Introduce fwmarkd: a service to set the fwmark of sockets.

At connect(), mark sockets with the default network's netId.

(cherry picked from commit 361154d38016ebeaabf1bb75534dabbacf5de5fa)

Change-Id: Ib6198e19dbc306521a26fcecfdf6e8424d163fc9
4 files changed