transport: Suppress warning when the connection is closing

[twz123]

Don't emit a warning when the connection is closing. A warning implies that something is not as it should be, but it's expected that the connection attempt is interrupted in this case.

RELEASE NOTES: N/A

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.83%. Comparing base (ae62635) to head (4edf517).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
clientconn.go	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8654      +/-   ##
==========================================
- Coverage   81.21%   80.83%   -0.38%     
==========================================
  Files         416      416              
  Lines       41002    41096      +94     
==========================================
- Hits        33298    33220      -78     
- Misses       6226     6331     +105     
- Partials     1478     1545      +67     

Files with missing lines	Coverage Δ
clientconn.go	78.61% <57.14%> (-10.83%)	⬇️

... and 26 files with indirect coverage changes

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[easwars]

@twz123 : Could you please describe the problem you are seeing in a little bit more detail and say how your change helps fix the problem? Thanks.

[twz123]

When connecting to etcd using their client, I'm seeing warnings during normal operations like this

2025/10/15 12:55:29 WARNING: [core] [Channel #1 SubChannel #2] grpc: addrConn.createTransport failed to connect to {Addr: "127.0.0.1:2379", ServerName: "127.0.0.1:2379", }. Err: connection error: desc = "transport: Error while dialing: dial tcp 127.0.0.1:2379: operation was canceled"

or this:

2025/10/15 12:56:24 WARNING: [core] [Channel #1 SubChannel #2] grpc: addrConn.createTransport failed to connect to {Addr: "127.0.0.1:2379", ServerName: "127.0.0.1:2379", }. Err: connection error: desc = "transport: authentication handshake failed: context canceled"

This broke something on our side (k0sproject/k0sctl#953), as we weren't prepared for the additional output. While that was an oversight and easy to fix in k0sctl, we were wondering why we're seeing the warning in the first place. It seems to happen when/after the GRPC client connection gets established. I don't have a clue about GRPC internals, but it seems that a subchannel gets cancelled while it's still creating its transport. This seems like "normal operations" to me. A warning implies that something is not as it should be, so I figured the warning would be inappropriate in this situation?

Below an example output of my test app, which connects to etcd, executes a command, and disconnects again:

Oct 17 12:58:48.922 Connecting.
2025/10/17 12:58:48 INFO: [core] original dial target is: "etcd-endpoints://0xc000334960/127.0.0.1:2379"
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel created for target "etcd-endpoints://0xc000334960/127.0.0.1:2379"
2025/10/17 12:58:48 INFO: [core] [Channel #1] parsed dial target is: resolver.Target{URL:url.URL{Scheme:"etcd-endpoints", Opaque:"", User:(*url.Userinfo)(nil), Host:"0xc000334960", Path:"/127.0.0.1:2379", RawPath:"", OmitHost:false, ForceQuery:false, RawQuery:"", Fragment:"", RawFragment:""}}
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel authority set to "127.0.0.1:2379"
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel switches to new LB policy "pick_first"
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel Connectivity change to CONNECTING
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #2] Subchannel created
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel switches to new LB policy "round_robin"
2025/10/17 12:58:48 INFO: [roundrobin] [0xc000368bd0] Created
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #3] Subchannel created
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel exiting idle mode
Oct 17 12:58:48.923 Connected, Sleeping one sec.
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #2] Subchannel Connectivity change to CONNECTING
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #2] Subchannel picks a new address "127.0.0.1:2379" to connect
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #3] Subchannel Connectivity change to CONNECTING
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #2] Subchannel Connectivity change to SHUTDOWN
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #2] Subchannel deleted
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #3] Subchannel picks a new address "127.0.0.1:2379" to connect
2025/10/17 12:58:48 WARNING: [core] [Channel #1 SubChannel #2] grpc: addrConn.createTransport failed to connect to {Addr: "127.0.0.1:2379", ServerName: "127.0.0.1:2379", }. Err: connection error: desc = "transport: authentication handshake failed: context canceled"
2025/10/17 12:58:48 WARNING: [core] [Channel #1 SubChannel #2] grpc: addrConn.createTransport failed to connect to {Addr: "127.0.0.1:2379", ServerName: "127.0.0.1:2379", }. Err: connection error: desc = "transport: authentication handshake failed: context canceled"
2025/10/17 12:58:48 INFO: [core] [Channel #1 SubChannel #3] Subchannel Connectivity change to READY
2025/10/17 12:58:48 INFO: [core] [Channel #1] Channel Connectivity change to READY
Oct 17 12:58:49.923 Listing members.
{"members":{"controller-0":"https://172.29.182.39:2380"}}
Oct 17 12:58:49.924 Disconnecting.
2025/10/17 12:58:49 INFO: [core] [Channel #1] Channel Connectivity change to SHUTDOWN
2025/10/17 12:58:49 INFO: [core] [Channel #1] Closing the name resolver
2025/10/17 12:58:49 INFO: [core] [Channel #1] ccBalancerWrapper: closing
2025/10/17 12:58:49 INFO: [core] [Channel #1 SubChannel #3] Subchannel Connectivity change to SHUTDOWN
2025/10/17 12:58:49 INFO: [core] [Channel #1 SubChannel #3] Subchannel deleted
2025/10/17 12:58:49 INFO: [core] [Channel #1] Channel deleted
Oct 17 12:58:49.924 Disconnected.
Done with warnings.