[lwip-users] netif/etharp assertion failure

[Robin Iddon]

Hi,

I am getting an assertion failure (after extended use) in etharp.c

LWIP assertion failure, file: netif/etharp.c, line: 886
no packet queues allowed!

Looking at the code:

     p = q;
     while (p) {
       LWIP_ASSERT("no packet queues allowed!", (p->len == p->tot_len) 
|| (p->next == 0));
       if(p->flags != PBUF_FLAG_ROM) {
         copy_needed = 1;
         break;
       }
       p = p->next;
     }

I think the intent is to ensure that only single packets are queued up 
on ARP entries, not queues of packets.

To me the code says that q must point to a pbuf that has just one 
element (p->len == p->tot_len case).  If there were two pbufs in a 
chain, the first pbuf would fail both conditions (p->len would 
presumably be less than p->tot_len and p->next wouldn't be NULL).

I think the code should have said:

     p = q;
     while (p) {
       LWIP_ASSERT("no packet queues allowed!", (p->tot_len == (p->len 
+ (p->next ? p->next->tot_len:0) );
       if(p->flags != PBUF_FLAG_ROM) {
         copy_needed = 1;
         break;
       }
       p = p->next;
     }

Or am I missing something?

Cheers,
Robin