ccl/sqlproxyccl: TestPrivateEndpointsACL failed

ccl/sqlproxyccl.TestPrivateEndpointsACL [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Ci_TestsAwsLinuxArm64_UnitTests/17962350?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Ci_TestsAwsLinuxArm64_UnitTests/17962350?buildTab=artifacts#/) on release-24.3 @ [232c636b5477e06c1b25b04b3a3c710fdf7a8b2e](https://github.com/cockroachdb/cockroach/commits/232c636b5477e06c1b25b04b3a3c710fdf7a8b2e):

```
=== RUN TestPrivateEndpointsACL
test_log_scope.go:165: test logs captured to: /artifacts/tmp/_tmp/8b67916b40b2ca2b9d724d711ff9c3e7/logTestPrivateEndpointsACL1324483565
test_log_scope.go:76: use -show-logs to present logs inline
test_server_shim.go:152: automatically injected an external process virtual cluster under test; see comment at top of test_server_shim.go for details.
proxy_handler_test.go:466: -- test log scope end --
test logs left over in: /artifacts/tmp/_tmp/8b67916b40b2ca2b9d724d711ff9c3e7/logTestPrivateEndpointsACL1324483565
--- FAIL: TestPrivateEndpointsACL (2.05s)
=== RUN TestPrivateEndpointsACL/private_connection_allowed
proxy_handler_test.go:395:
Error Trace: pkg/ccl/sqlproxyccl/proxy_handler_test.go:2944
Error: Expected nil, but got: &sqlproxyccl.errWithCode{
code: 4,
cause: &withstack.withStack{
cause: &errutil.withPrefix{
cause: &errors.errorString{s:"proxyproto: proxy protocol signature not present"},
prefix: "while receiving startup message",
},
stack: &withstack.stack{0x4336731, 0x43430fc, 0x4348c88, 0x1245eb8, 0x48ec44},
},
}
Test: TestPrivateEndpointsACL/private_connection_allowed
--- FAIL: TestPrivateEndpointsACL/private_connection_allowed (0.05s)
```
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

/cc @cockroachdb/sql-foundations @cockroachdb/server

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*TestPrivateEndpointsACL.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Jira issue: CRDB-45006

Start with pkg/ccl/sqlproxyccl/proxy_handler_test.go around the failing TestPrivateEndpointsACL and reproduce the private_connection_allowed failure on release-24.3. Inspect the linked TeamCity logs and artifacts, including the proxy protocol signature error. Done means the test passes without the startup-message error.

Written by the indexing model from the issue text.