Detailed Description

Raw Layer-2 Ethernet frame codec (DETWS_ENABLE_RAWL2).

The host-testable core of raw-L2 frame TX/RX: build and parse Ethernet II frames (and 802.1Q VLAN-tagged frames) so the app can inject/receive arbitrary L2 frames - the basis for the raw-L2 industrial protocols (PROFINET DCP, IEC 61850 GOOSE, POWERLINK, SERCOS) and for custom management / proprietary MAC framing. On device the bytes go out via esp_eth_transmit() (wired) or esp_wifi_80211_tx() (Wi-Fi); the MAC normally appends the FCS, so the builder emits the frame without it and detws_eth_fcs is provided for the cases that need it.

Ethernet II: [dst MAC 6][src MAC 6][ethertype 2][payload] 802.1Q: [dst 6][src 6][0x8100][TCI 2][ethertype 2][payload]

Pure, zero heap, no stdlib, host-testable.

Definition in file rawl2.h.