Is this on Linux only? Can you post details of your internet connection type and provider?
Also, we'll need your steam ID or account name, the game you were playing and the approximate time that you had a problem recently.
Yes, it seems to be linux only, i had no such problem in wine two years ago. Profile is http://steamcommunity.com/id/mittorn/. Internet connection splits to local ethernet connection (TOMTEL) and access to global internet through pptp, sometimes in weekend pptp breaks due to high load. It may rely to reconnect issue (https://github.com/ValveSoftware/steam-for-linux/issues/971). I have no NetworkManager, connection configured staticly, so steam does not recognize reconnect correctly, only handles disconnect. After disconnect there is no default internet route.
Games are HL and HL2DM.
I compiled this code: http://pastebin.com/4WFMbXEc to libnm-util.so and preloaded it, now reconnection works. Problem was in using libnm on systems that have no NetworkManager installed because of lock while waiting dbus connection to unexisting dbus service.
Thanks for the investigation.
Sometimes my internet provider breaks internet connection. After that i could not play on VAC servers without restarting steam client, because after some time i get this error: A connection to steam VAC servers could not be made... But i have internet connection and VAC servers fully works, there is a bug in steam, that prevents this connection. How to tell steam to reconnect without restarting steam? After steam restart connection works normally.