Fix fd leak in vsock.Dial in case of connect errors

[xelez]

Fixes #64

Before commit when trying to connect in cycle with no valid endpoint:

$ lsof -p 874838 | grep AF_VSOCK
lsof: WARNING: can't stat() nsfs file system /run/docker/netns/default
      Output information may be incomplete.
servicevm 874838 xelez    9u     sock                0,9      0t0  8504215 protocol: AF_VSOCK
servicevm 874838 xelez   11u     sock                0,9      0t0  8504763 protocol: AF_VSOCK
servicevm 874838 xelez   12u     sock                0,9      0t0  8505726 protocol: AF_VSOCK
servicevm 874838 xelez   13u     sock                0,9      0t0  8504774 protocol: AF_VSOCK
servicevm 874838 xelez   14u     sock                0,9      0t0  8507619 protocol: AF_VSOCK
servicevm 874838 xelez   15u     sock                0,9      0t0  8500873 protocol: AF_VSOCK
servicevm 874838 xelez   16u     sock                0,9      0t0  8502193 protocol: AF_VSOCK
servicevm 874838 xelez   17u     sock                0,9      0t0  8507691 protocol: AF_VSOCK
servicevm 874838 xelez   18u     sock                0,9      0t0  8504845 protocol: AF_VSOCK
servicevm 874838 xelez   19u     sock                0,9      0t0  8510828 protocol: AF_VSOCK

After this patch no FD are leaking:

$ lsof -p 876844 | grep AF_VSOCK
lsof: WARNING: can't stat() nsfs file system /run/docker/netns/default
      Output information may be incomplete.

Signed-off-by: Alex Ankudinov xelez0@gmail.com

[rn]

Hey, thanks for reporting this and providing a patch.

I'd be happy to merge bar this minor nit. This ignores the return value, which is fine since we want the error from the Connect() call. However this may trip some linters and the canonical way would be to write:

_ := closeFD(fd)

[xelez]

Thanks for the review! Good point.

:= gives me an error:

# github.com/linuxkit/virtsock/pkg/vsock
pkg/vsock/vsock_linux.go:57:6: no new variables on left side of :=

So I fixed it with just _ = .

[rn]

Great, thanks for the fix.