[jira] [Commented] (TS-4703) Adds an API call to retrieve transaction protocol

["Susan Hinrichs (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-4703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15470788#comment-15470788 ] 

Susan Hinrichs commented on TS-4703:
------------------------------------

[~amc]'s proposal that was sent around on dev@trafficserver.apache.org and is the description of the API.


.. include:: ../../../common.defs

.. default-domain:: c

TSClientProtocolStack
*********************

Synopsis
========

`#include <ts/ts.h>`

.. function:: TSReturnCode TSHttpTxnClientProtocolStackGet(TSHttpTxn txnp, int n, char const** result, int* actual)

.. function:: TSReturnCode TSHttpSsnClientProtocolStackGet(TSHttpSsn ssnp, int n, char const** result, int* actual)

.. function:: int TSHttpTxnClientProtocolStackContains(TSHttpTxn txnp, char const** tag)

.. function:: int TSHttpSsnClientProtocolStackContains(TSHttpSsn ssnp, char const** tag)

.. function:: char const* TSNormalizedProtocolTag(char const* tag)

.. function:: char const* TSRegisterProtocolTag(char const* tag)

Description
===========

These functions are used to explore the protocol stack of the client (user agent) connection to |TS|. The functions :func:`TSHttpTxnClientProtocolStackGet` and :func:`TSHttpSsnClientProtocolStackGet` can be used to retrieve the entire protocol stack for the user agent connection. :func:`TSHttpTxnClientProtocolStackContains` and :func:`TSHttpSsnClientProtocolStackContains` will check for a specific protocol :arg:`tag` being present in the stack.

Each protocol is represented by tag which is a null terminated string. A particular tag will always be returned as the same character pointer and so protocols can be reliably checked with pointer comparisons. :func:`TSNormalizedProtocolTag` will return this character pointer for a specific :arg:`tag`. A return value of :const:`NULL` indicates the provided :arg:`tag` is not registered as a known protocol tag. :func:`TSRegisterProtocolTag` registers the :arg:`tag` and then returns its normalized value. This is useful for plugins that provide custom protocols for user agents.

The protocols are ordered from higher level protocols to the lower level ones on which the higher operate. For instance a stack might look like "http/1.1,tls/1.2,tcp,ipv4". For :func:`TSHttpTxnClientProtocolStackGet` and :func:`TSHttpSsnClientProtocolStackGet` these values are placed in the array :arg:`result`. :arg:`count` is the maximum number of elements of :arg:`result` that may be modified by the function call. If :arg:`actual` is not :const:`NULL` then the actual number of elements in the protocol stack will be returned. If this is equal or less than :arg:`count` then all elements were returned. If it is larger then some layers were omitted from :arg:`result`. If the full stack is required :arg:`actual` can be used to resize :arg:`result` to be sufficient to hold all of the elements and the function called again with updated :arg:`count` and :arg:`result`. In practice the maximum number of elements will is almost certain to be less than 10 which therefore should suffice. These functions return :const:`TS_SUCCESS` on success and :const:`TS_ERROR` on failure which should only occurr if :arg:`txnp` or :arg:`ssnp` are invalid.

The :func:`TSHttpTxnClientProtocolStackContains` and :func:`TSHttpSsnClientProtocolStackContains` functions are provided for the convenience when only the presence of a protocol is of interest, not its location or the presence of other protocols. These functions return 0 if the protocol :arg:`tag` is not present, non-zero if it is present. The strings are matched with an anchor prefix search, as with debug tags. For instance if :arg:`tag` is "tls" then it will match "tls/1.2" or "tls/1.3". This makes checking for TLS or IP more convenient. If more precision is required the entire protocol stack can be retrieved and processed more thoroughly.

The protocol tags defined by |TS|.

=========== =========
Protocol    Tag
=========== =========
HTTP/1.1    http/1.1
HTTP/1.0    http/1.0
HTTP/2      h2
WebSocket   ws
TLS 1.3     tls/1.3
TLS 1.2     tls/1.2
TCP         tcp
UDP         udp
IPv4        ipv4
IPv6        ipv6
QUIC        quic
=========== =========

.. note::
   What should HTTP/2 connections return as the top protocol? There are several options
   
   *  "http/1.1,h2"
   *  "h2"
   *  "http/1.1,h2" for transctions and "h2" for sessions.


   

> Adds an API call to retrieve transaction protocol
> -------------------------------------------------
>
>                 Key: TS-4703
>                 URL: https://issues.apache.org/jira/browse/TS-4703
>             Project: Traffic Server
>          Issue Type: Improvement
>          Components: TS API
>            Reporter: Petar Penkov
>            Assignee: Alan M. Carroll
>             Fix For: 7.0.0
>
>          Time Spent: 2h 40m
>  Remaining Estimate: 0h
>
> It would be useful if there was a way to retrieve the underlying protocol for a given transaction through the tsapi at the very least for plugin logging purposes. This can be achieved with a very simple method since this information is already available internally. 



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