protocol . . . . . . . . . . . . . . . . . . . . 6 2.1.2. next-protocol . . . . . . . . . . . . . . . . . . . . 5
2.1.3. error . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.3. error . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.4. details . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.4. details . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Proxy Error Types . . . . . . . . . . . . . . . . . . . . 7 2.2. Defining New Proxy-Status Parameters . . . . . . . . . . 7
2.2.1. DNS Timeout . . . . . . . . . . . . . . . . . . . . . 7 2.3. Proxy Error Types . . . . . . . . . . . . . . . . . . . . 8
2.2.2. DNS Error . . . . . . . . . . . . . . . . . . . . . . 7 2.3.1. DNS Timeout . . . . . . . . . . . . . . . . . . . . . 8
2.2.3. Destination Not Found . . . . . . . . . . . . . . . . 7 2.3.2. DNS Error . . . . . . . . . . . . . . . . . . . . . . 8
2.2.4. Destination Unavailable . . . . . . . . . . . . . . . 8 2.3.3. Destination Not Found . . . . . . . . . . . . . . . . 8
2.2.5. Destination IP Prohibited . . . . . . . . . . . . . . 8 2.3.4. Destination Unavailable . . . . . . . . . . . . . . . 9
2.2.6. Destination IP Unroutable . . . . . . . . . . . . . . 8 2.3.5. Destination IP Prohibited . . . . . . . . . . . . . . 9
2.2.7. Connection Refused . . . . . . . . . . . . . . . . . 8 2.3.6. Destination IP Unroutable . . . . . . . . . . . . . . 9
2.2.8. Connection Terminated . . . . . . . . . . . . . . . . 9 2.3.7. Connection Refused . . . . . . . . . . . . . . . . . 9
2.2.9. Connection Timeout . . . . . . . . . . . . . . . . . 9 2.3.8. Connection Terminated . . . . . . . . . . . . . . . . 10
2.2.10. Connection Read Timeout . . . . . . . . . . . . . . . 9 2.3.9. Connection Timeout . . . . . . . . . . . . . . . . . 10
2.2.11. Connection Write Timeout . . . . . . . . . . . . . . 9 2.3.10. Connection Read Timeout . . . . . . . . . . . . . . . 10
2.2.12. Connection Limit Reached . . . . . . . . . . . . . . 10 2.3.11. Connection Write Timeout . . . . . . . . . . . . . . 10
2.2.13. HTTP Incomplete Response . . . . . . . . . . . . . . 10 2.3.12. Connection Limit Reached . . . . . . . . . . . . . . 11
2.2.14. HTTP Protocol Error . . . . . . . . . . . . . . . . . 10 2.3.13. TLS Protocol Error . . . . . . . . . . . . . . . . . 11
2.2.15. HTTP Response Header Block Too Large . . . . . . . . 10 2.3.14. TLS Certificate Error . . . . . . . . . . . . . . . . 11
2.2.16. HTTP Response Header Too Large . . . . . . . . . . . 11 2.3.15. TLS Alert Received . . . . . . . . . . . . . . . . . 11
2.2.17. HTTP Response Body Too Large . . . . . . . . . . . . 11 2.3.16. HTTP Request Error . . . . . . . . . . . . . . . . . 12
2.2.18. HTTP Response Transfer-Coding Error . . . . . . . . . 11 2.3.17. HTTP Request Denied . . . . . . . . . . . . . . . . . 12
2.2.19. HTTP Response Content-Coding Error . . . . . . . . . 12 2.3.18. HTTP Incomplete Response . . . . . . . . . . . . . . 12
2.2.20. HTTP Response Timeout . . . . . . . . . . . . . . . . 12 2.3.19. HTTP Response Header Block Too Large . . . . . . . . 13
2.2.21. TLS Handshake Error . . . . . . . . . . . . . . . . . 12 2.3.20. HTTP Response Header Too Large . . . . . . . . . . . 13
2.2.22. TLS Untrusted Peer Certificate . . . . . . . . . . . 12 2.3.21. HTTP Response Body Too Large . . . . . . . . . . . . 13
2.2.23. TLS Expired Peer Certificate . . . . . . . . . . . . 13 2.3.22. HTTP Response Transfer-Coding Error . . . . . . . . . 14
2.2.24. TLS Unexpected Peer Certificate . . . . . . . . . . . 13 2.3.23. HTTP Response Content-Coding Error . . . . . . . . . 14
2.2.25. TLS Missing Proxy Certificate . . . . . . . . . . . . 13 2.3.24. HTTP Response Timeout . . . . . . . . . . . . . . . . 14
2.2.26. TLS Rejected Proxy Certificate . . . . . . . . . . . 14 2.3.25. HTTP Upgrade Failed . . . . . . . . . . . . . . . . . 14
2.2.27. TLS Error . . . . . . . . . . . . . . . . . . . . . . 14 2.3.26. HTTP Protocol Error . . . . . . . . . . . . . . . . . 15
2.2.28. HTTP Request Error . . . . . . . . . . . . . . . . . 14 2.3.27. Proxy Internal Response . . . . . . . . . . . . . . . 15
2.2.29. HTTP Request Denied . . . . . . . . . . . . . . . . . 15 2.3.28. Proxy Internal Error . . . . . . . . . . . . . . . . 15
2.2.30. HTTP Upgrade Failed . . . . . . . . . . . . . . . . . 15 2.3.29. Proxy Configuration Error . . . . . . . . . . . . . . 15
2.2.31. Proxy Internal Response . . . . . . . . . . . . . . . 15 2.3.30. Proxy Loop Detected . . . . . . . . . . . . . . . . . 16
2.2.32. Proxy Internal Error . . . . . . . . . . . . . . . . 15 2.4. Defining New Proxy Error Types . . . . . . . . . . . . . 16
2.2.33. Proxy Loop Detected . . . . . . . . . . . . . . . . . 16
2.3. Defining New Proxy Error Types . . . . . . . . . . . . . 16
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
4. Security Considerations . . . . . . . . . . . . . . . . . . . 17 4. Security Considerations . . . . . . . . . . . . . . . . . . . 17
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1. Normative References . . . . . . . . . . . . . . . . . . 17 5.1. Normative References . . . . . . . . . . . . . . . . . . 17
5.2. Informative References . . . . . . . . . . . . . . . . . 18 5.2. Informative References . . . . . . . . . . . . . . . . . 18
5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
HTTP intermediaries - including both forward proxies and gateways HTTP intermediaries - including both forward proxies and gateways
(also known as "reverse proxies") - have become an increasingly (also known as "reverse proxies") - have become an increasingly
significant part of HTTP deployments. In particular, reverse proxies significant part of HTTP deployments. In particular, reverse proxies
and Content Delivery Networks (CDNs) form part of the critical and Content Delivery Networks (CDNs) form part of the critical
infrastructure of many Web sites. infrastructure of many Web sites.
Typically, HTTP intermediaries forward requests towards the origin Typically, HTTP intermediaries forward requests towards the origin
server and then forward their responses back to clients. However, if server and then forward their responses back to clients. However, if
an error occurs, the response is generated by the intermediary an error occurs before a response is obtained from upstream, the
itself. response is generated by the intermediary itself.
HTTP accommodates these types of errors with a few status codes; for HTTP accommodates these types of errors with a few status codes; for
example, 502 Bad Gateway and 504 Gateway Timeout. However, example, 502 Bad Gateway and 504 Gateway Timeout. However,
experience has shown that more information is necessary to aid experience has shown that more information is necessary to aid
debugging and communicate what's happened to the client. debugging and communicate what's happened to the client.
Additionally, intermediaries sometimes want to convey additional Additionally, intermediaries sometimes want to convey additional
information about their handling of a response, even if they did not information about their handling of a response, even if they did not
generate it. generate it.
To enable these uses, Section 2 defines a new HTTP response header To enable these uses, Section 2 defines a new HTTP response field to
field to allow intermediaries to convey details of their handling of allow intermediaries to convey details of their handling of a
a response, and Section 2.2 defines a set of Proxy Error Types for response, Section 2.1 enumerates the kind of information that can be
use when a proxy generates the response. Section 2.3 explains how to conveyed, and Section 2.3 defines a set of error types for use when a
define new Proxy Error Types. proxy generates the response.
1.1. Notational Conventions 1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This specification uses Structured Headers This specification uses Structured Headers
[I-D.ietf-httpbis-header-structure] to specify syntax. The terms sh- [I-D.ietf-httpbis-header-structure] to specify syntax. The terms sf-
param-list, sh-item, sh-string, sh-token and sh-integer refer to the list, sf-item, sf-string, sf-token, sf-integer and key refer to the
structured types defined therein. structured types defined therein.
Note that in this specification, "proxy" is used to indicate both Note that in this specification, "proxy" is used to indicate both
forward and reverse proxies, otherwise known as gateways. "Next hop" forward and reverse proxies, otherwise known as gateways. "Next hop"
indicates the connection in the direction leading to the origin indicates the connection in the direction leading to the origin
server for the request. server for the request.
2. The Proxy-Status HTTP Header Field 2. The Proxy-Status HTTP Field
The Proxy-Status HTTP response header field allows an intermediary to The Proxy-Status HTTP response field allows an intermediary to convey
convey additional information about its handling of a response and additional information about its handling of a response and its
its associated request. associated request.
It is a Structured Headers [I-D.ietf-httpbis-header-structure] List It is a List [I-D.ietf-httpbis-header-structure]:
of parameterised Tokens:
Cache-Status = sh-list Proxy-Status = sf-list
Each member of the list represents an intermediary that has handled Each member of the list represents an intermediary that has handled
the response. The first member of the list represents the the response. The first member of the list represents the
intermediary closest to the origin server, and the last member of the intermediary closest to the origin server, and the last member of the
list represents the intermediary closest to the user agent. list represents the intermediary closest to the user agent.
For example: For example:
Proxy-Status: FooProxy, ExampleCDN Proxy-Status: FooProxy, ExampleCDN
indicates that this response was handled first by FooAccelerator and indicates that this response was handled first by FooProxy and then
then ExampleCDN. ExampleCDN.
Parameters on each member convey additional information about that
intermediary's handling of the response; see Section 2.1 for defined
parameters.
Intermediaries determine when it is appropriate to add the Proxy- Intermediaries determine when it is appropriate to add the Proxy-
Status header field to a response. Some might decide to add it to Status field to a response. Some might decide to add it to all
all responses, whereas others might only do so when specifically responses, whereas others might only do so when specifically
configured to, or when the request contains a header that activates a configured to, or when the request contains a header that activates a
debugging mode. debugging mode.
When adding a value to the Proxy-Status header field, intermediaries
SHOULD preserve the existing contents of the header, to allow
debugging of the entire chain of intermediaries handling the request.
The list members identify the intermediary that inserted the value, The list members identify the intermediary that inserted the value,
and MUST have a type of either sh-string or sh-token. Depending on and MUST have a type of either sf-string or sf-token. Depending on
the deployment, this might be a product or service name (e.g., the deployment, this might be a product or service name (e.g.,
ExampleProxy or "Example CDN"), a hostname ("proxy-3.example.com"), ExampleProxy or "Example CDN"), a hostname ("proxy-3.example.com"),
and IP address, or a generated string. and IP address, or a generated string.
Each member of the list can also have a number of parameters that Parameters on each member convey additional information about that
describe that intermediary's handling of the request. While all of intermediary's handling of the response; see Section 2.1 for defined
these parameters are OPTIONAL, intermediaries are encouraged to parameters. While all of these parameters are OPTIONAL,
provide as much information as possible. intermediaries are encouraged to provide as much information as
possible.
When adding a value to the Proxy-Status field, intermediaries SHOULD
preserve the existing contents of the field, to allow debugging of
the entire chain of intermediaries handling the request.
Proxy-Status MAY be sent in HTTP trailers, but - as with all trailers Proxy-Status MAY be sent in HTTP trailers, but - as with all trailers
- it might be silently discarded along the path to the user agent, so - it might be silently discarded along the path to the user agent, so
this SHOULD NOT be done unless it is not possible to send it in this SHOULD NOT be done unless it is not possible to send it in
headers. For example, if an intermediary is streaming a response and headers. For example, if an intermediary is streaming a response and
the upstream connection suddenly terminates, Proxy-Status can be the upstream connection suddenly terminates, Proxy-Status can be
appended to the trailers of the outgoing message (since the headers appended to the trailers of the outgoing message (since the headers
have already been sent). have already been sent).
Note that there are various security considerations for Note that there are various security considerations for
intermediaries using the Proxy-Status header field; see Section 4. intermediaries using the Proxy-Status field; see Section 4.
Origin servers MUST NOT generate the Proxy-Status header field. Origin servers MUST NOT generate the Proxy-Status field.
2.1. Proxy-Status Parameters 2.1. Proxy-Status Parameters
This section lists parameters that can be used on the members of This section lists parameters that can be used on the members of
Proxy-Status. Proxy-Status.
2.1.1. origin 2.1.1. next-hop
The "origin" parameter's value is a sh-string or sh-token that
identifies the origin server selected (and used, if contacted) for
this response. Its contents might be a hostname, IP address, or
alias.
This is most useful for gateways (also known as "reverse proxies"), The "next-hop" parameter's value is a sf-string or sf-token that
since they are often configured to use an origin server other than identifies the intermediary or origin server selected (and used, if
that which appears in the URL, and sometimes they use several origins contacted) for this response. Its contents might be a hostname, IP
to serve a given site. address, or alias.
For example: For example:
Proxy-Status: cdn.example.org; origin=backend.example.org Proxy-Status: cdn.example.org; next-hop=backend.example.org
2.1.2. fwd-protocol 2.1.2. next-protocol
The "fwd-protocol" parameter's value is a sh-token indicating the The "next-protocol" parameter's value indicates the ALPN protocol
ALPN protocol identifier [RFC7301] used by the intermediary to identifier [RFC7301] used by the intermediary to connect to the next
connect to the next hop. This is only applicable when that hop. This is only applicable when that connection was actually
connection was actually established. established.
The value MUST be either a sf-token or sf-binary. If the protocol
identifier is able to be expressed as a sf-token using UTF-8
encoding, that form MUST be used.
For example: For example:
Proxy-Status: "proxy.example.org"; fwd-protocol=h2 Proxy-Status: "proxy.example.org"; next-protocol=h2
2.1.3. error 2.1.3. error
The "error" parameter's value is a sh-token that is a Proxy Error The "error" parameter's value is a sf-token that is a Proxy Error
Type. When present, it indicates that the response was generated by Type. When present, it indicates that the response was generated by
the proxy, not the origin server or any other upstream server. the proxy, not the origin server or any other upstream server.
Section 2.2 lists the Proxy Error Types defined in this document; new Section 2.3 lists the Proxy Error Types defined in this document; new
ones can be defined using the procedure outlined in Section 2.3. ones can be defined using the procedure outlined in Section 2.4.
For example: For example:
HTTP/1.1 504 Gateway Timeout HTTP/1.1 504 Gateway Timeout
Proxy-Status: SomeCDN; error=connection_timeout Proxy-Status: SomeCDN; error=connection_timeout
indicates that this 504 response was generated by SomeCDN, due to a indicates that this 504 response was generated by SomeCDN, due to a
connection timeout when going forward. connection timeout when going forward.
Or: Or:
HTTP/1.1 429 Too Many Requests HTTP/1.1 429 Too Many Requests
Proxy-Status: SomeReverseProxy; error=http_request_error Proxy-Status: SomeReverseProxy; error=http_request_error
indicates that this 429 Too Many Requests response was generated by indicates that this 429 Too Many Requests response was generated by
the intermediary, not the origin. the intermediary, not the origin.
When sending the error parameter, the most specific Proxy Error Type
SHOULD be sent, provided that it accurately represents the error
condition. If an appropriate Proxy Error Type is not defined, there
are a number of generic error types (e.g., proxy_internal_error,
http_protocol_error) that can be used. If they are not suitable,
consider registering a new Proxy Error Type (see Section 2.4).
Each Proxy Error Type has a Recommended HTTP Status Code. When Each Proxy Error Type has a Recommended HTTP Status Code. When
generating a HTTP response containing "error", its HTTP status code generating a HTTP response containing "error", its HTTP status code
SHOULD be set to the Recommended HTTP Status Code. However, there SHOULD be set to the Recommended HTTP Status Code. However, there
may be circumstances (e.g., for backwards compatibility with previous may be circumstances (e.g., for backwards compatibility with previous
behaviours) when another status code might be used. behaviours) when another status code might be used.
2.1.4. details 2.1.4. details
The "details" parameter's value is a sh-string containing additional The "details" parameter's value is a sf-string containing additional
information not captured anywhere else. This can include information not captured anywhere else. This can include
implementation-specific or deployment-specific information. implementation-specific or deployment-specific information.
For example: For example:
Proxy-Status: ExampleProxy; error="http_protocol_error"; Proxy-Status: ExampleProxy; error="http_protocol_error";
details="Malformed response header - space before colon" details="Malformed response header - space before colon"
2.2. Proxy Error Types 2.2. Defining New Proxy-Status Parameters
New Proxy-Status Parameters can be defined by registering them in the
HTTP Proxy-Status Parameters registry.
Registration requests are reviewed and approved by a Designated
Expert, as per [RFC8126], Section 4.5. A specification document is
appreciated, but not required.
The Expert(s) should consider the following factors when evaluating
requests:
o Community feedback
o If the value is sufficiently well-defined
o Generic parameters are preferred over vendor-specific,
application-specific or deployment-specific values. If a generic
value cannot be agreed upon in the community, the parameter's name
should be correspondingly specific (e.g., with a prefix that
identifies the vendor, application or deployment).
Registration requests should use the following template:
o Name: [a name for the Proxy-Status Parameter that matches key]
o Description: [a description of the parameter semantics and value]
o Reference: [to a specification defining this parameter]
See the registry at https://iana.org/assignments/http-proxy-status
[4] for details on where to send registration requests.
2.3. Proxy Error Types
This section lists the Proxy Error Types defined by this document. This section lists the Proxy Error Types defined by this document.
See Section 2.3 for information about defining new Proxy Error Types. See Section 2.4 for information about defining new Proxy Error Types.
2.2.1. DNS Timeout 2.3.1. DNS Timeout
o Name: dns_timeout o Name: dns_timeout
o Description: The intermediary encountered a timeout when trying to o Description: The intermediary encountered a timeout when trying to
find an IP address for the next hop hostname. find an IP address for the next hop hostname.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 504 o Recommended HTTP status code: 504
2.2.2. DNS Error 2.3.2. DNS Error
o Name: dns_error o Name: dns_error
o Description: The intermediary encountered a DNS error when trying o Description: The intermediary encountered a DNS error when trying
to find an IP address for the next hop hostname. to find an IP address for the next hop hostname.
o Extra Parameters: o Extra Parameters:
* rcode: A sh-string conveying the DNS RCODE that indicates the * rcode: A sf-string conveying the DNS RCODE that indicates the
error type. See [RFC8499], Section 3. error type. See [RFC8499], Section 3.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.3. Destination Not Found 2.3.3. Destination Not Found
o Name: destination_not_found o Name: destination_not_found
o Description: The intermediary cannot determine the appropriate o Description: The intermediary cannot determine the appropriate
next hop to use for this request; for example, it may not be next hop to use for this request; for example, it may not be
configured. Note that this error is specific to gateways, which configured. Note that this error is specific to gateways, which
typically require specific configuration to identify the "backend" typically require specific configuration to identify the "backend"
server; forward proxies use in-band information to identify the server; forward proxies use in-band information to identify the
origin server. origin server.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 500 o Recommended HTTP status code: 500
2.2.4. Destination Unavailable 2.3.4. Destination Unavailable
o Name: destination_unavailable o Name: destination_unavailable
o Description: The intermediary considers the next hop to be o Description: The intermediary considers the next hop to be
unavailable; e.g., recent attempts to communicate with it may have unavailable; e.g., recent attempts to communicate with it may have
failed, or a health check may indicate that it is down. failed, or a health check may indicate that it is down.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 503 o Recommended HTTP status code: 503
2.2.5. Destination IP Prohibited 2.3.5. Destination IP Prohibited
o Name: destination_ip_prohibited o Name: destination_ip_prohibited
o Description: The intermediary is configured to prohibit o Description: The intermediary is configured to prohibit
connections to the next hop IP address. connections to the next hop IP address.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.6. Destination IP Unroutable 2.3.6. Destination IP Unroutable
o Name: destination_ip_unroutable o Name: destination_ip_unroutable
o Description: The intermediary cannot find a route to the next hop o Description: The intermediary cannot find a route to the next hop
IP address. IP address.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.7. Connection Refused 2.3.7. Connection Refused
o Name: connection_refused o Name: connection_refused
o Description: The intermediary's connection to the next hop was o Description: The intermediary's connection to the next hop was
refused. refused.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.8. Connection Terminated 2.3.8. Connection Terminated
o Name: connection_terminated o Name: connection_terminated
o Description: The intermediary's connection to the next hop was o Description: The intermediary's connection to the next hop was
closed before any part of the response was received. If some part closed before any part of the response was received. If some part
was received, see http_response_incomplete. was received, see http_response_incomplete.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.9. Connection Timeout 2.3.9. Connection Timeout
o Name: connection_timeout o Name: connection_timeout
o Description: The intermediary's attempt to open a connection to o Description: The intermediary's attempt to open a connection to
the next hop timed out. the next hop timed out.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 504 o Recommended HTTP status code: 504
2.2.10. Connection Read Timeout 2.3.10. Connection Read Timeout
o Name: connection_read_timeout o Name: connection_read_timeout
o Description: The intermediary was expecting data on a connection o Description: The intermediary was expecting data on a connection
(e.g., part of a response), but did not receive any new data in a (e.g., part of a response), but did not receive any new data in a
configured time limit. configured time limit.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 504 o Recommended HTTP status code: 504
2.2.11. Connection Write Timeout 2.3.11. Connection Write Timeout
o Name: connection_write_timeout o Name: connection_write_timeout
o Description: The intermediary was attempting to write data to a o Description: The intermediary was attempting to write data to a
connection, but was not able to (e.g., because its buffers were connection, but was not able to (e.g., because its buffers were
full). full).
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 504 o Recommended HTTP status code: 504
2.2.12. Connection Limit Reached 2.3.12. Connection Limit Reached
o Name: connnection_limit_reached o Name: connnection_limit_reached
o Description: The intermediary is configured to limit the number of o Description: The intermediary is configured to limit the number of
connections it has to the next hop, and that limit has been connections it has to the next hop, and that limit has been
passed. passed.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 503 o Recommended HTTP status code: 503
2.2.13. HTTP Incomplete Response 2.3.13. TLS Protocol Error
o Name: http_response_incomplete o Name: tls_protocol_error
o Description: The intermediary received an incomplete response to o Description: The intermediary encountered a TLS error when
the request from the next hop. communicating with the next hop, either during handshake or
afterwards.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.14. HTTP Protocol Error Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors).
o Name: http_protocol_error 2.3.14. TLS Certificate Error
o Description: The intermediary encountered a HTTP protocol error o Name: tls_certificate_error
when communicating with the next hop. This error should only be
used when a more specific one is not defined. o Description: The intermediary encountered an error when verifying
the certificate presented by the next hop.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.15. HTTP Response Header Block Too Large Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors).
2.3.15. TLS Alert Received
o Name: tls_alert_received
o Description: The intermediary received a TLS alert from the next
hop.
o Extra Parameters:
* alert_message: a sf-token containing the applicable description
string from the TLS Alerts registry.
o Recommended HTTP status code: 502
2.3.16. HTTP Request Error
o Name: http_request_error
o Description: The intermediary is generating a client (4xx)
response on the origin's behalf. Applicable status codes include
(but are not limited to) 400, 403, 405, 406, 408, 411, 413, 414,
415, 416, 417, 429.
o Extra Parameters:
* status_code: a sf-integer containing the generated status code.
* status_phrase: a sf-string containing the generated status
phrase.
o Recommended HTTP status code: The applicable 4xx status code
This type helps distinguish between responses generated by
intermediaries from those generated by the origin.
2.3.17. HTTP Request Denied
o Name: http_request_denied
o Description: The intermediary rejected the HTTP request based on
its configuration and/or policy settings. The request wasn't
forwarded to the next hop.
o Extra Parameters: None.
o Recommended HTTP status code: 403
2.3.18. HTTP Incomplete Response
o Name: http_response_incomplete
o Description: The intermediary received an incomplete response to
the request from the next hop.
o Extra Parameters: None.
o Recommended HTTP status code: 502
2.3.19. HTTP Response Header Block Too Large
o Name: http_response_header_block_size o Name: http_response_header_block_size
o Description: The intermediary received a response to the request o Description: The intermediary received a response to the request
whose header block was considered too large. whose header block was considered too large.
o Extra Parameters: o Extra Parameters:
* header_block_size: a sh-integer indicating how large the * header_block_size: a sf-integer indicating how large the
headers received were. Note that they might not be complete; headers received were. Note that they might not be complete;
i.e., the intermediary may have discarded or refused additional i.e., the intermediary may have discarded or refused additional
data. data.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.16. HTTP Response Header Too Large 2.3.20. HTTP Response Header Too Large
o Name: http_response_header_size o Name: http_response_header_size
o Description: The intermediary received a response to the request o Description: The intermediary received a response to the request
containing an individual header line that was considered too containing an individual header line that was considered too
large. large.
o Extra Parameters: o Extra Parameters:
* header_name: a sh-string indicating the name of the header that * header_name: a sf-string indicating the name of the header that
triggered the error. triggered the error.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.17. HTTP Response Body Too Large 2.3.21. HTTP Response Body Too Large
o Name: http_response_body_size o Name: http_response_body_size
o Description: The intermediary received a response to the request o Description: The intermediary received a response to the request
whose body was considered too large. whose body was considered too large.
o Extra Parameters: o Extra Parameters:
* body_size: a sh-integer indicating how large the body received * body_size: a sf-integer indicating how large the body received
was. Note that it may not have been complete; i.e., the was. Note that it may not have been complete; i.e., the
intermediary may have discarded or refused additional data. intermediary may have discarded or refused additional data.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.18. HTTP Response Transfer-Coding Error 2.3.22. HTTP Response Transfer-Coding Error
o Name: http_response_transfer_coding o Name: http_response_transfer_coding
o Description: The intermediary encountered an error decoding the o Description: The intermediary encountered an error decoding the
transfer-coding of the response. transfer-coding of the response.
o Extra Parameters: o Extra Parameters:
* coding: a sh-token containing the specific coding that caused * coding: a sf-token containing the specific coding that caused
the error. the error.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.19. HTTP Response Content-Coding Error 2.3.23. HTTP Response Content-Coding Error
o Name: http_response_content_coding o Name: http_response_content_coding
o Description: The intermediary encountered an error decoding the o Description: The intermediary encountered an error decoding the
content-coding of the response. content-coding of the response.
o Extra Parameters: o Extra Parameters:
* coding: a sh-token containing the specific coding that caused * coding: a sf-token containing the specific coding that caused
the error. the error.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.20. HTTP Response Timeout 2.3.24. HTTP Response Timeout
o Name: http_response_timeout o Name: http_response_timeout
o Description: The intermediary reached a configured time limit o Description: The intermediary reached a configured time limit
waiting for the complete response. waiting for the complete response.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 504 o Recommended HTTP status code: 504
2.2.21. TLS Handshake Error 2.3.25. HTTP Upgrade Failed
o Name: tls_handshake_error
o Description: The intermediary encountered an error during TLS
handshake with the next hop.
o Extra Parameters:
* alert_message: a sh-token containing the applicable description
string from the TLS Alerts registry.
o Recommended HTTP status code: 502
2.2.22. TLS Untrusted Peer Certificate
o Name: tls_untrusted_peer_certificate
o Description: The intermediary received an untrusted peer
certificate during TLS handshake with the next hop.
o Extra Parameters: None.
o Recommended HTTP status code: 502
2.2.23. TLS Expired Peer Certificate
o Name: tls_expired_peer_certificate o Name: http_upgrade_failed
o Description: The intermediary received an expired peer certificate o Description: The HTTP Upgrade between the intermediary and the
during TLS handshake with the next hop. next hop failed.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.24. TLS Unexpected Peer Certificate 2.3.26. HTTP Protocol Error
o Name: tls_unexpected_peer_certificate
o Description: The intermediary received an unexpected peer
certificate (e.g., SPKI doesn't match) during the TLS handshake
with the next hop.
o Extra Parameters:
* identity: a sh-string containing a comma-separated list of
Subject Alternative Names from the certificate received from
the next hop.
* sha256: a sh-string containing the hex-encoded SHA-256 of the
certificate received from the next hop.
* spki: a sh-string containing the base64-encoded SHA-256 of the
Subject Public Key Info (SPKI) from the certificate received
from the next hop.
o Recommended HTTP status code: 502
2.2.25. TLS Missing Proxy Certificate
o Name: tls_missing_proxy_certificate
o Description: The next hop requested a client certificate from the
intermediary during TLS handshake, but it wasn't configured with
one.
o Extra Parameters: None.
o Recommended HTTP status code: 500
2.2.26. TLS Rejected Proxy Certificate
o Name: tls_rejected_proxy_certificate o Name: http_protocol_error
o Description: The next hop rejected the client certificate provided o Description: The intermediary encountered a HTTP protocol error
by the intermediary during TLS handshake. when communicating with the next hop. This error should only be
used when a more specific one is not defined.
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 500
2.2.27. TLS Error
o Name: tls_error
o Description: The intermediary encountered a TLS error when
communicating with the next hop.
o Extra Parameters:
* alert_message: a sh-token containing the applicable description
string from the TLS Alerts registry.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.2.28. HTTP Request Error Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors).
o Name: http_request_error
o Description: The intermediary is generating a client (4xx)
response on the origin's behalf. Applicable status codes include
(but are not limited to) 400, 403, 405, 406, 408, 411, 413, 414,
415, 416, 417, 429.
o Extra Parameters:
* status_code: a sh-integer containing the generated status code.
* status_phrase: a sh-string containing the generated status
phrase.
o Recommended HTTP status code: The applicable 4xx status code
This type helps distinguish between responses generated by
intermediaries from those generated by the origin.
2.2.29. HTTP Request Denied
o Name: http_request_denied
o Description: The intermediary rejected the HTTP request based on
its configuration and/or policy settings. The request wasn't
forwarded to the next hop.
o Extra Parameters: None.
o Recommended HTTP status code: 400
2.2.30. HTTP Upgrade Failed
o Name: http_upgrade_failed
o Description: The HTTP Upgrade between the intermediary and the
next hop failed.
o Extra Parameters: None.
o Recommended HTTP status code: 502
2.2.31. Proxy Internal Response 2.3.27. Proxy Internal Response
o Name: proxy_internal_response o Name: proxy_internal_response
o Description: The intermediary generated the response locally, o Description: The intermediary generated the response locally,
without attempting to connect to the next hop (e.g. in response to without attempting to connect to the next hop (e.g. in response to
a request to a debug endpoint terminated at the intermediary). a request to a debug endpoint terminated at the intermediary).
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: o Recommended HTTP status code:
2.2.32. Proxy Internal Error 2.3.28. Proxy Internal Error
o Name: proxy_internal_error o Name: proxy_internal_error
o Description: The intermediary encountered an internal error o Description: The intermediary encountered an internal error
unrelated to the origin. unrelated to the origin.
o Extra Parameters: o Extra Parameters: None
* error: a sh-string containing details about the error o Recommended HTTP status code: 500
condition.
Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors).
2.3.29. Proxy Configuration Error
o Name: proxy_configuration_error
o Description: The intermediary encountered an error regarding its
configuration.
o Extra Parameters: None
o Recommended HTTP status code: 500 o Recommended HTTP status code: 500
2.2.33. Proxy Loop Detected Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors).
2.3.30. Proxy Loop Detected
o Name: proxy_loop_detected o Name: proxy_loop_detected
o Description: The intermediary tried to forward the request to o Description: The intermediary tried to forward the request to
itself, or a loop has been detected using different means (e.g. itself, or a loop has been detected using different means (e.g.
[RFC8586]). [RFC8586]).
o Extra Parameters: None. o Extra Parameters: None.
o Recommended HTTP status code: 502 o Recommended HTTP status code: 502
2.3. Defining New Proxy Error Types 2.4. Defining New Proxy Error Types
New Proxy Error Types can be defined by registering them in the HTTP New Proxy Error Types can be defined by registering them in the HTTP
Proxy Error Types registry. Proxy Error Types registry.
Registration requests are reviewed and approved by a Designated Registration requests are reviewed and approved by a Designated
Expert, as per [RFC8126], Section 4.5. A specification document is Expert, as per [RFC8126], Section 4.5. A specification document is
appreciated, but not required. appreciated, but not required.
The Expert(s) should consider the following factors when evaluating The Expert(s) should consider the following factors when evaluating
requests: requests:
o Community feedback o Community feedback
o If the value is sufficiently well-defined o If the value is sufficiently well-defined
o If the value is generic; vendor-specific, application-specific and o Generic types are preferred over vendor-specific, application-
deployment-specific values are discouraged specific or deployment-specific values. If a generic value cannot
be agreed upon in the community, the types's name should be
correspondingly specific (e.g., with a prefix that identifies the
vendor, application or deployment).
Registration requests should use the following template: Registration requests should use the following template:
o Name: [a name for the Proxy Error Type that is matches sh-token] o Name: [a name for the Proxy Error Type that matches sf-token]
o Description: [a description of the conditions that generate the o Description: [a description of the conditions that generate the
Proxy Error Type] Proxy Error Type]
o Extra Parameters: [zero or more optional parameters, along with o Extra Parameters: [zero or more optional parameters, along with
their allowable type(s)] their allowable type(s)]
o Recommended HTTP status code: [the appropriate HTTP status code o Recommended HTTP status code: [the appropriate HTTP status code
for this entry] for this entry]
See the registry at https://iana.org/assignments/http-proxy-statuses See the registry at https://iana.org/assignments/http-proxy-status
[4] for details on where to send registration requests. [5] for details on where to send registration requests.
3. IANA Considerations 3. IANA Considerations
Upon publication, please create the HTTP Proxy Error Types registry Upon publication, please create the HTTP Proxy-Status Parameters
at https://iana.org/assignments/http-proxy-statuses [5] and populate registry and the HTTP Proxy Error Types registry at
it with the types defined in Section 2.2; see Section 2.3 for its https://iana.org/assignments/http-proxy-statuses [6] and populate
associated procedures. them with the types defined in Section 2.1 and Section 2.3
respectively; see Section 2.2 and Section 2.4 for its associated
procedures.
4. Security Considerations 4. Security Considerations
One of the primary security concerns when using Proxy-Status is One of the primary security concerns when using Proxy-Status is
leaking information that might aid an attacker. For example, leaking information that might aid an attacker. For example,
information about the intermediary's configuration and back-end information about the intermediary's configuration and back-end
topology can be exposed. topology can be exposed.
As a result, care needs to be taken when deciding to generate a As a result, care needs to be taken when deciding to generate a
Proxy-Status header. Note that intermediaries are not required to Proxy-Status field. Note that intermediaries are not required to
generate a Proxy-Status header field in any response, and can generate a Proxy-Status field in any response, and can conditionally
conditionally generate them based upon request attributes (e.g., generate them based upon request attributes (e.g., authentication
authentication tokens, IP address). tokens, IP address).
Likewise, generation of all parameters is optional. Likewise, generation of all parameters is optional.
5. References 5. References
5.1. Normative References 5.1. Normative References
[I-D.ietf-httpbis-header-structure] [I-D.ietf-httpbis-header-structure]
Nottingham, M. and P. Kamp, "Structured Headers for HTTP", Nottingham, M. and P. Kamp, "Structured Field Values for
draft-ietf-httpbis-header-structure-13 (work in progress), HTTP", draft-ietf-httpbis-header-structure-19 (work in
August 2019. progress), June 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>. July 2014, <https://www.rfc-editor.org/info/rfc7301>.
skipping to change at page 18, line 28 skipping to change at page 18, line 43
<https://www.rfc-editor.org/info/rfc8586>. <https://www.rfc-editor.org/info/rfc8586>.
5.3. URIs 5.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/ [1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] https://httpwg.org/ [2] https://httpwg.org/
[3] https://github.com/httpwg/http-extensions/labels/proxy-status [3] https://github.com/httpwg/http-extensions/labels/proxy-status
[4] https://iana.org/assignments/http-proxy-statuses [4] https://iana.org/assignments/http-proxy-status
[5] https://iana.org/assignments/http-proxy-statuses [5] https://iana.org/assignments/http-proxy-status
[6] https://iana.org/assignments/http-proxy-statuses
Authors' Addresses Authors' Addresses
Mark Nottingham Mark Nottingham
Fastly Fastly
made in
Prahran, VIC
Australia
Email: mnot@mnot.net Email: mnot@mnot.net
URI: https://www.mnot.net/ URI: https://www.mnot.net/
Piotr Sikora Piotr Sikora
Google Google
Email: piotrsikora@google.com Email: piotrsikora@google.com
 End of changes. 87 change blocks. 
288 lines changed or deleted 293 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/