[lwip-devel] [bug #55252] Gratuitous ARP sent before valid ip address is obtained

[Pelle Bergkvist]

URL:
  <https://savannah.nongnu.org/bugs/?55252>

                 Summary: Gratuitous ARP sent before valid ip address is
obtained
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: pellebk
            Submitted on: Thu 20 Dec 2018 07:06:52 AM UTC
                Category: ARP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.1.1

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Details:

In netif_set_link_up an etharp_gratuitous is done even if the interface
address is IPADDR_ANY. Suggest to change the etharp_gratuitous define to:
#define etharp_gratuitous(netif) if (!ip4_addr_isany(netif_ip4_addr(netif))) {
etharp_request((netif), netif_ip4_addr(netif)); }
as this should not ever(?) be done for IPADDR_ANY

Alternative solution could be to update the if statement in
netif_set_link_up(struct netif *) to 
    /* For Ethernet network interfaces, we would like to send a "gratuitous
ARP" */
    if (((netif->flags & (NETIF_FLAG_ETHARP | NETIF_FLAG_POINTTOPOINT)) ==
NETIF_FLAG_ETHARP) && !ip4_addr_isany(netif_ip4_addr(netif))) {
        etharp_gratuitous(netif);
    }

Using the latest 2.1.2 version


 




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