ping: Don't log idle timeout as error

[gonghao]

Problem

Every ICMP session that finishes normally leaves an ERROR line behind:

level=info  msg="[ICMP] icmp 192.168.188.63:0 --> 8.8.8.8:0 using DIRECT"
level=error msg="receive ICMP echo reply: read ip 192.168.10.1: i/o timeout"

The two lines are exactly idleTimeout apart (measured: 16:58:11.780184 → 16:58:21.780487, i.e. 10.0003s), and the pings themselves succeed — the client sees 0% loss. On a router where a device does periodic connectivity probes, this accumulates hundreds of ERROR entries that are pure noise.

The address in the message is also misleading: it is the local address the raw socket got bound to (ip route get 8.8.8.8 → src 192.168.10.1), not the ping target, so every direct ICMP session reports the same IP.

Cause

loopRead re-arms a read deadline on every iteration, so a destination that stops receiving echo replies exits with a deadline error. That is the intended end of an idle session — the defer d.Close() added in the same commit exists for exactly this path.

But the error classification was never updated to match. E.IsClosed only covers io.EOF, net.ErrClosed, io.ErrClosedPipe, os.ErrClosed, EPIPE, ECONNRESET and ENOTCONN, so the deadline error falls through to ErrorContext.

The check dates back to 53dbe7b ("Add ping support"), where ReadIP blocked forever and the only possible errors were genuine failures — correct at the time. 5133fee ("ping: Add timeout to destinations") introduced SetReadDeadline and a third, benign exit path, but left the branch untouched.

Fix

Use E.IsClosedOrCanceled, which is IsClosed || IsCanceled || IsTimeout.

E.IsTimeout matches through the net.Error interface, so it covers both conns:

• ping/destination.go — syscall conn, returns os.ErrDeadlineExceeded
• ping/destination_gvisor.go — gonet returns its own timeoutError{} with Timeout() == true; note that errors.Is(err, os.ErrDeadlineExceeded) would not work here even though the message string is identical

Genuine timeouts are not lost: in both loops the re-armed deadline is the only source of a timeout error.

Verification

go build and go vet pass for linux, darwin, windows and android/arm64, with and without the with_gvisor tag. go test ./ping/... passes.