VBoxNetBaseService hides all details of internal network implementation and become responsible for supporting receiving loop. Notification of children are done via introduced interface: virtual int processFrame(void *, size_t) = 0; virtual int processGSO(PCPDMNETWORKGSO, size_t) = 0; virtual int processUDP(void *, size_t) = 0; processFrame() and processGSO() might return VERR_IGNORED, to inform base service switch to processUDP() (e.g. for DHCP needs)

DHCP: G/c lines.

DHCP: first-level DHCP request packet processing moved to NetworkManager class. warning [-Wdelete-incomplete].