[OpenWrt-Devel] [PATCH][umdns] Fix advertised IPv6 addresses

[David Woodhouse]

The dns_reply_a() function appears to include *only* link-local IPv6
addresses. This seems wrong, and ends up publishing addresses which
can't be used to reach the host in question.

I believe the logic should be the other way around and we should be
*eliding* the link-local addresses but including the global ones.

With this fixed, I can run 'ubus call umdns hosts' on another AP in my
network and I see the correct global IPv6 address. Likewise, running
'ubus call umdns browse' shows the right address and I can set about
fixing https://github.com/berlin-open-wireless-lab/DAWN/issues/95

Fixes: https://bugs.openwrt.org/index.php?do=details&task_id=3167

diff --git a/dns.c b/dns.c
index 1d3362f..47c75ad 100644
--- a/dns.c
+++ b/dns.c
@@ -202,7 +202,7 @@ dns_reply_a(struct interface *iface, struct sockaddr *to, int ttl)
 		if (ifa->ifa_addr->sa_family == AF_INET6) {
 			uint8_t ll_prefix[] = {0xfe, 0x80 };
 			sa6 = (struct sockaddr_in6 *) ifa->ifa_addr;
-			if (!memcmp(&sa6->sin6_addr, &ll_prefix, 2))
+			if (memcmp(&sa6->sin6_addr, &ll_prefix, 2))
 				dns_add_answer(TYPE_AAAA, (uint8_t *) &sa6->sin6_addr, 16, ttl);
 		}
 	}
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