Adjust semantics of TTL adjustment after feedback from @wcawijngaards

diff --git a/cachedb/cachedb.c b/cachedb/cachedb.c
index 6a2b735aaf65358e35e89454470389ad7a42fdcc..e948a6b0dd34a14179630f3694cbf6947c0d1466 100644 (file)
--- a/cachedb/cachedb.c
+++ b/cachedb/cachedb.c
@@ -465,7 +465,7 @@ packed_rrset_ttl_subtract(struct packed_rrset_data* data, time_t subtract)
                        data->rr_ttl[i] -= subtract;
                else    data->rr_ttl[i] = 0;
        }
-       data->ttl_add = 0;
+       data->ttl_add = (subtract < data->ttl_add) ? (data->ttl_add - subtract) : 0;
 }
 
 /* Adjust the TTL of a DNS message and its RRs by 'adjust'.  If 'adjust' is