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runtime: SIGPIPE is raised when using net.DialTimeout and timeout is reached #18770

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akamensky opened this issue Jan 24, 2017 · 5 comments

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@akamensky
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commented Jan 24, 2017

What version of Go are you using (go version)?

1.7.4 darwin

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH=""
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rk/g9b46vzx70g86vhvqtmwtjxw0000gn/T/go-build402316604=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"

What did you do?

Application that connects to remote server using net.DialTimeout. The application part that connects remotely is written in Go, the application GUI is written in C++ (Qt5). And Go part is statically linked to GUI.

The pseudo-code that causes the issue:

	serverConn, err := net.DialTimeout("tcp", c.remoteServer, CONNECT_TIMEOUT) // 5 seconds timeout
	if err != nil {
		return err // Error is fully handled in calling method
	}

What did you expect to see?

Since error is handled and written to STDERR as a log message I expect to see message and app keep on running.

What did you see instead?

The app exits with code 141 (SIGPIPE). If in C++ part I specify to ignore SIGPIPE (such as signal(SIGPIPE, SIG_IGN);) then I can see log output. Without that the application exists silently**(!)**, which I believe should not be the case, if we raise SIGPIPE, then we at least should see stack trace leading us to the line where EPIPE happened....

Comment

I think preferred solution would be not to raise SIGPIPE at all. Since I can get err value on timeout and can handle it appropriately. FYI, net package has no error type for timeout error. so the only way to ensure that the error is due to timeout is to lookup for substring in error message...

@ianlancetaylor ianlancetaylor changed the title SIGPIPE is raised when using net.DialTimeout and timeout is reached runtime: SIGPIPE is raised when using net.DialTimeout and timeout is reached Jan 24, 2017

@ianlancetaylor

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commented Jan 24, 2017

We need to see a complete example that demonstrates the problem. See https://golang.org/pkg/os/signal for how the Go runtime handles SIGPIPE. What you are describing is not what is intended to happen, and the runtime has code that is intended to ensure that it does not happen. So we need a test case we can run ourselves so that we can find out why it is not working for you.

@bradfitz

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commented Jan 24, 2017

Also, please try Go 1.8. We're no longer fixing bugs (only security issues) in Go 1.7.

@dcu

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commented Jan 26, 2017

this is probably dup of #17393 isn't it @eliasnaur ?

@akamensky

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commented Jan 26, 2017

@dcu Thank you for the reference, looks like the same though slightly different use-case.

I agree with comment in referenced issue that in theory Go should not be raising SIGPIPE at all (instead of ignoring it). SIGPIPE is meant for environment where it is not possible to handle error upon write/read to/from closed socket, which is the case for low level languages. Go already provides necessary tools for managing socket errors.

I guess can close as a dup, though sad to see that (according to referenced issue) the fix for this won't be in 1.8.

@eliasnaur

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commented Jan 26, 2017

It looks like a dup of #17393. I'll try (again) to fix it for Go 1.9.

@eliasnaur eliasnaur closed this Jan 26, 2017

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