[lwip-users] question about compile minimal under Fedora 2

[Dyan Chiang]

I port lwip to Fedora 2(kernel 2.6). And just when I start to compiler the /minimal porject

gcc version is 3.3.3 and the make program exit with the following error:

minitapif.c:271:error: void value not ignored as it ought to be

minitapif.c:276:error: void value not ignored as it ought to be

 

and I check the minitapif.c file I find that on the line 271 and 276 is the "mintapif_input()" function as here(I mark it with red color).

it call void etharp_ip_input() and void etharp_arp_input()

static void
mintapif_input(struct netif *netif)
{
  struct mintapif *mintapif;
  struct eth_hdr *ethhdr;
  struct pbuf *p, *q;

 

  mintapif = netif->state;
 
  p = low_level_input(mintapif);

 

  if (p != NULL) {

 

#ifdef LINK_STATS
    lwip_stats.link.recv++;
#endif /* LINK_STATS */

 

    ethhdr = p->payload;

 

    q = NULL;
    switch (htons(ethhdr->type)) {
    case ETHTYPE_IP:
      q = etharp_ip_input(netif, p);
      pbuf_header(p, -14);
      netif->input(p, netif);
      break;
    case ETHTYPE_ARP:
      q = etharp_arp_input(netif, mintapif->ethaddr, p);
      break;
    default:
      pbuf_free(p);
      break;
    }
    if (q != NULL) {
      low_level_output(netif, q);
      pbuf_free(q);
    }

 

  }
} 

And I go to the lwip-1.0.0/src/netif/etharp.c and lwip-1.0.0/src/include/netif/etharp.h

find the

void etharp_ip_input(struct netif *netif, struct pbuf *p);

void etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr,
         struct pbuf *p);

change to the following:

struct pbuf *  etharp_ip_input(struct netif *netif, struct pbuf *p);

struct pbuf *  etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr,
         struct pbuf *p);

 

and I compiler again. Now compiling is success. 

I have some question to ask:

 

1. Is it OK if I do such changes?

2. Why it is declare as void and in minitapif.c call it again with return. What is it aim try to accomplish?

 

 

Thank you very much.

Please forgive me my ungreatefully asking question.