envoyproxy/envoy

upstream_bind_config does not work with UDP. (Connected to #15516)

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#15,590 opened on Mar 20, 2021

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area/udphelp wanted

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Description

This issue was opened because @mattklein123 asked to do it in #15516 Using upstream_bind_config field with UDP doesn't seem to work.

Repro steps + Config: Tested the following config with a socat UDP sender sending datagrams to 127.0.0.1:1234, and socat receiver listening at 127.0.0.1:1235 My full static config is: upstream_bind_config_test.txt

Expectation: The expectation was to bind the outgoing connection's source to 127.0.0.2:9999, but it did not happen. socat recv accepted connection from a randomly chosen port at 127.0.0.1 by envoy. 2021/03/17 14:10:30 socat[28284] N accepting UDP connection from AF=2 127.0.0.1:51755

Note: The same upstream_bind_config configuration works well with HTTP, as you would expect.

@mattklein123 as you mentioned that

The problem with bind config with a single port is it breaks session tracking

May I ask for a deeper explanation on this topic?

Contributor guide

Research direction
Investigate the UDP connection establishment path in Envoy and verify if upstream bind config is applied to UDP sockets similar to TCP. Look for where bind configuration is used in the connection factory and check for a missing implementation for UDP.
Tech stack
cpp
Domain
backendnetworking
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Envoynetworking
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60