[lwip-users] [lwip] ip_route and ip_addr_isbroadcast

[Ivarsson Magnus]

Hi, 
When dealing with PPP there are only two IP adresses per link.
These IP adresses does not always belong to the same 'subnet' 
and thus the need for a netmask of 255.255.255.255 arises.
Also the routing is affected. I had to make some changes in 
ip_addr.h and ip.c to make it work.

First question: 
 Does anybody see that this change in ip_addr_isbroadcast is erroneous?

#define ip_addr_isbroadcast(addr1, mask)          \
  (                                               \
    (                                             \
      (                                           \
        (                                         \
          (((addr1)->addr) & ~((mask)->addr))     \
            ==                                    \
          (0xffffffff & ~((mask)->addr))          \
        )                                         \
new:    && !((mask)->addr == 0xffffffff)          \
      )                                           \
    )                                             \
    || ((addr1)->addr == 0xffffffff)              \
    || ((addr1)->addr == 0x00000000)              \
  )



Second question:
 In ip_route (see below) we are searching for a subnet which is matching 
 our destination IP adress. To support the PPP specific behaivor without
 subnets I would like to compare with &(netif->gw) instead. Is it safe to 
 assume that gw always is set to something useful (like an adress within 
 the subnet)?

---8<----
struct netif *
ip_route(struct ip_addr *dest)
{
  struct netif *netif;
  
  for(netif = netif_list; netif != NULL; netif = netif->next) {
    if(ip_addr_maskcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
      return netif;
    }
  }

  return netif_default;
}
---->8---


BR, Magnus Ivarsson
[This message was sent through the lwip discussion list.]