1 files changed, 107 insertions, 3 deletions

diff --git a/src/resolve/resolved-dns-answer.c b/src/resolve/resolved-dns-answer.c
index 399b518644..b50558e280 100644
--- a/src/resolve/resolved-dns-answer.c
+++ b/src/resolve/resolved-dns-answer.c
@@ -125,10 +125,13 @@ int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex, DnsAnswerFl
                 if (r < 0)
                         return r;
                 if (r > 0) {
-                        /* Entry already exists, keep the entry with
-                         * the higher RR, or the one with TTL 0 */
+                        /* Don't mix contradicting TTLs (see below) */
+                        if ((rr->ttl == 0) != (a->items[i].rr->ttl == 0))
+                                return -EINVAL;
 
-                        if (rr->ttl == 0 || (rr->ttl > a->items[i].rr->ttl && a->items[i].rr->ttl != 0)) {
+                        /* Entry already exists, keep the entry with
+                         * the higher RR. */
+                        if (rr->ttl > a->items[i].rr->ttl) {
                                 dns_resource_record_ref(rr);
                                 dns_resource_record_unref(a->items[i].rr);
                                 a->items[i].rr = rr;
@@ -137,6 +140,21 @@ int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex, DnsAnswerFl
                         a->items[i].flags |= flags;
                         return 0;
                 }
+
+                r = dns_resource_key_equal(a->items[i].rr->key, rr->key);
+                if (r < 0)
+                        return r;
+                if (r > 0) {
+                        /* There's already an RR of the same RRset in
+                         * place! Let's see if the TTLs more or less
+                         * match. We don't really care if they match
+                         * precisely, but we do care whether one is 0
+                         * and the other is not. See RFC 2181, Section
+                         * 5.2.*/
+
+                        if ((rr->ttl == 0) != (a->items[i].rr->ttl == 0))
+                                return -EINVAL;
+                }
         }
 
         return dns_answer_add_raw(a, rr, ifindex, flags);
@@ -506,6 +524,92 @@ int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key) {
         return 1;
 }
 
+int dns_answer_remove_by_rr(DnsAnswer **a, DnsResourceRecord *rm) {
+        bool found = false, other = false;
+        DnsResourceRecord *rr;
+        unsigned i;
+        int r;
+
+        assert(a);
+        assert(rm);
+
+        /* Remove all entries matching the specified RR from *a */
+
+        DNS_ANSWER_FOREACH(rr, *a) {
+                r = dns_resource_record_equal(rr, rm);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        found = true;
+                else
+                        other = true;
+
+                if (found && other)
+                        break;
+        }
+
+        if (!found)
+                return 0;
+
+        if (!other) {
+                *a = dns_answer_unref(*a); /* Return NULL for the empty answer */
+                return 1;
+        }
+
+        if ((*a)->n_ref > 1) {
+                _cleanup_(dns_answer_unrefp) DnsAnswer *copy = NULL;
+                DnsAnswerFlags flags;
+                int ifindex;
+
+                copy = dns_answer_new((*a)->n_rrs);
+                if (!copy)
+                        return -ENOMEM;
+
+                DNS_ANSWER_FOREACH_FULL(rr, ifindex, flags, *a) {
+                        r = dns_resource_record_equal(rr, rm);
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                continue;
+
+                        r = dns_answer_add_raw(copy, rr, ifindex, flags);
+                        if (r < 0)
+                                return r;
+                }
+
+                dns_answer_unref(*a);
+                *a = copy;
+                copy = NULL;
+
+                return 1;
+        }
+
+        /* Only a single reference, edit in-place */
+
+        i = 0;
+        for (;;) {
+                if (i >= (*a)->n_rrs)
+                        break;
+
+                r = dns_resource_record_equal((*a)->items[i].rr, rm);
+                if (r < 0)
+                        return r;
+                if (r > 0) {
+                        /* Kill this entry */
+
+                        dns_resource_record_unref((*a)->items[i].rr);
+                        memmove((*a)->items + i, (*a)->items + i + 1, sizeof(DnsAnswerItem) * ((*a)->n_rrs - i - 1));
+                        (*a)->n_rrs --;
+                        continue;
+
+                } else
+                        /* Keep this entry */
+                        i++;
+        }
+
+        return 1;
+}
+
 int dns_answer_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key, DnsAnswerFlags or_flags) {
         DnsResourceRecord *rr_source;
         int ifindex_source, r;