net: fix bug in net.Interfaces: handle elastic sdl_data size correctly
net: fix bug in net.Interfaces: handle elastic sdl_data size correctly

Fixes issue 1921.

R=golang-dev, jeff
CC=golang-dev
http://codereview.appspot.com/4535120

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go