[6.0] Optionally respect HTTP/1.0 keep-Alive for HTTP.sys

[adityamandaleeka]

Optionally respect HTTP/1.0 Keep-Alive for HTTP.sys

#56558 was done in 9.0 and made it so we respect keep-alives from 1.0 clients in HTTP.sys. This effectively backports that logic to 6.0 but in an opt-in way (behind an AppContext switch).

Description

This change adds an AppContext switch that, when enabled (it's off by default), will allow our HTTP.sys server to respect HTTP/1.0 clients' Connection: Keep-Alive header.

Fixes #56223

Customer Impact

With this change, servers that serve HTTP/1.0 clients can opt in to respecting the keep-alive header, and thereby save on the fixed costs of connection set up/teardown. For situations where there is a significant amount of 1.0 traffic, this can lead to significant cost savings.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

This behavior is opt-in behind an AppContext switch.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A