Re: [lwip-users] LLDP Implementation for lwIP

[Sergio R. Caprile]

For a TCP/IP application:
the wiki http://lwip.wikia.com/wiki/LwIP_Wiki
the example applications in the contrib tree
the apps in the new tree (2.0.0RC2 and git head)

However, afaik (and I don't really know much), LLDP runs over bare 
Ethernet with ethertype=0x88CC, so you need to trap the frames from your 
driver before actually delivering them to lwIP. I think what you are 
probably looking for is this:
http://lwip.wikia.com/wiki/LwIP_with_or_without_an_operating_system
It explains how the driver interacts with lwIP to deliver the frames.

Take a look at the ethernetif code at /src/netif/ethernetif.c, the 
ethernetif_input() function:

  switch (htons(ethhdr->type)) {
  /* IP or ARP packet? */
  case ETHTYPE_IP:
  case ETHTYPE_ARP:
#if PPPOE_SUPPORT
  /* PPPoE packet? */
  case ETHTYPE_PPPOEDISC:
  case ETHTYPE_PPPOE:
#endif /* PPPOE_SUPPORT */
    /* full packet send to tcpip_thread to process */
    if (netif->input(p, netif)!=ERR_OK)
     { LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n"));
       pbuf_free(p);
       p = NULL;
     }
    break;

That is a skeleton, you need to implement something like that in your 
driver (Or the one who wrote it did something like that).

HOWEVER, this is so in 1.4.1. This has changed in git head, for some 
reason (I think PPPoE and layer-2 flexibility) this has been delegated 
to the lower level input function:

    /* pass all packets to ethernet_input, which decides what packets 
it supports */
    if (netif->input(p, netif) != ERR_OK) {

So basically your job is a layer-2 job; you have to work on your 
Ethernet driver. I suggest you go the git head or 2.0.0RC2 way, there 
have been numerous patches over 1.4.1