Re: [B.A.T.M.A.N.] [PATCH v2] alfred: Request MAC resolution for IPv4 address not in ARP cache

[Sven Eckelmann <sven@narfation.org>]

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On Mittwoch, 24. Oktober 2018 13:21:28 CEST Jonathan Haws wrote:
[...]
>  
> +       while (retries-- && !(arpreq.arp_flags & ATF_COM)) {
> +               ipv4_request_mac_resolve(addr);
> +               usleep(200000);
> +
> +               if (ioctl(interface->netsock, SIOCGARP, &arpreq) < 0)
> +                       return -1;
> +       }
> +
>         if (arpreq.arp_flags & ATF_COM) {
>                 memcpy(mac, arpreq.arp_ha.sa_data, sizeof(*mac));
>         } else {

According to gary [1], this doesn't work because the ioctl fails for him and 
then the function returns immediately (before the while loop).

Please adjust your patch - but please don't use his code - it looks rather
ugly and also doesn't work for multiple retries. You most likely want to
drop the if-ioctl completely and then put everything in your while loop:

	while (ioctl(interface->netsock, SIOCGARP, &arpreq) < 0 ||
	       !(arpreq.arp_flags & ATF_COM)) {
		if (retries-- <= 0)
			break;

		ipv4_request_mac_resolve(addr);
		usleep(200000);
	}

But feel to propose a different (cleaner) approach.

Kind regards,
	Sven

[1] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2018-October/018195.html

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