I got sockets that are listening to ICMP/UDP packets. If the socket receives a packet and the handling of this packet takes too long (code after socket.receive()), could following packets be missed, since I'm currently not at socket.receive() part?
Strictly speaking, yes. The implementation is free to discard packets any place it wishes to. However, it would be a pretty poor implementation if it didn't provide some reasonable amount of buffering, and Linux does.