int netif_rx (struct sk_buff * skb);
This function receives a packet from a device driver and queues it for the upper (protocol) levels to process. It always succeeds. The buffer may be dropped during processing for congestion control or by the protocol layers.
NET_RX_SUCCESS (no congestion) NET_RX_CN_LOW (low congestion) NET_RX_CN_MOD (moderate congestion) NET_RX_CN_HIGH (high congestion) NET_RX_DROP (packet was dropped)