arp: Fix a handful of small warts

This fixes a number of harmless but slightly ugly warts in the ARP
resolution code:
 * Use in4addr_any to represent 0.0.0.0 rather than hand constructing an
   example.
 * When comparing am->sip against 0.0.0.0 use sizeof(am->sip) instead of
   sizeof(am->tip) (same value, but makes more logical sense)
 * Described the guest's assigned address as such, rather than as "our
   address" - that's not usually what we mean by "our address" these days
 * Remove "we might have the same IP address" comment which I can't make
   sense of in context (possibly it's relating to the statement below,
   which already has its own comment?)

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/arp.c b/arp.c
index 53334da..fc482bb 100644
--- a/arp.c
+++ b/arp.c
@@ -59,14 +59,12 @@ int arp(const struct ctx *c, const struct pool *p)
 	    ah->ar_op  != htons(ARPOP_REQUEST))
 		return 1;
 
-	/* Discard announcements (but not 0.0.0.0 "probes"): we might have the
-	 * same IP address, hide that.
-	 */
-	if (memcmp(am->sip, (unsigned char[4]){ 0 }, sizeof(am->tip)) &&
+	/* Discard announcements, but not 0.0.0.0 "probes" */
+	if (memcmp(am->sip, &in4addr_any, sizeof(am->sip)) &&
 	    !memcmp(am->sip, am->tip, sizeof(am->sip)))
 		return 1;
 
-	/* Don't resolve our own address, either. */
+	/* Don't resolve the guest's assigned address, either. */
 	if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip)))
 		return 1;