pbuf_layer enum

Includes spare room for transport layer header, e.g. UDP header. Use this if you intend to pass the pbuf to functions like udp_send().

Includes spare room for IP header. Use this if you intend to pass the pbuf to functions like raw_send().

Includes spare room for link layer header (ethernet header). Use this if you intend to pass the pbuf to functions like ethernet_output(). @see PBUF_LINK_HLEN.

Includes spare room for additional encapsulation header before ethernet headers (e.g. 802.11). Use this if you intend to pass the pbuf to functions like netif->linkoutput(). @see PBUF_LINK_ENCAPSULATION_HLEN.

Use this for input packets in a netif driver when calling netif->input() in the most common case - ethernet-layer netif driver.